SLOWNESS-WEIGHTED DIFFRACTION STACK FOR MIGRATING WIDE-ANGLE SEISMIC DATA IN LATERALLY VARYING MEDIA

Abstract

Wide-angle prestack depth migration is an important tool for studying the nature of reflecting boundaries in the earth's crust. The slowness-weighted diffraction stack (SWDS) method has been used to incorporate both two-way traveltime constraints and slowness information in the migration. For this purpose, traveltimes and apparent slownesses of reflected arrivals must be calculated in the image space. Earlier applications of SWDS required a 1D or gently varying seismic velocity structure to obtain these quantities by ray tracing in the image space. I show that the apparent slownesses can also be derived directly from one-way traveltime maps using Fermat's principle. The SDWS is applied to an existing onshore-offshore wide-angle data set, and the example shows that the method can be used to image detailed reflectivity structure at great depths.