;
Oh+'0HP
$TU Delft Repository search results0TU Delft Repository search results (max. 1000)TU Delft LibraryTU Delft Library@q@@q@՜.+,0HPX`hp
x
WorksheetFeuilles de calcul
B=%r8X"1Calibri1Calibri1Calibri1
Calibri 83ffff̙̙3f3fff3f3f33333f33333.uTU Delft Repositoryg p7uuidrepository linktitleauthorcontributorpublication yearabstract
subject topiclanguagepublication type publisherisbnissnpatent
patent statusbibliographic noteaccess restrictionembargo datefaculty
departmentresearch group programmeprojectcoordinates)uuid:eb49b58e79174bd2a89d8e86a61009a9Dhttp://resolver.tudelft.nl/uuid:eb49b58e79174bd2a89d8e86a61009a9DUnified matrixvector wave equation, reciprocity and representations?Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)The matrixvector wave equation is a compact firstorder differential equation. It was originally used for the analysis of elastodynamic plane waves in laterally invariant media. It has been extended by various authors for laterally varying media. Other authors derived a similar formalism for other wave phenomena. This paper starts with a unified formulation of the matrixvector wave equation for 3D inhomogeneous, dissipative media. The wave vector, source vector and operator matrix are specified in the appendices for acoustic, quantum mechanical, electromagnetic, elastodynamic, poroelastodynamic, piezoelectric and seismoelectric waves. It is shown that the operator matrix obeys unified symmetry relations for all these wave phenomena. Next, unified matrixvector reciprocity theorems of the convolution and correlation type are derived, utilizing the symmetry properties of the operator matrix. These theorems formulate mathematical relations between two wave states in the same spatial domain. A unified wavefield representation is obtained by replacing one of the states in the convolutiontype reciprocity theorem by a Green's state. By replacing both states in the correlationtype reciprocity theorem by Green's states, a unified representation of the homogeneous Green's matrix is obtained. Applications of the unified reciprocity theorems and representations for forward and inverse wave problems are briefly indicated.@Electromagnetic theory; Theoretical seismology; Wave propagationenjournal article)uuid:c8f3dfa388cb4adab604fa1cb6c43fecDhttp://resolver.tudelft.nl/uuid:c8f3dfa388cb4adab604fa1cb6c43fec{Application of seismic interferometry by multidimensional deconvolution to earthquakes data recorded in Malargue, ArgentinaShirmohammadi, F. (University of Tehran); Weemstra, C. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)poster)uuid:c9de64832a054f05a25fcba2cf92ddb6Dhttp://resolver.tudelft.nl/uuid:c9de64832a054f05a25fcba2cf92ddb6eElastodynamic singlesided homogeneous Green s function representation: Theory and numerical examplesReinicke Urruticoechea, C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)The homogeneous Green s function is the difference between an impulse response and its timereversal. According to existing representation theorems, the homogeneous Green s function associated with source receiver pairs inside a medium can be computed from measurements at a boundary enclosing the medium. However, in many applications such as seismic imaging, timelapse monitoring, medical imaging, nondestructive testing, etc., media are only accessible from one side. A recent development of wave theory has provided a representation of the homogeneous Green s function in an elastic medium in terms of wavefield recordings at a single (open) boundary. Despite its singlesidedness, the elastodynamic homogeneous Green s function representation accounts for all orders of scattering inside the medium. We present the theory of the elastodynamic singlesided homogeneous Green s function representation and illustrate it with numerical examples for 2D laterallyinvariant media. For propagating waves, the resulting homogeneous Green s functions match the exact ones within numerical precision, demonstrating the accuracy of the the< ory. In addition, we analyse the accuracy of the singlesided representation of the homogeneous Green s function for evanescent wave tunnelling.?Elastic; Interferometry; Internal multiples; Layered; NumericalAccepted Author Manuscript
20210417)uuid:630be8fb2a1443f9a5a6af1ff80253f7Dhttp://resolver.tudelft.nl/uuid:630be8fb2a1443f9a5a6af1ff80253f7;An acoustic imaging method for layered nonreciprocal mediaWapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Reinicke Urruticoechea, C. (TU Delft Applied Geophysics and Petrophysics)Given the increasing interest for nonreciprocal materials, we propose a novel acoustic imaging method for layered nonreciprocal media. The method we propose is a modification of the Marchenko imaging method, which handles multiple scattering between the layer interfaces in a datadriven way. We start by reviewing the basic equations for wave propagation in a nonreciprocal medium. Next, we discuss Green s functions, focusing functions, and their mutual relations, for a nonreciprocal horizontally layered medium. These relations form the basis for deriving the modified Marchenko method, which retrieves the wave field inside the nonreciprocal medium from reflection measurements at the boundary of the medium. With a numerical example we show that the proposed method is capable of imaging the layer interfaces at their correct positions, without artefacts caused by multiple scattering.
20200308)uuid:3fbcd73e0bad4d308f42143dfbc431ebDhttp://resolver.tudelft.nl/uuid:3fbcd73e0bad4d308f42143dfbc431eb4Green's theorem in seismic imaging across the scalesWapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Brackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics)The earthquake seismology and seismic exploration communities have developed a variety of seismic imaging methods for passive and activesource data. Despite the seemingly different approaches and underlying principles, many of those methods are based in some way or another on Green's theorem. The aim of this paper is to discuss a variety of imaging methods in a systematic way, using a specific form of Green's theorem (the homogeneous Green's function representation) as a common starting point. The imaging methods we cover are timereversal acoustics, seismic interferometry, back propagation, source receiver redatuming and imaging by double focusing. We review classical approaches and discuss recent developments that fully account for multiple scattering, using the Marchenko method. We briefly indicate new applications for monitoring and forecasting of responses to induced seismic sources, which are discussed in detail in a companion paper.)uuid:85aa81cb4cf048c7a9fc95f6cef248bfDhttp://resolver.tudelft.nl/uuid:85aa81cb4cf048c7a9fc95f6cef248bfeTransmission compensated primary reflection retrieval in the data domain and consequences for imaging"Zhang, L. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics)We have developed a scheme that retrieves primary reflections in the twoway traveltime domain by filtering the data. The data have their own filter that removes internal multiple reflections, whereas the amplitudes of the retrieved primary reflections are compensated for twoway transmission losses. Application of the filter does not require any model information. It consists of convolutions and correlations of the data with itself. A truncation in the time domain is applied after each convolution or correlation. The retrieved data set can be used as the input to construct a better velocity model than the one that would be obtained by working directly with the original data and to construct an enhanced subsurface imag< e. Two 2D numerical examples indicate the effectiveness of the method. We have studied bandwidth limitations by analyzing the effects of a thin layer. The presence of refracted and scattered waves is a known limitation of the method, and we studied it as well. Our analysis indicates that a thin layer is treated as a more complicated reflector, and internal multiple reflections related to the thin layer are properly removed. We found that the presence of refracted and scattered waves generates artifacts in the retrieved data.acoustic; internal multiplesEGreen Open Access added to TU Delft Institutional Repository You share, we take care! Taverne project https://www.openaccess.nl/en/yousharewetakecare Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.
20191026)uuid:386ff8b1072049e284253de163aea36fDhttp://resolver.tudelft.nl/uuid:386ff8b1072049e284253de163aea36f<Reciprocitybased passive monitoring with individual sourcesAlmagro Vidal, C. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)GTimelapse changes in the subsurface can be analyzed by comparing seismic reflection data from two different states, one serving as the base survey and the second as the monitor survey. Conventionally, reflection data are acquired by placing active seismic sources at the acquisition surface. Alternatively, these data can be acquired from passive sources in the subsurface, using seismic interferometry (SI). Unfortunately, the reflection responses as retrieved by SI inherit an imprint of the passivesource distribution; therefore, monitoring with SI requires high passivesource repeatability, which is very often not achievable in practice.We have developed an alternative by using active seismic data for the base survey and a single passive source (e.g., a seismic tremor produced by induced seismicity) for the monitor survey. By constraining the sourceradiation pattern of the (active) base survey according to the characteristics of the (passive) monitor survey, we succeed in extracting the timelapse response in the image domain. We tested our method with numerically modeled data.)uuid:a06e8d0f20d845ed8ddaa3aa8512fadfDhttp://resolver.tudelft.nl/uuid:a06e8d0f20d845ed8ddaa3aa8512fadf<Wavefield finite time focusing with reduced spatial exposure/Meles, G.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); van Dongen, K.W.A. (TU Delft ImPhys/Acoustical Wavefield Imaging); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics; TU Delft ImPhys/Acoustical Wavefield Imaging)Wavefield focusing is often achieved by timereversal mirrors, where wavefields emitted by a source located at the focal point are evaluated at a closed boundary and sent back, after timereversal, into the medium from that boundary. Mathematically, timereversal mirrors are derived from closedboundary integral representations of reciprocity theorems. In heterogeneous media, timereversal focusing theoretically involves in and output signals that are infinite in time and the resulting waves propagate through the entire medium. Recently, integral representations have been derived for singlesided wavefield focusing. Although the required input signals for this approach are finite in time, the output signals are not and, similar to timereversal mirroring, the resulting waves propagate through the entire medium. Here, an alternative solution for doublesided wavefield focusing is derived. This solution is based on an integral representation where in and output signals are finite in time, and where the energy of the waves propagating in the layer embedding the focal point is smaller than with timereversal focusing. The potential of the proposed method is explored with numerical experiments involving a< head model consisting of a skull enclosing a brain.
20191218)uuid:2edcfd2945e848e58ba34201fa8d5069Dhttp://resolver.tudelft.nl/uuid:2edcfd2945e848e58ba34201fa8d5069AVirtual acoustics in inhomogeneous media with singlesided accessWapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Brackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Verschuur, D.J. (TU Delft ImPhys/Acoustical Wavefield Imaging)mA virtual acoustic source inside a medium can be created by emitting a timereversed pointsource response from the enclosing boundary into the medium. However, in many practical situations the medium can be accessed from one side only. In those cases the timereversal approach is not exact. Here, we demonstrate the experimental design and use of complex focusing functions to create virtual acoustic sources and virtual receivers inside an inhomogeneous medium with singlesided access. The retrieved virtual acoustic responses between those sources and receivers mimic the complex propagation and multiple scattering paths of waves that would be ignited by physical sources and recorded by physical receivers inside the medium. The possibility to predict complex virtual acoustic responses between any two points inside an inhomogeneous medium, without needing a detailed model of the medium, has large potential for holographic imaging and monitoring of objects with singlesided access, ranging from photoacoustic medical imaging to the monitoring of inducedearthquake waves all the way from the source to the earth's surface.)uuid:f47e0797e53d43e5afbc88d7316f3118Dhttp://resolver.tudelft.nl/uuid:f47e0797e53d43e5afbc88d7316f31183Virtual planewave imaging via Marchenko redatumingMeles, G.A. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics)Marchenko redatuming is a novel scheme used to retrieve up and downgoing Green's functions in an unknown medium.Marchenko equations are based on reciprocity theorems and are derived on the assumption of the existence of functions exhibiting spacetime focusing properties once injected in the subsurface. In contrast to interferometry but similarly to standard migration methods, Marchenko redatuming only requires an estimate of the direct wave from the virtual source (or to the virtual receiver), illumination from only one side of the medium and no physical sources (or receivers) inside the medium. In this contribution we consider a different timefocusing condition within the frame of Marchenko redatuming that leads to the retrieval of virtual planewave responses. As a result, it allows multiplefree imaging using only a 1D sampling of the targeted model at a fraction of the computational cost of standard Marchenko schemes. The potential of the new method is demonstrated on 2D synthetic models.UControlled source seismology; Seismic interferometry; Wave scattering and diffraction#Applied Geophysics and Petrophysics)uuid:13bf575c66d44321932929e99403660eDhttp://resolver.tudelft.nl/uuid:13bf575c66d44321932929e99403660eUMarchenkoBased Target Replacement, Accounting for All Orders of Multiple ReflectionsWapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Staring, M. (TU Delft Applied Geophysics and Petrophysics)In seismic monitoring, one is usually interested in the response of a changing target zone, embedded in a static inhomogeneous medium. We introduce an efficient method that predicts reflection responses at the Earth's surface for different targetzone scenarios, from a single reflection response at the surface and a model of the changing target zone. The proposed process consists of two main ste< ps. In the first step, the response of the original target zone is removed from the reflection response, using the Marchenko method. In the second step, the modelled response of a new target zone is inserted between the overburden and underburden responses. The method fully accounts for all orders of multiple scattering and, in the elastodynamic case, for wave conversion. For monitoring purposes, only the second step needs to be repeated for each targetzone model. Since the target zone covers only a small part of the entire medium, the proposed method is much more efficient than repeated modelling of the entire reflection response./multiples; representations; seismic; timelapse)uuid:5c2a435d5004455f9ee34afcedc50283Dhttp://resolver.tudelft.nl/uuid:5c2a435d5004455f9ee34afcedc50283SLocating scatterers while drilling using seismic noise due to tunnel boring machineHarmankaya, U (Istanbul Technical University); Kaslilar, A. (Istanbul Technical University); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics)Unexpected geological structures can cause safety and economic risks during underground excavation. Therefore, predicting possible geological threats while drilling a tunnel is important for operational safety and for preventing expensive standstills. Subsurface information for tunneling is provided by exploratory wells and by surface geological and geophysical investigations, which are limited by location and resolution, respectively. For detailed information about the structures ahead of the tunnel face, geophysical methods are applied during the tunneldrilling activity. We present a method inspired by seismic interferometry and ambientnoise correlation that can be used for detecting scatterers, such as boulders and cavities, ahead of a tunnel while drilling. A similar method has been proposed for activesource seismic data and validated using laboratory and field data. Here, we propose to utilize the seismic noise generated by a Tunnel Boring Machine (TBM), and recorded at the surface. We explain our method at the hand of data from finitedifference modelling of noisesource wave propagation in a medium where scatterers are present. Using the modelled noise records, we apply crosscorrelation to obtain correlation gathers. After isolating the scattered arrivals in these gathers, we crosscorrelate again and invert for the correlated traveltime to locate scatterers. We show the potential of the method for locating the scatterers while drilling using noise records due to TBM.Body waves; Finitedifference modelling; Locating scatterers; Seismicnoise correlation; Traveltime inversion; Tunnel seismicwhiledrilling
20200405)uuid:324bfb26265a4299b4e8c2d55be43643Dhttp://resolver.tudelft.nl/uuid:324bfb26265a4299b4e8c2d55be43643LRetrieval of Elastodynamic Reflections From Passive DoubleCouple RecordingsHartstra, I.E. (TU Delft Applied Geophysics and Petrophysics); AlmagroVidal, C.; Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)Virtual Green's functions obtained by seismic interferometry (SI) can provide valuable reflectivity data that can complement tomographic inversion schemes. However, virtual reflections are affected by illumination irregularities that are typical of earthquakeinduced wavefields recorded by the receiver array. As a consequence, irregular source distributions, scattering (in case of suboptimal illumination), and complex source mechanisms can significantly disturb the retrieval of Green's function approximations by conventional SI methods. We introduce SI by fullfield multidimensional deconvolution (MDD) for elastodynamic wavefields as an alternative method to obtain body wave Green's functions under those typical circumstances. The advantage of this method compared to other MDD methods is that the kernel of its governing equation is exact. This alternative formulation of the kernel pertains to several advantages: the solution is less sensitive to artif< acts and utilizes the freesurface multiples in the data to estimate primary reflections. Moreover, the point spread function of the fullfield MDD method corrects more affectively for irregular illumination because it also addresses irregularities caused by scattering inside the medium. In order to compare fullfield MDD to existing SI methods, we model synthetic earthquake recordings in a subduction zone setting using an elastodynamic finitedifference scheme with double couples of different orientations and peak frequencies. Our results show that SI by cross correlation suffers most under these circumstances. Higherquality reflections are obtained by the MDD methods, of which fullfield MDD involves the most stable inversion, and its results are least contaminated by artifacts.^body waves; elastodynamic; multidimensional deconvolution; reflections; seismic interferometry)uuid:74b21e406dfc4ff4be4ddffdc8ffba34Dhttp://resolver.tudelft.nl/uuid:74b21e406dfc4ff4be4ddffdc8ffba34$Artifactfree reverse time migration%Zhang, L. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)We have derived an improved reverse time migration (RTM) scheme to image the medium without artifacts arising from internal multiple reflections. This is based on a revised implementation of Marchenko redatuming using a new timetruncation operator. Because of the new truncation operator, we can use the timereversed version of the standard wavefieldextrapolation operator as initial estimate for retrieving the upgoing focusing function. Then, the retrieved upgoing focusing function can be used to directly image the medium by correlating it with the standard wavefieldextrapolation operator. This imaging scheme can be seen as an artifactfree RTM scheme with two terms. The first term gives the conventional RTM image with the wrong amplitude and artifacts due to internal multiple reflections. The second term gives a correction image that can be used to correct the amplitude and remove artifacts in the image generated by the first term. We evaluated the success of the method with a 2D numerical example.)uuid:971090a1d8f64e1396cc4f022707d87aDhttp://resolver.tudelft.nl/uuid:971090a1d8f64e1396cc4f022707d87a[Sourcereceiver Marchenko redatuming on field data using an adaptive doublefocusing method Staring, M. (TU Delft Applied Geophysics and Petrophysics); Pereira, Roberto (CGG, Rio de Janeiro); Douma, Huub (CGG, Rio de Janeiro); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)We have developed an adaptive doublefocusing method that is specifically designed for the fielddata application of sourcereceiver Marchenko redatuming. Typically, the singlefocusing Marchenko method is combined with a multidimensional deconvolution (MDD) to achieve redatuming. Our method replaces the MDD step by a second focusing step that naturally complements the singlefocusing Marchenko method. Instead of performing the MDD method with the directionally decomposed Green's functions that result from singlefocusing, we now use the retrieved upgoing Green's function and the retrieved downgoing focusing function to obtain a redatumed reflection response in the physical medium. Consequently, we only remove the strongest overburden effects instead of removing all of the overburden effects. However, the gain is a robust method that is less sensitive to imperfections in the data and a sparse acquisition geometry than the MDD method. In addition, it is computationally much cheaper, more straightforward to implement, and it can be parallelized over pairs of focal points, which makes it suitable for application to large data volumes. We evaluate the successful application of our method to 2D field data of the Santos Basin.IAdaptive subtraction; Autofocusing; Datuming; Int< ernal multiples; Subsalt)uuid:dfe1055f645e475396dfc49ba4df838dDhttp://resolver.tudelft.nl/uuid:dfe1055f645e475396dfc49ba4df838dRPassive bodywave interferometric imaging with directionally constrained migrationEAlmagro Vidal, C. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Verdel, Arie (TNO); Hartstra, I.E. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)Passive seismic interferometry enables the estimation of the reflection response of the subsurface using passive receiver recordings at the surface from sources located deep in the Earth. Interferometric imaging makes use of this retrieved reflection response in order to study the subsurface. Successful interferometric imaging relies on the availability of passive recordings from sufficient sources in the subsurface. Ideally, these sources should be homogeneously distributed, which is unlikely to happen in practical applications. Incomplete source distributions result in the retrieval of inaccurate reflection responses, containing artefacts which can disturb the interferometric imaging process. We propose an alternative imaging method for passive data based on illumination diagnosis and directionally constrained migration. In this method, passive responses from single transient sources are crosscorrelated individually, and the dominant radiation direction from each virtual source is estimated. The correlated responses are imaged individually, thereby limiting the source wavefield to the dominant radiation direction of the virtual source. This constraint enables the construction of accurate images from individual sources with a significantly reduced amount of migrated interferometric artefacts. We also show that the summation of all individual imaging results improves the subsurface image by constructive interference, while migrated crosstalk and artefacts experience cancellation. This process, called Image Interferometry, shows that in case of limited subsurface illumination the interferometric integration can be applied in the image domain rather than in the virtual reflectionresponse domain, thus eliminating the need for the retrieval of the reflection response as an intermediate step.3Seismic Interferometry; Body waves; Crustal imaging)uuid:3091b118e9554727912779a34d026cd8Dhttp://resolver.tudelft.nl/uuid:3091b118e9554727912779a34d026cd8AA tour of Marchenko redatuming: Focusing the subsurface wavefieldCui, Tianci (Schlumberger Gould Research); Vasconcelos, Ivan (Utrecht University); Manen, Dirk Jan Van (Institute of Geophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)Marchenko redatuming can retrieve the impulse response to a subsurface virtual source from the singlesided surface reflection data with limited knowledge of the medium. We illustrate the concepts and practical aspects of Marchenko redatuming on a simple 1D acoustic lossless medium in which the coupled Marchenko equations are exact. Defined in a truncated version of the actual medium, the Marchenko focusing functions focus the wavefields at the virtual source location and are responsible for the subsequent retrieval of the downgoing and upgoing components of the medium's impulse response. In real seismic exploration, where we have no access to the truncated medium, we solve the coupled Marchenko equations by iterative substitution, relying on the causality relations between the focusing functions and the desired Green's functions along with an initial estimate of the downgoing focusing function. We show that the amplitude accuracy of the initial focusing function influences that of the retrieved Green's functions. During each iteration, propagating an updated focusing function into the actual medium can be approximated by explicit convolution with the broadband reflection seismic data after appropriate processing, which acts as a proxy for the true medium's reflection response.6Acoustic; Autofoc< using; Internal multiples; Processing)uuid:ce065c7e00424bb59a3310950d2d0343Dhttp://resolver.tudelft.nl/uuid:ce065c7e00424bb59a3310950d2d03435Acoustic directional snapshot wavefield decompositionHolicki, M.E. (TU Delft Applied Geophysics and Petrophysics); Drijkoningen, G.G. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)tUp down wavefield decomposition is effectuated by a scaled addition or subtraction of the pressure and vertical particle velocity, generally on horizontal or vertical surfaces, and works well for data given on such surfaces. The method, however, is not applicable to decomposing a wavefield when it is given at one instance in time, i.e. on snapshots. Such situations occur when a wavefield is modelled with methods like finitedifference techniques, for the purpose of, for example, reverse time migration, where the entire wavefield is determined per time instance. We present an alternative decomposition method that is exact when working on snapshots of an acoustic wavefield in a homogeneous medium, but can easily be approximated to heterogeneous media, and allows the wavefield to be decomposed in arbitrary directions. Such a directional snapshot wavefield decomposition is achieved by recasting the acoustic system in terms of the time derivative of the pressure and the vertical particle velocity, as opposed to the vertical derivative in up down decomposition for data given on a horizontal surface. As in up down decomposition of data given at a horizontal surface, the system can be eigenvalue decomposed and the inverse of the eigenvector matrix decomposes the wavefield snapshot into fields of opposite directions, including up down decomposition. As the vertical particle velocity can be rotated at will, this allows for decomposition of the wavefield into any spatial direction; even spatially varying directions are possible. We show the power and effectiveness of the method by synthetic examples and models of increasing complexity..Acoustics; Modelling; Multicomponent; Seismics)uuid:7f83193e43f04d35a33498e56c0e73fcDhttp://resolver.tudelft.nl/uuid:7f83193e43f04d35a33498e56c0e73fc`A singlesided representation for the homogeneous Green's function, accounting for all multiplesmWapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Brackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics)Marchenko imaging is a novel imaging technique that is capable to retrieve images from singlesided reflection measurements free of artefacts related to internal multiples (e.g. Behura et al., 2014; Broggini et al., 2012). An essential ingredient of Marchenko imaging is the socalled focusing function which can<br/>be retrieved from reflection data and a background model. Initially, the focusing function was defined such that it focuses inside the medium of interest as a point in time and in space (e.g. Wapenaar et al., 2014). The focusing property is used to retrieve the up and downgoing Green s functions associated to a virtual point source or receiver inside the medium. Subsequently, the retrieved Green s functions are used to compute an image. Meles et al. (2017) introduced a new focusing function that focuses as a plane wave inside the medium. The new focusing function allows to retrieve medium responses associated to<br/>virtual plane wave sources or receivers inside the medium. Hence, imaging based on arealsources as suggested by Rietveld et al. (1992) becomes possible including the benefits of the Marchenko method. In the following we compare Marchenko imaging using point and plane wave focusing.conference paperEAGE
20181215)uuid:ec82b4a83f0945c295061453e3a8d6feDhttp://resolver.tudelft.nl/uuid:ec82b4a83f0945c295061453e3a8d6feDFast nonrecursive 1D inversion by filtering acousticreflection< dataSlob, E.C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Treitel, Sven (Tridekon)We derive a fast acoustic inversion method for a piecewise homogeneous horizontally layered medium. The method obtains medium parameters from the reflection response. The method can be implemented to obtain the parameters on either side of a reflector at an arbitrary depth. Three processing steps lead to the inversion result. First, we solve a modified Marchenko type equation to obtain a focusing wavefield. We then apply wavefield continuation across a reflecting boundary to the focusing wavefield and retrieve the reflection coefficient of a reflector as a function of horizontal slowness. Finally, we use the reflection coefficient to obtain the velocities and the ratio of the densities above and below the reflector. Because the twoway traveltime difference of the primary reflection and the one above it becomes known during the process, the thickness of the layer above the reflector is also found. The method can be applied multiple times in different zones, or recursively in a target zone without having to solve more Marchenko type equations. The numerical example illustrates that the method works well on modeled data without the need for a priori model information.inversion; processing; acousticSEG
20190419)uuid:8511a3bce21c49938438af7e39c77388Dhttp://resolver.tudelft.nl/uuid:8511a3bce21c49938438af7e39c77388`Marchenko redatuming for multiple prediction and removal in situations with a complex overburdenStaring, M. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)8Internal multiples can create severe artefacts in seismic imaging, especially when our zone of interest is overlain by a complex overburden. These artefacts can mask structures, which has a strong effect on the interpretation of the image. Therefore, multiple prediction and removal is of significant importance for correct imaging and interpretation in settings with a complex overburden.<br/>We propose an adaptive doublefocusing method to predict and subtract the internal multiples that were generated in the overburden. This method is a form of the Marchenko method, that can retrieve the directionallydecomposed Green's functions between virtual sources and virtual receivers anywhere inside the subsurface. The retrieved Green's functions contain all orders of multiple scattering. The method only requires the singlesided reflection response and a smooth velocity model as input. Instead of conventional imaging methods, that assume that the wavefield only consists of singlescattered waves (and thus create imaging artefacts when multiple scattering is present), we now use the multiplescattered Marchenko wavefields for correct redatuming and imaging.<br/><br/>We apply our method to 2D and 3D field data that were recorded in settings where imaging and interpretation is hindered by a complex overburden. First, we create virtual sources and virtual receivers directly above our zone of interest. Next, we use the retrieved Marchenko wavefields to predict and subtract the internal multiples that were generated in the overburden. Masked structures become visible after multiple removal, which significantly improves the geological interpretability. Therefore, we conclude that the adaptive doublefocusing method (Marchenko redatuming) is capable of correctly predicting and removing internal multiples generated in the overburden.Abstract S24A03 presented at 2018 Fall Meeting, AGU, Washington, D.C., 1014 Dec. Session: [S24A] Frontiers in Theoretical and Computational Seismology I
20190611)uuid:201a046842284f75a579a29f62b825f2Dhttp://resolver.tudelft.nl/uuid:201a046842284f75a579a29f62b825f2QQ factor Estimation and Redatuming in a Lossy Medium Using the Marchenko EquationBrackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Del< ft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)Marchenko Imaging is a new technology in geophysics, which enables us to retrieve Green's functions at any point in the subsurface having only reflection data. One of the assumptions of the Marchenko method is that the medium is lossless. One way to circumvent this assumption is to find a compensation parameter for the lossy reflection series so that the lossless Marchenko scheme can be applied. The main goals of this work are to: [1] use the Marchenko equation to estimate the attenuation in the subsurface, [2] find a compensation<br/>parameter for the lossy reflection series so that the lossless Marchenko scheme can be applied. We propose a novel approach which makes it possible to calculate an effective temporal Q factor of the medium between a virtual source in the subsurface and receivers at the surface. This method is based on the minimization of the artefacts produced by the lossless Marchenko scheme. Artefacts have a very specific behavior: if the input data to the Marchenko equation are over or under compensated, the resulting artefacts will have an opposite polarity. Thus, they can be recognized. This approach is supported by a synthetic example for a 1D acoustic medium without a free surface.
