Epicentral Location of Regional Seismic Events Based on Empirical Green's Functions from Ambient Noise.

摘要

The purpose of this research is to develop and test a novel method of regional seismic event location based on exploiting Empirical Green's Functions (EGF) that are produced from ambient noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long ambient noise time-series recorded at the two stations. The EGFs principally contain Rayleigh and Love wave energy and our focus is placed on utilizing these signals between 5- and 15-sec periods. By comparing the tabulated EGFs in the frequency-time domain with similarly transformed records of seismic events (earthquakes, explosions, mine collapses) obtained by a network of remote stations, we have tested the method by locating events in the western USA for which other methods provide accurate locations (Californian Ground Truth earthquakes, the mine collapse in Utah). Data from the EarthScope USArray were used primarily. The location errors for GT1 earthquakes in California and the Crandall mine collapse in Utah were on average less than 1 km with origin time errors less than 1 s. These results were described in detail in Ritzwoller et al. (2009). During the past year we continued to refine the method and evaluate its capabilities. The ability of this approach to locate seismic events using a limited number of recording stations with significant open azimuth has been shown. We applied this method to less ideal environments locating small seismic events with magnitude 3.0-3.7 in Utah, with location accuracy better than 0.5 km relative to the University of Utah network locations. The effects of unknown source mechanism and depth on location were studied and are presented here. All research to date is described in detail by Barmin et al. (2010). Future work will continue to refine the location procedure and explore it ability to constrain depth and the moment tensor using ambient noise.