Epicenter Location Capability of a Small Aperture Array

Abstract

The epicenter estimation capability if a small aperture array is investigated by examining the bachazimuth anomalies of eighty-eight local earthquakes in the vicinity of the Pinyon Flat of southern California. The backazimuths with reliable reference backazimuths directly computed from the known locations as reported by the Anza and Caltech seismic networks. Further, the observed backazimuths are computed by using a beamforming technique to analyze arrivals of the first P-waves recorded at a small dense array with 25 stations within an aperture of about 3 km. A plot of the backazimuths anomalies with reference backazimuths shows that the first order backazumyth anomalies are strongly dependent on the backazimuths in a sine-like function. This result generally agrees with the theoretical calculation from a simple crustal model with an interface dipping twenty-five degrees to the northeast and, consequently, indicates that the epicenter location capability of a small aperture array may improved with the correction of anomalous backazimuths based on the crustal model with a dipping interface.

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