HR: 1340h
AN: S33A-1081    [Abstracts]
TI: Waveform tomography at a ground water contamination site: comparison with depth migration
AU: * Gao, F
EM: fcgao@rice.edu
AF: Center for Computational Geophysics, Rice University, 6100, Main St, Houston, TX 77251 United States
AU: Fradelizio, G
AF: Center for Computational Geophysics, Rice University, 6100, Main St, Houston, TX 77251 United States
AU: Levander, A
EM: alan@rice.edu
AF: Center for Computational Geophysics, Rice University, 6100, Main St, Houston, TX 77251 United States
AU: Pratt, G
EM: pratt@geol.queensu.ca
AF: Department of Geological Sciences and Engineering, Queen's University, 99 University Avenue, Kingston, K7L 3N6 Canada
AU: Zelt, C
EM: czelt@rice.edu
AF: Center for Computational Geophysics, Rice University, 6100, Main St, Houston, TX 77251 United States
AU: Symes, W
EM: symes@caam.rice.edu
AF: Center for Computational Geophysics, Rice University, 6100, Main St, Houston, TX 77251 United States
AB: We have previously applied 2D acoustic waveform tomography to surface and VSP seismic data from a groundwater contamination site, where the results were compared with images from a 3D reflection dataset. In this study, 2-D waveform tomograms from the reflection dataset acquired at Hill Air Force Base (HAFB) are extensively compared with depth migrated images from the same dataset. Comparisons of tomograms and depth migrated images from a small subset of the data show good agreement in terms of the structural features identified in both types of images. In terms of shallow seismic imaging, the advantages of waveform tomography over depth migration are that the former can be applied using both direct and refracted waves, eliminating a number of processing steps while achieving resolution scales similar to depth migration. Further more, the images provide quantitative estimates of material property perturbations. The disadvantage of waveform tomography is its computational expense when compared with migration. This restricts waveform tomography to 2D applications at present. Thus far we have applied acoustic waveform tomography to first arrival waveforms from land data as an approximation to the elastic case. To improve the applicability of waveform inversion, we present initial efforts to develop a form of elastic waveform tomography in the frequency-space domain. The frequency domain approach has distinct computational advantages over time domain in 2D applications. The technique is being developed in Cartesian as well as cylindrical coordinates to take the curvature of the Earth into account, in order to allow application to teleseismic data.
DE: 7260 Theory and modeling
DE: 7294 Instruments and techniques
DE: 7203 Body wave propagation
SC: Seismology [S]
MN: 2004 AGU Fall Meeting