HR: 1330h
AN: S42E-0206    [PDF]
TI: Surface-wave Derived Focal Mechanisms in Mid-America
AU: * Herrmann, R B
EM: rbh@eas.slu.edu
AF: Department of Earth and Atmospheric Sciences, Saint Louis University 3507 Laclede Avenue, St. Louis, MO 63122 United States
AU: Ammon, C J
EM: cammon@geosc.psu.edu
AF: Department of Geosciences, Penn State University, University Park, PA 16802 United States
AU: Benz, H M
EM: benz@usgs.gov
AF: U. S. Geological Survey, Denver Federal Center MS 967, Box 25046, Denver, CO 80225 United States
AB: In regions of low-to-moderate seismic activity, quantitative estimates of source size and faulting mechanism are important for definition of regional tectonics and for notification of the public. This task is challenging because the lack of low-frequency signal content, often due to a low signal-to-noise ratio, precludes the use of standard waveform inversion techniques, which would require detailed path-dependent velocity models to describe the high-frequency waveforms. Surface-wave spectral amplitudes, chosen using an expected Love- and Rayleigh-wave group velocity can be used to determine the source depth, seismic moment and to provide four candidate focal mechanisms from which the final solution is selected using the few waveforms with good signal-to-noise. The advantage of fitting the surface-wave spectral amplitudes is that the source parameter estimates are much less sensitive to the details of the Earth model than are time-domain waveforms. We have successfully determine source for moment magnitudes as small as 3.9 for mid-America and 3.4 elsewhere. As a result of determining focal mechanisms for 8 recent earthquakes, details of automatic processing will be presented.
DE: 7215 Earthquake parameters
DE: 7230 Seismicity and seismotectonics
DE: 7255 Surface waves and free oscillations
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting