HR: 1340h
AN: S53A-0192    [Abstracts]
TI: Delineation of Rupture Propagation of Large Earthquakes Using Source-Scanning Algorithm: A Control Study
AU: * Kao, H
EM: hkao@nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre 9860 West Saanich Road P.O.Box 6000, Sidney, BC V8L4B2 Canada
AU: Shan, S
EM: sshan@nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre 9860 West Saanich Road P.O.Box 6000, Sidney, BC V8L4B2 Canada
AB: Determination of the rupture propagation of large earthquakes is important and of wide interest to the seismological research community. The conventional inversion method determines the distribution of slip at a grid of subfaults whose orientations are predefined. As a result, difference choices of fault geometry and dimensions often result in different solutions. In this study, we try to reconstruct the rupture history of an earthquake using the newly developed Source-Scanning Algorithm (SSA) without imposing any a priori constraints on the fault's orientation and dimension. The SSA identifies the distribution of seismic sources in two steps. First, it calculates the theoretical arrival times from all grid points inside the model space to all seismic stations by assuming an origin time. Then, the absolute amplitudes of the observed waveforms at the predicted arrival times are added to give the "brightness" of each time-space pair, and the brightest spots mark the locations of sources. The propagation of the rupture is depicted by the migration of the brightest spots throughout a prescribed time window. A series of experiments are conducted to test the resolution of the SSA inversion. Contrary to the conventional wisdom that seismometers should be placed as close as possible to the fault trace to give the best resolution in delineating rupture details, we found that the best results are obtained if the seismograms are recorded at a distance about half of the total rupture length away from the fault trace. This is especially true when the rupture duration is longer than ~10 s. A possible explanation is that the geometric spreading effects for waveforms from different segments of the rupture are about the same if the stations are sufficiently away from the fault trace, thus giving a uniform resolution to the entire rupture history.
DE: 7294 Instruments and techniques
SC: Seismology [S]
MN: 2004 AGU Fall Meeting