THE GEOLOGICAL BACKGROUND OF 1679 GREAT EARTHQUALE IN SANHE-PINGGU AND THE POTENTIAL SEITMIC RISK IN JIZHONG AREA

The 1679 Shanhe-Pinggu great earthquake Occurred in Dachang fault-depression. On the basis of artifcial seismological data, the seismostructure of the earthquake has been ftudied by the authors. The fault is the margin fault of the Dachang fault-depression and is considered as the main structure of generating earthquake. The Shaih-DiaHn fault is a Eocene fault and characterized by dextral strike-slip normal fault with gentle dip extending in s-shape. The present authors infer that the earthquake occured at the turnning site from NE to NEE in north section of Shian-Diahn fault whict was a seismic structure. This site is a barrier where the earthquake occurred. Morever, the authors compared the Dachang fault-depression, as a representation, with Shulu fault-depressioa and so on, and discussed the seismic risk in Jizhong area. It is shown that the crust in mid-part of Jizhong area is stable and that in southern part and northern is active eitger in geology or in seismilogy.