小湾水库影响区地震活动性探讨

Preliminary Study of the Seismicity around Xiaowan Reservoir,Yunnan,China

利用区域构造、小湾库区水载荷变化及云南省区域地震台网2000—2021年的地震监测资料,对小湾水库影响区内水库蓄水前后地震活动空间、频度、强度等进行综合分析,并对区域断层性质、库水位载荷变化、震源机制解、地震应力降参数进行深入分析。结果显示:小湾水库影响区及附近第四纪断裂构造交汇,环境复杂且存在应力水平较高区域;水库蓄水对库区基底岩层及库岸岩体影响显著,地震活动明显增强;水库影响区地震空间分布明显受区域构造控制;在水载荷变化的影响下,触发了构造区的应力释放,发生了走滑断层性质破裂的2015年昌宁5.1级地震。

By using of the data of regional tectonics,reservoir loading variation,regional seismicity from 2000 to 2021,we synthetically analyzed the regional seismic spatial distribution,frequency and intensity around Xiaowan Reservoir before and after retain water,including the regional fault character,focal mechanism and seismic stress drop.The main results are as follows:①The Xiaowan reservoir locates in the cross area of Quaternary faults with complicated tectonic environment and local higher stress;②The seismicity increases obviously with the process of retain water which may make impact the bed and bank rock mass;③The seismic spatial distribution around the reservoir was controlled by regional tectonics;④The mechanism of the M 5.1 earthquake is strike-slip which was mainly cause by the tectonic stress release with the water loading variation of Xiaowan reservoir.