Regional Seismic Event Identification and Improved Locations with Small Arrays and Networks.
Final rept. 7 May 93-30 Sep 95,
SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA
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This final report contains a summary of our work on the use of seismic networks and arrays to improve locations and identify small seismic event. The research can be divided into three main areas. We have developed techniques to migrate 3-component array records of local, regional and teleseismic wavetrains to directly image buried two- and three-dimensional heterogeneities e.g. layer irregularities, volumetric heterogeneities in the vicinity of the array. The initial intent of this research effort was to identify noise sources excited by incident signals and isolate their contributions to seismic coda. This technique has been applied to small-aperture array data collected in southern California. We have developed a technique to empirically characterize local and regional seismic code by binning and stacking network recordings of dense aftershock sequences. The principle motivation for this work was to look for robust coda phases dependent on source depth. Weve used these empirical results, obtained by examining ANZA network recordings of Lande and Superstition Hills aftershocks, and have developed a technique to constrain sour depth. We have extended our ripple-fired event discriminant based on the time-independence of coda produced by ripple firing by looking for an independence of the coda from the recording direction also indicative of ripple-firing. MM
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