PRIMARY RESEARCH ON STRESS DROP IN SOURCE REGION OF CONTINUOUS 5 M_L ≥ 4.0 EARTHQUAKE SEQUENCE IN SHANXI PROVINCE

After primary research on relationship among quantities of inelastic attenuation coefficient, site response and new source parameters, using data of 612 M_L ≥ 2.0 earthquakes occurred between August 2008 and May 2012 in Shanxi area, this paper calculates the new source parameters of 148 earthquakes.It focuses on the background stress drop in the source regions of continuously occurred 5 M_L ≥ 4.0 earthquakes in Shanxi seismic zone during this period, obtaining that the average stress drop of Yangqu seismic region is 2.586 MPa, and those of other 4 seismic regions are among 1~2 MPa.While the stress drops after the earthquakes of Yangqu source region, Yuanping source region and Datong source region in central Shanxi trend towards steady low, analytically it finds the earthquake stress drops are still in the trend of continued accumulation and gradual strengthening after the earthquakes near Hongdong and Hejin source regions in the south-central region of Shanxi, so the south-central region of Shanxi should be paid close attention.