oa A 3D Pseudo-Spectral Method for qP-Wave Simulation in TTI Media and its Application in RTM

A pure qP-wave equation that is free of shear-wave artefacts is usually desired during imaging seismic data in tilted transversely isotropic (TTI) media, by which, crosstalks caused by the interference between different wave modes can be eliminated. However, an undesired SVwave energy could be generated during modeling, even if an acoustic anisotropic wave equation is used. In this study, we first extend the temporal fourth-order pseudospectral time domain (PSTD) PSTD scheme to 3D qP-wavefield simulation in anisotropic media by using Zhou’s equation (Zhou et al., 2006) and the S-wave energy is still detected. And then, a new fully decoupled P-wave equation in TTI media is developed in this study to avoid unwanted energy during migration. During wavefield simulation, the finite difference (FD) and pseudospectral (PS) method are combined in order to accelerate the computation. The comparisons of phase velocities between the new decoupled wave equations and the other approximations are illustrated to validate the precision in different anisotropic medium. To eliminate the artificial boundary reflections, the H-PML in second order wavenumber domain is applied, comparisons of different absorbing boundary layers are illustrated to validate the wave number domain H-PML. The new algorithm is further applied in a new 3D anisotropic reverse time migration (RTM), which has been tested on 3D synthetic SEAM data and field data. As a result, seismic images with high resolution are produced. Benchmarks against commercial implementations are also demonstrated, which proves that the positioning of structure is more reliable and accurate with the new algorithm.