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
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.