Imaging structures below dipping TI media

Seismic anisotropy in dipping shales causes imaging and positioning problem s for underlying structures. We developed an anisotropic depth-migration ap proach for P-wave seismic data in transversely isotropic (TI) media with a tilted axis of symmetry normal to bedding. We added anisotropic and dip par ameters to the depth-imaging velocity model and used prestack depth-migrate d image gathers in a diagnostic manner to refine the anisotropic velocity m odel. The apparent position of structures below dipping anisotropic overburden ch anges considerably between isotropic and anisotropic migrations. The ray-tr acing algorithm used in a 2-D prestack Kirchhoff depth migration was modifi ed to calculate traveltimes in the presence of TI media with a tilted symme try axis. The resulting anisotropic depth-migration algorithm was applied t o physical-model seismic data and field seismic data from the Canadian Rock y Mountain Thrust and Fold Belt. The anisotropic depth migrations offer sig nificant improvements in positioning and reflector continuity over those ob tained using isotropic algorithms.