Single Station Event Location: Epicentral Distance, Bearing, and Focal Depth
Abstract
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? (1) 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. (2) 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. (3) For signals with SNR greater than 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 6 deg - 10 deg of the expected bearing; at many other stations, the 66th percentile of the bearings was 10 deg-30 deg. (4) There were no obvious differences in the geographic or tectonic character of 'good' and 'other' stations. Our original method for determining event-station distance relied solely on the ratios of short-term and long-term averages to find S-P times and thus distance; this method was able to determine distances to within 20 km of the true distance for only 10% of the records we studied. Currently, we are revisiting the phase=identification method to incorporate information about signal polarization.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2000
- Accession Number
- ADA529924
Entities
People
- Ben Phillips
- Cliff Frohlich
- Jay Pulliam
Organizations
- University of Texas at Austin