20181214)uuid:013a0e813a844013975c4a2624fb4b0eDhttp://resolver.tudelft.nl/uuid:013a0e813a844013975c4a2624fb4b0eWVirtual seismology: from hydrocarbon reservoir imaging to induced earthquake monitoringfWapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Brackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); Staring, M. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics)Recent developments in exploration seismology have enabled the creation of virtual sources and/or virtual receivers in the subsurface from reflection measurements at the earth's surface. Unlike in seismic interferometry, no physical instrument (receiver or source) is needed at the position of the virtual source or receiver. Moreover, no detailed knowledge of the subsurface parameters and structures is required: a smooth velocity model suffices. Yet, the responses to the virtual sources, observed by the virtual receivers, fully account for multiple scattering. This new methodology, which we call virtual seismology, has led to a breakthrough in hydrocarbon reservoir imaging, as is demonstrated in a companion paper (Staring et al., Marchenko redatuming for multiple prediction and removal in situations with a complex overburden). The aim of the present paper is to discuss applications of virtual seismology beyond exploration seismology, in particular induced earthquake monitoring, and to highlight the connections between these applications. The ability to retrieve the entire wave field between (virtual or real) sources and receivers anywhere in the subsurface, without needing a detailed subsurface model, has large potential for monitoring induced seismicity, characterizing the source properties (such as the moment tensor of extended sources along a fault plane), and forecasting the response to potential future induced earthquakes. This will be demonstrated with numerical models and preliminary realdata results.Abstract S53A03 presented at 2018 Fall Meeting, AGU, Washington, D.C., 1014 Dec. Session: S53A On the Symbiosis Between Fundamental and Exploration Geophysics I
20190614)uuid:69b76fb785ff46df98652375ebda01deDhttp://resolver.tudelft.nl/uuid:69b76fb785ff46df98652375ebda01de3ArtefactFree Imaging by a Revised Marchenko Scheme%Zhang, L. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imagi< ng)DA revised Marchenko scheme that avoids the need to compute the Green s function is presented for artefactfree image of the subsurface with singlesided reflection response as input. The initial downgoing Green s function which can be modelled from a macro model is needed for solving the revised Marchenko equations instead of its inverse. The retrieved upgoing focusing function can be correlated with the modelled initial downgoing Green s function to image the medium without artefacts. The numerical example shows the effectiveness of the revised scheme in a 2D layered case.)uuid:459fdf96c15d45a3aa9389c03b17e985Dhttp://resolver.tudelft.nl/uuid:459fdf96c15d45a3aa9389c03b17e985&Implementation of the marchenko methodmThorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Brackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)nThe Marchenko method makes it possible to compute subsurfacetosurface Green's functions from reflection measurements at the surface. Applications of the Marchenko method have already been discussed in many papers, but its implementation aspects have not yet been discussed in detail. Solving the Marchenko equation is an inverse problem. The Marchenko method computes a solution of the Marchenko equation by an (adaptive) iterative scheme or by a direct inversion. We have evaluated the iterative implementation based on a Neumann series, which is considered to be the conventional scheme. At each iteration of this scheme, a convolution in time and an integration in space are performed between a socalled focusing (update) function and the reflection response. In addition, by applying a time window, one obtains an update, which becomes the input for the next iteration. In each iteration, upgoing and downgoing focusing functions are updated with these terms. After convergence of the scheme, the resulting upgoing and downgoing focusing functions are used to compute the upgoing and downgoing Green's functions with a virtualsource position in the subsurface and receivers at the surface. We have evaluated this algorithm in detail and developed an implementation that reproduces our examples. The software fits into the Seismic Unix software suite of the Colorado School of Mines.)uuid:048b6e7c398b42ee8d9b53c693cc3023Dhttp://resolver.tudelft.nl/uuid:048b6e7c398b42ee8d9b53c693cc3023YA new approach to separate seismic timelapse time shifts in the reservoir and overburdenLiu, Y. (Norwegian University of Science and Technology); Landr, Martin (Norwegian University of Science and Technology); Arntsen, Brge (Norwegian University of Science and Technology); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)For a robust way of estimating time shifts near horizontal boreholes, we have developed a method for separating the reflection responses above and below a horizontal borehole. Together with the surface reflection data, the method uses the direct arrivals from borehole data in the Marchenko method. The first step is to retrieve the focusing functions and the updown wavefields at the borehole level using an iterative Marchenko scheme. The second step is to solve two linear equations using a leastsquares minimizing method for the two desired reflection responses. Then, the time shifts that are directly linked to the changes on either side of the borehole are calculated using a standard crosscorrelation technique. The method is applied with good results to synthetic 2D pressure data from the North Sea. One example uses purely artificial velocity changes (negative above the borehole and positive below), and the other example uses more realistic changes based on well logs. In the 2D case with< an adequate survey coverage at the surface, the method is completely data driven. In the 3D case inwhich there is a limited number of horizontal wells, a kinematic correct velocity model is needed, but only for the volume between the surface and the borehole. Possible error factors related to the Marchenko scheme, such as an inaccurate source wavelet, imperfect surface multiples removal, and medium with loss are not included in this study.#ImPhys/Acoustical Wavefield Imaging)uuid:ee0b3190beb44de6bdc82a25c569dbbbDhttp://resolver.tudelft.nl/uuid:ee0b3190beb44de6bdc82a25c569dbbbsA lossless earth Green's function representation between any two subsurface points from surface reflection GPR dataSlob, E.C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)iWe present a threedimensional scheme that can be used to compute the electromagnetic impulse response between any two subsurface points from surface reflection data measured at a single surface of a lossless medium. The scheme first computes a virtual vertical radar profile using the Marchenko scheme from which focusing wavefields are computed. With the aid of the Green's functions of the virtual vertical radar profiles these focusing wavefields are then used to compute the Green's function between any two points in the subsurface. One point is a virtual receiver and the other point is a virtual source. Virtual radar images can be created as well as the whole time evolution of the radar wave field throughout the subsurface generated by any subsurface virtual source. We show with a numerical example that the method works well in a onedimensional configuration.F3D GPR; autofocusing; interferometry; virtual receiver; virtual source6Institute of Electrical and Electronics Engineers Inc.)uuid:0ec47f8d06ec4d2a8cb62532fb2cd38cDhttp://resolver.tudelft.nl/uuid:0ec47f8d06ec4d2a8cb62532fb2cd38c9A Marchenko equation for acoustic inverse source problems4van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Johnson, Jami L. (University of Auckland); van Wijk, K. (University of Auckland); Singh, S. (University of Edinburgh); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics){From acoustics to medical imaging and seismology, one strives to make inferences about the structure of complex media from acoustic wave observations. This study proposes a solution that is derived from the multidimensional Marchenko equation, to learn about the acoustic source distribution inside a volume, given a set of observations outside the volume. Traditionally, this problem has been solved by backpropagation of the recorded signals. However, to achieve accurate results through backpropagation, a detailed model of the medium should be known and observations should be collected along a boundary that completely encloses the volume of excitation. In practice, these requirements are often not fulfilled and artifacts can emerge, especially in the presence of strong contrasts in the medium. On the contrary, the proposed methodology can be applied with a single observation boundary only, without the need of a detailed model. In order to achieve this, additional multioffset ultrasound reflection data must be acquired at the observation boundary. The methodology is illustrated with onedimensional synthetics of a photoacoustic imaging experiment. A distribution of simultaneously acting sources is recovered in the presence of sharp density perturbations both below and above the embedded sources, which result in significant scattering that complicates the use of conventional methods.
20171231)uuid:644e9cc51e9a43ecb7cf7f96fc3557bfDhttp://resolver.tudelft.nl/uuid:644e9cc51e9a43ecb7cf7f96fc3557bfdA singlesided representation for the homogeneous Green's function of a unified scalar wave equation)uuid:fd8655a135e54fa0803b361e98b8d5afDhttp://resolver.tudelft.nl/uuid:fd8655a135e54fa0803b361e98b8d5afCrossco< rrelation beamformingRuigrok, E.N. (Utrecht University; Royal Netherlands Meteorological Institute); Gibbons, Steven; Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)An areal distribution of sensors can be used for estimating the direction of incoming waves through beamforming. Beamforming may be implemented as a phaseshifting and stacking of data recorded on the different sensors (i.e., conventional beamforming). Alternatively, beamforming can be applied to crosscorrelations between the waveforms on the different sensors. We derive a kernel for beamforming crosscorrelated data and call it crosscorrelation beamforming (CCBF). We point out that CCBF has slightly better resolution and aliasing characteristics than conventional beamforming. When autocorrelations are added to CCBF, the array response functions are the same as for conventional beamforming. We show numerically that CCBF is more resilient to noncoherent noise. Furthermore, we illustrate that with CCBF individual receiverpairs can be removed to improve mapping to the slowness domain. An additional flexibility of CCBF is that crosscorrelations can be timewindowed prior to beamforming, e.g., to remove the directionality of a scattered wavefield. The observations on synthetic data are confirmed with field data from the SPITS array (Svalbard). Both when beamforming an earthquake arrival and when beamforming ambient noise, CCBF focuses more of the energy to a central beam. Overall, the main advantage of CCBF is noise suppression and its flexibility to remove station pairs that deteriorate the signalrelated beampower.9Beamforming; Crosscorrelation; Waveform characterization)uuid:19810c33dcb148de9eec87376d1fa01cDhttp://resolver.tudelft.nl/uuid:19810c33dcb148de9eec87376d1fa01cgFullfield multidimensional deconvolution to retrieve bodywave reflections from sparse passive sourcesHartstra, I.E. (TU Delft Applied Geophysics and Petrophysics); Almagro Vidal, C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)Our objective is to complement lithospheric seismic tomography with an interferometric method to retrieve highresolution reflectivity images from local earthquake recordings. The disadvantage of using local earthquakes for the retrieval of reflected bodywaves is their usual sparse distribution. We propose an alternative formulation of passive seismic interferometry by multidimensional deconvolution (MDD) which uses the multiples in the full recordings to compensate for missing illumination angles. This method only requires particlevelocity recordings at the surface from passive transient sources and retrieves bodywave reflection responses without freesurface multiples. We conduct an acoustic modelling experiment to compare this formulation to a previous MDD method and Green s function retrieval by crosscorrelation for different source distributions. We find that in the case of noisecontaminated recordings obtained under severely limited and irregular illumination conditions, the alternative MDD method introduced here still retrieves the complete reflection response without freesurface multiples where the other interferometric methods break down.&Interferometry; Body waves; Coda waves)uuid:5bf1b74f158240e0bdc39ec696cdb67dDhttp://resolver.tudelft.nl/uuid:5bf1b74f158240e0bdc39ec696cdb67d^Deep ocean sound speed characteristics passively derived from the ambient acoustic noise field&Evers, L.G. (TU Delft Applied Geophysics and Petrophysics; Royal Netherlands Meteorological Institute); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Heaney, KD (Ocean Acoustical Services and Instrumentation Systems); Snellen, M. (TU Delft Aircraft Noise and Climate Effects)nThe propagation of acoustic waves in the ocean strongly depends on the temperature. Lowfrequency acoustic waves can penetrate the ocean down to depths where few in situ measurements are available. It is therefore attractive to obtain a measure of the deep ocean temperature from acoustic waves. The lat< ter is especially true if the ambient acoustic noise field can be used instead of deterministic transient signals. In this study the acoustic velocity, and hence the temperature, is derived in an interferometric approach from hydrophone array recordings. The arrays were separated by over 125 km, near Ascension Island in the Atlantic Ocean, at a depth of 850 m. Furthermore, the dispersive characteristics of the deep ocean sound channel are resolved based on the retrieved lag times for different modes. In addition, it is shown how the resolution of the interferometric approach can be increased by cross correlating array beams rather than recordings from singlesensor pairs. The observed acoustic lag times between the arrays corresponds well to modelled values, based on fullwave modelling through bestknown oceanic models.EAtlantic Ocean; Interferometry; Acoustic properties; Wave propagation)uuid:61610d9adb9e44efaa18a4b178fb620cDhttp://resolver.tudelft.nl/uuid:61610d9adb9e44efaa18a4b178fb620cJUpDown Wavefields Reconstruction in Boreholes Using SingleComponent DataLiu, Y. (Norwegian University of Science and Technology); Arntsen, B (Norwegian University of Science and Technology); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics).A standard procedure in processing vertical seismic profile (VSP) data is the separation of upand downgoing wavefields. We show that the updown wavefields in boreholes can be reconstructed using only singlecomponent borehole data, given that a full set of surface reflection data is also available. No medium parameters are required. The method is waveequation based for a general inhomogeneous lossless medium with moderately curved interfaces. It relies on a focusing wavefield from the Marchenko method, which gives the recipe for finding this wavefield that satisfies certain focusing conditions in a reference medium. The updown wavefields are then reconstructed at borehole positions using this focusing wavefields and the surface reflection response. We show that the method is applicable to boreholes with any general orientation. The requirement is that the source positions in the surface data are regularized to be the same as those in the borehole data, and that source deconvolution and surface multiple removal are applied for the surface data. Numerical results from a field in the North Sea are shown, and three different borehole geometries (horizontal, deviated and vertical) are tested. The result shows that the reconstructed updown wavefields agree well with those by conventional separation methods.
20180601)uuid:8517ffa72f2848f6bb96fe93885541feDhttp://resolver.tudelft.nl/uuid:8517ffa72f2848f6bb96fe93885541fe_Velocity analysis using surfaceseismic primariesonly data obtained without removing multiplesDokter, E. (University of Edinburgh); Meles, G.A. (TU Delft Applied Geophysics and Petrophysics; University of Edinburgh); Curtis, A (University of Edinburgh); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)JA number of seismic processing methods, including velocity analysis (Sheriff and Geldart, 1999), make the assumption that recorded waves are primaries  that they have scattered only once (the Born approximation). Multiples then represent a source of coherent noise and must be suppressed to avoid artefacts. There are different approaches to mitigate free surface multiples (see Dragoset et al. (2010) for an overview), but internal multiples still pose a problem and usually cannot be removed without high computational cost or knowledge of the medium. Recently, Marchenko redatuming has been developed to image a medium in the presence of internal multiples (Wapenaar et al., 2014). Using Marchenko redatuming in combination with convolutional interferometry, Meles et al. (2016) have developed a method which allows the construction of a primariesonly data set from existing seismic reflection data and an initial velocity model. The method was proposed for the acoustic case and appears to b< e robust with respect to even huge inaccuracies in the employed velocity model. In this paper we investigate the impact of such primariesonly data on a simple velocity analysis workflow, as opposed to using the full data set with multiples. We use semblance analysis (Sheriff and Geldart, 1999) and compare the results obtained with three different data sets: the full reflection data with multiples, primaries data calculated with prior knowledge of the subsurface, and primaries data calculated with an entirely incorrect constant velocity model. We then use the velocity models that we construct to perform reverse time migration (RTM) of each of the data sets. We find that the velocities found are robust with respect to errors in the initial model used for Marchenko redatuming, and the method produces good results if nonhyperbolic moveout effects are avoided.)uuid:7226c2a4f5164b3caaed1d2ea7da0ab2Dhttp://resolver.tudelft.nl/uuid:7226c2a4f5164b3caaed1d2ea7da0ab2On the role of multiples in Marchenko imagingWapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics))uuid:a6b425dad87743c1ac288c1b3cd54f09Dhttp://resolver.tudelft.nl/uuid:a6b425dad87743c1ac288c1b3cd54f09:Accounting for freesurface multiples in Marchenko imagingSingh, S.; Snieder, R; van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)Imagine placing a receiver at any location in the earth and recording the response at that location to sources on the surface. In such a world, we could place receivers around our reservoir to better image the reservoir and understand its properties. Realistically, this is not a feasible approach for understanding the subsurface. We have developed an alternative and realizable approach to obtain the response of a buried virtual receiver for sources at the surface. Our method is capable of retrieving the Green s function for a virtual point in the subsurface to the acquisition surface. In our case, a physical receiver is not required at the subsurface point; instead, we require the reflection measurements for sources and receivers at the surface of the earth and a macromodel of the velocity (no smallscale details of the model are necessary). We can interpret the retrieved Green s function as the response to sources at the surface for a virtual receiver in the subsurface. We obtain this Green s function by solving the Marchenko equation, an integral equation pertinent to inverse scattering problems. Our derivation of the Marchenko equation for the Green s function retrieval takes into account the freesurface reflections present in the reflection response (previous work considered a response without freesurface multiples). We decompose the Marchenko equation into up and downgoing fields and solve for these fields iteratively. The retrieved Green s function not only includes primaries and internal multiples as do previous methods, but it also includes freesurface multiples. We use these up and downgoing fields to obtain a 2D image of our area of interest, in this case, below a synclinal structure.)uuid:6f56a5a1f3204b0e8ae7d4eada60ca08Dhttp://resolver.tudelft.nl/uuid:6f56a5a1f3204b0e8ae7d4eada60ca08ZTheory for Marchenko imaging of marine seismic data with free surface multiple eliminationzSlob, E.C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)OThe theory of datadriven true amplitude migration is presented for multicomponent marine seismic data. The Marchenko scheme is adapted to account for the ghost, free surface and internal multiple effects and works without the need to know the source wavelet. A true amplitude image is formed from the obtained focusing functions without ghost effects and artefacts from free surface and< internal multiples. The resulting reflectivity at image times can be input for a final step of full waveform inversion. The numerical example shows the effectiveness of the method in a simple 1D problem.
20180101)uuid:8b5b6fd78a4a468c91dd77f6a3627a2eDhttp://resolver.tudelft.nl/uuid:8b5b6fd78a4a468c91dd77f6a3627a2eASnapshot wavefield decomposition for heterogeneous velocity medianWe propose a novel directional decomposition operator for wavefield snapshots in heterogeneousvelocity media. The proposed operator demonstrates the link between the amplitude of pressure and particlevelocity plane waves in the wavenumber domain. The proposed operator requires two spatial Fourier transforms (one forward and one backward) per spatial dimension and time slice. To illustrate the operator we demonstrate its applicability to heterogeneous velocity models using a simple velocitybox model and a more heterogeneous velocity model, based on real data, from close to the Annerveen gas field, The Netherlands.)uuid:c3eb7eb227cf43ae8d990ae92fd057b0Dhttp://resolver.tudelft.nl/uuid:c3eb7eb227cf43ae8d990ae92fd057b08Why multiples do not contribute to deconvolution imagingWapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics)The question whether multiples are signal or noise is subject of ongoing debate. In this paper we consider correlation and deconvolution imaging methods and analyse to what extent multiples contribute to the image in these methods. Our starting point is the assumption that at a specific depth level the full downgoing and upgoing fields (both including all multiples) are available. First we show that by cross correlating the full downgoing and upgoing wave fields, primaries and multiples contribute to the image. This image is not trueamplitude and is contaminated by crosstalk artefacts. Next we show that by deconvolving the full upgoing field by the full downgoing field, multiples do not contribute to the image. We use minimumphase arguments to explain this somewhat counterintuitive conclusion. The deconvolution image is trueamplitude and not contaminated by crosstalk artefacts. The conclusion that multiples do not contribute to the image applies to the type of deconvolution imaging analysed in this paper, but should not be extrapolated to other imaging methods. On the contrary, much research is dedicated to using multiples for imaging, for example in full wavefield migration, resonant migration and Marchenko imaging.)uuid:b1b4381d721940b984e76d7fb8a6120aDhttp://resolver.tudelft.nl/uuid:b1b4381d721940b984e76d7fb8a6120a]Sparse Inversion for Solving the Coupled Marchenko Equations Including Freesurface MultiplesStaring, M. (TU Delft Applied Geophysics and Petrophysics); Grobbe, N. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)We compare the coupled Marchenko equations without freesurface multiples to the coupled Marchenko equations including freesurface multiples. When using the conventional method of iterative substitution to solve these equations, a difference in convergence behaviour is observed, suggesting that there is a fundamental difference in the underlying dynamics. Both an intuitive explanation, based on an interferometric interpretation, as well as a mathematical explanation, confirm this difference, and suggest that iterative substitution might not be the most suitable method for solving the system of equations including freesurface multiples. Therefore, an alternative method is required. We propose a sparse inversion, aimed at solving an underdetermined system of equations. Results show that the sparse inversion is indeed capable of correctly solving the coupled Marchenko equations including freesurface multiples, even when the iterative scheme fails. Using sparsity promotion and additional constraints, it is expected to< perform better than iterative substitution when working with incomplete data or in the presence of noise. Also, simultaneous estimation of the source wavelet is a potential possibility.)uuid:f12f14ab7ad4425c833538daea5dce1dDhttp://resolver.tudelft.nl/uuid:f12f14ab7ad4425c833538daea5dce1dGTimelapse data prediction by Marchenkobased reservoir transplantationWapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics)/Mihai Popovici, A. (editor); Fomel, S. (editor) In a timelapse experiment, changes in a reservoir cause changes in the reflection response. We discuss a method which predicts these changes from the baseline survey and a model of the changed reservoir. This method, which takes all multiple<br/>scattering into account, is significantly more efficient than modeling the response of the entire medium containing the changed reservoir. This can be particularly attractive for applications in timelapse full wave form inversion, which requires<br/>repeated modelling of the reflection response.)uuid:81609a44821747dbb6722302af612d40Dhttp://resolver.tudelft.nl/uuid:81609a44821747dbb6722302af612d40VAdaptive doublefocusing method for sourcereceiver Marchenko redatuming on field data6Staring, M. (TU Delft Applied Geophysics and Petrophysics); Pereira, R (CGG); Douma, H; van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)]We present an adaptive doublefocusing method for applying sourcereceiver Marchenko redatuming to field data. Receiver redatuming is achieved by a first focusing step, where the coupled Marchenko equations are iteratively solved for the oneway Green s functions. Next, source redatuming is typically performed by a multidimensional deconvolution of these Green s functions. Instead, we propose a second focusing step for source Marchenko redatuming, using the upgoing Green s function and the downgoing focusing function to obtain a redatumed reflection response in the physical medium. This method makes adaptive processing more straightforward, making it less sensitive to imperfections in the data and the acquisition geometry and more suitable for the application to field data. In addition, it is cheaper and can be parallelized by pair of focal points.)uuid:95b79ea8bb0341d38dea96bdabc8bd41Dhttp://resolver.tudelft.nl/uuid:95b79ea8bb0341d38dea96bdabc8bd41UDeconvolution and correlationbased interferometric redatuming by wavefield inversionBarrera Pacheco, D.F.; Schleicher, J.; van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)iSeismic interferometry is a method to retrieve Green s functions for sources (or receivers) where there are only receivers (or sources, respectively). This can be done by correlationor deconvolutionbased methods. In this work we present a<br/>new approach to reposition the seismic array from the earth s surface to an arbitrary datum at depth using the oneway reciprocity theorems of convolution and correlation type. The redatuming process is done in three steps: (a) retrieving the downward Green s function for sources at the earth s surface<br/>and receivers at the datum, (b) retrieving the corresponding upward Green s function, and (c) retrieving the reflected upward wavefield for sources and receivers at the datum. Input for steps (a) and (b) are the surface data and wavefields simulated in a velocity model of the datum overburden. Step (c)<br/>uses the responses of steps (a) and (b) as input data in the convolutionbased interferometric equation. The method accounts for inhomogeneities in the overburden medium, thus reducing anticausal events and artefacts as compared to a purely correlationbased procedure.)uuid:65a6e1< bcfd87494482d36551b2d973a2Dhttp://resolver.tudelft.nl/uuid:65a6e1bcfd87494482d36551b2d973a2YObtaining local reflectivity at twoway travel time by filtering acoustic reflection dataSlob, E.C. (TU Delft Applied Geophysics and Petrophysics); Zhang, L. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)iA modified implementation of Marchenko redatuming leads to a filter that removes internal multiples from reflection data. It produces local reflectivity at twoway travel time. The method creates new primary reflections resulting from emitted events that eliminate internal multiples. We call these nonphysical<br/>primaries and their presence is a disadvantage. The advantage is that the filter is model free. We give the 3D filter and demonstrate with 1D arguments that starting the focusing wavefield with a unit impulse at zero time, while focusing below the bottom reflector, is the choice that leads to a model free implementation. The starting impulse generates the reflection data. Every later emitted pulse eliminates an internal multiple somewhere in the model and helps removing the transmission<br/>amplitude effects in a physical primary. We show that<br/>the amplitude of the nonphysical primaries are a product of<br/>three reflections, making them generally smaller than those of<br/>the physical primaries. A 2D modeled shotgather at different<br/>stages of filtering the data shows that the filter works well.)uuid:6990bd1bf6694dc0ae215cf98c0261f4Dhttp://resolver.tudelft.nl/uuid:6990bd1bf6694dc0ae215cf98c0261f4BDecomposition of the Green's function using the Marchenko equation Brackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)RThe Marchenko equation can be used to retrieve the Green s function at depth as a full function or decomposed into its upand downgoing parts. We show that the equation can be rewritten to create a decomposition scheme that can decompose a full wavefield, that was recorded at depth, into its up and downgoing parts. We show that this can be done without a smooth velocity model that the Marchenko scheme requires and without any knowledge of the medium properties that traditional decomposition methods require. Instead we only need a the reflection response and a wavefield that has been recorded at the<br/>surface due to a source at depth or (by using sourcereceiver reciprocity) that was measured down in a borehole due to a source at the surface. We also validate our results by comparing them to directly modeled up and downgoing wavefields.)uuid:159931587871409bbb47c941ef170a41Dhttp://resolver.tudelft.nl/uuid:159931587871409bbb47c941ef170a41bReflecting boundary conditions for interferometry by multidimensional deconvolution: invited paperWeemstra, C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); van Dalen, K.N. (TU Delft Applied Mechanics)Seismic interferometry (SI) takes advantage of existing (ambient) wavefield recordings by turning receivers into socalled virtualsources. The medium s response to these virtual sources can be harnessed to image that medium. Applications of SI include surfacewave imaging of the Earth s shallow subsurface and medical imaging. Most interferometric applications, however, suffer from the fact that the retrieved virtualsource responses deviate from the true medium responses. The accrued artifacts are often predominantly due to a nonisotropic illumination of the medium of interest, and prohibit accurate interferometric imaging. Recently, it has been shown that illuminationrelated artifacts can be removed by means of a socalled multidimensional deconvolution (MDD) process. However, The current MDD formulation, and hence method, relies on separat< ion of waves traveling inward and outward through the boundary of the medium of interest. As a consequence, it is predominantly useful when receivers are illuminated from one side only. This puts constraints on the applicability of the current MDD formulation to omnidirectional wavefields. We present a modification of the formulation of the theory underlying SI by MDD. This modification eliminates the requirement to separate inwardand outward propagating wavefields and, consequently, holds promise for the application of MDD to nonisotropic, omnidirectional wavefields
20180501)uuid:ec71f4f135ac49e6a1d9889e36a2f831Dhttp://resolver.tudelft.nl/uuid:ec71f4f135ac49e6a1d9889e36a2f831Application of seismic interferometry by multidimensional deconvolution to ambient seismic noise recorded in Malarge, Argentina~Weemstra, C. (TU Delft Applied Geophysics and Petrophysics; Utrecht University); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics); Ruigrok, E.N. (Royal Netherlands Meteorological Institute; Utrecht University); Hunziker, J.W. (University of Lausanne); Gomez, Martin (Comision Nacional de Energia Atomica); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics))Obtaining new seismic responses from existing recordings is generally referred to as seismic interferometry (SI). Conventionally, the SI responses are retrieved by simple crosscorrelation of recordings made by separate receivers: one of the receivers acts as a virtual source whose response is retrieved at the other receivers.When SI is applied to recordings of ambient seismic noise, mostly surface waves are retrieved. The newly retrieved surface wave responses can be used to extract receiverreceiver phase velocities. These phase velocities often serve as input parameters for tomographic inverse problems. Another application of SI exploits the tempo ral stability of the multiply scattered arrivals of the newly retrieved surface wave responses. Temporal variations in the stability and/or arrival time of these multiply scattered arrivals can often be linked to temporally varying parameters such as hydrocarbon production and precip itation. For all applications, however, the accuracy of the retrieved responses is paramount. Correct response retrieval relies on a uniform illumination of the receivers: irregularities in the illumination pattern degrade the accuracy of the newly retrieved responses. In practice, the illumination pattern is often far from uniform. In that case, simple crosscorrelation of separate receiver recordings only yields an estimate of the actual, correct virtualsource response. Re formulating the theory underlying SI by crosscorrelation as a multidimensional deconvolution (MDD) process, allows this estimate to be improved. SI by MDD corrects for the nonuniform illumination pattern by means of a socalled pointspread function (PSF), which captures the irregularities in the illumination pattern. Deconvolution by this PSF removes the imprint of the irregularities on the responses obtained through simple crosscorrelation. We apply SI by MDD to surface wave data recorded by theMalargue seismic array in western Argentina. The aperture of the array is approximately 60 km and it is located on a plateau just east of the Andean mountain range. The array has a Tshape: the receivers along one of the two lines act as virtual sources whose responses are recorded by the receivers along the other (perpendicular) line.We select time windows dominated by surface wave noise travelling in a favourable direction, that is, traversing the line of virtual sources before arriving at the receivers at which we aim to retrieve the virtualsource responses. These time windows are selected through a frequencydependent slowness analysis along the two receiver lines. From the selected time windows, estimates of virtualsource responses are retrieved by means of crosscorrelations. Similarly, crosscorrelations between the positions of the virtual sources are computed to build the PSF. We use the PSF to deconvolve the effect of illumination irregulariti< es and the source function from the virtualsource responses retrieved by crosscorrelation. The combined effect of timewindow selection and MDD results in more accurate and temporally stable surface wave responses.Broadband seismometers; Seismic monitoring and testban treaty verification; Surfacewaves and free oscillations; Interfacewaves; Seismic attenuation; Seismic tomography)uuid:2cc566bf9d4943b68abbbdb6e2d4bcbdDhttp://resolver.tudelft.nl/uuid:2cc566bf9d4943b68abbbdb6e2d4bcbdeApplying sourcereceiver Marchenko redatuming to field data, using an adaptive doublefocusing method!Staring, M. (TU Delft Applied Geophysics and Petrophysics); Pereira, Roberto (CGG, Rio de Janeiro); Douma, Huub; van der Neut, J.R. (TU Delft ImPhys/Acoustical Wavefield Imaging); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)In this paper, we focus on the field data application of sourcereceiver Marchenko redatuming. Conventionally, a sourcereceiver redatumed reflection response is obtained by first applying the Marchenko method for receiverredatuming and then performing a multidimensional deconvolution (MDD) for sourceredatuming (Wapenaar et al. (2014)). The obtained reflection response is free from any interactions with the overburden. However, the MDD solves an illposed inverse problem (van der Neut et al. (2011a)), which makes it sensitive to imperfections in the data and the acquisition geometry. This is a problem for the field data application, since neither the data nor the acquisition geometry are ever perfect. In addition, MDD is computationally expensive.)uuid:0b3a6327387d4d8a97d392d0c0340f9fDhttp://resolver.tudelft.nl/uuid:0b3a6327387d4d8a97d392d0c0340f9fAHomogeneous Green s function retrieval using the Marchenko methodBrackenhoff, J.A. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)JIn wave theory, a Green s function is defined as the response of a medium to an impulsive point source. The homogeneous Green s function is the combination of the Green s function and its timereversal. Homogeneous Green s functions can be retrieved if the medium is enclosed by a boundary where the full wavefield is recorded. In recent years, the Marchenko method has gained popularity, because unlike many conventional methods it does not require an enclosing boundary. Instead a singlesided boundary is all that is required. The method is sensitive to attenuation, which makes it difficult to apply to field data. We will show that by using corrections on the attenuated data, we can retrieve the Green s functions in the subsurface. These results can be visualized in order to see how the wavefield propagates through the subsurface.<br)uuid:95ea33ec4f454b199a85fbef153ecb51Dhttp://resolver.tudelft.nl/uuid:95ea33ec4f454b199a85fbef153ecb51[Elastodynamic singlesided homogeneous Green's function representation: Theory and examplesWapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Reinicke Urruticoechea, C. (TU Delft Applied Geophysics and Petrophysics)The homogeneous Green s function is the Green s function minus its timereversal. Many wavefield imaging applications make use of the homogeneous Green s function in form of a closed boundary integral. Wapenaar et al. (2016a) derived an accurate singlesided homogeneous Green s function representation that only requires sources/receivers on an open boundary. In this abstract we will present a numerical example of elastodynamic singlesided homogeneous Green s function representation using a 2D laterally invariant medium. First, we will outline the theory of the singlesided homogeneous Green s function representation. Second, we will show numerical results for the elastodynamic case.)uuid:ef4dd2961e6442fa9c8a56e2bb515b9aDhttp://resolver.tudelft.nl/uuid:ef4dd2961e6442fa9c8a56e2bb515b9aTReflecting boundary conditions for interferometry< by multidimensional deconvolution.Weemstra, C. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); van Dalen, K.N. (TU Delft Dynamics of Structures)TSession 1pUWc: Underwater Acoustics: Topics in Underwater Acoustics (Poster Session))uuid:d32648a716e7439dbe9fbd40e3161a7dDhttp://resolver.tudelft.nl/uuid:d32648a716e7439dbe9fbd40e3161a7dmCrustalscale reflection imaging and interpretation by passive seismic interferometry using local earthquakeshNishitsuji, Y. (TU Delft Applied Geophysics and Petrophysics); Minato, S. (TU Delft Applied Geophysics and Petrophysics); Boullenger, B. (TU Delft Applied Geophysics and Petrophysics); Gomez, M (Comision Nacional de Energia Atomica); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics)GWe have developed an application of passive seismic interferometry (SI) using Pwave coda of local earthquakes for the purpose of crustalscale reflection imaging. We processed the reflection gathers retrieved from SI following a standard seismic processing in exploration seismology. We applied SI to the Pwave coda using crosscorrelation, crosscoherence, and multidimensional deconvolution (MDD) approaches for data recorded in the Malarge region, Argentina. Comparing the results from the three approaches, we found that MDD based on the truncated singularvalue decomposition scheme gave us substantially better structural imaging. Although our results provided higher resolution images of the subsurface, they showed less clear images for the Moho in comparison with previous seismic images in the region obtained by the receiver function and globalphase SI. Above the Moho, we interpreted a deep thrust fault and the possible melting zones, which were previously indicated by activeseismic and magnetotelluric methods in this region, respectively. The method we developed could be an alternative option not only for crustalscale imaging, e.g., in enhanced geothermal systems, but also for lithosphericscale as well as basinscale imaging, depending on the availability of local earthquakes and the frequency bandwidth of their Pwave coda.Cacoustic; crustal structure; earthquake; interferometry; geothermal)uuid:f940c8aba08f4404b5294491af1d6887Dhttp://resolver.tudelft.nl/uuid:f940c8aba08f4404b5294491af1d6887]Reflection imaging of aseismic zones of the Nazca slab by globalphase seismic interferometryNishitsuji, Y. (TU Delft Applied Geophysics and Petrophysics); Ruigrok, E (Utrecht University); Gomez, M (Comision Nacional de Energia Atomica); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics)Obtaining detailed images of aseismic parts of subducting slabs remains a large challenge for understanding slab dynamics. Hypocenter mapping cannot be used for the purpose due to the absence of seismicity, whereas the use of receiver functions might be compromised by the presence of melt. Global tomography can be used to identify the presence of the slab, but it does not reveal the structure in detail. We have determined how detailed images can be obtained using globalphase seismic interferometry. The method provides highresolution (<15km in depth) pseudo zerooffset (i.e., colocated source and receiver) reflection information. We have applied the method to aseismic zones of the Nazca slab in which initiation of possible slab tearing and plume decapitation was identified by global tomography and electrical conductivity, respectively. We have obtained an image of the Moho and the mantle and found an attenuated area in the image consistent with the presence of an aseismic dipping subducting slab. However, our interpretation was not unambiguous. The results confirmed that the method is useful for imaging aseismic transects of slabs.Bacoustic; earthquake; illumination; interferometry; interpretation)uuid:18cd9b2807ea4151995281aca9f8d65fDhttp://resolver.tu< delft.nl/uuid:18cd9b2807ea4151995281aca9f8d65fUReflection imaging of the Moon's interior using deepmoonquake seismic interferometryNishitsuji, Y. (TU Delft Applied Geophysics and Petrophysics); Rowe, CA (Los Alamos National Laboratory); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics)RThe internal structure of the Moon has been investigated over many years using a variety of seismic methods, such as travel time analysis, receiver functions, and tomography. Here we propose to apply bodywave seismic interferometry to deep moonquakes in order to retrieve zerooffset reflection responses (and thus images) beneath the Apollo stations on the nearside of the Moon from virtual sources colocated with the stations. This method is called deepmoonquake seismic interferometry (DMSI). Our results show a laterally coherent acoustic boundary around 50 km depth beneath all four Apollo stations. We interpret this boundary as the lunar seismic Moho. This depth agrees with Japan Aerospace Exploration Agency's (JAXA) SELenological and Engineering Explorer (SELENE) result and previous travel time analysis at the Apollo 12/14 sites. The deeper part of the image we obtain from DMSI shows laterally incoherent structures. Such lateral inhomogeneity we interpret as representing a zone characterized by strong scattering and constant apparent seismic velocity at our resolution scale (0.2 2.0 Hz).)uuid:9289514b58c64e80948bfed8dcafa4e1Dhttp://resolver.tudelft.nl/uuid:9289514b58c64e80948bfed8dcafa4e1MUnified double and singlesided homogeneous Green's function representationsIn wave theory, the homogeneous Green s function consists of the impulse response to a point source, minus its timereversal. It can be represented by a closed boundary integral. In many practical situations, the closed boundary integral needs to be approximated by an open boundary integral because the medium of interest is often accessible from one side only. The inherent approximations are acceptable as long as the effects of multiple scattering are negligible. However, in case of strongly inhomogeneous media, the effects of multiple scattering can be severe. We derive double and singlesided homogeneous Green s function representations. The singlesided representation applies to situations where the medium can be accessed from one side only. It correctly handles multiple scattering. It employs a focusing function instead of the backward propagating Green s function in the classical (doublesided) representation. When reflection measurements are available at the accessible boundary of the medium, the focusing function can be retrieved from these measurements. Throughout the paper, we use a unified notation which applies to acoustic, quantummechanical, electromagnetic and elastodynamic waves. We foresee many interesting applications of the unified singlesided homogeneous Green s function representation in holographic imaging and inverse scattering, timereversed wave field propagation and interferometric Green s function retrieval.
