Anisotropic depth migration: Reducing lateral‐position uncertainty of subsurface structures in thrust‐belt environments

Abstract

Seismic velocity anisotropy causes lateral-positioning errors on seismic images (Isaac and Lawton, 1999, Alkhalifah and Larner, 1994). The application of anisotropic depth migration (ADM) corrects lateral mispositioning of subsurface targets (Vestrum, Lawton and Schmid, 1999, Di Nicola-Carena, E., 1997, Vestrum and Muenzer, 1997, Ball, 1995). The assumption of isotropic seismic velocities means traditional depth migration only corrects positioning errors due to lateral velocity heterogeneity. Mispositioning caused by seismic anisotropy remained uncorrected on these depth-migrated sections. Furthermore, isotropic depth migration was only applied where significant lateral velocity changes were present, and lateral mispositioning caused by seismic anisotropy remained uncorrected on time-migrated sections. If seismic data are to accurately image the subsurface, we need to reconsider the assumptions made in depth imaging and we need to reconsider where depth migration applies to our seismic data.