Evaluation of Seismic Event Location Methods on the Regional Event Location System (RELS).

摘要

Several location methods developed at SDAC are evaluated by comparing location errors of these methods against errors computed with the standard method. The new methods include: Using P travel times in laterally heterogeneous media: A station travel time residual correlation matrix in the normal equations; Location with simultaneous determination of Pn, Pg, and Lg velocities; Combination of the correlation matrix method and the simultaneous determination method. All the methods evaluated in this report appear to give smaller absolute epicenter and depth errors than the standard method of locating events. Furthermore, these methods do not use station corrections; therefore the locations obtained are not station- or region-dependent. They can be used to locate seismic events in any source region, with any set of stations. When average location errors are compared against errors with the standard method, the correlation matrix is about 3 km better, e.g., about 17 kilometers as compared to 20 kilometers; the regional models method is 3 to 6 km better, e.g., about 5 kilometers as compared to 9 kilometers, depending on whether near-regional stations are used. The average location errors from the true epicenters using regional data are approximately 6 km. The addition of Lg arrivals to locate events did not result in better locations. Typically, we added 6 Lg arrival times to a total of 15 Pn and Pg arrival times. The lack of improvement may be attributed to a greater variance in Lg travel times.