Wave equation based prestack depth migration using generalized screen propagator

Computational efficiency and accuracy of seismic wave propagators are major concerns for 3-D prestack depth migration. Generalized screen propagator (GSP) is a dual-domain one-way propagator, which neglects reverberations between heterogeneities but correctly handles the forward multiple-scattering including focusing, diffraction, refraction and interference of seismic waves. Downward continuation of the wavefield using GSP is performed with a phase shift in a background medium followed by a wide-angle correction that accommodates strong lateral velocity variations. In this paper, we implement GSP in double square root equation and propose an efficient and accurate offset domain prestack depth migration method for 2-D common offset and 3-D common azimuth seismic data. Combined with common angle imaging (CAI) condition, offset domain GSP migration produces high quality images at a number of angles (or offset ray parameter values). Since offset ray parameter is proportional to angle of incidence at the reflector, CAI gathers provide a complete set of tools for migration velocity analysis and AVO analysis.