Relocation of small to moderate earthquakes in Shanxi Province and its relation to the seismogenic structures

Based on the phase reports of analog seismic stations from 1981-2001, and those of digital seismographs from 2002-2008, we relocated the small to moderate earthquakes with unprecedented precision by absolute and relative relocating methods. Results show that: (1) comparing with precious researches, the percentage of relocated earthquakes with horizontal locating error ≤5 km increases from 65. 8% to 86. 2%, and 7498 earthquakes which were not located previously are located in this work; (2) The general pattern of seismicity has no big changes in horizontal directions. Most earthquakes occurred in the central rift belt, with a few earthquakes located at the two sides of the Fenhe-Weihe Rift While in vertical direction, the relocated earthquakes have an obvious trend that the earthquake depths increase from north to south part of the Fenhe Rift (3) The distribution of relocated earthquakes can outline the profile of the lower seismogenic boundaries of the basins, as well as the boundaries between the extensional basins and the uplifted areas. (4) There is a good correlation between the focal depths and the structures of the basin and range system.