20170731)uuid:0d0cf38be8ea4b7a9e8fb0a0e81e97a1Dhttp://resolver.tudelft.nl/uuid:0d0cf38be8ea4b7a9e8fb0a0e81e97a1LAdaptive overburden elimination with the multidimensional Marchenko equationvan der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics))uuid:aeefaee33d1f48f8b9a2131971ca5e55Dhttp://resolver.tudelft.nl/uuid:aeefaee33d1f48f8b9a2131971ca5e55SCombination of surface and borehole seismic data for robust targetoriented imagingLiu, Yi (Norwegian University of Science and Technology); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Arntsen, B; Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)A novel application of seismic interferometry (SI) and Marchenko imaging using both surface and borehole data is presented. A series of redatuming schemes is proposed to combine both data sets for robust deep local imaging in the presence of velocity < uncertainties. The redatuming schemes create a virtual acquisition geometry where both sources and receivers lie at the horizontal borehole level, thus only a local velocity model near the borehole is needed for imaging, and erroneous velocities in the shallow area have no effect on imaging around the borehole level. By joining the advantages of SI and Marchenko imaging, a macrovelocity model is no longer required and the proposed schemes use only singlecomponent data. Furthermore, the schemes result in a set of virtual data that have fewer spurious events and internal multiples than previous virtual source redatuming methods. Two numerical examples are shown to illustrate the workflow and to demonstrate the benefits of the method. One is a synthetic model and the other is a realistic model of a field in the North Sea. In both tests, improved local images near the boreholes are obtained using the redatumed data without accurate velocities, because the redatumed data are close to the target.BInverse theory; Downhole methods; Interferometry; Wave propagation)uuid:3b45c9ece3da49978f92e89271b442c9Dhttp://resolver.tudelft.nl/uuid:3b45c9ece3da49978f92e89271b442c9A singlesided homogeneous Green's function representation for holographic imaging, inverse scattering, timereversal acoustics and interferometric Green's function retrievalWapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics)Green's theorem plays a fundamental role in a diverse range of wavefield imaging applications, such as holographic imaging, inverse scattering, timereversal acoustics and interferometric Green's function retrieval. In many of those applications, the homogeneous Green's function (i.e. the Green's function of the wave equation without a singularity on the righthand side) is represented by a closed boundary integral. In practical applications, sources and/or receivers are usually present only on an open surface, which implies that a significant part of the closed boundary integral is by necessity ignored. Here we derive a homogeneous Green's function representation for the common situation that sources and/or receivers are present on an open surface only. We modify the integrand in such a way that it vanishes on the part of the boundary where no sources and receivers are present. As a consequence, the remaining integral along the open surface is an accurate singlesided representation of the homogeneous Green's function. This singlesided representation accounts for all orders of multiple scattering. The new representation significantly improves the aforementioned wavefield imaging applications, particularly in situations where the firstorder scattering approximation breaks down.MControlled source seismology; Interferometry; Wave scattering and diffraction)uuid:26ff8cc883154c9590c6e540b645703aDhttp://resolver.tudelft.nl/uuid:26ff8cc883154c9590c6e540b645703aoReconstructing the primary reflections in seismic data by Marchenko redatuming and convolutional interferometryMeles, Giovanni (University of Edinburgh); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Curtis, A (University of Edinburgh)uStateoftheart methods to image the earth s subsurface using activesource seismic reflection data involve reverse time migration. This and other standard seismic processing methods such as velocity analysis provide best results only when all waves in the data set are primaries (waves reflected only once). A variety of methods are therefore deployed as processing to predict and remove multiples (waves reflected several times); however, accurate removal of those predicted multiples from the recorded data using adaptive subtraction techniques proves challenging, even in cases in which they can be predicted with reasonable accuracy. We present a new, alternative strategy to construct a parallel data set consisting only of primaries, which is calculated directly from recorded data. This obviates< the need for multiple prediction and removal methods. Primaries are constructed by using convolutional interferometry to combine the firstarriving events of upgoing and directwave downgoing Green s functions to virtual receivers in the subsurface. The required upgoing wavefields to virtual receivers are constructed by Marchenko redatuming. Crucially, this is possible without detailed models of the earth s subsurface reflectivity structure: Similar to the most migration techniques, the method only requires surface reflection data and estimates of direct (nonreflected) arrivals between the virtual subsurface sources and the acquisition surface. We evaluate the method on a stratified synclinal model. It is shown to be particularly robust against errors in the reference velocity model used and to improve the migrated images substantially.)uuid:8ea16a770ce54464af8bba4e4a1c309dDhttp://resolver.tudelft.nl/uuid:8ea16a770ce54464af8bba4e4a1c309d\Marchenko equations for acoustic Green's function retrieval and imaging in dissipative mediaSlob, E.C. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)2Sicking, Charles (editor); Ferguson, John (editor)We present a scheme for Marchenko imaging in a dissipative heterogeneous medium. The scheme requires measured reflection and transmission data at two sides of the dissipative medium. The effectual medium is the same as the dissipative medium, but with negative dissipation. We show how the measured doublesided data can be combined to obtain the singlesided reflection response of the effectual medium. Two sets of singlesided Marchenko equations follow that are used to compute to the focusing wavefield and the Green functions. Each uses singlesided reflection responses of the dissipative and effectual medium. To start the solution for these equations an initial estimate of the dissipation is required in addition to the estimate of the travel time of the first arrival. Avoiding the estimate of dissipation of the first arrival in a lowloss medium does not have a detrimental effects on the image quality. The numerical example shows the effectiveness of this strategy.(attenuation; autofocusing; multiples; 3D)uuid:a6cb1a3123c946f09a52b1f68378d57fDhttp://resolver.tudelft.nl/uuid:a6cb1a3123c946f09a52b1f68378d57f"Timeslice wavefield decompositionHolicki, M.E. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Drijkoningen, G.G. (TU Delft Applied Geophysics and Petrophysics)We propose a novel acoustic decomposition operator for time slices, loosely based on conventional surface decomposition operators. The proposed operators hold for constant velocity models and require two 2D Fourier Transforms (one forward, one backward) per decomposed time slice per decomposition direction. We then demonstrate the capabilities of our operators on a constant velocity model and the Marmousi model. The decomposition results prove that we can decompose into up, down, left and rightgoing waves for complex velocity media.imaging; internal multiples)uuid:e5a476136f6c48a6a81e16430c319586Dhttp://resolver.tudelft.nl/uuid:e5a476136f6c48a6a81e16430c319586=Electromagnetic Marchenko imaging in 1D for dissipative media3Zhang, L. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Staring, M. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)We present a onedimensional lossless scheme to compute an image of a dissipative medium from two singlesided reflection responses. One reflection response is measured at or above the top reflector of a dissipative medium and the other reflection response is computed as if measured at or above the top reflector of a medium with negative dissipation which we call the effectual medium. These two< reflection responses together can be used to construct the approximate reflection data of the corresponding lossless medium by multiplying and taking the square root in time domain. The corresponding lossless medium has the same reflectors as the dissipative medium. Then the constructed reflection data can be used to compute the focusing wavefield which focuses at the chosen location in subsurface of the dissipative medium. From the focusing function and constructed reflection response the Green s function for a virtual receiver can be obtained. Because the up and downgoing parts of the Green s function are retrieved separately, these are used to compute the image. We show with an example that the method works well for a sample in a synthesized waveguide that could be used for measurements in a laboratory.Delectromagnetic; conductivity; internal multiples; permeability; GPR)uuid:55668444877344cea542b28883d3654cDhttp://resolver.tudelft.nl/uuid:55668444877344cea542b28883d3654cRMarchenko wavefield redatuming, imaging conditions, and the effect of model errorsde Ridder, Sjoerd (University of Edinburgh); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Curtis, A (University of Edinburgh); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)Recently, a novel method to redatum the wavefield in the subsurface from a reflection response measured at the surface has gained interest for imaging primaries in the presence of strong internal multiples. A prerequisite for the algorithm is an accurate and correct estimate of the directwave Green's function. However, usually we use an estimate for the directwave Green's function computed in a background velocity medium. Here, we investigate the effect of amplitude and phase errors in that estimate. We formulate two novel imaging conditions based on doublefocusing the measured reflection response inside the subsurface. These yield information on the amplitude error in the estimate for the directwave Green's function which we can then correct, but the phase error remains elusive.>inversion; autofocusing; imaging; internal multiples; velocity)uuid:170cc1de39a64906ad7a935382da4232Dhttp://resolver.tudelft.nl/uuid:170cc1de39a64906ad7a935382da4232MNew method for discriminating 4D time shifts in the overburden and reservoirr5Liu, Yi (Norwegian University of Science and Technology); Arntsen, B (Norwegian University of Science and Technology); Landr, M (Norwegian University of Science and Technology); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)Understanding seismic changes in the subsurface is important for reservoir management and health, safety and environmental (HSE) issues. Typically the changes are interpreted based on the time shifts in seismic timelapse (4D) data, where sources are at the surface and receivers are either at the surface or in a borehole. With these types of acquisition geometry, it is more straightforward to detect and interpret changes in the overburden, close to the source and receivers, than changes in the deeper part close to the reservoir, because the time shift is accumulative along its ray path from source to receiver. We propose a new method for reconstructing the reflection responses of the overburden and the reservoir, separately, for 4D time shift analysis. This method virtually moves sources and receivers to a horizontal borehole level, which enables a more direct interpretation of the time shifts to the changes close to the borehole, instead of to the surface. A realistic field model is used to demonstrate the method, and we observe a clear discrimination of the different time shifts in the overburden and reservoir, which is not obvious in the original datasets.Nreconstruction; timelapse; traveltime; downhole receivers; internal multiples)uuid:0527c923f2f4422f928cc8fd3d9e6295Dhttp://resolver.tudelft.nl/uuid:0527c923f2f4422f928cc8fd3d9e6295SBeyond Marchenko: Obtaining virtual receivers and virtual sources in the subsurfa< ceSingh, S. (Colorado School of Mines); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Snieder, R (Colorado School of Mines)By solving the Marchenko equations, the Green s function can be retrieved between a virtual receiver in the subsurface to points at the surface (no physical receiver is required at the virtual location). We extend the idea of these equations to retrieve the Green s function between any two points in the subsurface; i.e, between a virtual source and a virtual receiver (no physical source or physical receiver is required at either of these locations). This Green s function is called the virtual Green s function and includes all the primaries, internal and freesurface multiples. Similar to the Marchenko Green s function, we require the reflection response at the surface (singlesided illumination) and an estimate of the first arrival travel time from the virtual location to the surface.Imultiples; scattering; downhole sources; downhole receivers; autofocusing)uuid:37a5a787e38849f59c22579dee5aa1efDhttp://resolver.tudelft.nl/uuid:37a5a787e38849f59c22579dee5aa1efQFrom closedboundary to singlesided homogeneous Green's function representations,Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Singh, Satyan (University of the West Indies)The homogeneous Green s function (i.e., the Green s function and its timereversed counterpart) plays an important role in optical, acoustic and seismic holography, in inverse scattering methods, in the field of timereversal acoustics, in reversetime migration and in seismic interferometry. Starting with the classical closedboundary representation of the homogeneous Green s function, we modify the configuration to two parallel boundaries. We discuss stepbystep a process that eliminates the integral along the lower boundary. This leads to a singlesided representation of the homogeneous Green s function. Apart from imaging, we foresee interesting applications in inverse scattering, timereversal acoustics, seismic interferometry, passive source imaging, etc.)uuid:752f1f2226f542e09d5e70aaf95042aaDhttp://resolver.tudelft.nl/uuid:752f1f2226f542e09d5e70aaf95042aaZAn interferometric interpretation of Marchenko redatuming including freesurface multiplesStaring, M. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)We present an interferometric interpretation of the iterative Marchenko scheme including both freesurface multiples and internal multiples. Crosscorrelations are used to illustrate the combination of causal and acausal events that are essential for the process of multiple removal. The first 4 steps in the scheme are discussed in detail, where the effect of different contributions on the result is displayed and the formation of individual events is illustrated. We highlight the events that are necessary to understand the process that removes both internal multiples and freesurface multiples from the data. We demonstrate that additional contributions are needed to correct for the presence of freesurface multiples.multiples; seismic; autofocusing; correlation)uuid:1924c75734c24f4699306727c6381615Dhttp://resolver.tudelft.nl/uuid:1924c75734c24f4699306727c6381615:No more multiple removal: Construct Primaries then MigrateMeles, G.A. (University of Edinburgh); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Curt, A (University of Edinburgh))uuid:28ababd6a8bb46b88145699d1b07106bDhttp://resolver.tudelft.nl/uuid:28ababd6a8bb46b88145699d1b07106b?Imaging the earth's interior with virtual sources and receiversWapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geo< physics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Snieder, R (Extern))uuid:56af8349c1ae48f08bc1beb4a15c4c7fDhttp://resolver.tudelft.nl/uuid:56af8349c1ae48f08bc1beb4a15c4c7fFullfield MDD for bodywave reflections from passive transientsources under severely limited and irregular illumination conditionsSeismic interferometry (SI) presents a set of inexpensive and noninvasive methods that can be applied to any array at the surface to retrieve virtual bodywave reflection responses from earthquake recordings. Conventional SI by crosscorrelation requires recordings of wavefields in lossless media generated by a smooth continuous distribution of passive sources with isotropic source radiation patterns and similar power spectra. These conditions are unlikely to be met in the lithosphere: earthquakes are distributed sparsely and generated by complex mechanisms. The resulting anisotropy in the illumination of the receiver array causes the retrieved virtualsource radiation patterns to be irregular, leading to artifacts which can obscure the desired bodywave reflections. SI by multidimensional deconvolution (MDD) can inherently correct for anisotropic illumination of the array and does not rely on the medium being lossless. We propose an alternative formulation of MDD for twoway wavefields: fullfield MDD. Different from previous MDD methods for passive twoway wavefield recordings, fullfield MDD uses multiples in the passive data to construct the reflection response without freesurface interaction. Therefore, this MDD method profits from additional wavenumbers provided by scattering to compensate for sparse earthquake distributions. Besides, this method does not require wavefield decomposition, which is sensitive to velocity variations at the receiver level. We compare the reflection retrieval by fullfield MDD and crosscorrelation for a limited passive source distribution in a lithospheric model with a discontinuous Moho at a depth of 50 km. We simulate earthquakes generated by dipole sources along a listric faultsystem with power spectra varying within bandwidth 0.22.6 Hz. The reflection response retrieved by fullfield MDD shows a continuous highresolution Moho reflection, while crosscorrelation yields a very low resolution response obscured by artifacts./Geen BTA classificatie; Geen VSNUclassificatieAGU)uuid:ea874d1d9b2b4510a446ae9caec4fcacDhttp://resolver.tudelft.nl/uuid:ea874d1d9b2b4510a446ae9caec4fcacEvers, Laeslo G (Royal Netherlands Meteorological Institute); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Heaney, Kevin D (OASIS Inc.); Snellen, M. (TU Delft Aircraft Noise and Climate Effects)lThe propagation of acoustic waves in the ocean strongly depends on the temperature. Low frequency acoustic waves can penetrate the ocean down to depths where few insitu measurements are available. It is therefore attractive to obtain a measure of the deep ocean temperature from acoustic waves. The latter is especially true if the ambient acoustic noise field can be used instead of deterministic transient signals. In this study the acoustic velocity, and hence the temperature, is derived in an interferometric approach from hydrophone array recordings. The arrays were separated by over 125 km, near Ascension Island in the Atlantic Ocean, at a depth of 800m. Furthermore, the dispersive characteristics of the deep ocean sound channel are resolved based on the retrieved lag times for different modes. In addition, it is shown how the resolution of the interferometric approach can be increased by cross correlating array beams rather than recordings from singlesensor pairs. The observed acoustic lag times between the arrays corresponds well to modeled values, based on fullwave modeling through bestknown oceanic models.)uuid:c74b17ead39e4536b21862227a4a97e7Dhttp://resolver.tudelft.nl/uuid:c74b17ead39e4536b21862227a4a97e7Improved surfacewave res< ponse from ambient noise in Malarge, Argentina, using seismic interferometry by multidimensional deconvolutionWeemstra, C. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics); Ruigrok, E.N. (Royal Netherlands Meteorological Institute); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Gomez, Martn (Comision Nacional de Energia Atomica)C Generating new seismic responses from existing recordings is generally referred to as seismic interferometry (SI). Conventially, the new responses are retrieved by simple crosscorrelation of recordings made by separate receivers: a first receiver acts as `virtual source' whose response is retrieved at the other receivers. The newly retrieved responses can be used to extract receiverreceiver phase velocities, which often serve as input parameter for tomographic inverse problems, or which can be linked to temporally varying parameters such as hydrocarbon production and precipitation. For all applications, however, the accuracy of the retrieved responses is of great importance. In practice, this accuracy is often degraded by irregularities in the illumination pattern: correct response retrieval relies on a uniform illumination of the receivers. Reformulating the theory underlying seismic interferometry by crosscorrelation as a multidimensional deconvolution (MDD) process, allows for correction of these nonuniform illumination patterns by means of a socalled pointspread function (PSF). We apply SI by MDD to surfacewave data recorded by the Malarge seismic array in western Argentina. The aperture of the array is approximately 60 km and it is located on a plateau just east of the Andean mountain range. The array has a Tshape: the receivers along one of the two lines act as virtual sources whose responses are retrieved by the receivers along the other (perpendicular) line of receivers. Because SI by MDD relies on oneway wavefields, we select time windows dominated by surfacewave noise traveling in a favorable direction, that is, traversing the line of virtual sources before arriving at the receivers at which we aim to reconstruct the virtualsource responses. These time windows are selected through a frequencydependent slowness analysis along the two receiver lines. From the selected time windows, virtualsource responses are retrieved by computation of ensembleaveraged crosscorrelations. Similarly, ensembleaveraged crosscorrelations between virtual sources are computed: the pointspread function. We use the PSF to deconvolve the effect of illumination irregularities and the source function from the virtualsource responses. The combined effect of timewindow selection and MDD results in more accurate surfacewave responses.)uuid:ea4c851a94bd40f3b71d885c1eaff00cDhttp://resolver.tudelft.nl/uuid:ea4c851a94bd40f3b71d885c1eaff00c.Imaging an unknown object in an unknown mediumfSnieder, R (Colorado School of Mines); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)_
Imaging an unknown object in a medium that is known, such as a medium with constant velocity, is not difficult because one knows exactly where the waves are when they interact with the object. It is much more challenging to image an object in an unknown medium, because in that case one may know the waves that one sends into the medium, but one may does not know the waves that illuminate the object because the waves are distorted during their propagation to the object and back. Yet in many applications the medium is strongly scattering and the wavefield is strongly distorted as it propagates to the object. This is like imaging through frosted glass. How can one create an image in such media? And related to this, how can one focus a wavefield through a complicated medium that one does not know? Inverse scattering methods, as developed in quantum mechanics[1, 2], make it possible to estimate the model or object at a prescribed location without knowing the medium between that location and the point where reflected waves are recorded. These inverse s< cattering methods are known as the Marchenko equation or Gel FandLevitan equation. Recently, these inverse scattering methods have been generalized to applications in seismology[3, 4, 5, 6] where one seeks to image a target, such as a reservoir, under a complicated overburden, such as a salt body. The main issue we will address is how it is possible that one can image the object at one location without knowing the medium between the observation point and the reconstruction point. The reason why inverse scattering make it possible to do this is that these methods involve an integral equation[7], and the function that one solves for is akin to the Green s function for the unknown medium. The function obtained by solving the Marchenko equation is, in fact, the incident wavefield that will focus the waves at a specified target location. In order to solve this integral equation one only needs to know a smooth estimate of he velocity model and the reflected waves recorded at the acquisition surface, but the details of the complexity of the medium need not be known. That means there exists a recipe to determine, given the reflected waves, the incident wavefield that focuses at a specified target point. Such focusing is exactly what is needed to determine the image at the target point. There are many applications in geophysics where one seeks to create an image in strongly scattering media. These include hydrocarbon reservoirs under a complicated overburden, the interior of volcanoes, possibly the core mantle boundary, and crustal structure from highfrequency seismic waves.imaging; inverse scattering)uuid:7a7a5d241b584e58aa33b9b527ea7b41Dhttp://resolver.tudelft.nl/uuid:7a7a5d241b584e58aa33b9b527ea7b41Weemstra, C. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics); Ruigrok, Elmer (Royal Netherlands Meteorological Institute); Huniziker, Jrg (University of Lausanne); Gomez, Martin (Argentina National Atomic Energy Commission); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics) Obtaining new seismic responses from existing recordings is generally referred to as seismic interferometry (SI). Conventionally, these seismic interferometric responses are retrieved by simple crosscorrelation of recordings made by separate receivers: a first receiver acts as a 'virtual source' whose response is retrieved at the other receivers. When surface waves are retrieved, the newly retrieved responses can be used to extract receiverreceiver phase velocities. These phase velocities often serve as input parameters for tomographic inverse problems. Another application of SI exploits the temporal stability of the multiply scattered arrivals (the coda). For all applications, however, the accuracy of the retrieved responses is paramount. In practice, this accuracy is often degraded by irregularities in the illumination pattern: correct response retrieval relies on a uniform illumination of the receivers. Reformulating the theory underlying seismic interferometry by crosscorrelation as a multidimensional deconvolution (MDD) process, allows for correction of these nonuniform illumination patterns by means of a socalled pointspread function (PSF). We apply SI by MDD to surfacewave data recorded by the Malarge seismic array in western Argentina. The aperture of the array is approximately 60 km and it is located on a plateau just east of the Andean mountain range. The array has a Tshape, which makes it very well suited for the application of SI by MDD. We select time windows dominated by surfacewave noise traveling in a favorable direction, that is, traversing the line of virtual sources before arriving at the receivers at which we aim to retrieve the virtualsource responses. These time windows are selected based upon the slownesses along the two receiver lines. From the selected time windows, virtualsource responses are retrieved by computation of ensembleaveraged crosscorrelations. Similarly, ensembleaveraged crosscorrelations betwe< en the positions of the virtual sources are computed: the PSF. We use the PSF to deconvolve the effect of illumination irregularities and the source function from the virtualsource responses retrieved by crosscorrelation. The combined effect of timewindow selection and MDD results in more accurate and temporally stable surfacewave responses.)uuid:c1362afbddd549ef8563f3fcf737532fDhttp://resolver.tudelft.nl/uuid:c1362afbddd549ef8563f3fcf737532f0Weemstra, C. (TU Delft Applied Geophysics and Petrophysics); Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics); Ruigrok, E.N. (Utrecht University); Hunziker, J.W. (cole Polytechnique Fdrale de Lausanne); Gomez, Martin (CNEA); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics) Obtaining new seismic responses from existing recordings is generally referred to as seismic interferometry (SI). Conventionally, these seismic interferometric responses are retrieved by simple crosscorrelation of recordings made<br/>by separate receivers: a first receiver acts as a 'virtual source' whose response is retrieved at the other receivers. When surface waves are retrieved, the newly retrieved responses can be used to extract receiverreceiver phase velocities. These phase velocities often serve as input parameters for tomographic inverse problems. Another application of SI exploits the temporal stability of the multiply scattered arrivals (the coda). For all applications, however, the accuracy of the retrieved responses is paramount. In practice, this accuracy is often degraded by irregularities in the illumination pattern: correct response retrieval relies on a uniform illumination of the receivers. Reformulating the theory underlying seismic interferometry by crosscorrelation as a multidimensional deconvolution (MDD) process, allows for correction of these nonuniform illumination patterns by means of a socalled pointspread function (PSF). We apply SI by MDD to surfacewave data recorded by the Malarge seismic array in western Argentina. The aperture of the array is approximately 60 km and it is located on a plateau just east of the Andean mountain range. The array has a Tshape, which makes it very well suited for the application of SI by MDD. We select time windows dominated by surfacewave noise traveling in a favorable direction, that is, traversing the