SINGLE STATION EVENT LOCATION: EPICENTRAL DISTANCE, BEARING, AND FOCAL DEPTH

The most sensitive and reliable methods for locating small-magnitude regional seismic events using records from a single, three-component station require knowledge of the near-station and along-path crustal structure. Unfortunately, obtaining information about crustal structure is time-consuming and may be costly. Furthermore, different location methods may be required depending on the lateral complexity of the crust. Here we address a simpler problem: How often can single-station methods accurately determine event-station bearing and distance information if no information about crustal structure is available? • Neither bearing nor distance determination was generally possible for signals if the SNR was less than about 2.0; bearing determination was most successful at most stations if signals were high-pass filtered with a cut-off frequency of about 0.5 Hz. • Bearing determination for low-magnitude signals was possible even if they had no impulsive P phases if covariance methods were applied to the entire P-to-S time window. • For signals with SNR> 2.0, there were clear differences between stations with respect to how well they could determine bearing direction. At many ‘good ’ stations, 66 % of the bearings determined by the 2-D covariance method were within about 6o-10o of the expected bearing; at many other stations, the 66th percentile of th