DETERMINATION OF SONGPINGGOU FAULT IN DIEXI, SICHUAN

The M_S 7.5 earthquake occurred in Diexi,Sichuan on August 25,1933. A representative view is that the Songpinggou fault is the seismogenic structure of this earthquake. However,scholars still have certain differences about the existence,development,and activity of the Songpinggou fault. Based on previous studies,this paper determines the existence and the spatial distribution characteristics of the Songpinggou fault through field geological survey and geophysical exploration. Meanwhile,this paper also analyzes the active strength of the Songpinggou fault using ArcGIS software. The results show that the Songpinggou fault develops along the Songping gully and strikes NW-trending with a dip angle of 55°~80°. It is composed of NW,middle,and SE segments,where the NW segment inclines into NE and the others inclines into SW. The Songpinggou fault is a strike-slip reverse fault dominated by counterclockwise horizontal dislocation,which has been active since about 20,000 years ago. And the activity of the middle segment and SE segment of the Songpinggou fault is stronger than that of the NW segment.