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.
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