Prototype autonomous earthquake locator for regional networks

Abstract

A fully autonomous source location algorithm, which identifies the local earthquake P and S phases by finding the network seismogram envelope maxima P max and S max, is designed. These picks are approximated to theoretical travel times of the wavefield intensity by varying epicenter and origin time, thus providing initial estimates for source coordinates, origin time and phase onsets. Then the onsets are improved by detection of the time-series discrepancy points with the subsequent fitting to the theoretical first arrival times for the final source location. Fitting is performed using a grid-search robust optimization procedure based on the bell-like factor functions. Application of the algorithm to 61 local earthquakes recorded by the Israel Seismic Network shows location accuracy of 3 km for epicenter and ±7 km for depth. For the four blasts from a quarry near the Dead Sea with known coordinates and ignition time the automatic locator provided accuracy of 0.3 - 1.7 km and even outperformed the analyst solutions.