line of virtual sources before arriving at the receivers at which we aim to retrieve the virtualsource responses. These time windows are selected based upon the slownesses along the two receiver lines. From the selected time windows, virtualsource responses are retrieved by computation of ensembleaveraged crosscorrelations. Similarly, ensembleaveraged crosscorrelations between the positions of the virtual sources are computed: the PSF. We use the PSF to deconvolve the effect of illumination irregularities and the source function from the virtualsource responses retrieved by crosscorrelation. The combined effect of timewindow selection and MDD results in more accurate and temporally stable surfacewave responses.Campus only)uuid:4df9ab6673584539b392b43c09013030Dhttp://resolver.tudelft.nl/uuid:4df9ab6673584539b392b43c09013030[Estimating the location of a tunnel using interferometric times of Rayleighwave scattering>Kaslilar, A.; Harmankaya, U.; Wapenaar, C.P.A.; Draganov, D.S./Inspired by a technique called seismic interferometry, we estimate the location of a scatterer using scattered waves. We isolate the scattered wavefield and evaluate the result of correlating scattered waves at different receiver locations. The crosscorrelation eliminates the travel path between a source and a scatterer, making the estimation of the scatterers locations dependent only on properties between the receivers and the scatterer. We illustrate the potential of this method by locating a tunnel from seismic 23 field data, recorded along a line with multiple source and receiver locations. As nearsurface scatterers are potential weak zones and may pose risk for the environment, to mitigate geo and environmental hazards< , this method can be an efficient alternative in detection of such structures.!Civil Engineering and GeosciencesGeoscience & Engineering)uuid:64f2fc04f957410dbc10a7b285ef4f06Dhttp://resolver.tudelft.nl/uuid:64f2fc04f957410dbc10a7b285ef4f06/Creating virtual receivers from drillbit noise6Liu, Y.; Draganov, D.S.; Wapenaar, C.P.A.; Arntsen, B.In the field of seismic interferometry using noise, surface waves and body waves between receivers have been retrieved by crosscorrelating recordings of uncorrelated noise sources to extract useful subsurface information. When the positions of the noise sources are known, intersource interferometry can be applied to retrieve the wavefileds between sources, thus turning sources into virtual receivers. Previous applications of this form of interferometry assume impulsive point sources or transient sources with similar signatures. We investigate the requirements of applying intersource seismic interferometry using drillbit noise to retrieve the reflection responses at those positions. We show that an accurate estimate of the source function is essential for such application. The preprocessing involves using standard seismicwhiledrilling procedures, such as pilot crosscorrelation and pilot deconvolution to remove the drillbit signatures in the data, and then applying crosscorrelation interferometry. Provided that pilot signals are reliable, drillbit data can be redatumed from surface to the depth of boreholes using this intersource interferometry approach without any velocity information of the medium. We show that a wellpositioned image below the borehole can be obtained with just a simple velocity model using these reflection responses. We also discuss some of the practical hurdles that restrict its application offshore.)uuid:4f470bea639d49beaf8dfa3556691801Dhttp://resolver.tudelft.nl/uuid:4f470bea639d49beaf8dfa3556691801Reflection imaging of the Moho and the aseismic Nazca slab in the Malarge region with globalphase seismic interferometry; abstractHNishitsuji, Y.; Draganov, D.S.; Ruigrok, E.; Gomez, M.; Wapenaar, C.P.A.Geoscience and Engineering)uuid:d70af4b3b5b740e6b1bc0a7b08880bacDhttp://resolver.tudelft.nl/uuid:d70af4b3b5b740e6b1bc0a7b08880bacKSeismic reflection imaging, accounting for primary and multiple reflections\Wapenaar, C.P.A.; Van der Neut, J.R.; Thorbecke, J.W.; Broggini, F.; Slob, E.C.; Snieder, R. European Geosciences Union (EGU))uuid:5c46a3e34341468985000d2408cda5dfDhttp://resolver.tudelft.nl/uuid:5c46a3e34341468985000d2408cda5dfSReflecting boundary conditions for interferometry by multidimensional deconvolution/Weemstra, C.; Wapenaar, C.P.A.; Van Dalen, K.N.!In this work we investigate a modification of the formulation of the theory underlying seismic interferometry (SI) by multidimensional deconvolution (MDD). The current formulation, and hence method, relies on separation of waves traveling inward and outward of a volume bounded by receivers. As a consequence, it is predominantly useful when receivers are illuminated from one side only. This puts constraints on the applicability of SI by MDD to omnidirectional wave fields. The proposed modification eliminates the requirement to separate inwardand outward propagating wave field and, consequently, improves the applicability of MDD to omnidirectional wave fields. We therefore envisage the modified MDD formulation to hold significant promise in the application to ambientnoise surface wave data.2illumination; deconvolution; passive; surface wave)uuid:26d929d605b84583b13b6a2fa0ef35fbDhttp://resolver.tudelft.nl/uuid:26d929d605b84583b13b6a2fa0ef35fbfImaging and monitoring of subsurface structures using reflection retrieves from seismic interferometry Draganov, D.S.; Wapenaar, C.P.A.)uuid:ef15255ec92c4615bd63b9525f7e25dbDhttp://resolver.tudelft.nl/uuid:ef15255ec92c4615bd63b9525f7e25dbYMarchenko imaging: Imaging with primaries, internal multiples, and freesurface multiplesTSingh, S.; Snieder, R.; Behura, J.; van der Neut, J.R.; Wapenaar, C.P.A.; Slob, E.C.Recent< work on retrieving the Green s function with the Marchenko equation shows how these functions for a virtual source in the subsurface can be obtained from reflection data. The response to the virtual source is the Green s function from the location of the virtual source to the surface. The Green s function is retrieved using only the reflection response of the medium and an estimate of the first arrival at the surface from the virtual source. Current techniques, however, only include primaries and internal multiples. Therefore, all surfacerelated multiples must be removed from the reflection response prior to Green s function retrieval. We have extended the Marchenko equation to retrieve the Green s function that includes primaries, internal multiples, and freesurface multiples. In other words, we have retrieved the Green s function in the presence of a free surface. The information needed for the retrieval is the same as the current techniques, with the only difference being that the reflection response now also includes freesurface multiples. The inclusion of these multiples makes it possible to include them in the imaging operator, and it obviates the need for surfacerelated multiple elimination. This type of imaging with Green s functions is called Marchenko imaging.9multiples; scattering; imaging; reflectivity; reciprocity$Society of Exploration Geophysicists)uuid:54461b72390d4755ad4d51a80c1bd352Dhttp://resolver.tudelft.nl/uuid:54461b72390d4755ad4d51a80c1bd352=Geophysical noise interferometry: Repairing the broken mirror4Wapenaar, C.P.A.; Van der Neut, J.R.; Draganov, D.S.fUnder conditional circumstances, the correlation of noise at two receivers is approximately proportional to the Green s function between these receivers. Hence, the correlation process turns one of the receivers into a virtual source, of which the response is observed by the other receiver. This principle, also known as ambientnoise interferometry, is used by researchers in geophysics, ultrasonics and underwater acoustics to infer information about an unknown object from passive noise measurements. In geophysics, ambientnoise interferometry is used for tomographic velocity inversion when surface waves are dominant, or for highresolution reflection imaging when a significant amount of body waves is present in the noise field. The virtualsource response obtained with geophysical noise interferometry is accurate when the medium is lossless and the noise field is equipartitioned. In practice these assumptions are often violated: the medium of interest is often illuminated from one side only, the sources may be irregularly distributed and losses may be significant. For those cases, it is as if the virtual source is viewed in a broken (timereversal) mirror, which causes blurring of the source. This blurring is quantified by the socalled pointspread function, which, like the correlation function, can be derived from the observed data (that is, without the need to know the actual sources and the medium). The broken mirror can be repaired by deconvolving the correlation function for the pointspread function. As a result, the virtual source is refocused and hence the virtualsource response becomes more reliable.)uuid:835a8461b85346e49a707d8e19a95485Dhttp://resolver.tudelft.nl/uuid:835a8461b85346e49a707d8e19a95485An illustration of adaptive Marchenko imagingRVan der Neut, J.R.; Wapenaar, C.P.A.; Thorbecke, J.W.; Slob, E.C.; Vasconcelos, I.In Marchenko imaging, wavefields are retrieved at specified focal points in the subsurface through an iterative scheme derived from the multidimensional Marchenko equation. The method requires seismicreflection data at the earth s surface (after freesurface multiple elimination) and an estimate of the direct wavefield from the surface to each focal point, which can be computed, for instance, in a macrovelocity model. In the first iteration, the direct wavefield is crosscorrelated with the reflection data. This operation is identical to inversewavefield extrapolation as is applied commonly in various< imaging schemes, for instance, in reverse time migration (RTM). At each succeeding iteration, the result of the previous iteration is truncated in time and crosscorrelated with the reflection data again. To obtain a seismic image, a multidimensional deconvolutionbased imaging condition can be applied to the retrieved wavefields. By this approach, both primary reflections and internal multiples contribute to the construction of the image. Alternatively, a crosscorrelationbased imaging condition can be used in which only the primary reflections are imaged and the contributions of internal multiples are subtracted. The latter strategy offers more flexibility because the subtraction of redatumed internal multiples can be implemented adaptively. Through this approach, the artifacts from internal multiples can be removed effectively from a conventional RTM image.)uuid:f5b72d69b9ee4e27be153751a68ca753Dhttp://resolver.tudelft.nl/uuid:f5b72d69b9ee4e27be153751a68ca7534Inversion of the multidimensional marchenko equationAVan der Neut, J.R.; Thorbecke, J.W.; Wapenaar, C.P.A.; Slob, E.C.Focusing functions are defined as wavefields that focus at a specified location in a heterogeneous subsurface. These functions can be directly related to Green's functions and hence they can be used for seismic imaging of complete wavefields, including not only primary reflections but all orders of internal multiples. Recently, it has been shown that focusing functions can be retrieved from singlesided reflection data and an initial operator (which can be computed in a smooth background velocity model of the subsurface) by iterative substitution of the multidimensional Marchenko equation. In this work, we show that the Marchenko equation can also be inverted directly for the focusing functions. Although this approach is computationally more expensive than iterative substitution, additional constraints can easily be imposed. Such a flexibility might be beneficial in specific cases, for instance when the recorded data are incomplete or when additional measurements (e.g. from downhole receivers) are available.)uuid:d3a88b74a1584df2ae3a9bb8bc5b6cf6Dhttp://resolver.tudelft.nl/uuid:d3a88b74a1584df2ae3a9bb8bc5b6cf6SEstimating the location of scatterers using correlation of scattered rayleigh wavesLHarmankaya, U.; Kaslilar, A.; Van Wijk, K.; Wapenaar, C.P.A.; Draganov, D.S.Inspired by a technique called seismic interferometry, we estimate the location of scatterers in a scaled model, where many nearsurface scatterers are present. We isolate the scattered wavefield and evaluate correlation of scattered waves at different receiver locations. The crosscorrelation eliminates the travel path between a source and a scatterer, making the estimation of the scatterers locations dependent only on properties between the receivers and the scatterer. We illustrate the potential of this method by locating scatterers with ultrasonic laboratory measurements of scattered Rayleigh waves recorded on two parallel and orthogonal lines of receivers. As nearsurface scatterers are potential weak zones and may pose risk for the environment, to mitigate geo and environmental hazards, this method can be an efficient alternative that can be used in detection of such structures.)uuid:6d23442709344f868f18c17a4045293dDhttp://resolver.tudelft.nl/uuid:6d23442709344f868f18c17a4045293dHElastodynamic Marchenko focusing, green's function retrieval and imagingWapenaar, C.P.A.; Slob, E.C.Building on acoustic autofocusing in 1D media, we previously proposed acoustic Marchenko imaging for 1D and 3D media. Recently, the first steps have been set towards extending the singlesided Marchenko method to the elastodynamic situation. Here we discuss the extension of singlesided Marchenko focusing, Green's function retrieval and imaging to the elastodynamic situation. With numerical examples in a horizontally layered medium we show that, at least in principle, a true amplitude image can be obtained, free of artefacts related to multiple reflections and wave conversions. The meth< od can be extended to 3D situations, in a similar way as we extended the acoustic 1D method to the 3D situation.)uuid:f2a1c8145fa349a982577244c2d46f68Dhttp://resolver.tudelft.nl/uuid:f2a1c8145fa349a982577244c2d46f68rRetrieving surface waves from ambient seismic noise using seismic interferometry by multidimensional deconvolution@Van Dalen, K.N.; Mikesell, T.D.; Ruigrok, E.N.; Wapenaar, C.P.A.Retrieving virtual source surface waves from ambient seismic noise by cross correlation assumes, among others, that the noise field is equipartitioned and the medium is lossless. Violation of these assumptions reduces the accuracy of the retrieved waves. A pointspread function computed from the same ambient noise quantifies the associated virtual source's spatial and temporal smearing. Multidimensional deconvolution (MDD) of the retrieved surface waves by this function has been shown to improve the virtual source's focusing and the accuracy of the retrieved waves using synthetic data. We tested MDD on data recorded during the Batholiths experiment, a passive deployment of broadband seismic sensors in British Columbia, Canada. The array consisted of two approximately linear station lines. Using 4 months of recordings, we retrieved fundamentalmode Rayleigh waves (0.05 0.27 Hz). We only used noise time windows dominated by waves that traverse the northern line before reaching the southern (2.5% of all data). Compared to the conventional crosscorrelation result based on this subset, the MDD waveforms are better localized and have significantly higher signaltonoise ratio. Furthermore, MDD corrects the phase, and the spatial deconvolution fills in a spectral (f, k domain) gap between the singlefrequency and doublefrequency microseism bands. Frequency whitening of the noise also fills the gap in the crosscorrelation result, but the signaltonoise ratio of the MDD result remains higher. Comparison of the extracted phase velocities shows some differences between the methods, also when all data are included in the conventional cross correlation.American Geophysical Union
20150806Structural Engineering)uuid:c27b50de0d8a4a8c923da64633ec9568Dhttp://resolver.tudelft.nl/uuid:c27b50de0d8a4a8c923da64633ec9568ZOn Green s function retrieval by iterative substitution of the coupled Marchenko equations5Van der Neut, J.R.; Vasconcelos, I.; Wapenaar, C.P.A.jIterative substitution of the coupled Marchenko equations is a novel methodology to retrieve the Green's functions from a source or receiver array at an acquisition surface to an arbitrary location in an acoustic medium. The methodology requires as input the singlesided reflection response at the acquisition surface and an initial focusing function, being the timereversed direct wavefield from the acquisition surface to a specified location in the subsurface. We express the iterative scheme that is applied by this methodology explicitly as the successive actions of various linear operators, acting on an initial focusing function. These operators involve multidimensional crosscorrelations with the reflection data and truncations in time. We offer physical interpretations of the multidimensional crosscorrelations by subtracting traveltimes along common ray paths at the stationary points of the underlying integrals. This provides a clear understanding of how individual events are retrieved by the scheme. Our interpretation also exposes some of the scheme's limitations in terms of what can be retrieved in case of a finite recording aperture. Green's function retrieval is only successful if the relevant stationary points are sampled. As a consequence, internal multiples can only be retrieved at a subsurface location with a particular ray parameter if this location is illuminated by the direct wavefield with this specific ray parameter. Several assumptions are required to solve the Marchenko equations. We show that these assumptions are not always satisfied in arbitrary heterogeneous media, which can result in incomplete Green's function retrieval and the emergence of artefacts. Despite< these limitations, accurate Green's functions can often be retrieved by the iterative scheme, which is highly relevant for seismic imaging and inversion of internal multiple reflections.=controlled source seismology; wave scattering and diffractionOxford University Press)uuid:6debab436c3848ceacb755cbae48f654Dhttp://resolver.tudelft.nl/uuid:6debab436c3848ceacb755cbae48f654A method to retrieve an improved high resolution reflection response from HiCLIMB array recordings of local earthquake scattering coda (PPT)Hartstra, I.E. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics)We discuss a method to interferometrically retrieve the body wave reflection response from local highfrequency scattering coda wave fields with the purpose to obtain an input dataset suitable for the application of advanced explorationtype imaging methodsscattering coda; interferometry; scattering mean free path; reflection response; impedance contrasts; advanced explorationtype imaging; coda attenuation factor; HiCLIMB array)uuid:f7957d42891049eb8ba55bd98374ea00Dhttp://resolver.tudelft.nl/uuid:f7957d42891049eb8ba55bd98374ea00[The life cycle of a Sudden Stratospheric Warming from infrasonic ambient noise observations(Smets, P.; Evers, L.G.; Wapenaar, C.P.A.EGU)uuid:6d0ac8a138804df6bfb4d4b96563284aDhttp://resolver.tudelft.nl/uuid:6d0ac8a138804df6bfb4d4b96563284a^Creating virtual vertical radar profiles from surface reflection ground penetrating radar data=Slob, E.C.; Hunziker, J.W.; Thorbecke, J.W.; Wapenaar, C.P.A.Fvirtual source; virtual receiver; interferometry; autofocusing; 3D GPR
UCL , COST)uuid:5c923f77d6d2470dbda608d1dff30b80Dhttp://resolver.tudelft.nl/uuid:5c923f77d6d2470dbda608d1dff30b80@Singlesided Marchenko focusing of compressional and shear wavesWapenaar, C.P.A.In timereversal acoustics, waves recorded at the boundary of a strongly scattering medium are sent back into the medium to focus at the original source position. This requires that the medium can be accessed from all sides. We discuss a focusing method for media that can be accessed from one side only.We show how complex focusing functions, emitted from the top surface into the medium, cause independent foci for compressional and shear waves. The focused fields are isotropic and act as independent virtual sources for these wave types inside the medium.We foresee important applications in nondestructive testing of construction materials and seismological monitoring of processes inside the Earth.)uuid:049d25c010124ec48df19b8bfdaffe66Dhttp://resolver.tudelft.nl/uuid:049d25c010124ec48df19b8bfdaffe66In timereversal acoustics, waves recorded at the boundary of a strongly scattering medium are sent back into the medium to focus at the original source position. This requires that the medium can be accessed from all sides. We discuss a focusing method for media that can be accessed from one side only. We show how complex focusing functions, emitted from the top surface into the medium, cause independent foci for compressional and shear waves. The focused fields are isotropic and act as independent virtual sources for these wave types inside the medium. We foresee important applications in nondestructive testing of construction materials and seismological monitoring of processes inside the Earth.American Physical Society)uuid:a26e5c46b6a2469296bc43656b9a2ad4Dhttp://resolver.tudelft.nl/uuid:a26e5c46b6a2469296bc43656b9a2ad4gCombining intersource seismic interferometry and sourcereceiver interferometry for deep local imaging:Liu, Y.; Arntsen, B.; Wapenaar, C.P.A.; Van der Neut, J.R.0The virtual source method has been applied successfully to retrieve the impulse response between pairs of receivers in the subsurface. This method is further improved by an updown separation prior to the crosscorrelation to suppress the reflections from the overburden and the free surface. In a reversed situation where the sources are in the subs< urface and receivers are on the surface, in principle, one can apply the same logic to retrieve the virtual response between pairs of sources by sourcereceiver reciprocity, turning the physical borehole sources into virtual receivers. However, since the updown separation is not applicable on the source side, the simple crosscorrelation of the total fields results in spurious events due to the incomplete receiver coverage around the sources. We show with a numerical example that for this configuration of borehole sources and surface receivers, one can replace such an updown separation at the source side by that of the direct and reflected waves as a first order approximation. This procedure produces the virtual receiver data that is adequate for local imaging below the source depth and is completely independent of the accuracy of the overburden velocity model. We implement this intersource type of interferometry by multidimensional deconvolution (MDD). Further, if the conventional surface survey data is available, we test the methodology from sourcereceiver interferometry (SRI) for this reverse configuration with borehole sources to retrieve the virtual receiver data with reflections coming from above, using also only the separation of the direct and reflected waves. By migrating the two sets of virtual receiver data, one can create a local image around the borehole sources in a deep area with better focusing and localization without a sophisticated velocity model.)uuid:36fc8b483f70418789930072d90ada9fDhttp://resolver.tudelft.nl/uuid:36fc8b483f70418789930072d90ada9f}A method to suppress spurious multiples in virtualsource gathers retrieved using seismic interferometry with reflection data0Boullenger, B.; Wapenaar, C.P.A.; Draganov, D.S.KSeismic interferometry applied to surface reflection data (with source and receivers at the surface) allows to retrieve virtualsource gathers at the position of receivers, where no source was shot. As a result of the crosscorrelation of all primary and multiple reflections, the virtualsource gathers contain retrieved physical reflections as well as nonphysical (ghost) reflections also called spurious multiples. We show that a significant part of the ghost reflections can be suppressed by using surfacerelated multiple elimination on the active data advantageously. The method that we propose consists in retrieving the strong ghost reflections mainly from the crosscorrelation of primaries only and in subtracting this result from the virtualsource gather retrieved from all the data. The resulting new virtualsource gathers provide a better estimate of the reflection response since it is now less polluted by undesired nonphysical events that may bring ambiguity in the interpretation. This is better to make a more effective use of the virtualsource gathers, for example for imaging.Icorrelation; estimation; reflection; reconstruction; adaptive subtraction)uuid:7b0b9d5d78954d469b03d618bd9734faDhttp://resolver.tudelft.nl/uuid:7b0b9d5d78954d469b03d618bd9734fa>Internal multiple suppression by adaptive Marchenko redatumingFVan der Neut, J.R.; Wapenaar, C.P.A.; Thorbecke, J.W.; Vasconcelos, I.Recently, a novel iterative scheme was proposed to retrieve Green's functions in an unknown medium from its singlesided reflection response and an estimate of the propagation velocity. In Marchenko imaging, these Green's functions are used for seismic imaging with complete wavefields, including internal multiple reflections. In this way, common artifacts from these internal reflections are avoided and illumination of the subsurface can potentially be improved. However, Marchenko imaging requires accurate input data, with correct amplitudes, a deconvolved source signature, without freesurface multiples and source / receiver ghosts. Hence, a significant amount of preprocessing is required, which should be done accurately. To relax these requirements, we propose a scheme to remove artifacts due to internal multiples from inverseextrapolated wavefields, by adaptively subtracting an estimate of th< ese artifacts that is constructed with the Marchenko equation. autofocusing; internal multiples)uuid:097d4a01a0ae47418bbf023b10226dfbDhttp://resolver.tudelft.nl/uuid:097d4a01a0ae47418bbf023b10226dfbdOn the focusing conditions in timereversed acoustics, seismic interferometry, and Marchenko imagingcWapenaar, C.P.A.; Van der Neut, J.R.; Thorbecke, J.W.; Vasconcelos, I.; Van Manen, D.J.; Ravasi, M.yDespite the close links between the fields of timereversed acoustics, seismic interferometry and Marchenko imaging, a number of subtle differences exist. This paper reviews the various focusing conditions of these methods, the causality/acausality aspects of the corresponding focusing wavefields, and the requirements with respect to omnidirectional/singlesided acquisition.Applied SciencesImPhys/Imaging Physics)uuid:a3762abc0fae4b0bbea6aa571f2db3e2Dhttp://resolver.tudelft.nl/uuid:a3762abc0fae4b0bbea6aa571f2db3e2[Autofocusing imaging: Imaging with primaries, internal multiples and freesurface multiples#Recent work on autofocusing with the Marchenko equation has shown how the Green's function for a virtual source in the subsurface can be obtained from reflection data. The response to the virtual source is the Green's function from the location of the virtual source to the surface. The Green's function is retrieved using only the reflection response of the medium and an estimate of the first arrival at the surface from the virtual source. Current techniques, however, only include primaries and internal multiples. Therefore, all surfacerelated multiples must be removed from the reflection response prior to Green's function retrieval. Here, we extend the Marchenko equation to retrieve the Green's function that includes primaries, internal multiples, and freesurface multiples. In other words, we retrieve the Green's function in the presence of a free surface. We use the associated Green's function for imaging the subsurface. The information needed for the retrieval are the reflection response at the surface and an estimate of the first arrival at the surface from the virtual source. The reflection response, in this case, includes the freesurface multiples; this makes it possible to include these multiples in the imaging operator and it obviates the need for surfacerelated multiple elimination.@imaging; multiples; scattering; autofocusing; internal multiples)uuid:0717bd465ec445358ddafd74cfd874eeDhttp://resolver.tudelft.nl/uuid:0717bd465ec445358ddafd74cfd874eesInfrasonic interferometry applied to microbaroms observed at the Large Aperture Infrasound Array in the NetherlandsHFricke, J.T.; Evers, L.G.; Smets, P.S.M.; Wapenaar, C.P.A.; Simons, D.G.;We present the results of infrasonic interferometry applied to microbaroms, obtained from ambient noise. For this purpose the Large Aperture Infrasound Array (LAIA) was used, which has been installed in the Netherlands. Preprocessing appeared to be an essential step in enhancing the microbarom signals from ambient noise that strongly influences the results of the interferometry. Both the state of the atmosphere and the noise characteristics are taken into account to assess the strength of the cross correlation. The delay time of the microbaroms between two stations is determined through cross correlating the recordings. By calculating the cross correlations between all 55 station pairs of LAIA, we are able to find the delay time of microbaroms up to a interstation distance of 40.6 km. Using the strength of the cross correlations, we are able to show that the coherence of the microbaroms along the direction of arrival is higher than orthogonal to it. A comparison of the atmospheric state, with a cross correlation, over a period of 10 days, reveals that the infrasound propagation over the array is correlated with the tropospheric temperature and wind. Based on the cross correlations between the three closest stations, we are able to passively estimate the effective sound speed and the wind speed as a function of time.3infrasonic interferometry; microbaroms; troposphere<
20150219)uuid:84266f03b9e64fe69e74a727c641d9f5Dhttp://resolver.tudelft.nl/uuid:84266f03b9e64fe69e74a727c641d9f5Marchenko imaging\Wapenaar, C.P.A.; Thorbecke, J.W.; Van der Neut, J.R.; Broggini, F.; Slob, E.C.; Snieder, R.
