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Performing wave-equation migration directly from topographic surfaces
is achievable with a minimum of preprocessing in topographic
coordinate systems. We show that conformal mapping generates the required
topographic coordinate systems, and that the conformal map transform
determines the appropriate wavefield extrapolation equations. We also
conclude that multiple reference media are likely needed to image
under complicated topography, which is consistent with wavefield
extrapolation practice in a Cartesian coordinate system.
By extension, we show that upward datuming on a coordinate system
generated through conformal mapping transformation could work as a
pre-imaging processing step. Moreover, upward datuming could be
more effective than downward migration direct from topography, since a
constant velocity function would likely improve the range over which
the phase-screen approximation is accurate. Standard Cartesian-based
migration technology could then be used to downward continue the
upward datumed wavefields.

** Next:** Acknowledgments
** Up:** Shragge and Sava: Migration
** Previous:** Discussion and Future Work
Stanford Exploration Project

10/23/2004