HR: 1340h
AN: S43B-1006    [Abstracts]
TI: Finite-Difference Modeling of Seismic Reflection Data in a Hard Rock Environment: An Example from the Mineralized Otago Schist, New Zealand
AU: * Leslie, A
EM: aleslie@clear.net.nz
AF: University of Otago, Department of Geology, P.O. Box 56, Dunedin, 9015 New Zealand
AU: Gorman, A R
EM: andrew.gorman@otago.ac.nz
AF: University of Otago, Department of Geology, P.O. Box 56, Dunedin, 9015 New Zealand
AB: The interpretation of seismic reflection data in non-sedimentary environments is problematic. In the Macraes Flat region near Dunedin (South Island, New Zealand), ongoing mining of mineralized schist has prompted the development of a seismic interpretation scheme that is capable of imaging a gold-bearing shear zone and associated mineralized structures accurately to the meter scale. The anisotropic and complex structural nature of this geological environment necessitates a cost-effective computer-based modeling technique that can provide information on the physical characteristics of the schist. Such a method has been tested on seismic data acquired in 1993 over a region that has since been excavated and logged. Correlation to measured structural data permits a direct comparison between the seismic data and the actual geology. Synthetic modeling utilizes a 2D visco-elastic finite difference routine to constrain the interpretation of observed seismic characteristics, including the velocity, anisotropy, and contrast, of the shear zone structures. Iterative refinements of the model result in a more representative synthetic model that most closely matches the seismic response. The comparison between the actual and synthetic seismic sections provides promising results that will be tested by new data acquisition over the summer of 2004/2005 to identify structures and zones of potential mineralization. As a downstream benefit, this research could also contribute to earthquake risk assessment analyses at active faults with similar characteristics.
DE: 7260 Theory and modeling
DE: 8015 Local crustal structure
DE: 8025 Mesoscopic fabrics
DE: 0902 Computational methods, seismic
SC: Seismology [S]
MN: 2004 AGU Fall Meeting