lecture notes)uuid:ca8cdd02139a423c94f2540330603ccfDhttp://resolver.tudelft.nl/uuid:ca8cdd02139a423c94f2540330603ccfZShear wave seismic interferometry for lithospheric imaging: Application to southern Mexico,Frank, J.G.; Ruigrok, E.N.; Wapenaar, C.P.A.Seismic interferometry allows for the creation of new seismic traces by cross correlating existing ones. With sufficient sampling of remotesource positions, it is possible to create a virtual source record by transforming a receiver location into a virtual source. The imaging technique developed here directly retrieves reflectivity information from the subsurface. Other techniques, namely receiverfunction and tomography, rely on modeconverted energy and perturbations in a velocity field, respectively, to make inferences regarding structure. We select shear phases as an imaging source because of their lower propagation velocity, sensitivity to melt, and ability to treat vertical shear and horizontal shear wavefields independently. Teleseismic shear phases approximate a plane wave due to the extent of wavefront spread compared to a finite receiver array located on the free surface. The teleseismic shear phase transmission responses are used as input to the seismic interferometry technique. We create virtual shear source records by converting each receiver in the array into a virtual source. By cross correlating the received signals, the complex source character of distant earthquakes is imprinted on the virtual source records as the average autocorrelation of individual sourcetime functions. We demonstrate a technique that largely removes this imprint by filtering in the commonoffset domain. A field data set was selected from the MesoAmerica Subduction Experiment. Despite the suboptimal remotesource sampling, an image of the lithosphere was produced that confirms features of the subduction zone that were previously found with the receiverfunction technique.9lithosphere; seismic interferometry; imaging; shear waves
20150117)uuid:6b6317a19e4f4d6bbb2c9e2d803e6625Dhttp://resolver.tudelft.nl/uuid:6b6317a19e4f4d6bbb2c9e2d803e6625JAutofocus imaging: Image reconstruction based on inverse scattering theory)Behura, J.; Wapenaar, C.P.A.; Snieder, R.Conventional imaging algorithms assume single scattering and therefore cannot image multiply scattered waves correctly. The multiply scattered events in the data are imaged at incorrect locations resulting in spurious subsurface structures and erroneous interpretation. This drawback of current migration/imaging algorithms is especially problematic for regions where illumination is poor (e.g., subsalt), in which the spurious events can mask true structure. Here we discuss an imaging technique that not only images primaries but also internal multiples accurately. Using only surface reflection data and directarrivals, we generate the up and downgoing wavefields at every image point in the subsurface. An imaging condition is applied to these up and downgoing wavefields directly to generate the image. Because the above algorithm is based on inversescattering theory, the reconstructed wavefields are accurate and contain multiply scattered energy in addition to the primary event. As corroborated by our synthetic examples, imaging of these multiply scattered energy helps eliminate spurious reflectors in the image. Other advantages of this imaging algorithm over existing imaging algorithms include more accurate amplitudes, targetoriented imaging, and a highly parallelizable algorithm.)uuid:640f712ddd994a5ca65f6e2fdcc50ba9Dhttp://resolver.tudelft.nl/uuid:640f712ddd994a5ca65f6e2fdcc50ba9uWavefield decomposition of field data, using a shallow horizontal downhole sensor array and a freesurface constraintWGrobbe, N.; van der Neut, J.R.; Almagro Vidal, C.; Drijkoningen, G.G.; Wapenaar, C.P.< A.Separation of recorded wavefields into downgoing and upgoing constituents is a technique that is used in many geophysical methods. The conventional, multicomponent (MC) wavefield decomposition scheme makes use of different recorded wavefield components. In recent years, land acquisition designs have emerged that make use of shallow horizontal downhole sensor arrays. Inspired by marine acquisitiondesigns that make use of recordings at multiple depth levels for wavefield decomposition, we have recently developed a multidepth level (MDL) wavefield decomposition scheme for land acquisition. Exploiting the underlying theory of this scheme, we now consider conventional, multicomponent (MC) decomposition as an inverse problem, which we try to constrain in a better way. We have overdetermined the inverse problem by adding an MDL equation that exploits the Dirichlet freesurface boundary condition. To investigate the successfulness of this approach, we have applied both MC and combined MCMDL decomposition to a real land dataset acquired in Annerveen, the Netherlands. Comparison of the results of overdetermined MCMDL decomposition with the results of MC wavefield decomposition, clearly shows improvements in the obtained oneway wavefields, especially for the downgoing fields.)uuid:50734e453a084986b8ba5c711daa76bfDhttp://resolver.tudelft.nl/uuid:50734e453a084986b8ba5c711daa76bfILocating cavities using ghost scattered waves in a scalemodel experimentiHarmankaya, U.; Kaslilar, A.; Verstraeten, B.; Creten, S.; Glorieux, C.; Wapenaar, C.P.A.; Draganov, D.S.The investigation and detection of nearsurface structures (cavities, caves, tunnels, mineshafts, buried objects, archeological ruins, water reservoir, etc.) is important to mitigate geo and environmental hazards. We use a method inspired by seismic interferometry to estimate the location of a cavity in a scaled ultrasonic experiment, representative for geophysical field problems. We use only one source at the surface and retrieve ghost scattered waves by evaluating the correlation of scattered waves at different receiver locations. As an exploitation of the ghost arrival information, the ghost travel times are determined and combined to estimate the location of a cavity with good accuracy.)uuid:f9b8ba0dc83d4b1c9450ca1cc2ae8bcbDhttp://resolver.tudelft.nl/uuid:f9b8ba0dc83d4b1c9450ca1cc2ae8bcbZTurning subsurface noise sources into virtual receivers by multidimensional deconvolution&Liu, Y.; Wapenaar, C.P.A.; Arntsen, B.The retrieval of the Green's functions between receiver pairs by multidimensional deconvolution can be extended to extract the impulse response between source pairs through sourcereceiver reciprocity. However in general, the procedure requires the separation of the outgoing and incoming wavefields at the sources, which reduces to the separation of the direct waves and the reflected waves in the absence of freesurface and interlayer multiples. We show that in theory, for nontransient noise sources where the separation may not be obvious in the data domain, the separation can be achieved by timewindowing in an intermediate crosscorrelation step, which can be readily included in the MDD scheme. We illustrate the method with a synthetic model.)uuid:8c2fce50b63b4eac99ad70265c9f275eDhttp://resolver.tudelft.nl/uuid:8c2fce50b63b4eac99ad70265c9f275e9An interferometric interpretation of Marchenko redatumingRecently, an iterative scheme was introduced to retrieve up and downgoing Green s functions at an arbitrary location F in the subsurface. The scheme uses the reflection data as acquired at the surface as input, together with an estimate of the direct arrival from the surface to location F, which is referred to as the initial focusing function. We interpret the overall action of the scheme as the successive actions of various linear filters, acting on the initial focusing function. These filters involve multidimensional crosscorrelations with the reflection response, time reversals and truncations in time. Inspired by literature on seismic int< erferometry, we interpret multidimensional crosscorrelation in terms of the subtraction of traveltimes along stationary raypaths. The scheme has been designed for layered media with smooth interfaces. Our interferometric interpretation reveals some of the scheme s limitations when it is applied to more complex configurations. It can be concluded that (downgoing or upgoing) internal multiples that arrive at F with a particular angle can be retrieved only if the initial focusing function (i.e., the direct wave) has visited F with this angle. Consequently, shadow zones that cannot be imaged with primary reflections can theoretically also not be imaged with internal multiples, when the current iterative scheme is used for their retrieval. Finally, we observe that the current scheme does not yet optimally perform in media with point scatterers, since an underlying assumption (generally referred to as the ansatz) is not perfectly obeyed in this case. It is envisioned that this can be improved if truncations in time that are implemented after each iteration are replaced by more advanced filtering methods.)uuid:e1657f41faa44d63a407a34dc49cdbd0Dhttp://resolver.tudelft.nl/uuid:e1657f41faa44d63a407a34dc49cdbd0<Marchenko imaging below an overburden with random scatterersRWapenaar, C.P.A.; Thorbecke, J.W.; Van der Neut, J.R.; Vasconcelos, I.; Slob, E.C.Marchenko imaging is a new way to deal with internal multiple scattering in migration. It has been designed for layered media with smooth interfaces. Here we analyze the performance of the Marchenko scheme for a medium with many point scatterers. Although the conditions for Marchenko imaging are violated, we observe from a numerical experiment that the signaltonoise ratio of the obtained image is significantly higher than with standard imaging.)uuid:6954f84f20e24a93919b41a26298ae02Dhttp://resolver.tudelft.nl/uuid:6954f84f20e24a93919b41a26298ae02eOverview of marine controlledsource electromagnetic interferometry by multidimensional deconvolution,Hunziker, J.W.; Slob, E.C.; Wapenaar, C.P.A.Interferometry by multidimensional deconvolution for marine ControlledSource Electromagnetics can suppress the direct field and the airwave in order to increase the detectability of the reservoir. For monitoring, interferometry by multidimensional deconvolution can increase the source repeatability. We give an overview over the method and discuss a possible path of research for the future.)uuid:4dab07ba394d456a9bda2632a45e5ed4Dhttp://resolver.tudelft.nl/uuid:4dab07ba394d456a9bda2632a45e5ed4IOn the Marchenko equation for multicomponent singlesided reflection dataLRecent work on the Marchenko equation has shown that the scalar 3D Green s function for a virtual source in the subsurface can be retrieved from the singlesided reflection response at the surface and an estimate of the direct arrival. Here, we discuss the first steps towards extending this result to multicomponent data. After introducing a unified multicomponent 3D Green s function representation, we analyse its 1D version for elastodynamic waves in more detail. It follows that the main additional requirement is that the multicomponent direct arrival, needed to initiate the iterative solution of the Marchenko equation, includes the forwardscattered field. Under this and other conditions, the multicomponent Green s function can be retrieved from singlesided reflection data, and this is demonstrated with a 1D numerical example.Minterferometry; controlled source seismology; wave scattering and diffraction)uuid:8e8655c94b234f9e933937c372be931bDhttp://resolver.tudelft.nl/uuid:8e8655c94b234f9e933937c372be931b)uuid:1f984a23467a499c90a168e98b728ad8Dhttp://resolver.tudelft.nl/uuid:1f984a23467a499c90a168e98b728ad8Datadriven wavefield focusing and imaging with multidimensional deconvolution: Numerical examples for reflection data with internal multiples+Broggini, F.; Snieder, R.; Wapenaar, C.P.A.]Standard imaging techniques rely on the single scattering assumption. This requires that the recorded data do< not include internal multiples, i.e., waves that have bounced multiple times between reflectors before reaching the receivers at the acquisition surface. When multiple reflections are present in the data, standard imaging algorithms incorrectly image them as ghost reflectors. These artifacts can mislead interpreters in locating potential hydrocarbon reservoirs. Recently, we introduced a new approach for retrieving the Green s function recorded at the acquisition surface due to a virtual source located at depth. We refer to this approach as datadriven wavefield focusing. Additionally, after applying sourcereceiver reciprocity, this approach allowed us to decompose the Green s function at a virtual receiver at depth in its downgoing and upgoing components. These wavefields were then used to create a ghostfree image of the medium with either crosscorrelation or multidimensional deconvolution, presenting an advantage over standard prestack migration. We tested the robustness of our approach when an erroneous background velocity model is used to estimate the firstarriving waves, which are a required input for the datadriven wavefield focusing process. We tested the new method with a numerical example based on a modification of the Amoco model.3multiples; migration; reciprocity; crosscorrelation)uuid:61ad5e42e10d470ca500382090e1bff5Dhttp://resolver.tudelft.nl/uuid:61ad5e42e10d470ca500382090e1bff5aTraditionally, the Marchenko equation forms a basis for 1D inverse scattering problems. A 3D extension of the Marchenko equation enables the retrieval of the Green s response to a virtual source in the subsurface from reflection measurements at the earth s surface. This constitutes an important step beyond seismic interferometry. Whereas seismic interferometry requires a receiver at the position of the virtual source, for the Marchenko scheme it suffices to have sources and receivers at the surface only. The underlying assumptions are that the medium is lossless and that an estimate of the direct arrivals of the Green s function is available. The Green s function retrieved with the 3D Marchenko scheme contains accurate internal multiples of the inhomogeneous subsurface. Using sourcereceiver reciprocity, the retrieved Green s function can be interpreted as the response to sources at the surface, observed by a virtual receiver in the subsurface. By decomposing the 3D Marchenko equation, the response at the virtual receiver can be decomposed into a downgoing field and an upgoing field. By deconvolving the retrieved upgoing field with the downgoing field, a reflection response is obtained, with virtual sources and virtual receivers in the subsurface. This redatumed reflection response is free of spurious events related to internal multiples in the overburden. The redatumed reflection response forms the basis for obtaining an image of a target zone. An important feature is that spurious reflections in the target zone are suppressed, without the need to resolve first the reflection properties of the overburden.!multiples; migration; reciprocity)uuid:c9d6af445c034d03b5b7a9895cc37864Dhttp://resolver.tudelft.nl/uuid:c9d6af445c034d03b5b7a9895cc37864hGreen's function retrieval from reflection data, in absence of a receiver at the virtual source positionThe methodology of Green s function retrieval by crosscorrelation has led to many interesting applications for passive and controlledsource acoustic measurements. In all applications, a virtual source is created at the position of a receiver. Here a method is discussed for Green s function retrieval from controlledsource reflection data, which circumvents the requirement of having an actual receiver at the position of the virtual source. The method requires, apart from the reflection data, an estimate of the direct arrival of the Green s function. A singlesided threedimensional (3D) Marchenko equation underlies the method. This equation relates the reflection response, measured at one side of the medium, to the scattering coda of a socalled focusing function. By iteratively solv< ing the 3D Marchenko equation, this scattering coda is retrieved from the reflection response. Once the scattering coda has been resolved, the Green s function (including all multiple scattering) can be constructed from the reflection response and the focusing function. The proposed methodology has interesting applications in acoustic imaging, properly accounting for internal multiple scattering.Acoustical Society of America
20141101)uuid:493d1089c8624cea96b2e4345cb41fe5Dhttp://resolver.tudelft.nl/uuid:493d1089c8624cea96b2e4345cb41fe5`Intersource seismic interferometry by multidimensional deconvolution (MDD) for borehole sources'Liu, Y.; Wapenaar, C.P.A.; Romdhane, A.Seismic interferometry (SI) is usually implemented by crosscorrelation (CC) to retrieve the impulse response between pairs of receiver positions. An alternative approach by multidimensional deconvolution (MDD) has been developed and shown in various studies the potential to suppress artifacts due to irregular source distribution and intrinsic loss. Following previous theories on SI by MDD, we extend it to retrieve the impulse response between pairs of source positions by invoking source and receiver reciprocity. We verify the theory using a simple twolayered model and show that the retrieved response by MDD is more accurate than that by CC, and furthermore, it is free of freesurface multiples. We discuss the necessary preprocessing required for this method. This intersource SI approach creates a virtual acquisition geometry with both borehole sources and receivers without the need to deploy receivers in the borehole, which might be of interest to applications such as seismic while drilling (SWD).@Chinese Petroleum Society / Society of Exploration Geophysicists)uuid:43c9747096cc474aa1eaf61685040f49Dhttp://resolver.tudelft.nl/uuid:43c9747096cc474aa1eaf61685040f49ODatadriven inversion of GPR surface reflection data for lossless layered mediaSlob, E.C.; Wapenaar, C.P.A._Two wavefields can be retrieved from the measured reflection response at the surface. One is the Green s function at a chosen virtual receiver depth level in a layered model generated by a source at the surface. The other wavefield consists of the upgoing and downgoing parts of a wavefield that focuses at the virtual receiver depth level. From the upgoing part of the focusing wavefield an image can be computed at oneway vertical travel time and with correct amplitudes of the local reflection coefficients as a function of incidence angle. These reflection coefficient values can be used to invert for electric permittivity and magnetic permeability. From these values and the known image times the layer thickness values can be obtained for each layer. This method renders the full waveform inversion problem for horizontally layered media a linear problem.!antenna; propagation; measurement0European Association on Antennas and Propagation)uuid:33dea67941a945b7953f987cdd26babdDhttp://resolver.tudelft.nl/uuid:33dea67941a945b7953f987cdd26babdPSeismic reflector imaging using internal multiples with Marchenkotype equations7Slob, E.C.; Wapenaar, C.P.A.; Broggini, F.; Snieder, R.{We present an imaging method that creates a map of reflection coefficients in correct oneway time with no contamination from internal multiples using purely a filtering approach. The filter is computed from the measured reflection response and does not require a background model. We demonstrate that the filter is a focusing wavefield that focuses inside a layered medium and removes all internal multiples between the surface and the focus depth. The reflection response and the focusing wavefield can then be used for retrieving virtual vertical seismic profile data, thereby redatuming the source to the focus depth. Deconvolving the upgoing by the downgoing vertical seismic profile data redatums the receiver to the focus depth and gives the desired image. We then show that, for oblique angles of incidence in horizontally layered media, the image of the same quality as for 1D waves can be constructed. This< step can be followed by a linear operation to determine velocity and density as a function of depth. Numerical simulations show the method can handle finite frequency bandwidth data and the effect of tunneling through thin layers.2imaging; reverse time migration; velocity analysis)uuid:8e10d71b962d47c18a88a00a02331765Dhttp://resolver.tudelft.nl/uuid:8e10d71b962d47c18a88a00a02331765/Marchenko redatuming below a complex overburdenComplex overburdens can severely distort transmitted wavefields, posing serious challenges for seismic imaging. In Marchenko redatuming, we use an iterative scheme to estimate socalled focusing functions, which can be used to redatum seismic wavefields to a specified level below the major complexities in the subsurface. Unlike in conventional redatuming methods, internal scattering in the overburden is accounted for by this methodology. Through Marchenko redatuming, internal multiple reflections are effectively utilized and common artefacts that are caused by these multiples are suppressed. The redatumed data can be interpreted as if it were acquired at the redatuming level and as if the medium above this level were nonreflecting. We provide an interpretation of the iterative scheme that is used for Marchenko redatuming and we evaluate its performance in a medium with a strongly heterogeneous overburden.KAUST)uuid:f17503749a254f81a5d5e99279aec31eDhttp://resolver.tudelft.nl/uuid:f17503749a254f81a5d5e99279aec31eeDatadriven Green's function retrieval and application to imaging with multidimensional deconvolution?Broggini, F.; Wapenaar, C.P.A.; Van der Neut, J.R.; Snieder, R.An iterative method is presented that allows one to retrieve the Green's function originating from a virtual source located inside a medium using reflection data measured only at the acquisition surface. In addition to the reflection response, an estimate of the travel times corresponding to the direct arrivals is required. However, no detailed information about the heterogeneities in the medium is needed. The iterative scheme generalizes the Marchenko equation for inverse scattering to the seismic reflection problem. To give insight in the mechanism of the iterative method, its steps for a simple layered medium are analyzed using physical arguments based on the stationary phase method. The retrieved Green's wavefield is shown to correctly contain the multiples due to the inhomogeneities present in the medium. Additionally, a variant of the iterative scheme enables decomposition of the retrieved wavefield into its downgoing and upgoing components. These wavefields then enable creation of a ghostfree image of the medium with either cross correlation or multidimensional deconvolution, presenting an advantage over standard prestack migration.Eautofocusing; Marchenko; scattering; interferometry; Green's function
20140717)uuid:192ce582153c4bd9961ab0a864b6ce22Dhttp://resolver.tudelft.nl/uuid:192ce582153c4bd9961ab0a864b6ce22_Estimating the location of a tunnel using correlation and inversion of Rayleigh wave scattering?Kasililar, A.; Harmankaya, U.; Wapenaar, C.P.A.; Draganov, D.S.
The investigation of nearsurface scatterers, such as cavities, tunnels, abandoned mine shafts, and buried objects, is important to mitigate geohazards and environmental hazards. By inversion of travel times of crosscorrelated scattered waves, due to the incident Rayleigh waves, we estimate the location of a nearsurface tunnel from seismic field data. The cross correlation eliminates the travel path between a source and a scatterer, thus eliminating the need to know the position of the source, making the estimation of the scatterers' locations dependent only on properties between the receivers and the scatterer. First time using a numerically verified method on seismic field data, we show the potential of the method for estimating the location of a buried scatterer.llocating scatterers; ghostscattered waves; seismic interferometry; Rayleigh waves; inversion; active source
20140610)uuid:c7f6428c08464d2584ea4090725836d3Dhtt< p://resolver.tudelft.nl/uuid:c7f6428c08464d2584ea4090725836d3
The investigation of nearsurface scatterers, such as cavities, tunnels, abandoned mine shafts, and buried objects, is important to mitigate geohazards and environmental hazards. By inversion of travel times of crosscorrelated scattered waves, due to the incident Rayleigh waves, we estimate the location of a nearsurface tunnel from seismic field data. The cross correlation eliminates the travel path between a source and a scatterer, thus eliminating the need to know the position of the source, making the estimation of the scatterers locations dependent only on properties between the receivers and the scatterer. First time using a numerically verified method on seismic field data, we show the potential of the method for estimating the location of a buried scatterer.)uuid:ed7d7c1645704c65a898aeda07de6b8cDhttp://resolver.tudelft.nl/uuid:ed7d7c1645704c65a898aeda07de6b8cfSurface wave retrieval in layered media using seismic interferometry by multidimensional deconvolution1Van Dalen, K.N.; Wapenaar, C.P.A.; Halliday, D.F.@Virtualsource surface wave responses can be retrieved using the crosscorrelation (CC) of wavefields observed at two receivers. Higher mode surface waves cannot be properly retrieved when there is a lack of subsurface sources that excite these wavefields, as is often the case. In this paper, we present a multidimensionaldeconvolution (MDD) scheme that is based on an approximate convolution theorem. The scheme introduces an additional processing step in which the CC result is deconvolved by a socalled pointspread tensor. The involved pointspread functions capture the imprint of the lack of subsurface sources and possible anelastic effects, and quantify the associated spatial and temporal smearing of the virtualsource components that leads to the poor surfacewave retrieval. The functions can be calculated from the same wavefields as used in the CC method. For a 2D example that is representative of the envisaged applications, we show that the deconvolution partially corrects for the smearing. The retrieved virtualsource response only has some amplitude error in the ideal situation of having the depth of the required vertical array equal to the depth penetration of the surface waves. The error is due to ignored crossmode terms in the approximate convolution theorem. Shorter arrays are also possible. In the limit case of only a single surface receiver, the retrieved virtualsource response is still more accurate than the CC result. The MDD scheme is valid for horizontally layered media that are laterally invariant, and includes exclusively multicomponent pointforce responses (rather than their spatial derivatives) and multicomponent observations. The improved retrieval of multimode surface waves can facilitate dispersion analyses in shallowsubsurface inversion problems and monitoring, and surface wave removal algorithms.Dinterferometry; surface waves and free oscillations; interface waves)uuid:5ac5be234fc04b2d9ec51b799e8944f1Dhttp://resolver.tudelft.nl/uuid:5ac5be234fc04b2d9ec51b799e8944f1KGreen's function retrieval with Marchenko equations: A sensitivity analysis5Thorbecke, J.W.; Van der Neut, J.R.; Wapenaar, C.P.A.=Recent research showed that the Marchenko equation can be used to construct the Green s function for a virtual source position in the subsurface. The method requires the reflection response at the surface and an estimate of the direct arrival of the wavefield, traveling from the virtual source location to the acquisition surface. In this paper, we investigate the sensitivity of this method. We demonstrate its robustness with respect to significant amplitude and phase errors in the direct arrival. The erroneous operators introduce low amplitude artefacts. The main reflections and internal multiples are still presents and disturbing ghost events are not introduced. In case the reflection data is modeled in a medium with losses, ghost events seem to be visible in the upgoing wavefield, but not in the downgoing wavefield.< <imaging; migration; multiples; decomposition; reconstruction)uuid:1f1bee172f4e4b7c916dc951f25339f6Dhttp://resolver.tudelft.nl/uuid:1f1bee172f4e4b7c916dc951f25339f6VCoupled Marchenko equations for electromagnetic Green s function retrieval and imagingRecently a new theory has been developed to retrieve a wavefield generated by a source on the surface and recorded at a point in the subsurface without the need for a receiver at that subsurface location. The scheme is presented for threedimensional wavefields. It decomposes the electromagnetic field in up and downgoing electric fields and in TE and TMmodes. Each mode can be treated separately to construct the Green s function. We derive two coupled Marchenko equations from which the up and downgoing Green s functions can be obtained. These two directional Green s functions have applications in trueamplitude subsurface imaging without effects from internal multiple reflections.GPR; imaging; reconstruction)uuid:586e95fbbfba4ca5907799de795a6415Dhttp://resolver.tudelft.nl/uuid:586e95fbbfba4ca5907799de795a6415AInterferometric reservoir monitoring with a single passive source5Almagro Vidal, C.; Van der Neut, J.; Wapenaar, C.P.A.+Changes in the subsurface can be imaged by subtracting seismic reflection data at two different states, one serving as the initial survey or base, and the second as the monitor survey. Conventionally, the reflection data are acquired by placing active seismic sources at the acquisition surface. Alternatively, these data can be acquired from passive sources in the subsurface, using seismic interferometry. Unfortunately, the reflection responses as retrieved by seismic interferometry inherit an imprint of the passive source distribution. Therefore, monitoring with seismic interferometry requires high passive source repeatability, which is often not achievable in practice. We propose an alternative, by using active seismic data for the base survey and a single passive source for the monitor survey. By constraining the radiation pattern of the (active) base survey according to the characteristics of the (passive) monitor survey, we succeed to extract timelapse response in the image domain. The proposed method is illustrated with numerically modeled data.1earthquake; imaging; monitoring; passive; seismic)uuid:020d09eaf8394a5a8e7f2a18f151e92eDhttp://resolver.tudelft.nl/uuid:020d09eaf8394a5a8e7f2a18f151e92eJInterferometric redatuming of autofocused primaries and internal multiplesZVan der Neut, J.; Slob, E.C.; Wapenaar, C.P.A.; Throbecke, J.W.; Snieder, R.; Broggini, F.Recently, an iterative scheme has been introduced to retrieve the down and upgoing Green's functions at an arbitrary level ?F inside an acoustic medium as if there were a source at the surface. This scheme requires as input the reflection response acquired at the surface and the direct arrival of the transmission response from the surface to level ?F. The source locations of these Green's functions can be effectively redatumed to level ?F by interferometric redatuming, which requires solving a multidimensional deconvolution problem, essentially being a Fredholm integral equation of the first kind. We show how this problem can be simplified by rewriting it as a Fredholm integral equation of the second kind that can be expanded as a Neumann series. Redatumed data can be used for multiplefree trueamplitude imaging at or in the vicinity of ?F. For imaging the closest reflector to ?F only, the Neumann series can be truncated at the first term without losing accuracy.*datuming; illumination; multiples; seismic)uuid:09ea03c7f34c4407804da37531037f2aDhttp://resolver.tudelft.nl/uuid:09ea03c7f34c4407804da37531037f2aDatadriven Green's function retrieval and imaging with multidimensional deconvolution: Numerical examples for reflection data with internal multiplesStandard imaging techniques rely on the single scattering assumption. This requires that the recorded data do not include internal multiples, i.e. waves bouncing multiple times between layers before reaching t< he receivers at the acquisition surface. When multiple reflections are present in the data, standard imaging algorithms incorrectly image them as ghost reflectors. These artifacts can mislead the interpreters in locating potential hydrocarbon reservoirs. Recently, we introduced a new approach for retrieving the Greens function recorded at the acquisition surface due to a virtual source located at depth. Additionally, our approach allows us to decompose the Green's function in its downgoing and upgoing components. These wave fields are then used to create a ghostfree image of the medium with either crosscorrelation or multidimensional deconvolution, presenting an advantage over standard prestack migration. We illustrate the new method with a numerical example based on a modification of the Amoco model.acoustic; migration; multiples)uuid:337306c14ad949a090debed90539994aDhttp://resolver.tudelft.nl/uuid:337306c14ad949a090debed90539994acThreedimensional Marchenko equation for Green's function retrieval beyond seismic interferometry ZWapenaar, C.P.A.; Slob, E.C.; Van der Neut, J.; Thorbecke, J.W.; Broggini, F.; Snieder, R.tIn recent work we showed with heuristic arguments that the Green's response to a virtual source in the subsurface can be obtained from reflection data at the surface. This method is called Green's function retrieval beyond seismic interferometry , because, unlike in seismic interferometry, no receiver is needed at the position of the virtual source. Here we present a formal derivation of Green's function retrieval beyond seismic interferometry, based on a 3D extension of the Marchenko equation. We illustrate the theory with a numerical example and indicate the potential applications in seismic imaging and AVA analysis.3multiples; reciprocity; wave equation; reversetime)uuid:3f9194dc95ba47998feb2edfc3e8d512Dhttp://resolver.tudelft.nl/uuid:3f9194dc95ba47998feb2edfc3e8d512WInfrasonic interferometry of stratospherically refracted microbaroms: A numerical studyYFricke, J.T.; El Allouche, N.; Simons, D.G.; Ruigrok, E.N.; Wapenaar, C.P.A.; Evers, L.G.The atmospheric wind and temperature can be estimated through the traveltimes of infrasound between pairs of receivers. The traveltimes can be obtained by infrasonic interferometry. In this study, the theory of infrasonic interferometry is verified and applied to modeled stratospherically refracted waves. Synthetic barograms are generated using a raytracing model and taking into account atmospheric attenuation, geometrical spreading, and phase shifts due to caustics. Two types of source wavelets are implemented for the experiments: blast waves and microbaroms. In both numerical experiments, the traveltimes between the receivers are accurately retrieved by applying interferometry to the synthetic barograms. It is shown that microbaroms can be used in practice to obtain the traveltimes of infrasound through the stratosphere, which forms the basis for retrieving the wind and temperature profiles.
