Relocation of Earthquakes by Source‐Specific Station Corrections in Iran

Abstract

Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Nuclear‐Test‐Ban Treaty. Modeling errors of calculated travel times, in addition to the density of the stations, their epicentral distances, and their azimuthal coverage, may have the effect of shifting the computed epicenters far from the real locations, regardless of the accuracy in picking seismic phase arrivals.

In the present study, we compare the regional locations for one set of earthquakes obtained by arrival times reported by the Iranian Seismological Center with teleseismic locations obtained by arrival times reported by the International Seismological Center. We found location differences on the order of 10–20 km or larger, affecting both epicentral coordinates and depths. Average travel‐time residuals to each station of the global network were computed for a set of sources located in the study area. We show that systematic shifts of hypocentral coordinates, as well as the sizes of their error ellipses, can be substantially reduced by applying source‐specific station corrections. Finally, the validity of the calibration method was confirmed by a test carried out on a dataset different from that used for computing the travel‐time corrections.

This study includes an analysis of the effect of removing arrival times of critical stations from the dataset used for the locations, showing that this effect is largely reduced by the application of travel‐time corrections.