Gaussian beam prestack depth migration of converted wave in TI media

摘要

Increasing amounts of multi-component seismic data are being acquired on land and offshore because more complete seismic wavefield information is beneficial for structural imaging, fluid detection, and reservoirmonitoring. S-waves are typically influencedmore by anisotropy in amediumthan are P-waves; as a result, the anisotropy cannot be ignored during the converted PS-wave imaging. Gaussian beam migration, an elegant and efficient depth migration method, is becoming a new topic in the study of PS-wave migration; its accuracy is comparable to that of wave-equation migration, and its flexibility is comparable to that of Kirchhoff migration. In this paper, we introduce an anisotropic Gaussian beam prestack depth migration (GB-PSDM) method for the converted PS-wave, in which the anisotropic media can be a transversely isotropic (TI) medium with a vertical or tilted symmetry axis. We present the PS-wave common shot gathers GB-PSDM imaging condition and derive the ray tracing of P-and SV-waves in two-dimensional TI media. The migration impulse responses of P-and SV-propagation modes in TI media with both vertical and tilted symmetry axes are presented. The results of numerical examples indicate that the method introduced here offers significant improvements in the quality of converted PS-wave imaging compared with an isotropic algorithm.