Searched for: faculty%3A%22Civil%255C%252BEngineering%255C%252Band%255C%252BGeosciences%22
(61 - 80 of 104)
- document
-
Broggini, F. (author), Snieder, R. (author), Wapenaar, C.P.A. (author)With seismic interferometry one can retrieve the response to a virtual source inside an unknown medium, if there is a receiver at the position of the virtual source. Using inverse scattering theory, we demonstrate that, for a 1D medium, the requirement of having an actual receiver inside the medium can be circumvented, going beyond seismic...journal article 2012
- document
-
Ruigrok, E.N. (author), Wapenaar, C.P.A. (author)A number of seismic methods exist to image the lithosphere below a collection of receivers, using distant earthquakes. In the current practice, especially mode-conversions in teleseismic phases are utilized. We present a new method that takes advantage of the availability of global phases. This method is called global-phase seismic...journal article 2012
- document
-
Hunziker, J.W. (author), Slob, E.C. (author), Fan, Y. (author), Snieder, R. (author), Wapenaar, C.P.A. (author)Interferometry by multidimensional deconvolution applied to Controlled-Source 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 air-water...conference paper 2012
- document
-
Wapenaar, C.P.A. (author), Thorbecke, J.W. (author), Van der Neut, J.R. (author), Broggini, F. (author), Snieder, R. (author)It 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...conference paper 2012
- document
-
Harmankaya, U. (author), Kaslilar, A. (author), Thorbecke, J.W. (author), Wapenaar, C.P.A. (author), Draganov, D.S. (author)In this study, non-physical (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 virtual-source...conference paper 2012
- document
-
Wapenaar, C.P.A. (author), Douma, H. (author)The generalized optical theorem is an integral relation for the angle-dependent scattering amplitude of an inhomogeneous scattering object embedded in a homogeneous background. It has been derived separately for several scalar and vectorial wave phenomena. Here a unified optical theorem is derived that encompasses the separate versions for...journal article 2012
- document
-
Wapenaar, C.P.A. (author), Van der Neut, J.R. (author), Thorbecke, J.W. (author)Deblending of simultaneous-source data is usually considered to be an underdetermined inverse problem, which can be solved by an iterative procedure, assuming additional constraints like sparsity and coherency. By exploiting the fact that seismic data are spatially band-limited, deblending of densely sampled sources can be carried out as a...journal article 2012
- document
-
Ruigrok, E.N. (author), Campman, X. (author), Wapenaar, K. (author)The last few years there has been a growing number of body-wave observations in noise records. In 1973 Vinnik conjectured that P-waves would even be the dominant wavemode, at epicentral distances of about 40 degrees and onwards from an oceanic source. At arrays far from offshore storms, surface waves induced by nearby storms would not mask the...journal article 2011
- document
-
Van der Neut, J.R. (author), Thorbecke, J.W. (author), Mehta, K. (author), Slob, E.C. (author), Wapenaar, C.P.A. (author)Various researchers have shown that accurate redatuming of controlled seismic sources to downhole receiver locations can be achieved without requiring a velocity model. By placing receivers in a horizontal or deviated well and turning them into virtual sources, accurate images can be obtained even below a complex near-subsurface. Examples...journal article 2011
- document
-
Hunziker, J.W. (author), Slob, E.C. (author), Wapenaar, C.P.A. (author)In time-lapse controlled-source electromagnetics, it is crucial that the source and the receivers are positioned at exactly the same location at all times of measurement. We use interferometry by multidimensional deconvolution (MDD) to overcome problems in repeatability of the source location. Interferometry by MDD redatums the source to a...journal article 2011
- document
-
Van der Neut, J.R. (author), Tatanova, M. (author), Thorbecke, J.W. (author), Slob, E.C. (author), Wapenaar, C.P.A. (author)With controlled-source seismic interferometry we aim to redatum sources to downhole receiver locations without requiring a velocity model. Interferometry is generally based on a source integral over cross-correlation (CC) pairs of full, perturbed (time-gated), or decomposed wavefields. We provide an overview of ghosts, multiples, and spatial...journal article 2011
