Elastic RTM: anisotropic wave‐mode separation and converted‐wave polarization correction

Lu, Ruqian; Jia, Yanmin; Traynin, Peter; Anderson, John E.; Dickens, Thomas A.

doi:10.1190/1.3513505

Cited by 32 publications

(18 citation statements)

References 12 publications

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“…Ravasi and Curtis Denli and Huang, 2008;Lu et al, 2010). Other than transmission artifacts, present also in the PP images and significantly attenuated by the application of a nonlinear imaging condition (Figure 22d), polarity reversals are evident.…”

Section: S150mentioning

confidence: 94%

“…Denli and Huang (2008) defined a wavefield-separation imaging condition based on the separation of wavefields with respect to a given direction using f-k filters after the elastic wavefields are downward propagated. Rosales et al (2008) and Lu et al (2010) suggested an approach in which the angle-domain common-image gathers (Sava and Fomel, 2003) are computed at every image point and the polarity is corrected in the angle domain before stacking. Finally, Du et al (2012) introduced a sign factor to represent the polarity distribution of the S-wave component; this sign factor is computed using the energy flux density vector.…”

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confidence: 99%

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Nonlinear scattering based imaging in elastic media: Theory, theorems, and imaging conditions

Ravasi

Curtis

2013

GEOPHYSICS

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With the more widespread introduction of multicomponent recording devices in land and marine ocean-bottom seismic acquisition, elastic imaging may become mainstream in coming years. We have derived new, nonlinear, elastic imaging conditions. A correlation-type representation theorem for perturbed elastic media, commonly used in seismic interferometry to explain how a scattered wave response between two receivers/ sources may be predicted given a boundary of sources/receivers, can be considered as a starting point for the derivation. Here, we use this theorem to derive and interpret imaging conditions for elastic migration by wavefield extrapolation (e.g., elastic reverse-time migration). Some approximations lead to a known, heuristically derived imaging condition that crosscorrelates P-and S-wave potentials that are separated in the subsurface after full-wavefield extrapolation. This formal connection reveals that the nonapproximated correlation-type representation theorem can be interpreted as a nonlinear imaging condition, that accounts also for multiply scattered and multiply converted waves, properly focusing such energy at each image point. We present a synthetic data example using either an ideal (acquisition on a full, closed boundary) or a real (partial boundary) seismic exploration survey, and we demonstrate the importance of nonlinearities in pure-and converted-mode imaging. In PP imaging, they result in better illumination and artifact reduction, whereas in PS imaging they show how zero time-lag and zero space-lag crosscorrelation imaging conditions are not ideal for imaging of converted-mode waves because no conversion arises from zero-offset experiments.

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Section: S150mentioning

confidence: 94%

mentioning

confidence: 99%

Nonlinear scattering based imaging in elastic media: Theory, theorems, and imaging conditions

Ravasi

Curtis

2013

GEOPHYSICS

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“…The implementations and applications described above are acoustic. Elastic RTM has already been studied (Teng et al, 1986;Chang and McMechan, 1987;Cunha Filho, 1992;Sun et al, 2006;Lu et al, 2010;Xiao and Leaney, 2010;Anderson et al, 2012;Jiao et al, 2012;Yan and Xie, 2012;Luo et al, 2013). These studies have generally omitted, or used approximate, P-S wave separations, amplitude and phase corrections, and S-polarity correction, and do not deal with storage issues.…”

Section: Introductionmentioning

confidence: 96%

Five ways to avoid storing source wavefield snapshots in 2D elastic prestack reverse time migration

2015

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Five alternative algorithms were evaluated to circumvent the excessive storage requirement imposed by saving source wavefield snapshots used for the crosscorrelation image condition in 2D prestack elastic reverse time migration. We compared the algorithms on the basis of their ability, either to accurately reconstruct (not save) the source wavefield or to use an alternate image condition so that neither saving nor reconstruction of full wavefields was involved. The comparisons were facilitated by using the same (velocity-stress) extrapolator in all the algorithms, and running them all on the same hardware. We assumed that there was enough memory in a node to do an extrapolation, and that all input data were stored on disk rather than residing in randomaccess memory. This should provide a fair and balanced comparison. Reconstruction of the source wavefield from boundary and/or initial values reduced the required storage to a very small fraction of that needed to store source wavefield snapshots for conventional crosscorrelation, at the cost of adding an additional source extrapolation. Reverse time checkpointing avoided recursive forward recomputation. Two nonreconstructive imaging conditions do not require full snapshot storage or an additional extrapolation. Timebinning the imaging criteria removed the need for image time searching or sorting. Numerical examples using elastic data from the Marmousi2 model showed that the quality of the elastic prestack PP and PS images produced by the cost-optimized alternative algorithms were (virtually) identical to the higher cost images produced by traditional crosscorrelation.

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“…First, as mentioned above, the amplitude polarity change is generally one of the most important issues with elastic imaging and velocity analysis. Many studies address this issue and provide different solutions either correcting it in angle domain common image gathers (Lu et al, 2010) or with the help of the Poynting vector (Shang et al, 2012). However, for our synthetic study, we simply correct the amplitudes in the image domain as well as in the extended local offset domain (i.e for negative offsets we multiply the obtained image for each source by -1).…”

Section: Practical Considerationsmentioning

confidence: 99%

“…P-and S-wave speeds). Yan (2010) analyzed the behavior of the objective function for converted P to S phases for reflection-type WEMVA and showed that it appears to be convex. Because of this, we expect transmission WEMVA to also exhibit favorable properties for estimating large-scale velocity models.…”

Section: Introductionmentioning

confidence: 99%

Converted phase elastic migration velocity analysis

Shabelansky

Malcolm

Fehler

et al. 2013

SEG Technical Program Expanded Abstracts 2013

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SUMMARYMulti-component elastic seismic data collected at large offsets have the potential to be used in seismic imaging and velocity analysis. In this study, we present an approach for convertedphase elastic-transmission migration velocity analysis with an application for VSP and micro-seismic studies. Our approach is based on the cross-correlation between converted-phase Pand S-waves propagated backward in time, and is formulated as an inverse problem with a differential semblance criterium objective function for the simultaneous update of both P-and S-wave velocity models. The merit of this approach is that it is fully data-driven and requires only one elastic backward propagation to form an image rather than the two (one forward and one backward) acoustic propagations needed for standard RTM. Moreover, as the method does not require forward propagation, it does not suffer from migration operator source aliasing when a small number of shots are used. We present a derivation of the method and test it with the synthetic Marmousi model. We also show the differences between the standard reflection offset domain common image gathers and the converted-phase image gathers that we use for model updates.

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Elastic RTM: anisotropic wave‐mode separation and converted‐wave polarization correction

Cited by 32 publications

References 12 publications

Nonlinear scattering based imaging in elastic media: Theory, theorems, and imaging conditions

Nonlinear scattering based imaging in elastic media: Theory, theorems, and imaging conditions

Five ways to avoid storing source wavefield snapshots in 2D elastic prestack reverse time migration

Converted phase elastic migration velocity analysis

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