20140401Aerospace EngineeringControl & Operations)uuid:9034f45965bf45fe9ea236e499de1803Dhttp://resolver.tudelft.nl/uuid:9034f45965bf45fe9ea236e499de1803USeismic exploration?scale velocities and structure from ambient seismic noise (>1?Hz)JDraganov, D.S.; Campman, X.; Thorbecke, J.W.; Verdel, A.; Wapenaar, C.P.A.The successful surface waves retrieval in solid?Earth seismology using long?time correlations and subsequent tomographic images of the crust have sparked interest in extraction of subsurface information from noise in the exploration seismology. Subsurface information in exploration seismology is usually derived from body?wave reflections >?1?Hz, which is challenging for utilization of ambient noise. We use 11?h of noise recorded in the Sirte basin, Libya. First, we study the characteristics of the noise. We show that the bulk of the noise is composed of surface waves at frequencies below 6?Hz. Some noise panels contain nearly vertically traveling events. We further characterize these events using a beamforming algorithm. From the beamforming,< we conclude that these events represent body?wave arrivals with a fairly rich azimuthal distribution. Having body?wave arrivals in the noise is a prerequisite for body?wave reflections retrieval. We crosscorrelate and sum the recorded ambient?noise panels to retrieve common?source gathers, following two approaches using all the noise and using only noise panels containing body?wave arrivals likely to contribute to the reflections retrieval. Comparing the retrieved gathers with active seismic data, we show that the two?way traveltimes at short offsets of several retrieved events coincide with those of reflections in the active data and thus correspond to apexes of reflections. We then compare retrieved stacked sections of the subsurface from both approaches with the active?data stacked section and show that the reflectors are consistent along a line. The results from the second approach exhibit the reflectors better.Aseismic noise; crosscorrelation; imaging; body waves; reflections
20140228)uuid:f9f4a01995374040b1d54c33a2093c18Dhttp://resolver.tudelft.nl/uuid:f9f4a01995374040b1d54c33a2093c18ODatadriven green's function retrieval from reflection data: Theory and example\Wapenaar, C.P.A.; Slob, E.C.; Broggini, F.; Snieder, R.; Thorbecke, J.W.; Van der Neut, J.R.Recently we introduced a new approach for retrieving the Green's response to a virtual source in the subsurface from reflection data at the surface. Unlike in seismic interferometry, no receiver is needed at the position of the virtual source. Here we present the theory behind this new method. First we introduce the Green's function G and a socalled fundamental solution F of an inhomogeneous medium. Next we derive a relation between G and F, using reciprocity theorems. This relation is used as the basis for deriving a 3D singlesided Marchenko equation. We show that this equation is solved by a 3D autofocusing scheme and that the Green's function is obtained by combining the focusing wave field and its response in a specific way. We illustrate the method with a numerical example.Eage)uuid:b7664c488b2a4ca79cc12fab32183a87Dhttp://resolver.tudelft.nl/uuid:b7664c488b2a4ca79cc12fab32183a87iTurning Onesided Illumination into Twosided Illumination by Targetenclosing Interferometric RedatumingCVan der Neut, J.R.; Almagro Vidal, C.; Grobbe, N.; Wapenaar, C.P.A.We present a novel method to transform seismic data with sources at the surface and receivers above and below a selected target zone in the subsurface into virtual data with sources and receivers located at the initial receiver locations. The method is based on inverting a series of multidimensional equations of the convolution and the correlationtype. The required input data can be computed from surface seismic data with a new iterative scheme that is currently being developed. The output data contains virtual sources that illuminate the target not only from above (as in the original data), but also from below, facilitating the needs of seismic imaging and inversion in an optimal way. The method is nonlinear in the sense that all internal multiples are correctly accounted for and true amplitude in the sense that the virtual sources are forced to inherit uniform radiation patterns even though the overburden is strongly heterogeneous.)uuid:f752f3d45f5249e6a3095786f58dfae8Dhttp://resolver.tudelft.nl/uuid:f752f3d45f5249e6a3095786f58dfae8s3D Marine CSEM Interferometry by Multidimensional Deconvolution in the Wavenumber Domain for a Sparse Receiver GridBHunziker, J.W.; Slob, E.C.; Fan, Y.; Snieder, R.; Wapenaar, C.P.A.We use interferometry by multidimensional deconvolution in combination with synthetic aperture sources in 3D to suppress the airwave and the direct field, and to decrease source uncertainty in marine ControlledSource electromagnetics. We show with this numerical study that the method works for very large receiver spacing distances, even though the thereby retrieved reflection response may be aliased.)uuid:d5828eb0cde34ab5adcc07168d34c45eDhttp://resolver.tudelft.nl/uuid:d582< 8eb0cde34ab5adcc07168d34c45eVLocating scatterers by nonphysical scattered waves obtained by seismic interferometryOHarmankaya, U.; Kaslilar, A.; Thorbecke, J.W.; Wapenaar, C.P.A.; Draganov, D.S.~The investigation and detection of nearsurface structures (such as cavities, caves, sinkholes, tunnels, mineshafts, buried objects, archeological ruins, water reservoir, etc.) is important to mitigate geo and environmental hazards. In a former study, we suggested a method based on activesource seismic interferometry for locating the scatterers and we showed the applicability of the method in a simple model. In our method, we use only one source at the surface and nonphysical scattered waves retrieved by seismic interferometry to estimate the location of the scatterer. In this paper, we show the effectiveness of the method in case of lateral variations. We use both scattered body and surface waves to estimate the location of a corner diffractor and a scatterer, respectively, and we obtain very good estimations. The method is promising for nearsurface seismic field applications.)uuid:757ea06c40064a60a03d31388da7a94dDhttp://resolver.tudelft.nl/uuid:757ea06c40064a60a03d31388da7a94dcRetrieving highermode surface waves using seismic interferometry by multidimensional deconvolutionxVirtualsource surfacewave responses can be retrieved using the crosscorrelation of wavefields observed at two receivers. Highermode surface waves cannot be properly retrieved when there is a lack of subsurface sources, which is often the case. In this paper, we present a multidimensionaldeconvolution scheme that introduces an additional processing step in which the crosscorrelation result is deconvolved by a pointspread function. The scheme is based on an approximate convolution theorem that includes pointforce responses only, which is advantageous for applications with contemporary fieldacquisition geometries. The pointspread function captures the imprint of the lack of subsurface sources and quantifies the associated smearing of the virtual source in space and time. The function can be calculated from the same wavefields used in the correlation method, provided that one or more vertical arrays of subsurface receivers are present and the illumination is from one side. We show that the retrieved surfacewave response, including the higher modes, becomes much more accurate. The waveforms are properly reconstructed and there is only a small amplitude error, which is due to noncanceling cross terms in the employed approximate convolution theorem. The improved retrieval of the multimode surface waves can facilitate dispersion analyses and nearsurface inversion algorithms.)uuid:b67674f6c10f48158a44a746b9510521Dhttp://resolver.tudelft.nl/uuid:b67674f6c10f48158a44a746b9510521oCreating the green's response to a virtual source inside a medium using reflection data with internal multiples<Broggini, F.; Snieder, R.; Wapenaar, C.P.A.; Thorbecke, J.W.ZSeismic interferometry is a technique that allows one to reconstruct the full wavefield originating from a virtual source inside a medium, assuming a receiver is present at the virtual source location. We discuss a method that creates a virtual source inside a medium from reflection data measured at the surface, without needing a receiver inside the medium and, hence, presenting an advantage over seismic interferometry. An estimate of the direct arriving wavefront is required in addition to the reflection data. However, no information about the medium is needed. We illustrate the method with numerical examples in a lossless acoustic medium with laterallyvarying velocity and density. We examine the reconstructed wavefield when a macro model is used to estimate the direct arrivals and we take into consideration finite acquisition aperture. Additionally, a variant of the iterative scheme allows us to decompose the reconstructed wave field into downgoing and upgoing fields. These wave fields are then used to create an image of the medium with either crosscorrelation or multidimensional deconvolution.< )uuid:c6380fc3f2f4484cae6ed11c499990c5Dhttp://resolver.tudelft.nl/uuid:c6380fc3f2f4484cae6ed11c499990c5QElectromagnetic interferometry in wavenumber and space domains in a layered earthWith interferometry applied to controlledsource electromagnetic data, the direct field and the airwave and all other effects related to the airwater interface can be suppressed in a datadriven way. Interferometry allows for retreival of the scattered field Green s function of the subsurface or, in other words, the subsurface reflection response. This reflection response can then be further used to invert for the subsurface conductivity distribution. To perform interferometry in 3D, measurements on an areal grid are necessary. We discuss 3D interferometry by multidimensional deconvolution in the frequencywavenumber and in the frequencyspace domains and provide examples for a layered earth model. We use the synthetic aperture source concept to damp the signal at high wavenumbers to allow large receiver sampling distances. Interferometry indeed increases the detectability of a subsurface reservoir. Finally, we discuss the dependency of the accuracy of the retrieved reflection response on the two crucial parameters: the conductivity of the seabed at the receiver location and the stabilization parameter of the leastsquares inversion.+electromagnetics; 3D; deconvolution; marine)uuid:9bccad08b39248a1972efe68e4f7eba9Dhttp://resolver.tudelft.nl/uuid:9bccad08b39248a1972efe68e4f7eba9ThreeDimensional SingleSided Marchenko Inverse Scattering, DataDriven Focusing, Green s Function Retrieval, and their Mutual Relations7Wapenaar, C.P.A.; Broggini, F.; Slob, E.C.; Snieder, R.The onedimensional Marchenko equation forms the basis for inverse scattering problems in which the scattering object is accessible from one side only. Here we derive a threedimensional (3D) Marchenko equation which relates the singlesided reflection response of a 3D inhomogeneous medium to a field inside the medium. We show that this equation is solved by a 3D iterative datadriven focusing method, which yields the 3D Green s function with its virtual source inside the medium. The 3D singlesided Marchenko equation and its iterative solution method form the basis for imaging of 3D strongly scattering inhomogeneous media that are accessible from one side only.)uuid:52a36d7411354cf6b843b5ce2acef15aDhttp://resolver.tudelft.nl/uuid:52a36d7411354cf6b843b5ce2acef15aLOn the Retrieval of the Directional Scattering Matrix from Directional Noise!Wapenaar, C.P.A.; Thorbecke, J.W.The crosscorrelation of ambient acoustic noise observed at two receivers yields the impulse response between these receivers, assuming that the noise field is diffuse. In practical situations the noise field exhibits directionality, which imprints the angledependent correlation function. For the situation of a directional scatterer in a directional noise field, the correlation function contains the product of the directional scattering matrix and the directional noise. This seemingly underdetermined problem can be resolved by exploiting a relation between the causal and acausal parts of the correlation function. For a given pair of receivers, the causal and acausal parts of the correlation function contain the same element of the scattering matrix (by reciprocity) but different elements of the directional noise field. This property can be used to estimate the directionality of the noise (apart from an undetermined scaling factor) and, subsequently, of the scattering matrix1scattering matrix; optical theorem; ambient noise5Society for Industrial and Applied Mathematics (SIAM))uuid:f911ba40d51042c8a6bfd64527330d67Dhttp://resolver.tudelft.nl/uuid:f911ba40d51042c8a6bfd64527330d67.Seismic interferometry by midpoint integration2Ruigrok, E.N.; Almagro Vidal, C.; Wapenaar, C.P.A.With seismic interferometry reflections can be retrieved between station positions. In the classical form, the reflections are retrieved by an integration over sources. For a specific dataset, however, the actu< al source distribution might not be sufficient to approximate the source integral. Yet, there might be a dense distribution of receivers allowing integration over the receiver domain. We rewrite the source integral to an integration over midpoints. With this formulation, a reflection can be retrieved even in the limiting case of only a single source. However, with respect to the classical formulation, an additional stationaryphase analysis is required.&Deutsche Geophysikalische Gesellschaft)uuid:fe7e739e0f194a77ba516273e92ba199Dhttp://resolver.tudelft.nl/uuid:fe7e739e0f194a77ba516273e92ba199QFocusing the wavefield inside an unknown 1D medium: Beyond seismic interferometryWith seismic interferometry one can retrieve the response to a virtual source inside an unknown medium, if there is a receiver at the position of the virtual source. Using inverse scattering theory, we demonstrate that, for a 1D medium, the requirement of having an actual receiver inside the medium can be circumvented, going beyond seismic interferometry. In this case, the wavefield can be focused inside an unknown medium with independent variations in velocity and density using reflection data only.)uuid:3cc6b08fa7e1443a8c1d67b461eb915aDhttp://resolver.tudelft.nl/uuid:3cc6b08fa7e1443a8c1d67b461eb915a]Globalphase seismic interferometry unveils Pwave reflectivity below the Himalayas and TibetRuigrok, E.N.; Wapenaar, C.P.A.A number of seismic methods exist to image the lithosphere below a collection of receivers, using distant earthquakes. In the current practice, especially modeconversions in teleseismic phases are utilized. We present a new method that takes advantage of the availability of global phases. This method is called globalphase seismic interferometry (GloPSI). With GloPSI, zerooffset reflections are extracted from reverberations near the array caused by global seismicity. We exemplify GloPSI with data from the HiCLIMB experiment (2002 2005) and migrate the obtained reflection responses. This results in a 800 km long reflectivity profile through the Himalayas and a large part of the Tibetan Plateau.
20121205)uuid:aa01d8e7778248c18552c97bbfdbee67Dhttp://resolver.tudelft.nl/uuid:aa01d8e7778248c18552c97bbfdbee67LSynthesized 2D CSEMinterferometry Using Automatic Source Line Determination=Interferometry by multidimensional deconvolution applied to ControlledSource Electromagnetic data replaces the medium above the receivers by a homogeneous halfspace, suppresses the direct field and redatums the source positions to the receiver locations. In that sense, the airwave and any other interactions of the signal with the airwater interface and the water layer are suppressed and the source uncertainty is reduced. Interferometry requires grid data and cannot be applied to line data unless the source is infinitely long in the crossline direction. To create such a source, a set of source lines is required. We use an iterative algorithm to determine the optimal locations of these source lines and show that more source lines are required if the source is towed closer to the sea bottom and closer to the receivers.)uuid:be874ea3215143d9b4f659dbd459e091Dhttp://resolver.tudelft.nl/uuid:be874ea3215143d9b4f659dbd459e091ZEstimating the Location of Scatterers by Seismic Interferometry of Scattered Surface Waves/In this study, nonphysical (ghost) scattered surface waves are used to obtain the location of a near surface scatterer. The ghost is obtained from application of seismic interferometry to only one source at the surface. Different locations for virtual sources are chosen and ghost scattered surface waves for each of these virtualsource locations are retrieved. The retrieved ghost traveltimes are inverted by solving the inverse problem to determine the location of the scatterer. It is seen that the location of the scatterer is reasonably well estimated.)uuid:569fa57fbd3f4e269c74f544326125bdDhttp://resolver.tudelft.nl/uuid:569fa57fbd3f4e269c74f544326125bdwCreating Virtual Sources Inside an Unknown Medium from Refl< ection Data: A New Approach to Internal Multiple EliminationPWapenaar, C.P.A.; Thorbecke, J.W.; Van der Neut, J.R.; Broggini, F.; Snieder, R.nIt has recently been shown that the response to a virtual source in the subsurface can be derived from reflection data at the surface and an estimate of the direct arrivals between the virtual source and the surface. Hence, unlike for seismic interferometry, no receivers are needed inside the medium. This new method recovers the complete wavefield of a virtual source, including all internal multiple scattering. Because no actual receivers are needed in the medium, the virtual source can be placed anywhere in the subsurface. With some additional processing steps (decomposition and multidimensional deconvolution) it is possible to obtain a redatumed reflection response at any depth level in the subsurface, from which all the overburden effects are eliminated. By applying standard migration between these depth levels, a true amplitude image of the subsurface can be obtained, free from ghosts due to internal multiples. The method is nonrecursive and therefore does not suffer from error propagation. Moreover, the internal multiples are eliminated by deconvolution, hence no adaptive prediction and subtraction is required.)uuid:5f224a8069d040bf8cee7ee22d89afffDhttp://resolver.tudelft.nl/uuid:5f224a8069d040bf8cee7ee22d89afff>A unified optical theorem for scalar and vectorial wave fieldsWapenaar, C.P.A.; Douma, H.The generalized optical theorem is an integral relation for the angledependent scattering amplitude of an inhomogeneous scattering object embedded in a homogeneous background. It has been derived separately for several scalar and vectorial wave phenomena. Here a unified optical theorem is derived that encompasses the separate versions for scalar and vectorial waves. Moreover, this unified theorem also holds for scattering by anisotropic elastic and piezoelectric scatterers as well as bianisotropic (nonreciprocal) EM scatterers.=acoustic field; acoustic wave scattering; inhomogeneous media
20121130)uuid:419c882f51cc4723af404ef71fd4b3cdDhttp://resolver.tudelft.nl/uuid:419c882f51cc4723af404ef71fd4b3cdDeblending by direct inversion5Wapenaar, C.P.A.; Van der Neut, J.R.; Thorbecke, J.W.>Deblending of simultaneoussource data is usually considered to be an underdetermined inverse problem, which can be solved by an iterative procedure, assuming additional constraints like sparsity and coherency. By exploiting the fact that seismic data are spatially bandlimited, deblending of densely sampled sources can be carried out as a direct inversion process without imposing these constraints. We applied the method with numerically modeled data and it suppressed the crosstalk well, when the blended data consisted of responses to adjacent, densely sampled sourcesacquisition; inversion)uuid:e23dede0cc57464ead4277b49a1bb6e1Dhttp://resolver.tudelft.nl/uuid:e23dede0cc57464ead4277b49a1bb6e11Extraction of Pwave reflections from microseisms(Ruigrok, E.N.; Campman, X.; Wapenaar, K.DThe last few years there has been a growing number of bodywave observations in noise records. In 1973 Vinnik conjectured that Pwaves would even be the dominant wavemode, at epicentral distances of about 40 degrees and onwards from an oceanic source. At arrays far from offshore storms, surface waves induced by nearby storms would not mask the bodywave signal and hence primarily Pwaves would be recorded. We measured at such an array in Egypt and indeed found a large proportion of Pwaves. At the same time, a new methodology is under development to characterize the lithosphere below an array of receivers, without active sources or local earthquakes. Instead, transmitted waves are used which are caused by distant sources. These sources may either be transient or more stationary. With this new methodology, called seismic interferometry, reflection responses are extracted from the coda of transmissions. Combining the two developments it is clear that there is a large potential for obtaining reflection re< sponses from lowfrequency noise. A potential practical advantage of using noise instead of earthquake responses would be that an array only needs to be deployed for a few days or weeks instead of months, to gather enough illumination. We used a few days of continuous noise, recorded with an array in the Abu Gharadig basin, Egypt. We split up the record in three distinct frequency bands and in many small time windows. Using array techniques and taking advantage of all threecomponent recordings we could unravel the dominant wavemodes arriving in each time window and in each frequency band. The recorded wavemodes, and hence the noise sources, varied significantly per frequency band, and to a lesser extent per time window. Primarily Pwaves were detected on the vertical component for two of the three frequency bands. For these frequency bands, we only selected the time windows with a favorable illumination. By subsequently applying seismic interferometry, we retrieved Pwave reflection responses and delineated reflectors in the crust, the Moho and possibly the Lehmann discontinuity.Bbody waves; interferometry; ambient noise; microseism; lithosphereElsevier
Geotechnology)uuid:55fabcd8043548baaba0a0bad1e05033Dhttp://resolver.tudelft.nl/uuid:55fabcd8043548baaba0a0bad1e05033tControlledsource interferometric redatuming by crosscorrelation and multidimensional deconvolution in elastic mediaLVan der Neut, J.R.; Thorbecke, J.W.; Mehta, K.; Slob, E.C.; Wapenaar, C.P.A.{Various researchers have shown that accurate redatuming of controlled seismic sources to downhole receiver locations can be achieved without requiring a velocity model. By placing receivers in a horizontal or deviated well and turning them into virtual sources, accurate images can be obtained even below a complex nearsubsurface. Examples include controlledsource interferometry and the virtualsource method, both based on crosscorrelated signals at two downhole receiver locations, stacked over source locations at the surface. Because the required redatuming operators are taken directly from the data, even multiple scattered waveforms can be focused at the virtualsource location, and accurate redatuming can be achieved. To reach such precision in a solid earth, representations for elastic wave propagation that require multicomponent sources and receivers must be implemented. Wavefield decomposition prior to crosscorrelation allows us to enforce virtual sources to radiate only downward or only upward. Virtualsource focusing and undesired multiples from the overburden can be diagnosed with the interferometric pointspread function (PSF), which can be obtained directly from the data if an array of subsurface receivers is deployed. The quality of retrieved responses can be improved by filtering with the inverse of the PSF, a methodology referred to as multidimensional deconvolution.acoustic wave interferometry; correlation methods; deconvolution; filtering theory; geophysical signal processing; geophysical techniques; seismic waves; seismology)uuid:5aee14ca5e054fec9138dc6f306c1b7cDhttp://resolver.tudelft.nl/uuid:5aee14ca5e054fec9138dc6f306c1b7cRDeghosting, demultiple, and deblurring in controlledsource seismic interferometryOVan der Neut, J.R.; Tatanova, M.; Thorbecke, J.W.; Slob, E.C.; Wapenaar, C.P.A.With controlledsource seismic interferometry we aim to redatum sources to downhole receiver locations without requiring a velocity model. Interferometry is generally based on a source integral over crosscorrelation (CC) pairs of full, perturbed (timegated), or decomposed wavefields. We provide an overview of ghosts, multiples, and spatial blurring effects that can occur for different types of interferometry. We show that replacing crosscorrelation by multidimensional deconvolution (MDD) can deghost, demultiple, and deblur retrieved data. We derive and analyze MDD for perturbed and decomposed wavefields. An interferometric point spread function (PSF) is introduced that can be obtained directly from downhole data. Ghosts, multiples, and blurring effects < that may populate the retrieved gathers can be locally diagnosed with the PSF. MDD of perturbed fields can remove ghosts and deblur retrieved data, but it leaves particular multiples in place. To remove all overburdenrelated effects, MDD of decomposed fields should be applied.Hindawi Publishing Corporation)uuid:db579f8a3b144c1e949ed63f883cca2eDhttp://resolver.tudelft.nl/uuid:db579f8a3b144c1e949ed63f883cca2e]Improved surface?wave retrieval from ambient seismic noise by multi?dimensional deconvolutionCWapenaar, C.P.A.; Ruigrok, E.N.; Van der Neut, J.R.; Draganov, D.S.The methodology of surface?wave retrieval from ambient seismic noise by crosscorrelation relies on the assumption that the noise field is equipartitioned. Deviations from equipartitioning degrade the accuracy of the retrieved surface?wave Green's function. A point?spread function, derived from the same ambient noise field, quantifies the smearing in space and time of the virtual source of the Green's function. By multidimensionally deconvolving the retrieved Green's function by the point?spread function, the virtual source becomes better focussed in space and time and hence the accuracy of the retrieved surface?wave Green's function may improve significantly. We illustrate this at the hand of a numerical example and discuss the advantages and limitations of this new methodology.Green's function; ambient noise; surface wave)uuid:c4772e2ccaae4123b4afc462f23f3489Dhttp://resolver.tudelft.nl/uuid:c4772e2ccaae4123b4afc462f23f3489Seismic interferometry using multidimensional deconvolution and crosscorrelation for crosswell seismic reflection data without borehole sourcesUMinato, S.; Matsuoka, T.; Tsuji, T.; Draganov, D.S.; Hunziker, J.W.; Wapenaar, C.P.A.Crosswell reflection method is a highresolution seismic imaging method that uses recordings between boreholes. The need for downhole sources is a restrictive factor in its application, for example, to timelapse surveys. An alternative is to use surface sources in combination with seismic interferometry. Seismic interferometry (SI) could retrieve the reflection response at one of the boreholes as if from a source inside the other borehole. We investigate the applicability of SI for the retrieval of the reflection response between two boreholes using numerically modeled field data. We compare two SI approaches crosscorrelation (CC) and multidimensional deconvolution (MDD). SI by MDD is less sensitive to underillumination from the source distribution, but requires inversion of the recordings at one of the receiver arrays from all the available sources. We find that the inversion problem is illposed, and propose to stabilize it using singularvalue decomposition. The results show that the reflections from deep boundaries are retrieved very well using both the CC and MDD methods. Furthermore, the MDD results exhibit more realistic amplitudes than those from the CC method for downgoing reflections from shallow boundaries. We find that the results retrieved from the application of both methods to field data agree well with crosswell seismicreflection data using borehole sources and with the logged Pwave velocity.Ageophysical techniques; interferometry; seismic waves; seismology)uuid:c43b79fe17134fdca310ee70325cfaffDhttp://resolver.tudelft.nl/uuid:c43b79fe17134fdca310ee70325cfaffHighresolution reservoir characterization by an acoustic impedance inversion of a Tertiary deltaic clinoform system in the North Sea>Tetyukhina, D.; Van Vliet, L.J.; Luthi, S.M.; Wapenaar, C.P.A.IFluviodeltaic sedimentary systems are of great interest for explorationists because they can form prolific hydrocarbon plays. However, they are also among the most complex and heterogeneous ones encountered in the subsurface, and potential reservoir units are often close to or below seismic resolution. For seismic inversion, it is therefore important to integrate the seismic data with higher resolution constraints obtained from well logs, whereby not only the acoustic properties are used but also the detailed layering charac< teristics. We have applied two inversion approaches for poststack, timemigrated seismic data to a clinoform sequence in the North Sea. Both methods are recursive tracebased techniques that use well data as a priori constraints but differ in the way they incorporate structural information. One method uses a discrete layer model from the well that is propagated laterally along the clinoform layers, which are modeled as sigmoids. The second method uses a constant sampling rate from the well data and uses horizontal and vertical regularization parameters for lateral propagation. The first method has a low level of parameterization embedded in a geologic framework and is computationally fast. The second method has a much higher degree of parameterization but is flexible enough to detect deviations in the geologic settings of the reservoir; however, there is no explicit geologic significance and the method is computationally much less efficient. Forward seismic modeling of the two inversion results indicates a good match of both methods with the actual seismic data.Ngeology; geophysical techniques; hydrocarbon reservoirs; sediments; seismology)uuid:7b865e3f1f3b4225b3d697d5f4fca724Dhttp://resolver.tudelft.nl/uuid:7b865e3f1f3b4225b3d697d5f4fca724QA representation for Green s function retrieval by multidimensional deconvolution$Wapenaar, C.P.A.; Van der Neut, J.R.Green s function retrieval by crosscorrelation may suffer from irregularities in the source distribution, asymmetric illumination, intrinsic losses, etc. Multidimensional deconvolution (MDD) may overcome these limitations. A unified representation for Green s function retrieval by MDD is proposed. From this representation, it follows that the traditional crosscorrelation method gives a Green s function of which the source is smeared in space and time. This smearing is quantified by a space time pointspread function (PSF), which can be retrieved from measurements at an array of receivers. MDD removes this PSF and thus deblurs and deghosts the source of the Green s function obtained by correlation.)uuid:bffc466e307347c0a35d32c6366ae2bfDhttp://resolver.tudelft.nl/uuid:bffc466e307347c0a35d32c6366ae2bf@Highresolution lithospheric imaging with seismic interferometry8Ruigrok, E.N.; Campman, X.; Draganov, D.S.; Wapenaar, K.In recent years, there has been an increase in the deployment of relatively dense arrays of seismic stations. The availability of spatially densely sampled global and regional seismic data has stimulated the adoption of industrystyle imaging algorithms applied to converted and scatteredwave energy from distant earthquakes, leading to relatively highresolution images of the lower crust and upper mantle.We use seismic interferometry to extract reflection responses from the coda of transmitted energy from distant earthquakes. In theory, higher resolution images can be obtained when migrating reflections obtained with seismic interferometry rather than with conversions, traditionally used in lithospheric imaging methods. Moreover, reflection data allow the straightforward application of algorithms previously developed in exploration seismology. In particular, the availability of reflection data allows us to extract from it a velocity model using standard multichannel dataprocessing methods. However, the success of our approach relies mainly on a favourable distribution of earthquakes. In this paper, we investigate how the quality of the reflection response obtained with interferometry is influenced by the distribution of earthquakes and the complexity of the transmitted wavefields. Our analysis shows that a reasonable reflection response could be extracted if (1) the array is approximately aligned with an active zone of earthquakes, (2) different phase responses are used to gather adequate angular illumination of the array and (3) the illumination directions are properly accounted for during processing. We illustrate our analysis using a synthetic data set with similar illumination and sourceside reverberation characteristics as field data record< ed during the 2000 2001 Laramie broadband experiment. Finally, we apply our method to the Laramie data, retrieving reflection data. We extract a 2D velocity model from the reflections and use this model to migrate the data. On the final reflectivity image, we observe a discontinuity in the reflections. We interpret this discontinuity as the Cheyenne Belt, a suture zone between Archean and Proterozoic terranes.9seismology; interferometry; body waves; crustal structureWileyBlackwell)uuid:a751046354464a49a8fc81f44db1d984Dhttp://resolver.tudelft.nl/uuid:a751046354464a49a8fc81f44db1d984NTutorial on seismic interferometry: Part 1 Basic principles and applicationsFWapenaar, C.P.A.; Draganov, D.S.; Snieder, R.; Campman, X.; Verdel, A.Seismic interferometry involves the crosscorrelation of responses at different receivers to obtain the Green's function between these receivers. For the simple situation of an impulsive plane wave propagating along the xaxis, the crosscorrelation of the responses at two receivers along the xaxis gives the Green's function of the direct wave between these receivers. When the source function of the plane wave is a transient (as in exploration seismology) or a noise signal (as in passive seismology), then the crosscorrelation gives the Green's function, convolved with the autocorrelation of the source function. Directwave interferometry also holds for 2D and 3D situations, assuming the receivers are surrounded by a uniform distribution of sources. In this case, the main contributions to the retrieved direct wave between the receivers come from sources in Fresnel zones around stationary points. The main application of directwave interferometry is theretrieval of seismic surfacewave responses from ambient noise and the subsequent tomographic determination of the surfacewave velocity distribution of the subsurface. Seismic interferometry is not restricted to retrieving direct waves between receivers. In a classic paper, Claerbout shows that the autocorrelation of the transmission response of a layered medium gives the planewave reflection response of that medium. This is essentially 1D reflectedwave interferometry. Similarly, the crosscorrelation of the transmission responses, observed at two receivers, of an arbitrary inhomogeneous medium gives the 3D reflection response of that medium. One of the main applications of reflectedwave interferometry is retrieving the seismic reflection response from ambient noise and imaging of the reflectors in the subsurface. A common aspect of direct and reflectedwave interferometry is that virtual sources are created at positions where there are only receivers without requiring knowledge of the subsurface medium parameters or of the positions of the actual sources.