- document
-
Wapenaar, C.P.A. (author), Ruigrok, E.N. (author), Van der Neut, J.R. (author), Draganov, D.S. (author)The methodology of surface?wave retrieval from ambient seismic noise by crosscorrelation relies on the assumption that the noise field is equipartitioned. Deviations from equipartitioning degrade the accuracy of the retrieved surface?wave Green's function. A point?spread function, derived from the same ambient noise field, quantifies the...journal article 2011
- document
-
Minato, S. (author), Matsuoka, T. (author), Tsuji, T. (author), Draganov, D.S. (author), Hunziker, J.W. (author), Wapenaar, C.P.A. (author)Crosswell reflection method is a high-resolution seismic imaging method that uses recordings between boreholes. The need for downhole sources is a restrictive factor in its application, for example, to time-lapse surveys. An alternative is to use surface sources in combination with seismic interferometry. Seismic interferometry (SI) could...journal article 2011
- document
-
Tetyukhina, D. (author), Van Vliet, L.J. (author), Luthi, S.M. (author), Wapenaar, C.P.A. (author)Fluvio-deltaic sedimentary systems are of great interest for explorationists because they can form prolific hydrocarbon plays. However, they are also among the most complex and heterogeneous ones encountered in the subsurface, and potential reservoir units are often close to or below seismic resolution. For seismic inversion, it is therefore...journal article 2010
- document
-
Wapenaar, C.P.A. (author), Van der Neut, J.R. (author)Green’s function retrieval by crosscorrelation may suffer from irregularities in the source distribution, asymmetric illumination, intrinsic losses, etc. Multidimensional deconvolution (MDD) may overcome these limitations. A unified representation for Green’s function retrieval by MDD is proposed. From this representation, it follows that the...journal article 2010
- document
-
Ruigrok, E.N. (author), Campman, X. (author), Draganov, D.S. (author), Wapenaar, K. (author)In recent years, there has been an increase in the deployment of relatively dense arrays of seismic stations. The availability of spatially densely sampled global and regional seismic data has stimulated the adoption of industry-style imaging algorithms applied to converted- and scattered-wave energy from distant earthquakes, leading to...journal article 2010
- document
-
Wapenaar, C.P.A. (author), Draganov, D.S. (author), Snieder, R. (author), Campman, X. (author), Verdel, A. (author)Seismic interferometry involves the crosscorrelation of responses at different receivers to obtain the Green's function between these receivers. For the simple situation of an impulsive plane wave propagating along the x-axis, the crosscorrelation of the responses at two receivers along the x-axis gives the Green's function of the direct wave...journal article 2010
- document
-
Wapenaar, C.P.A. (author), Slob, E.C. (author), Snieder, R. (author), Curtis, A. (author)In the 1990s, the method of time-reversed acoustics was developed. This method exploits the fact that the acoustic wave equation for a lossless medium is invariant for time reversal. When ultrasonic responses recorded by piezoelectric transducers are reversed in time and fed simultaneously as source signals to the transducers, they focus at the...journal article 2010
- document
-
Frijlink, M. (author), Wapenaar, C.P.A. (author)One-way wave equations conveniently describe wave propagation in media with discontinuous and/or rapid variations in one direction, but with smooth and slow variations in the complementary transverse directions. In the past, reciprocity theorems have been developed in terms of one-way wave fields. The boundaries of the integration volumes and...journal article 2010
- document
-
Wapenaar, C.P.A. (author), Slob, E.C. (author), Snieder, R. (author)We have analyzed the far-field approximation of the Green's function representation for seismic interferometry. By writing each of the Green's functions involved in the correlation process as a superposition of a direct wave and a scattered wave, the Green's function representation is rewritten as a superposition of four terms. When the...journal article 2010
Searched for: faculty%3A%22Civil%255C%252BEngineering%255C%252Band%255C%252BGeosciences%22
(61 - 80 of 104)