STUDY ON SEISMIC FAULT AND SOURCE RUPTURE TECTONIC DYNAMIC MECHANISM OF JIUZHAIGOU M_S 7.0 EARTHQUAKE

The seismic fault and source rupture tectonic dynamics mechanism of Jiuzhaigou M_S7.0 Earthquake were studied in this paper based on the combination of geological investigation, test and source tectonic dynamic theoretical analysis. This earthquake occurred at the intersection of the northern margin of the Minshan uplift belt and the south of Wenxian-Maqin fault in the south margin of the West Qinling trough, where is under sinistral shear stress with high law stress. There are two tectonic ruptures with NW trending fissure zone along the line of "Jiuzhaigou Paradise"-epicenter-Wuhuahai and Shangsizhai Village-Zhongcha-Bimang, which is ground coseismic rupture caused by "hidden" earthquake fault, former is the structure controlling this earthquake, the later is the sub-coseismic resurrection and extension of the NW-trending fault; the displacement of source fault in this earthquake is strike-slip shear fracture dominated by deep angle fault with strike NW331ånd dip angle ∠87°, and the aftershock activity is controlled by two NW-trending faults, the shear fracture at both ends of the fault showed continuous expansion trends. The source tectonic dynamic mechanism is actually sinistral cutting "protrusion" along NW in the deep of crust. The continuous expansion of rupture at both ends of seismic fault will produce the gradual breakthrough of the crustal "protrusion".