甘孜-玉树断裂带的新构造特征与地震危险性估计

本文综合野外调查,卫、航影象判读,地震活动及震源机制等资料,初步研究了北西向甘孜-玉树断裂带的新构造特征,探讨了拉分构造的发育与强震活动的关系。结果表明:该断裂带是一自中生代以来形成和发展的大型活动断裂带;第四纪以来以强烈的水平左旋剪切错动为主,水平与垂直位错之比约为10:1。从历史地震活动规律推断了在未来20—30年内,该带将进入一个新的地震活跃期,并具有发生M≥7级地震的危险性

NEOTECTONIC FEATURES OF THE GANZI-YUSHU FAULT ZONE AND ASSESSMENT OF ITS EARTHQUAKE RISK

Based on the data of field investigations,interpretations of both Landsat images and air photos,seismicity and focal mechanism,this paper describes the neotectonic features of the Ganzi-Yushu fault zone in western Sichuan.The relationship between the forming of pull-apart basins and the occurring of strong earthquakes is also discussed here.The result shows that this fault zone is another large strike-slip fault zone in western Sichuan,which formed and developed from Mesozoic era.It has been dominated by intensive left-lateral dislocation,its maximum horizontal offset is up to about 100 m and the ratio of horizontal offset to vertical offset is about 10 :1 since the Late Quaternary period.Up to 1984,the earthquake eneigy of this fault zone had been so accu-mlated as to cause an earthquake of magnitude 7.4.Therefore,on the basis of historical earthquake activity,it is inferred that this fault zone would enter into a new active period of earth-quake activity with the risk of occurring of an earthquake of magnitude 7 or greater in the next 20-30 years.