Fast prestack depth migration using a Kirchhoff integral method , by John T. Etgen

A Kirchhoff integral method using approximate Green's function calculations can accurately migrate data before-stack, faster than previous implementations. Traveltimes and amplitudes of the WKB Green's functions for either stratified or laterally varying media are precomputed using an efficient top-down approach and stored on disk. Two-point ray tracing is avoided. For any given surface point, only a sparse fan of rays is calculated; and extensive interpolation creates a traveltime map from that surface point to all image points. For laterally varying media, only a "few" surface locations are used for ray tracing. The traveltime maps for locations not ray-traced are found by interpolation of existing traveltime maps. These results apply to post-stack depth migration as readily as they do to prestack depth migration. Two examples demonstrate the method.


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