2-METHODS FOR COMPUTING THE IMAGING CONDITION FOR COMMON-SHOT PRESTACK MIGRATION

Two alternative ways to compute the imaging condition for prestack migration of common-shot data are presented. The same finite-difference scheme is used for both data extrapolation and image condition computation with little modification by switching the direction of extrapolation. The imaging condition is obtained by modeling, using either a minimum-time or a maximum-amplitude criterion. It is expected that computing the imaging condition using finite differences will be faster on parallel or vector computers than the original ray tracing plus interpolation procedure. It is felt that while finite differences can be executed efficiently in parallel and interpolation requires additional condition checks of raypath intersecting with image grid points, computing the imaging condition is of special importance in 3-D prestack migration (Chang and McMechan, 1990). -Authors