Station Travel‐Time Calibration Method Improves Location Accuracy on a Global Scale

Abstract

Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Test Ban Treaty. Earthquake location accuracy is related to the degree of knowledge about the 3-D structure of seismic wave velocity in the Earth. It is well known that modeling errors of calculated travel times may have the effect of shifting the computed epicenters far from the real locations by a distance even larger than the size of the statistical error ellipses, regardless of the accuracy in picking seismic phase arrivals. In the present study, we develop a method of seismic location based on a set of well located events recorded by the dense national seismic network in a seismically active region of central Japan. We show that mislocations of the order of 10-20 km affecting the epicenters calculated from a global seismic network and using the standard IASPEI91 travel times can be effectively removed by applying station-source-specific corrections. The results show a clear correlation of the travel time residuals with the subduction structure beneath Japan.