Earthquake relocations in Huoshan area, Anhui province, by applying the Source-Specific Station Term Method

The article mainly introduces an earthquake location method-Source-Specific Station Term (SSST) approach, and presents the application of this method to relocate earthquakes between 1976 and 2008 in the Huoshan area, located in Dabie Mountain in Anhui province. After relocation, the location accuracy is significantly improved and the epicenter distribution is more compact. The location errors, estimated by using a bootstrap approach, are 0. 4 km, 0. 6 km, and 0.9 km in the east-west, north-south, and vertical directions, respectively. The root-meansquares (RMS) of arrival time residuals have a sharp reduction after the SSST relocation from 1. 34 to 0. 11 s. We also make a concise comparison between the SSST method and the DoubleDifference (DD) algorithm. The result shows that the SSST method can easily be used, and can almost relocate all the events. In addition, it also has achieved some improvements in absolute location. After the SSST relocation, we apply the results to seismicity analysis in the Huoshan area, there are three obvious compact stripes and we divide them into three seismic density zones. Based on the analysis of temporal-spatial distribution characteristics, we find that the three zones all have shallow focal depths, although the temporal-distributions are different. To further improve the location accuracy, the waveform cross-correlation could be combined with the SSST method when conditions permit in the future.