[geophysical techniques; Green's function methods; interferometry; seismic waves; seismology)uuid:07504f32d9fb46b98095dcfa5b3e817bDhttp://resolver.tudelft.nl/uuid:07504f32d9fb46b98095dcfa5b3e817bOTutorial on seismic interferometry: Part 2 Underlying theory and new advances5Wapenaar, C.P.A.; Slob, E.C.; Snieder, R.; Curtis, A.`In the 1990s, the method of timereversed acoustics was developed. This method exploits the fact that the acoustic wave equation for a lossless medium is invariant for time reversal. When ultrasonic responses recorded by piezoelectric transducers are reversed in time and fed simultaneously as source signals to the transducers, they focus at the position of the original source, even when the medium is very complex. In seismic interferometry the timereversed responses are not physically sent into the earth, but they are convolved with other measured responses. The effect is essentially the same: The timereversed signals focus and create a virtual source which radiates waves into the medium that are subsequently recorded by receivers. A mathematical derivation, based on reciprocity theory, formalizes this principle: The crosscorrelation of responses at two receivers, integrated over different sources, gives the Green's function emitted by a virtual source at the< position of one of the receivers and observed by the other receiver. This Green's function representation for seismic interferometry is based on the assumption that the medium is lossless and nonmoving. Recent developments, circumventing these assumptions, include interferometric representations for attenuating and/or moving media, as well as unified representations for waves and diffusion phenomena, bending waves, quantum mechanical scattering, potential fields, elastodynamic, electromagnetic, poroelastic, and electroseismic waves. Significant improvements in the quality of the retrieved Green's functions have been obtained with interferometry by deconvolution. A tracebytrace deconvolution process compensates for complex source functions and the attenuation of the medium. Interferometry by multidimensional deconvolution also compensates for the effects of onesided and/or irregular illumination.jdeconvolution; geophysical techniques; Green's function methods; interferometry; seismic waves; seismology)uuid:82033a1584024b47b7ae733b3a1f03acDhttp://resolver.tudelft.nl/uuid:82033a1584024b47b7ae733b3a1f03acNReciprocity Theorems for OneWay Wave Fields in Curvilinear Coordinate SystemsFrijlink, M.; Wapenaar, C.P.A.Oneway wave equations conveniently describe wave propagation in media with discontinuous and/or rapid variations in one direction, but with smooth and slow variations in the complementary transverse directions. In the past, reciprocity theorems have been developed in terms of oneway wave fields. The boundaries of the integration volumes and the variations of the medium parameters must adhere to strict conditions. The variations must have the smoothness required by pseudodifferential operators, while the boundaries have to be flat. To extend the applicability to nonflat boundaries, this paper formulates oneway wave equations and corresponding reciprocity theorems in terms of curvilinear coordinates of the semiorthogonal (SO) type. In SO coordinate systems, one of the covariant basis vectors is orthogonal to the others, which can be nonorthogonal among each other. The same applies to the contravariant basis vectors. Furthermore, the orthogonal directions coincide; that is, the orthogonal co and contravariant basis vectors coincide. SO coordinates are characterized by a local property of the basis vectors. An extra specification is necessary to make them conform in any way to nonflat boundaries. This can be done in terms of socalled lateral Cartesian (LC) coordinates. Cartesian coordinates are mapped to LC coordinates by applying an invertible transformation to one coordinate while keeping the others the same. LC coordinates are a straightforward means to describe or conform to nonflat boundaries. Applications of the extended reciprocity theorems include removal of multiple reflections, removal of complex propagation effects, wave field extrapolation, and synthesis of unrecorded data.Breciprocity theorems; curvilinear coordinates; oneway wave fields.Society for Industrial and Applied Mathematics)uuid:9bf7fc0a55ba4cd091ddb51b2064b638Dhttp://resolver.tudelft.nl/uuid:9bf7fc0a55ba4cd091ddb51b2064b638jOn seismic interferometry, the generalized optical theorem, and the scattering matrix of a point scatterer)Wapenaar, C.P.A.; Slob, E.C.; Snieder, R.We have analyzed the farfield approximation of the Green's function representation for seismic interferometry. By writing each of the Green's functions involved in the correlation process as a superposition of a direct wave and a scattered wave, the Green's function representation is rewritten as a superposition of four terms. When the scattered waves are modeled with the Born approximation, it appears that a threeterm approximation of the Green's function representation (omitting the term containing the crosscorrelation of the scattered waves) yields a nearly exact retrieval, whereas the full fourterm expression leads to a significant nonphysical event. This is because the Born approximation does not conserve energy and therefore is an insufficient model to ex< plain all aspects of seismic interferometry. We use the full fourterm expression of the Green's function representation to derive the generalized optical theorem. Unlike other recent derivations, which use stationary phase analysis, our derivation uses reciprocity theory. From the generalized optical theorem, we derive the nonlinear scattering matrix of a point scatterer. This nonlinear model accounts for primary and multiple scattering at the point scatterer and conforms with wellestablished scattering theory of classical waves. The model is essential to explain fully the results of seismic interferometry, even when it is applied to the response of a single point scatterer. The nonlinear scattering matrix also has implications for modeling, inversion, and migration.)uuid:84703eaca0504e85bf3268bbae218732Dhttp://resolver.tudelft.nl/uuid:84703eaca0504e85bf3268bbae218732,Reflection images from ambient seismic noise`One application of seismic interferometry is to retrieve the impulse response (Green's function) from crosscorrelation of ambient seismic noise. Various researchers show results for retrieving the surfacewave part of the Green's function. However, reflection retrieval has proven more challenging. We crosscorrelate ambient seismic noise, recorded along eight parallel lines in the Sirte basin east of Ajdabeya, Libya, to obtain shot gathers that contain reflections. We take advantage of geophone groups to suppress part of the undesired surfacewave noise and apply frequencywavenumber filtering before crosscorrelation to suppress surface waves further. After comparing the retrieved results with data from an active seismic exploration survey along the same lines, we use the retrieved reflection data to obtain a migrated reflection image of the subsurface.dgeophysical signal processing; interference suppression; seismic waves; seismology; signal denoising)uuid:b71c6656d7614fb4b0795c8f363383e9Dhttp://resolver.tudelft.nl/uuid:b71c6656d7614fb4b0795c8f363383e9_Raybased stochastic inversion of prestack seismic data for improved reservoir characterization.Van der Burg, D.; Verdel, A.; Wapenaar, C.P.A.Trace inversion for reservoir parameters is affected by angle averaging of seismic data and wavelet distortion on the migration image. In an alternative approach to stochastic trace inversion, the data are inverted prestack before migration using 3D dynamic ray tracing. This choice makes it possible to interweave trace inversion with Kirchhoff migration. The new method, called raybased stochastic inversion, is a generalization of current amplitude versus offset/amplitude versus angle (AVO/AVA) inversion techniques. The new method outperforms standard stochastic inversion techniques in cases of reservoir parameter estimation in a structurally complex subsurface with substantial lateral velocity variations and significant reflector dips. A simplification of the method inverts the normalincidence response from reservoirs with approximately planar layering at the subsurface target locations selected for inversion. It operates along raypaths perpendicular to the reflectors, the direction that offers optimal resolution to discern layering in a reservoir. In a test on field data from the Gulf of Mexico, reservoir parameter estimates obtained with the simplified method, the estimates found by conventional stochastic inversion, and the actual values at a well drilled after the inversion are compared. Although the new method uses only 2% of the prestack data, the result indicates it improves accuracy on the dipping part of the reservoir, where conventional stochastic inversion suffers from wavelet stretch caused by migration._geophysical techniques; hydrocarbon reservoirs; seismic waves; seismology; stochastic processes)uuid:f8c088076c084ea59be387fec54423adDhttp://resolver.tudelft.nl/uuid:f8c088076c084ea59be387fec54423ad:Virtual reflector representation theorem (acoustic medium)Poletto, F.; Wapenaar, C.P.A.The virtual reflector method simulates new seismic signals by processing traces recorded by a plurality of < sources and receivers. The approach is based on the crossconvolution of the recorded signals and makes it possible to obtain the Green s function of virtual reflected signals as if in the position of the receivers (or sources) there were a reflector, even if said reflector is not present. This letter presents the virtual reflector theory based on the Kirchhoff integral representation theorem for wave propagation in an acoustic medium with and without boundary and a generalization to variable reflection coefficients for scattered wavefields.\acoustic signal processing; boundaryvalue problems; Green's function methods; seismic waves)uuid:015bf386811f4587b50b9bac69f19699Dhttp://resolver.tudelft.nl/uuid:015bf386811f4587b50b9bac69f19699@Passive seismic interferometry by multidimensional deconvolution3Wapenaar, C.P.A.; Van der Neut, J.R.; Ruigrok, E.N.We introduce seismic interferometry of passive data by multidimensional deconvolution (MDD) as an alternative to the crosscorrelation method. Interferometry by MDD has the potential to correct for the effects of source irregularity, assuming the first arrival can be separated from the full response. MDD applications can range from reservoir imaging using microseismicity to crustal imaging with teleseismic data.Udeconvolution; geophysical techniques; multidimensional signal processing; seismology)uuid:7d656a13c0f1425a8835616a1ccfdb0aDhttp://resolver.tudelft.nl/uuid:7d656a13c0f1425a8835616a1ccfdb0aBGlobalscale seismic interferometry: Theory and numerical examples+Ruigrok, E.N.; Draganov, D.S.; Wapenaar, K.Progress in the imaging of the mantle and core is partially limited by the sparse distribution of natural sources; the earthquake hypocenters are mainly along the active lithospheric plate boundaries. This problem can be approached with seismic interferometry. In recent years, there has been considerable progress in the development of seismic interferometric techniques. The term seismic interferometry refers to the principle of generating new seismic responses by crosscorrelating seismic observations at different receiver locations. The application of interferometric techniques on a global scale could create sources at locations where no earthquakes occur. In this way, yet unknown responses would become available for the application of traveltime tomography and surfacewave dispersion studies. The retrieval of a denseenough sampling of source gathers would largely benefit the application of reflection imaging. We derive new elastodynamic representation integrals for globalscale seismic interferometry. The relations are different from other seismic interferometry relations for transient sources, in the sense that they are suited for a rotating closed system like the Earth. We use a correlation of an observed response with a response to which freesurface multiple elimination has been applied to account for the closed system. Despite the fact that the rotation of the Earth breaks sourcereceiver reciprocity, the seismic interferometry relations are shown to be valid. The Coriolis force is included without the need to evaluate an extra term. We synthesize globalscale earthquake responses and use them to illustrate the acoustic versions of the new interferometric relations. When the sampling of real source locations is dense enough, then both the responses with and without freesurface multiples are retrieved. When we do not take into account the responses from the sources in the direct neighborhood of the seismic interferometryconstructed source location, the response with freesurface multiples can still be retrieved. Even when only responses from sources at a certain range of epicentral distances are available, some events in the Green s function between two receiver locations can still be retrieved. The retrieved responses are not perfect, but the artefacts can largely be ascribed to numerical errors. The reconstruction of internal events the response as if there was a source and a receiver on (major) contrasts within the model could possibly be of use for imag< ing. With modelling it is possible to discover in which region of the correlation panel stationary phases occur that contribute to the retrieval of events. This knowledge opens up a new way of filtering out undesired events and of discovering whether specific events could be retrieved with a given sourcereceiver configuration..seismology; body waves; seismic interferometry)uuid:b68278f691fb471b9d49decc2927f766Dhttp://resolver.tudelft.nl/uuid:b68278f691fb471b9d49decc2927f766KSimulating migrated and inverted seismic data by filtering a geologic modelXToxopeus, G.; Thorbecke, J.W.; Wapenaar, C.P.A.; Petersen, S.; Slob, E.C.; Fokkema, J.T.%The simulation of migrated and inverted data is hampered by the high computational cost of generating 3D synthetic data, followed by processes of migration and inversion. For example, simulating the migrated seismic signature of subtle stratigraphic traps demands the expensive exercise of 3D forward modeling, followed by 3D migration of the synthetic seismograms. This computational cost can be overcome using a strategy for simulating migrated and inverted data by filtering a geologic model with 3D spatialresolution and angle filters, respectively. A key property of the approach is this: The geologic model that describes a target zone is decoupled from the macrovelocity model used to compute the filters. The process enables a targetorientedapproach, by which a geologically detailed earth model describing a reservoir is adjusted without having to recalculate the filters. Because a spatialresolution filter combines the results of the modeling and migration operators, the simulated images can be compared directly to a real migration image. We decompose the spatialresolution filter into two parts and show that applying one of those parts produces output directly comparable to 1D inverted real data. Twodimensional synthetic examples that include seismic uncertainties demonstrate the usefulness of the approach. Results from a real data example show that horizontal smearing, which is not simulated by the 1D convolution model result, is essential to understand the seismic expression of the deformation related to sulfate dissolution and karst collapse.Bdeformation; geochemistry; seismic waves; seismology; stratigraphy)uuid:e599c89e0186472394b5364e85ddb0afDhttp://resolver.tudelft.nl/uuid:e599c89e0186472394b5364e85ddb0afTOn the relation between seismic interferometry and the migration resolution function!Thorbecke, J.W.; Wapenaar, C.P.A.Seismic interferometry refers to the process of retrieving new seismic responses by crosscorrelating seismic observations at different receiver locations. Seismic migration is the process of forming an image of the subsurface by wavefield extrapolation. Comparing the expressions for backward propagation known from migration literature with the Green's function representations for seismic interferometry reveals that these seemingly distinct concepts are mathematically equivalent. The frequencydomain representation for the resolution function of migration is identical to that for the Green's function retrieved by seismic interferometry (or its square, in the case of double focusing). In practice, they differ because the involved Green's functions in seismic interferometry are all defined in the actual medium, whereas in migration one of the Green's functions is defined in a background medium.<geophysical techniques; Green's function methods; seismology)uuid:0797113de33f491e82bde23b570903a6Dhttp://resolver.tudelft.nl/uuid:0797113de33f491e82bde23b570903a6Retrieving reflection responses by crosscorrelating transmission responses from deterministic transient sources: Application to ultrasonic data8Draganov, D.; Wapenaar, K.; Thorbecke, J.; Nishizawa, O.By crosscorrelating transmission recordings of acoustic or elastic wave fields at two points, one can retrieve the reflection response between these two points. This technique has previously been applied to measured elastic data using diffuse wavefield recordings. These recordings should be relativ< ely very long. The retrieval can also be achieved by using deterministic transient sources with the advantage of using short recordings, but with the necessity of using many Pwave and Swave sources. Here, it is shown how reflections were retrieved from the cross correlation of transient ultrasonic transmission data measured on a heterogeneous granite sample.Jacoustic signal processing; ultrasonic reflection; ultrasonic transmission)uuid:a89005f207e14c2eb29320ef631cf2aeDhttp://resolver.tudelft.nl/uuid:a89005f207e14c2eb29320ef631cf2aeJGeneral representations for wavefield modeling and inversion in geophysicsAcoustic, electromagnetic, elastodynamic, poroelastic, and electroseismic waves are all governed by a unified matrixvector wave equation. The matrices in this equation obey the same symmetry properties for each of these wave phenomena. This implies that the wave vectors for each of these phenomena obey the same reciprocity theorems. By substituting Green's matrices in these reciprocity theorems, unified wavefield representations are obtained. Analogous to the wellknown acoustic wavefield representations, these unified representations find applications in geophysical modeling, migration, inversion, multiple elimination, and interferometry.Facoustic waves; seismic waves; vectors; matrix algebra; interferometry)uuid:5bf81d4cd7b24c228e7081a00dc17e7cDhttp://resolver.tudelft.nl/uuid:5bf81d4cd7b24c228e7081a00dc17e7ckElectromagnetic Green's functions retrieval by cross?correlation and cross?convolution in media with lossesIt is shown that the electromagnetic Green's functions of any linear medium with arbitrary heterogeneity can be obtained from the cross?correlation, or the cross?convolution, of two recordings at different receiver locations in an open system. Existing representations are known for cross?correlations where time?reversal invariance is exploited and hence they are considered in lossless media. We show here that the cross?correlation type representations are exact in a configuration with sources on a closed boundary and the medium has non?zero loss terms only outside this boundary. Furthermore, we show that for cross?convolution representations the loss mechanisms may exist anywhere in space. Many sources of electromagnetic signals exist in the atmosphere and in populated areas, and these can be used in a large variety of practical passive applications exploiting eddy current or electromagnetic wave techniques.;representation theory; crossconvolution; crosscorrelation)uuid:d16d586072e645e99f560cfcb41d86ceDhttp://resolver.tudelft.nl/uuid:d16d586072e645e99f560cfcb41d86ceCRetrieval of reflections from seismic background?noise measurements@Draganov, D.S.; Wapenaar, K.; Mulder, W.; Singer, J.; Verdel, A.The retrieval of the earth's reflection response from cross?correlations of seismic noise recordings can provide valuable information, which may otherwise not be available due to limited spatial distribution of seismic sources. We cross?correlated ten hours of seismic background?noise data acquired in a desert area. The cross?correlation results show several coherent events, which align very well with reflections from an active survey at the same location. Therefore, we interpret these coherent events as reflections. Retrieving seismic reflections from background?noise measurements has a wide range of applications in regional seismology, frontier exploration and long?term monitoring of processes in the earth's subsurface.Jcrosscorrelation; Green's function retrieval; reflections; interferometry)uuid:b8934b2b1b8e41dd95a911deed023b0dDhttp://resolver.tudelft.nl/uuid:b8934b2b1b8e41dd95a911deed023b0dZUnified Green's function retrieval by crosscorrelation: Connection with energy principles%Snieder, R.; Wapenaar, K.; Wegler, U.)uuid:5857194a8e974b28aaeee77953dfc4bcDhttp://resolver.tudelft.nl/uuid:5857194a8e974b28aaeee77953dfc4bc7Unified Green s Function Retrieval by Cross CorrelationIt has been shown by many authors that the cross correlation of two recordings of a diffuse wave< field at different receivers yields the Green s function between these receivers. Recently the theory has been extended for situations where timereversal invariance does not hold (e.g., in attenuating media) and where sourcereceiver reciprocity breaks down (in moving fluids). Here we present a unified theory for Green s function retrieval that captures all these situations and, because of the unified form, readily extends to more complex situations, such as electrokinetic Green s function retrieval in poroelastic or piezoelectric media. The unified theory has a wide range of applications in remote sensing without a source. )uuid:58eadba7e1bd4ad8a24d40cbd195c444Dhttp://resolver.tudelft.nl/uuid:58eadba7e1bd4ad8a24d40cbd195c444QGreen's function retrieval by cross?correlation in case of one?sided illuminationgThe crosscorrelation of acoustic wave fields at two receivers yields the exact Green's function between these receivers, provided the receivers are surrounded by sources on a closed surface. In most practical situations the sources are located on an open surface and as a consequence the illumination of the receivers is onesided. In this Letter we discuss the conditions for accurate Green's function retrieval for the situation of onesided illumination. It appears that the Green's function retrieval method benefits from the fact that the earth is inhomogeneous, without relying on assumptions about disorder.)uuid:bc09960947bd4ad891ad2a4a9a949c0fDhttp://resolver.tudelft.nl/uuid:bc09960947bd4ad891ad2a4a9a949c0f0Seismic interferometryturning noise into signalACurtis, A.; Gerstoft, P.; Sato, H.; Snieder, R.; Wapenaar, C.P.A.Turning noise into useful data every geophysicist's dream? And now it seems possible. The field of seismic interferometry has at its foundation a shift in the way we think about the parts of the signal that are currently filtered out of most analyses complicated seismic codas (the multiply scattered parts of seismic waveforms) and background noise (whatever is recorded when no identifiable active source is emitting, and which is superimposed on all recorded data). Those parts of seismograms consist of waves that reflect and refract around exactly the same subsurface heterogeneities as waves excited by active sources. The key to the rapid emergence of this field of research is our new understanding of how to unravel that subsurface information from these relatively complexlooking waveforms. And the answer turned out to be rather simple. This article explains the operation of seismic interferometry and provides a few examples of its application.Wgeophysical techniques; seismology; structural engineering; earthquakes; interferometry)uuid:c0512fe5692e47e398a2a24cf29c0d09Dhttp://resolver.tudelft.nl/uuid:c0512fe5692e47e398a2a24cf29c0d099Spurious multiples in seismic interferometry of primaries)Snieder, R.; Wapenaar, C.P.A.; Larner, K.Seismic interferometry is a technique for estimating the Green's function that accounts for wave propagation between receivers by correlating the waves recorded at these receivers. We present a derivation of this principle based on the method of stationary phase. Although this derivation is intended to be educational, applicable to simple media only, it provides insight into the physical principle of seismic interferometry. In a homogeneous medium with one horizontal reflector and without a free surface, the correlation of the waves recorded at two receivers correctly gives both the direct wave and the singly reflected waves. When more reflectors are present, a product of the singly reflected waves occurs in the crosscorrelation that leads to spurious multiples when the waves are excited at the surface only. We give a heuristic argument that these spurious multiples disappear when sources below the reflectors are included. We also extend the derivation to a smoothly varying heterogeneous background medium.)interferometry; seismic waves; seismology)uuid:fc9a5a03cbfa40ca8f4d9652ecd325f5Dhttp://resolver.tudelft.nl/uuid:fc9a5a03cbfa40ca8f4d9652ecd32< 5f5FSeismic interferometry: Reconstructing the earth's reflection response1Draganov, D.S.; Wapenaar, C.P.A.; Thorbecke, J.W.PIn 1968, Jon Claerbout showed that the reflection response of a 1D acoustic medium can be reconstructed by autocorrelating the transmission response. Since then, several authors have derived relationships for reconstructing Green's functions at the surface, using crosscorrelations of (noise) recordings that were taken at the surface and that derived from subsurface sources.For acoustic media, we review relations between the reflection response and the transmission response in 3D inhomogeneous lossless media. These relations are derived from a oneway wavefield reciprocity theorem. We use modeling results to show how to reconstruct the reflection response in the presence of transient subsurface sources with distinct excitation times, as well as in the presence of simultaneously acting noise sources in the subsurface. We show that the quality of reconstructed reflections depends on the distribution of the subsurface sources. For a situation with enough subsurface sources that is, for a distribution that illuminates the subsurface area of interest from nearly alldirections the reconstructed reflection responses and the migrated depth image exhibit all the reflection events and the subsurface structures of interest, respectively. With only a few subsurface sources, that is, with insufficient illumination, the reconstructed reflection responses are noisy and can even become kinematically incorrect. At the same time, however, the depth image, which was obtained from their migration, still shows clearly all the illuminated subsurface structures at their correct positions.For the elastic case, we review a relationship between the reflection Green's functions and the transmission Green's functions derived from a twoway wavefield reciprocity theorem. Using modeling examples, we show how to reconstruct the different components of the particle velocity observed at the surface and resulting from a surface traction source. This reconstruciton is achieved using crosscorrelations of particle velocity components measured at the surface and resulting from separate P and Swave sources in the subsurface.Cseismology; interferometry; seismic waves; Green's function methods)uuid:68e13eb252e7499c8a04ddee6fa0d6ddDhttp://resolver.tudelft.nl/uuid:68e13eb252e7499c8a04ddee6fa0d6dd;Green's function representations for seismic interferometryWapenaar, C.P.A.; Fokkema, J.T.The term seismic interferometry refers to the principle of generating new seismic responses by crosscorrelating seismic observations at different receiver locations. The first version of this principle was derived by Claerbout (1968), who showed that the reflection response of a horizontally layered medium can be synthesized from the autocorrelation of its transmission response. For an arbitrary 3D inhomogeneous lossless medium it follows from Rayleigh's reciprocity theorem and the principle of timereversal invariance that the acoustic Green's function between any two points in the medium can be represented by an integral of crosscorrelations of wavefield observations at those two points. The integral is along sources on an arbitrarily shaped surface enclosing these points. No assumptions are made with respect to the diffusivity of the wavefield. The RayleighBetti reciprocity theorem leads to a similar representation of the elastodynamic Green's function. When a part of the enclosing surface is the earth's free surface, the integral needs only to be evaluated over the remaining part of the closed surface. In practice, not all sources are equally important: The main contributions to the reconstructed Green's function come from sources at stationary points. When the sources emit transient signals, a shaping filter can be applied to correct for the differences in source wavelets. When the sources are uncorrelated noise sources, the representation simplifies to a direct crosscorrelation of wavefield observations at two points, similar as in methods that retr< ieve Green's functions from diffuse wavefields in disordered media or in finite media with an irregular bounding surface.)uuid:f2026ee0a0234c4f8655bef577d28c44Dhttp://resolver.tudelft.nl/uuid:f2026ee0a0234c4f8655bef577d28c448Introduction to the supplement on seismic interferometry0Wapenaar, C.P.A.; Draganov, D.S.; Robertsson, J.)uuid:810a9ed635724271b99a183b0afe3f7fDhttp://resolver.tudelft.nl/uuid:810a9ed635724271b99a183b0afe3f7f=Nonreciprocal Green s function retrieval by cross correlationThe cross correlation of two recordings of a diffuse acoustic wave field at different receivers yields the Green s function between these receivers. In nearly all cases considered so far the wave equation obeys timereversal invariance and the Green s function obeys sourcereceiver reciprocity. Here the theory is extended for nonreciprocal Green s function retrieval in a moving medium. It appears that the cross correlation result is asymmetric in time. The causal part represents the Green s function from one receiver to the other whereas the acausal part represents the timereversed version of the Green s function along the reverse path.Racoustic field; acoustic wave scattering; Green's function methods; wave equations)uuid:c3fd77aa1a0f4a7192d286a722ed1366Dhttp://resolver.tudelft.nl/uuid:c3fd77aa1a0f4a7192d286a722ed1366fRetrieving the Green s function in an open system by cross correlation: A comparison of approaches (L)*Wapenaar, C.P.A.; Fokkema, J.; Snieder, R.&We compare two approaches for deriving the fact that the Green s function in an arbitrary inhomogeneous open system can be obtained by cross correlating recordings of the wave field at two positions. One approach is based on physical arguments, exploiting the principle of timereversal invariance of the acoustic wave equation. The other approach is based on Rayleigh s reciprocity theorem. Using a unified notation, we show that the result of the timereversal approach can be obtained as an approximation of the result of the reciprocity approach.Green's function methods; acoustic wave propagation; acoustic wave scattering; vibrations; structural acoustics; acoustic signal processing; seismology)uuid:29ed1385a3fc4c09b5db9de3255a8482Dhttp://resolver.tudelft.nl/uuid:29ed1385a3fc4c09b5db9de3255a8482gRetrieving the elastodynamic green's function of an arbitrary inhomogeneous medium by cross correlationWapenaar, K.)uuid:657c227553f44feea4ed2cedcd302446Dhttp://resolver.tudelft.nl/uuid:657c227553f44feea4ed2cedcd302446Seismische reflecties
Intreeredenlpublic lecture)uuid:81188ea4990447608771ab83a58f3650Dhttp://resolver.tudelft.nl/uuid:81188ea4990447608771ab83a58f36508Dynamics of classical wave scattering by small obstacles/Bauer, G.E.W.; Ferreira, M.S.; Wapenaar, C.P.A.)uuid:42a624a7721a4b12a06cb1254e16fff4Dhttp://resolver.tudelft.nl/uuid:42a624a7721a4b12a06cb1254e16fff4!A proposal for 4D seismic imaging/Fokkema, J.T.; Dillen, M.W.P.; Wapenaar, C.P.A.development earthquakes elastic waves equations Europe four dimensional models geologic hazards geophysical methods Green function heavy oil induced earthquakes land subsidence measurement while drilling monitoring natural gas Netherlands northern NetherlIEuropean Association of Geoscientists and Engineers (EAGE), International)uuid:c31a699bf4064235ac85df9b933becbfDhttp://resolver.tudelft.nl/uuid:c31a699bf4064235ac85df9b933becbf/The reflectivity operator for curved interfacesEFokkema, J.T.; Van Vroonhoven, M.; Wapenaar, C.P.A.; De Bruin, C.G.M.boundary conditions curved seismic interface elastic waves geophysical methods heterogeneous materials homogeneous materials mathematical methods reflection seismic methods seismic waves two dimensional models 20 Applied geophysics)uuid:3db3eeb2766342ccbb72a8aa1c10a67eDhttp://resolver.tudelft.nl/uuid:3db3eeb2766342ccbb72a8aa1c10a67e'Extrapolation operators by beam tracing/Kremer, S.R.G.; Fokkema, J.T.; Wapenaar, C.P.A.vamplitude beam tracing data processing extrapolation geophysical methods imagery seismic methods 20< Applied geophysics)uuid:68eea8de85ef4630bae8409e46402940Dhttp://resolver.tudelft.nl/uuid:68eea8de85ef4630bae8409e46402940(Beam tracing for migration and inversion/Fokkema, J.T.; Kremer, S.R.G.; Wapenaar, C.P.A.accuracy direct problem evaluation geophysical methods Green function inverse problem propagation raypaths seismic methods seismic migration 20 Applied geophysics)uuid:04e20e93964d4e3c9b706eafc43a888dDhttp://resolver.tudelft.nl/uuid:04e20e93964d4e3c9b706eafc43a888d/Prestack migration in two and three dimensionsBerkhout, A.J. (promotor)doctoral thesis)uuid:03efef4f1a9c49548ca1fcd61f4ab6b3Dhttp://resolver.tudelft.nl/uuid:03efef4f1a9c49548ca1fcd61f4ab6b3EVan der Neut, J.; Tatanova, M.; Thorbecke, J.; Slob, E.; Wapenaar, K.With controlledsource seismic interferometry we aim to redatum sources to downhole receiver locations without requiring a velocity model. Interferometry is generally based on a source integral over crosscorrelation (CC) pairs of full, perturbed (timegated), or decomposed wavefields. We provide an overview of ghosts, multiples, and spatial blurring effects that can occur for different types of interferometry. We show that replacing crosscorrelation by multidimensional deconvolution (MDD) can deghost, demultiple, and deblur retrieved data. We derive and analyze MDD for perturbed and decomposed wavefields. An interferometric point spread function (PSF) is introduced that can be obtained directly from downhole data. Ghosts, multiples, and blurring effects that may populate the retrieved gathers can be locally diagnosed with the PSF. MDD of perturbed fields can remove ghosts and deblur retrieved data, but it leaves particular multiples in place. To remove all overburdenrelated effects, MDD of decomposed fields should be applied.)uuid:fc6ffb9d163948279f8c85d94a74bd2eDhttp://resolver.tudelft.nl/uuid:fc6ffb9d163948279f8c85d94a74bd2eBTimelapse controlledsource electromagnetics using interferometryIn timelapse controlledsource electromagnetics, it is crucial that the source and the receivers are positioned at exactly the same location at all times of measurement. We use interferometry by multidimensional deconvolution (MDD) to overcome problems in repeatability of the source location. Interferometry by MDD redatums the source to a receiver location and replaces the medium above the receivers with a homogeneous halfspace. In this way, changes in the source position and changes of the conductivity in the waterlayer become irrelevant. The only remaining critical parameter to ensure a good repeatability of a controlledsource electromagnetic measurement is the receiver position.obathymetry; deconvolution; electromagnetic wave interferometry; geophysical prospecting; hydrocarbon reservoirs
*+&ffffff?'ffffff?(?)?"dXX333333?333333?U}}}}}}}}}} }
}}}
}}}}}}}}}}}}
@
!
