HR: 0800h
AN: S31B-1064    [Abstracts]
TI: Incorporating topography into crustal-scale wave-equation imaging through conformal mapping
AU: * Shragge, J
EM: jeff@sep.stanford.edu
AF: Stanford University, Geophysics Department Mitchell Building, Stanford, CA 94305 United States
AU: Sava, P
EM: paul@sep.stanford.edu
AF: Stanford University, Geophysics Department Mitchell Building, Stanford, CA 94305 United States
AB: Migration of seismic land data acquired over topography presents significant challenges for seismic imaging technology. One technique commonly used to alleviate the deleterious effects of topography is to include a wavefield datuming step in the pre-migration processing flow. Locations exhibiting strong, near-surface lateral velocity contrast accompanying topography, though, may have significant wavefield triplication that leads to non-optimal datuming procedures; especially if Kirchhoff-based methods are used. Accordingly, the use of novel wave-equation approaches that naturally handle wavefield-multipathing should lead in these situations to significantly improved datuming or migration procedures. Conformal mapping is a technique used widely in applied physics and engineering fields to facilitate numerical solution of boundary value problems involving surfaces exhibiting complex geometry. The general reason for applying this procedure is to transform solution domains marked by complicated boundaries, such as topography, to domains that are more regular, such as Cartesian. The conformal mapping transforms may then be used to define wavefield-extrapolation equations appropriate for using in the new domain. In this paper, we demonstrate that the conformal mapping transform coupled with the Riemannian wavefield extrapolation (Sava, 2004) generate orthogonal meshes, herein termed topographic-coordinate systems, and governing equations appropriate for incorporating topography directly into wave-equation migration. This premise is illustrated with poststack and prestack crustal-scale sized synthetic data sets with a topographic surface taken from the Foothills region of British Columbia, Canada.
UR: http://sepwww.stanford.edu/sep/students/jeff.html
DE: 7260 Theory and modeling
DE: 7294 Instruments and techniques
DE: 7203 Body wave propagation
DE: 7205 Continental crust (1242)
SC: Seismology [S]
MN: 2004 AGU Fall Meeting