滇西北地区强震危险性分析

Analysis on Strong Earthquake Risk in Northwestern Yunnan

利用1965年1月—2018年11月云南地震台网提供的月报目录和1999年1月—2018年10月中小地震震源机制解,对滇西北地区主要断裂的b值和震源机制一致性参数进行了空间扫描,结合历史强震空区,分析了滇西北地区的强震危险性。结果表明:①2000年1月以来程海断裂、龙蟠—乔后断裂及维西—乔后断裂南段b值显著降低,而中甸断裂地震空区两端、程海断裂及邻区则为低b值(b<0.7)主体区域。②震源机制一致性较好的区域分布于程海断裂中部、龙蟠—乔后断裂及维西—乔后断裂南段及邻区。分析认为,低b值和震源机制一致性好可能是区域应力水平增强所致,据此判断程海断裂、龙蟠—乔后断裂及维西—乔后断裂南段及邻区可能是滇西北地区未来发生强震的潜在危险区。

Using the monthly report catalog provided by Yunnan Seismic Network from Jan.,1965 to Nov.,2018 and the focal mechanisms of small-moderate earthquakes from Jan.,1999 to Oct.,2018,we calculated the spatial distribution characteristics of b -value and focal mechanism consistency parameters in the Northwest Yunnan. And then combined with the seismic gap of historical strong earthquakes,we analyzed the strong earthquake risk in northwest Yunnan. The results show that:①Since Jan.,2000, b -value in the Chenghai fault,southern sections of the Longpan-Qiaohou fault and Weixi-Qiaohou fault has been significantly reduced. And the main area of the low b -value( b <0.7)in the research area is at both ends of Zhongdian fault seismic gap,Chenghai fault zone and its adjacent areas.②The regions with good consistency in the source mechanism are located in the middle of the Chenghai fault,the southern sections of Longpan-Qiaohou fault and the Weixi-Qiaohou fault and their adjacent areas. It is concluded that the low b -value and the best consistency of the source mechanisms may be due to the increase of regional stress. Based on this,it can be judged that Chenghai fault,the southern sections of Longpan-Qiaohou fault and Weixi-Qiaohou fault and their adjacent areas are the potential seismic hazard areas for strong earthquakes in Northwestern Yunnan in future.