HR: 1330h
AN: S52E-0171    [PDF]
TI: Numerical Seismic Studies of Fault Detection in Geothermal Reservoirs
AU: * Gritto, R
EM: rgritto@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road, MS 90-1116, Berkeley, CA 94720 United States
AU: Majer, E L
EM: elmajer@lbl.gov
AF: Lawrence Berkeley National Laboratory, One Cyclotron Road, MS 90-1116, Berkeley, CA 94720 United States
AB: A finite-difference modeling study of seismic wave propagation was conducted to determine how to best investigate subsurface faults and fracture zones in geothermal areas. The numerical model was created based on results from a previous seismic reflection field experiment. A suite of fault models was investigated including blind faults and faults with surface expressions. The seismic data suggest that blind faults can be detected by a sudden attenuation of seismic wave amplitudes, as long as the fault is located below the receiver array. Additionally, a conversion from P- to S-waves indicates the reflection and refraction of the P-waves while propagating across the fault. It was found that the initial P-waves interfere with the tip of the fault and their energy is scattered in the process (elastic scattering) leading to a reduction in amplitude of the wave front in the shadow of the fault tip. However, the P-waves experience wave front healing during their propagate away from the fault. The drop in amplitudes and the excitation of S-waves can be used to estimate the location of the fault at depth. The accuracy of the numerical modeling depends on the availability of a priori in situ information (velocity and density) from borehole experiments in the geothermal area.
DE: 0902 Computational methods, seismic
DE: 5144 Wave attenuation
DE: 7203 Body wave propagation
DE: 8010 Fractures and faults
SC: Seismology [S]
MN: 2003 Fall Meeting