"
#@
$
%
&
'
(@
)
*
+
,

.
/
0@
1
+
2
3
4
5
6@
7
8
9
:
;@
<
=
>
?
@
A
B
C@
D
+
E
F
G
H@
I
+
J
K
L
M
N @
O
P
Q
R
S
@
T
U
V
W
X
Y
Z@
[
\
]
^
_
`@
a
b
c
d
e
f
g
@
h
i
V
j
k
l
m@
n
V
o
p
q
r@
s
t
u
v
w
x@
y
z
{

}
~@
@
@
>
@
>
@
@
>
@
@
>
@
V
@
@
þʡB
V
@
V
@
V
@
V
@
V
@
V
!
!
!
!!@
!
!
!
!
!
!V
"
"
"
""@
"
"
"
"
"
"V
#
#
#
##@
#
#
#V
$
$
$
$$@
$
$
$
$V
%
%
%
%%@
%
%
%
%
%
%V
&
&
&
&&@
&
&
&
&
&
&V
'
'
'
''@
'
'
'
'
'
'V
(
(
(
((@
(
(
(
(
(
(V
)
)
)
)
) )@
)
)
)
)
*
*
*
*
* *@
*
*
*
*
+
+
+
+
+ +@
+
+
+
+
,
,
,
,
, ,@
,
,
,
,




 @




.
.
.!
.".@
.#
.
.
.$
/%
/&
/'
/(/@
/)
/*
/
/
0+
0,
0
0.0@
0/
0
0
10
11
12
131@
14
1
1
25
26
27
282@
29
2
2
2
2
3:
3;
3<
3=3@
3>
3
3
4?
4@
4A
4B4@
4C
4D
4
4
5E
5F
5G
5H5@
5I
5J
5
5
6K
6L
6M
6N6@
6O
6
6
6V
7P
7Q
7R
77@
7S
7
7
7T
7V
8U
8V
8W
8X8@
8
8
8
8V
9Y
9Z
9[
9\9@
9]
9^
9
9
9V
:_
:`
:a
:b:@
:c
:d
:
:
:V
;e
;f
;g
;h;@
;i
;
;
;V
<j
<k
<l
<m
<n<@
<o
<p
<
<
<
=q
=r
=s
=t
=n=@
=u
=v
=
=
=
>w
>x
>y
>z
>n>@
>{
>
>
>
>
?}
?~
?
?
?n?@
?
?
?
?
?
@
@
@
@
@n@@
@
@
@
@
@
A
A
A
A
AnA@
A
A
A
A
A
B
B
B
B
BnB@
B
Bv
B
B
B
C
C
C
C
CnC@
C
C
C
C
C
D
D
D
DD@
D
D
E
E
E
EE@
E
E
F
F
F
FF@
F
F
F
F
F
G
G
G
GG@
G
G
G
G
H
H
H
HH@
H
H
H
I
I
I
II@
I
I
I
I
J
J
J'
JJ@
J
J
J
J
K
K
K'
KK@
K
K
K
K
L
L
L
LL@
L
L
L
L
L
L
M
M
M
MM@
M
M
M
M
M
M
N
N
N
NN@
N
N
N
N
N
O
O
O
OO@
O
O
O
O
O
P
P
P
PP@
P
P
P
P
P
P
P
Q
Q
Q
QQ@
Q
Q
Q
Q
R
R
R
RR@
R
R
R
R
R
R
R
S
S
S
SS@
S
S
S
S
S
T
T
T
TT@
T
T
T
T
T
T
U
U
U
UU@
U
U
U
U
U
U
V
V
V
VV@
V
V
V
V
V
V
W
W
W
WW@
W
W
W
W
W
W
X
X
X
XX@
X
X
X
X
X
X
X
Y
Y
Y
YY@
Y
Y
Y
Y
Y
Y
Y
Z
Z
Z
ZZ@
Z
Z
Z
Z
[
[
[
[[x@
[
[
[
[
[
\
\
\
\\x@
\
\
\
\
\
\
]
]!
]"
]#]x@
]$
]
]
]
]
^%
^&
^"
^#^x@
^'
^
^
^
(
^
^
_)
_*
_+
_,_x@
_
_
_
_
_
`.
`/
`0
`1`x@
`2
`3
`
`
`
`
`
a4
a5
a6
a7ax@
a8
a9
a
a
a
a
a
b:
b;
b<
b=bx@
b>
bv
b
b
b
b?
b@
cA
cB
cC
ccx@
cD
cE
c
c
c
c
c
dF
dG
dH
dIdx@
dJ
dK
d
d
d
dL
d
d
eM
eN
eO
ePex@
e
e Q
fR
fS
fT
fUfx@
fV
fW
f
f
f
fX
f
f
gY
gZ
g[
g\gx@
g]
g
g
g
g
g
h^
h_
h`
hahx@
hb
h
h
h
h
h
ic
id
ie
ifix@
ig
i
i
i
i
i
jh
ji
jj
jkjx@
jl
j
j
j
j
j
km
kn
ko
kkx@
kp
k
k
k
k
k
lq
lr
ls
ltlx@
lu
l
l
l
l
l
mv
mw
mx
mymx@
mz
m
m
m
m
m
n{
n
n}
nnx@
n~
n
n
n
n
n?
n@
o
o
oo
oox@
o
o Q
o
o
p
p
p
ppx@
p
p
p
p
p
p
p
q
q
qO
qPqx@
q
q
q
q
q
q
q
r
r
r
rPrx@
r
r
r
r
r
r
r
s
s
s
ssx@
s
s
s
s
s
s
t
t
t
ttx@
t
t
t
t
t
t
t
u
u
u
uux@
u
u
u
u
u
u
u
v
v
v
v7vx@
v
v
v
v
v
v
w
w
w
wwx@
w
w
w
w
w
w
w
w
x
x
x
xxt@
x
x
x
x
x
x
x
x
y
y
y
yyt@
y
y
y
y
y
y
y
z
z
z
zzt@
z
z
z
z
z
z
z
{
{
{
{{t@
{
{
{
{
{
{
{



t@







}
}
}
}}t@
}
}
}
}
}
}
}
~
~
~
~~t@
~
~
~
~
~
~
~
t@
t@
t@
t@
t@
t@
t@
t@
t@
t@
t@
t@
(
t@
!
"
#
$p@
%
&
'
(
)
p@
*
+
,

.p@
/
0
1
2
3
p@
4
5
6
7
p@
8
9
:
;
<p@
=
>
?
@
Ap@
B
C
D
E
F
G
Hp@
I
J
K
L
M
Nl@
O
P
Q
R
S
T
U
Vl@
W
X
Y
Z
[
\l@
]
^
V
_
`
a
bl@
c
d
R
e
f
g
hl@
i
j
k
l
m
nh@
o
p
q
r
s
th@
u
R
v
w
x
yh@
z
{

R
}
~
h@
h@
h@
R
h@
d@
R
d@
R
d@
R
`@
R
`@

R
`@
R
\@
R
\@
R
#\@
R
\@
R
\@
R
\@
(
X@
(
R
#X@
R
X@
X@
R
X@
R
X@
R
X@
#X@
R
T@
R
P@
(
#D@
D@
(
4@
$@
!
"@
#
$
%
&
'@
(
)
*
+
#
,@

.
/
[
0
1
^
R
2
3
4
y
5
6
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~>@ddyKyKhttp://resolver.tudelft.nl/uuid:eb49b58e79174bd2a89d8e86a61009a9yKyKhttp://resolver.tudelft.nl/uuid:c8f3dfa388cb4adab604fa1cb6c43fecyKyKhttp://resolver.tudelft.nl/uuid:c9de64832a054f05a25fcba2cf92ddb6yKyKhttp://resolver.tudelft.nl/uuid:630be8fb2a1443f9a5a6af1ff80253f7yKyKhttp://resolver.tudelft.nl/uuid:3fbcd73e0bad4d308f42143dfbc431ebyKyKhttp://resolver.tudelft.nl/uuid:85aa81cb4cf048c7a9fc95f6cef248bfyKyKhttp://resolver.tudelft.nl/uuid:386ff8b1072049e284253de163aea36fyKyKhttp://resolver.tudelft.nl/uuid:a06e8d0f20d845ed8ddaa3aa8512fadf yKyKhttp://resolver.tudelft.nl/uuid:2edcfd2945e848e58ba34201fa8d5069
yKyKhttp://resolver.tudelft.nl/uuid:f47e0797e53d43e5afbc88d7316f3118yKyKhttp://resolver.tudelft.nl/uuid:13bf575c66d44321932929e99403660eyKyKhttp://resolver.tudelft.nl/uuid:5c2a435d5004455f9ee34afcedc50283
yKyKhttp://resolver.tudelft.nl/uuid:324bfb26265a4299b4e8c2d55be43643yKyKhttp://resolver.tudelft.nl/uuid:74b21e406dfc4ff4be4ddffdc8ffba34yKyKhttp://resolver.tudelft.nl/uuid:971090a1d8f64e1396cc4f022707d87ayKyKhttp://resolver.tudelft.nl/uuid:dfe1055f645e475396dfc49ba4df838dyKyKhttp://resolver.tudelft.nl/uuid:3091b118e9554727912779a34d026cd8yKyKhttp://resolver.tudelft.nl/uuid:ce065c7e00424bb59a3310950d2d0343yKyKhttp://resolver.tudelft.nl/uuid:7f83193e43f04d35a33498e56c0e73fcyKyKhttp://resolver.tudelft.nl/uuid:ec82b4a83f0945c295061453e3a8d6feyKyKhttp://resolver.tudelft.nl/uuid:8511a3bce21c49938438af7e39c77388yKyKhttp://resolver.tudelft.nl/uuid:201a046842284f75a579a29f62b825f2yKyKhttp://resolver.tudelft.nl/uuid:013a0e813a844013975c4a2624fb4b0eyKyKhttp://resolver.tudelft.nl/uuid:69b76fb785ff46df98652375ebda01deyKyKhttp://resolver.tudelft.nl/uuid:459fdf96c15d45a3aa9389c03b17e985yKyKhttp://resolver.tudelft.nl/uuid:048b6e7c398b42ee8d9b53c693cc3023yKyKhttp://resolver.tudelft.nl/uuid:ee0b3190beb44de6bdc82a25c569dbbbyKyKhttp://resolver.tudelft.nl/uuid:0ec47f8d06ec4d2a8cb62532fb2cd38cyKyKhttp://resolver.tudelft.nl/uuid:644e9cc51e9a43ecb7cf7f96fc3557bfyKyKhttp://resolver.tudelft.nl/uuid:fd8655a135e54fa0803b361e98b8d5afyKyKhttp://resolver.tudelft.nl/uuid:19810c33dcb148de9eec87376d1fa01c yKyKhttp://resolver.tudelft.nl/uuid:5bf1b74f158240e0bdc39ec696cdb67d!!yKyKhttp://resolver.tudelft.nl/uuid:61610d9adb9e44efaa18a4b178fb620c""yKyKhttp://resolver.tudelft.nl/uuid:8517ffa72f2848f6bb96fe93885541fe##yKyKhttp://resolver.tudelft.nl/uuid:7226c2a4f5164b3caaed1d2ea7da0ab2$$yKyKhttp://resolver.tudelft.nl/uuid:a6b425dad87743c1ac288c1b3cd54f09%%yKyKhttp://resolver.tudelft.nl/uuid:6f56a5a1f3204b0e8ae7d4eada60ca08&&yKyKhttp://resolver.tudelft.nl/uuid:8b5b6fd78a4a468c91dd77f6a3627a2e''yKyKhttp://resolver.tudelft.nl/uuid:c3eb7eb227cf43ae8d990ae92fd057b0((yKyKhttp://resolver.tudelft.nl/uuid:b1b4381d721940b984e76d7fb8a6120a))yKyKhttp://resolver.tudelft.nl/uuid:f12f14ab7ad4425c833538daea5dce1d**yKyKhttp://resolver.tudelft.nl/uuid:81609a44821747dbb6722302af612d40++yKyKhttp://resolver.tudelft.nl/uuid:95b79ea8bb0341d38dea96bdabc8bd41,,yKyKhttp://resolver.tudelft.nl/uuid:65a6e1bcfd87494482d36551b2d973a2yKyKhttp://resolver.tudelft.nl/uuid:6990bd1bf6694dc0ae215cf98c0261f4..yKyKhttp://resolver.tudelft.nl/uuid:159931587871409bbb47c941ef170a41//yKyKhttp://resolver.tudelft.nl/uuid:ec71f4f135ac49e6a1d9889e36a2f83100yKyKhttp://resolver.tudelft.nl/uuid:2cc566bf9d4943b68abbbdb6e2d4bcbd11yKyKhttp://resolver.tudelft.nl/uuid:0b3a6327387d4d8a97d392d0c0340f9f22yKyKhttp://resolver.tudelft.nl/uuid:95ea33ec4f454b199a85fbef153ecb5133yKyKhttp://resolver.tudelft.nl/uuid:ef4dd2961e6442fa9c8a56e2bb515b9a44yKyKhttp://resolver.tudelft.nl/uuid:d32648a716e7439dbe9fbd40e3161a7d55yKyKhttp://resolver.tudelft.nl/uuid:f940c8aba08f4404b5294491af1d688766yKyKhttp://resolver.tudelft.nl/uuid:18cd9b2807ea4151995281aca9f8d65f77yKyKhttp://resolver.tudelft.nl/uuid:9289514b58c64e80948bfed8dcafa4e188yKyKhttp://resolver.tudelft.nl/uuid:0d0cf38be8ea4b7a9e8fb0a0e81e97a199yKyKhttp://resolver.tudelft.nl/uuid:aeefaee33d1f48f8b9a2131971ca5e55::yKyKhttp://resolver.tudelft.nl/uuid:3b45c9ece3da49978f92e89271b442c9;;yKyKhttp://resolver.tudelft.nl/uuid:26ff8cc883154c9590c6e540b645703a<<yKyKhttp://resolver.tudelft.nl/uuid:8ea16a770ce54464af8bba4e4a1c309d==yKyKhttp://resolver.tudelft.nl/uuid:a6cb1a3123c946f09a52b1f68378d57f>>yKyKhttp://resolver.tudelft.nl/uuid:e5a476136f6c48a6a81e16430c319586??yKyKhttp://resolver.tudelft.nl/uuid:55668444877344cea542b28883d3654c@@yKyKhttp://resolver.tudelft.nl/uuid:170cc1de39a64906ad7a935382da4232AAyKyKhttp://resolver.tudelft.nl/uuid:0527c923f2f4422f928cc8fd3d9e6295BByKyKhttp://resolver.tudelft.nl/uuid:37a5a787e38849f59c22579dee5aa1efCCyKyKhttp://resolver.tudelft.nl/uuid:752f1f2226f542e09d5e70aaf95042aaDDyKyKhttp://resolver.tudelft.nl/uuid:1924c75734c24f4699306727c6381615EEyKyKhttp://resolver.tudelft.nl/uuid:28ababd6a8bb46b88145699d1b07106bFFyKyKhttp://resolver.tudelft.nl/uuid:56af8349c1ae48f08bc1beb4a15c4c7fGGyKyKhttp://resolver.tudelft.nl/uuid:ea874d1d9b2b4510a446ae9caec4fcacHHyKyKhttp://resolver.tudelft.nl/uuid:c74b17ead39e4536b21862227a4a97e7IIyKyKhttp://resolver.tudelft.nl/uuid:ea4c851a94bd40f3b71d885c1eaff00cJJyKyKhttp://resolver.tudelft.nl/uuid:7a7a5d241b584e58aa33b9b527ea7b41KKyKyKhttp://resolver.tudelft.nl/uuid:c1362afbddd549ef8563f3fcf737532fLLyKyKhttp://resolver.tudelft.nl/uuid:4df9ab6673584539b392b43c09013030MMyKyKhttp://resolver.tudelft.nl/uuid:64f2fc04f957410dbc10a7b285ef4f06NNyKyKhttp://resolver.tudelft.nl/uuid:4f470bea639d49beaf8dfa3556691801OOyKyKhttp://resolver.tudelft.nl/uuid:d70af4b3b5b740e6b1bc0a7b08880bacPPyKyKhttp://resolver.tudelft.nl/uuid:5c46a3e34341468985000d2408cda5dfQQyKyKhttp://resolver.tudelft.nl/uuid:26d929d605b84583b13b6a2fa0ef35fbRRyKyKhttp://resolver.tudelft.nl/uuid:ef15255ec92c4615bd63b9525f7e25dbSSyKyKhttp://resolver.tudelft.nl/uuid:54461b72390d4755ad4d51a80c1bd352TTyKyKhttp://resolver.tudelft.nl/uuid:835a8461b85346e49a707d8e19a95485UUyKyKhttp://resolver.tudelft.nl/uuid:f5b72d69b9ee4e27be153751a68ca753VVyKyKhttp://resolver.tudelft.nl/uuid:d3a88b74a1584df2ae3a9bb8bc5b6cf6WWyKyKhttp://resolver.tudelft.nl/uuid:6d23442709344f868f18c17a4045293dXXyKyKhttp://resolver.tudelft.nl/uuid:f2a1c8145fa349a982577244c2d46f68YYyKyKhttp://resolver.tudelft.nl/uuid:c27b50de0d8a4a8c923da64633ec9568ZZyKyKhttp://resolver.tudelft.nl/uuid:6debab436c3848ceacb755cbae48f654[[yKyKhttp://resolver.tudelft.nl/uuid:f7957d42891049eb8ba55bd98374ea00\\yKyKhttp://resolver.tudelft.nl/uuid:6d0ac8a138804df6bfb4d4b96563284a]]yKyKhttp://resolver.tudelft.nl/uuid:5c923f77d6d2470dbda608d1dff30b80^^yKyKhttp://resolver.tudelft.nl/uuid:049d25c010124ec48df19b8bfdaffe66__yKyKhttp://resolver.tudelft.nl/uuid:a26e5c46b6a2469296bc43656b9a2ad4``yKyKhttp://resolver.tudelft.nl/uuid:36fc8b483f70418789930072d90ada9faayKyKhttp://resolver.tudelft.nl/uuid:7b0b9d5d78954d469b03d618bd9734fabbyKyKhttp://resolver.tudelft.nl/uuid:097d4a01a0ae47418bbf023b10226dfbccyKyKhttp://resolver.tudelft.nl/uuid:a3762abc0fae4b0bbea6aa571f2db3e2ddyKyKhttp://resolver.tudelft.nl/uuid:0717bd465ec445358ddafd74cfd874eeeeyKyKhttp://resolver.tudelft.nl/uuid:84266f03b9e64fe69e74a727c641d9f5ffyKyKhttp://resolver.tudelft.nl/uuid:ca8cdd02139a423c94f2540330603ccfggyKyKhttp://resolver.tudelft.nl/uuid:6b6317a19e4f4d6bbb2c9e2d803e6625hhyKyKhttp://resolver.tudelft.nl/uuid:640f712ddd994a5ca65f6e2fdcc50ba9iiyKyKhttp://resolver.tudelft.nl/uuid:50734e453a084986b8ba5c711daa76bfjjyKyKhttp://resolver.tudelft.nl/uuid:f9b8ba0dc83d4b1c9450ca1cc2ae8bcbkkyKyKhttp://resolver.tudelft.nl/uuid:8c2fce50b63b4eac99ad70265c9f275ellyKyKhttp://resolver.tudelft.nl/uuid:e1657f41faa44d63a407a34dc49cdbd0mmyKyKhttp://resolver.tudelft.nl/uuid:6954f84f20e24a93919b41a26298ae02nnyKyKhttp://resolver.tudelft.nl/uuid:4dab07ba394d456a9bda2632a45e5ed4ooyKyKhttp://resolver.tudelft.nl/uuid:8e8655c94b234f9e933937c372be931bppyKyKhttp://resolver.tudelft.nl/uuid:1f984a23467a499c90a168e98b728ad8qqyKyKhttp://resolver.tudelft.nl/uuid:61ad5e42e10d470ca500382090e1bff5rryKyKhttp://resolver.tudelft.nl/uuid:c9d6af445c034d03b5b7a9895cc37864ssyKyKhttp://resolver.tudelft.nl/uuid:493d1089c8624cea96b2e4345cb41fe5ttyKyKhttp://resolver.tudelft.nl/uuid:43c9747096cc474aa1eaf61685040f49uuyKyKhttp://resolver.tudelft.nl/uuid:33dea67941a945b7953f987cdd26babdvvyKyKhttp://resolver.tudelft.nl/uuid:8e10d71b962d47c18a88a00a02331765wwyKyKhttp://resolver.tudelft.nl/uuid:f17503749a254f81a5d5e99279aec31exxyKyKhttp://resolver.tudelft.nl/uuid:192ce582153c4bd9961ab0a864b6ce22yyyKyKhttp://resolver.tudelft.nl/uuid:c7f6428c08464d2584ea4090725836d3zzyKyKhttp://resolver.tudelft.nl/uuid:ed7d7c1645704c65a898aeda07de6b8c{{yKyKhttp://resolver.tudelft.nl/uuid:5ac5be234fc04b2d9ec51b799e8944f1yKyKhttp://resolver.tudelft.nl/uuid:1f1bee172f4e4b7c916dc951f25339f6}}yKyKhttp://resolver.tudelft.nl/uuid:586e95fbbfba4ca5907799de795a6415~~yKyKhttp://resolver.tudelft.nl/uuid:020d09eaf8394a5a8e7f2a18f151e92eyKyKhttp://resolver.tudelft.nl/uuid:09ea03c7f34c4407804da37531037f2ayKyKhttp://resolver.tudelft.nl/uuid:337306c14ad949a090debed90539994ayKyKhttp://resolver.tudelft.nl/uuid:3f9194dc95ba47998feb2edfc3e8d512yKyKhttp://resolver.tudelft.nl/uuid:9034f45965bf45fe9ea236e499de1803yKyKhttp://resolver.tudelft.nl/uuid:f9f4a01995374040b1d54c33a2093c18yKyKhttp://resolver.tudelft.nl/uuid:b7664c488b2a4ca79cc12fab32183a87yKyKhttp://resolver.tudelft.nl/uuid:f752f3d45f5249e6a3095786f58dfae8yKyKhttp://resolver.tudelft.nl/uuid:d5828eb0cde34ab5adcc07168d34c45eyKyKhttp://resolver.tudelft.nl/uuid:757ea06c40064a60a03d31388da7a94dyKyKhttp://resolver.tudelft.nl/uuid:b67674f6c10f48158a44a746b9510521yKyKhttp://resolver.tudelft.nl/uuid:c6380fc3f2f4484cae6ed11c499990c5yKyKhttp://resolver.tudelft.nl/uuid:9bccad08b39248a1972efe68e4f7eba9yKyKhttp://resolver.tudelft.nl/uuid:52a36d7411354cf6b843b5ce2acef15ayKyKhttp://resolver.tudelft.nl/uuid:f911ba40d51042c8a6bfd64527330d67yKyKhttp://resolver.tudelft.nl/uuid:fe7e739e0f194a77ba516273e92ba199yKyKhttp://resolver.tudelft.nl/uuid:3cc6b08fa7e1443a8c1d67b461eb915ayKyKhttp://resolver.tudelft.nl/uuid:aa01d8e7778248c18552c97bbfdbee67yKyKhttp://resolver.tudelft.nl/uuid:be874ea3215143d9b4f659dbd459e091yKyKhttp://resolver.tudelft.nl/uuid:569fa57fbd3f4e269c74f544326125bdyKyKhttp://resolver.tudelft.nl/uuid:5f224a8069d040bf8cee7ee22d89afffyKyKhttp://resolver.tudelft.nl/uuid:419c882f51cc4723af404ef71fd4b3cdyKyKhttp://resolver.tudelft.nl/uuid:e23dede0cc57464ead4277b49a1bb6e1yKyKhttp://resolver.tudelft.nl/uuid:55fabcd8043548baaba0a0bad1e05033yKyKhttp://resolver.tudelft.nl/uuid:5aee14ca5e054fec9138dc6f306c1b7cyKyKhttp://resolver.tudelft.nl/uuid:db579f8a3b144c1e949ed63f883cca2eyKyKhttp://resolver.tudelft.nl/uuid:c4772e2ccaae4123b4afc462f23f3489yKyKhttp://resolver.tudelft.nl/uuid:c43b79fe17134fdca310ee70325cfaffyKyKhttp://resolver.tudelft.nl/uuid:7b865e3f1f3b4225b3d697d5f4fca724yKyKhttp://resolver.tudelft.nl/uuid:bffc466e307347c0a35d32c6366ae2bfyKyKhttp://resolver.tudelft.nl/uuid:a751046354464a49a8fc81f44db1d984yKyKhttp://resolver.tudelft.nl/uuid:07504f32d9fb46b98095dcfa5b3e817byKyKhttp://resolver.tudelft.nl/uuid:82033a1584024b47b7ae733b3a1f03acyKyKhttp://resolver.tudelft.nl/uuid:9bf7fc0a55ba4cd091ddb51b2064b638yKyKhttp://resolver.tudelft.nl/uuid:84703eaca0504e85bf3268bbae218732yKyKhttp://resolver.tudelft.nl/uuid:b71c6656d7614fb4b0795c8f363383e9yKyKhttp://resolver.tudelft.nl/uuid:f8c088076c084ea59be387fec54423adyKyKhttp://resolver.tudelft.nl/uuid:015bf386811f4587b50b9bac69f19699yKyKhttp://resolver.tudelft.nl/uuid:7d656a13c0f1425a8835616a1ccfdb0ayKyKhttp://resolver.tudelft.nl/uuid:b68278f691fb471b9d49decc2927f766yKyKhttp://resolver.tudelft.nl/uuid:e599c89e0186472394b5364e85ddb0afyKyKhttp://resolver.tudelft.nl/uuid:0797113de33f491e82bde23b570903a6yKyKhttp://resolver.tudelft.nl/uuid:a89005f207e14c2eb29320ef631cf2aeyKyKhttp://resolver.tudelft.nl/uuid:5bf81d4cd7b24c228e7081a00dc17e7cyKyKhttp://resolver.tudelft.nl/uuid:d16d586072e645e99f560cfcb41d86ceyKyKhttp://resolver.tudelft.nl/uuid:b8934b2b1b8e41dd95a911deed023b0dyKyKhttp://resolver.tudelft.nl/uuid:5857194a8e974b28aaeee77953dfc4bcyKyKhttp://resolver.tudelft.nl/uuid:58eadba7e1bd4ad8a24d40cbd195c444yKyKhttp://resolver.tudelft.nl/uuid:bc09960947bd4ad891ad2a4a9a949c0fyKyKhttp://resolver.tudelft.nl/uuid:c0512fe5692e47e398a2a24cf29c0d09yKyKhttp://resolver.tudelft.nl/uuid:fc9a5a03cbfa40ca8f4d9652ecd325f5yKyKhttp://resolver.tudelft.nl/uuid:68e13eb252e7499c8a04ddee6fa0d6ddyKyKhttp://resolver.tudelft.nl/uuid:f2026ee0a0234c4f8655bef577d28c44yKyKhttp://resolver.tudelft.nl/uuid:810a9ed635724271b99a183b0afe3f7fyKyKhttp://resolver.tudelft.nl/uuid:c3fd77aa1a0f4a7192d286a722ed1366yKyKhttp://resolver.tudelft.nl/uuid:29ed1385a3fc4c09b5db9de3255a8482yKyKhttp://resolver.tudelft.nl/uuid:657c227553f44feea4ed2cedcd302446yKyKhttp://resolver.tudelft.nl/uuid:81188ea4990447608771ab83a58f3650yKyKhttp://resolver.tudelft.nl/uuid:42a624a7721a4b12a06cb1254e16fff4yKyKhttp://resolver.tudelft.nl/uuid:c31a699bf4064235ac85df9b933becbfyKyKhttp://resolver.tudelft.nl/uuid:3db3eeb2766342ccbb72a8aa1c10a67eyKyKhttp://resolver.tudelft.nl/uuid:68eea8de85ef4630bae8409e46402940yKyKhttp://resolver.tudelft.nl/uuid:04e20e93964d4e3c9b706eafc43a888dyKyKhttp://resolver.tudelft.nl/uuid:03efef4f1a9c49548ca1fcd61f4ab6b3yKyKhttp://resolver.tudelft.nl/uuid:fc6ffb9d163948279f8c85d94a74bd2egg
Root Entry Fn@n@@SummaryInformation( F<Workbook FON DocumentSummaryInformation8 F
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~
!"#$%&'()*+,./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{}~