Acoustic VTI Full Waveform Inversion: Sensitivity Analysis And Realistic Synthetic Examples

Full waveform inversion (FWI) is a seismic imaging method suitable for wide aperture / azimuth acquisitions thanks to its ability to account for waves propagating over a broad range of incidence angles. Wide aperture / azimuth acquisitions makes, however, the imaging quite sensitive to anisotropy because of the intrinsic difference between vertical and horizontal velocities in vertical transversely isotropic (VTI) media. In this study, we present a numerical procedure to define the best parametrization for acoustic VTI FWI. High-resolution velocity model for either the vertical, the horizontal or the normal move out (NMO) velocity can be developed by monoparameter FWI, when the considered wave speed is combined with the Thomsen’s parameters δ and e in the parametrization, and when available smooth background models of δ and e are kept fixed during FWI. An alternative is to jointly reconstruct two wavespeeds (for example, the vertical and the horizontal velocities) using a model parametrization that combines these two wavespeeds and δ . However, the spatial resolution of the two resulting velocity models is more limited that of the velocity model obtained with the first mentioned parametrization.