Abstract:A detailed tomographic image of the upper crustal structure in Bachu-Jiashi area,Xinjiang Uygur Autonomous Region,is determined by using P-wave arrival time from the Bachu-Jiashi MS6.8 earthquake in 2003.The inversion results as following：Over 5 km depth in the region,P-velocity imaging shows strongly horizontal heterogeneity,reflecting characteristics of sedimentary cover;Between 5～14 km dpeth,P-velocity imaging suggests that there exist two high and conjugated velocity zone encircled with relative low velocity body,one trending NWW and the other NNE.Combined with tectonic background and focal mechanism solutions,it is holded that the character of earthquakes in this region is similar under the action of double-couple,one of which is along NW-SE right-lateral strike-slip couple,and the other is along NNE-SSW compressive stress.The NWW and NNE zone of heterogeneity provided the fundation for strain energy accumulation and release,and was an important condition for occurence of the Bachu-Jiashi earthquake.Combined the macro damage and isoseismic feature from field investigation and the study on petroleum seismic exploration,it is considered that this earthquake occurred on Bashitupu fults in western tarim basin,which trends along NWW and is north dipping.
