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departmentresearch group programmeprojectcoordinates)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; acousticenconference paperSEGEGreen 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.
20190419)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 Delft 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.EAGE
20181214)uuid:013a0e813a844013975c4a2624fb4b0eDhttp://resolver.tudelft.nl/uuid:013a0e813a844013975c4a2624fb4b0eWVirtual seismology: from hydrocarbon reservoir imaging to induced earthquake monitor< ingfWapenaar, 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 Imaging)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: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 s< uch 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.
20181215)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: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 bet< ween 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.#Applied Geophysics and Petrophysics)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 be 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 f< ull 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.
20171231)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 mediaHolicki, 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)nWe 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 w< avefield 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:65a6e1bcfd87494482d36551b2d973a2Dhttp://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 sourcereceiv< er 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: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: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 f< ield data application, since neither the data nor the acquisition geometry are ever perfect. In addition, MDD is computationally expensive.)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 m< ethod 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 subsurfaceSingh, 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:56af8349c1ae48f08bc1beb4a15c4c7fDhttp://resolver.tudelft.nl/uuid:56af8349c1ae48f08bc1beb4a15c4c7fFullfield MDD for bodywave reflections from passive transientsources under severely limited and irregular illumination conditionsHartstra, 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)Seismic 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 ill< umination 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:7a7a5d241b584e58aa33b9b527ea7b41Dhttp://resolver.tudelft.nl/uuid:7a7a5d241b584e58aa33b9b527ea7b41Application of seismic interferometry by multidimensional deconvolution to ambient seismic noise recorded in Malarge, ArgentinaWeemstra, 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 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 t< emporally stable surfacewave responses.)uuid:ea874d1d9b2b4510a446ae9caec4fcacDhttp://resolver.tudelft.nl/uuid:ea874d1d9b2b4510a446ae9caec4fcac^Deep ocean sound speed characteristics passively derived from the ambient acoustic noise fieldEvers, 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: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 t< he 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: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: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:f5b72d69b9ee4e27be153751a68ca753Dhttp://resolver.tudelft.nl/uuid:f5b72d69b9ee4e27be153751a68ca7534Inversion of the multidimensional marchenko equationAVan der Neut, J.R.; Thorbecke, J.W.; Wa< penaar, 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 method can be extended to 3D situations, in a similar way as we extended the acoustic 1D method to the 3D situation.)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:6d0ac8a138804df6bfb4d4b96563284aDhttp://resolver.tudelft.nl/uuid:6d0ac8a138804df6bfb4d4b9< 6563284a^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: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 subsurface 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.$Society of Exploration Geophysicists)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 these 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 multiplesTSingh, S.; Snieder, R.; Behura, J.; van der Neut, J.R.; Wapenaar, C.P.A.; Slob, E.C.#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: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. Inspire< d 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 redatuming5Van der Neut, J.R.; Vasconcelos, I.; Wapenaar, C.P.A.Recently, 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 interferometry, 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: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: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: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: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.; Gro< bbe, 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:d5828eb0cde34ab5adcc07168d34c45eVLocating 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 deconvolution1Van Dalen, K.N.; Wapenaar, C.P.A.; Halliday, D.F.xVirtualsource 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: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 actual 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: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 Reflection 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: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
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