Inversion gradients for acoustic VTI wavefield tomography

Vladimir Li, Hui Wang, Ilya Tsvankin, Esteban Díaz, Tariq Ali Alkhalifah

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a generalized pseudospectral operator based on a separable approximation for the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified image-power objective functions. We also obtain the gradient expressions for a data-domain objective function that can more easily incorporate borehole information necessary for stable VTI velocity analysis. These gradients are similar to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations but the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show the potential advantages of the modified image-power objective function in estimating the anellipticity parameter η.
Original languageEnglish (US)
Pages (from-to)WA55-WA65
Number of pages1
JournalGEOPHYSICS
Volume82
Issue number4
DOIs
StatePublished - Jun 7 2017

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