A first-order quasi-SV-wave propagator in 2-dimensional vertical transversely isotropic (VTI) media

He Liu, Kristopher A. H. Innanen

The propagation of elastic waves in formations has been widely investigated in the development of seismic exploration. In a typical transversely isotropic medium (e.g., vertical transversely isotropic-VTI medium), qP- and qSV-waves are intrinsically coupled as described in elastic wave equations. Therefore, coupled qP-wave energy will inevitably contaminate the imaging results from performing elastic reverse time migration (ERTM) and imaging algorithms to qSV-mode waves. Other than directly separate qS-mode waves from full elastic waves in anisotropic media, some researchers have tried to find an alter-native way to solve it by the forward simulation of pure-qSV-mode waves. In this study, we propose a first-order wave propagator of pseudo-pure-qSV-mode wave in 2D heterogeneous VTI media, which can be easily employed for the simulation of qSV-mode wave propagation with staggered-grid finite difference scheme. This propagator will directly suppress qP-mode wave energy through projecting the wavefields onto isotropic references of local polarization direction. By further correction of projection deviation of simulated wavefield components, residual qP-waves will be completely eliminated and separated scalar pseudo-pure-qSV-mode waves can be achieved. We have performed the algorithm to isotropic medium, VTI media with weak/strong anisotropy, a two-layer VTI model and part of heterogeneous SEG/Hess VTI model, the synthetic results demonstrate the validity and feasibility of this algorithm. In addition, the more efficient and more stable first-order Hybrid-PML can be directly implemented in this staggered-grid finite difference algorithm, which shows better performance in the wavefield propagation simulation in VTI media with strong anisotropy.