白鹤滩水库蓄水前后邻区地震活动与应力场变化特征  

Characteristics of seismic activity and stress field changes in the adjacent area before and after the impoundment of Baihetan Reservoir

作　　者：刘恒 付真 吴建平[1,2] 许力生[1,2] 张旭[1,2] 李春来 李璐[1,2] LIU Heng;FU Zhen;WU JianPing;XU LiSheng;ZHANG Xu;LI ChunLai;LI Lu(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Earthquake Source Physics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局震源物理重点实验室,北京100081

出　　处：《地球物理学报》2023年第10期4189-4205,共17页Chinese Journal of Geophysics

基　　金：国家重点研发计划项目(2021YFC3000703-03);国家自然科学基金(U213905)共同资助。

摘　　要：水库诱发地震是水利水电工程和区域构造稳定性研究的重要内容.白鹤滩水库位于金沙江下游河段,地处小江断裂、则木河断裂和大凉山断裂等多条大型断裂交汇区域,属于地震高烈度区.2021年4月6日白鹤滩水库开始蓄水,本文利用小江断裂带中北段巧家台阵2020年1月—2021年12月地震记录,确定了水库邻区11477个地震事件,采用广义极性振幅技术反演获得了1.5级以上地震震源机制解654个.对水库蓄水前后地震活动和震源机制解分布特征的分析表明:整体而言研究区地震活动时序与水库水位密切相关,水位抬升时地震活动增强,水位维持不变或回落时,地震活动减弱,白鹤滩水库蓄水约6个月后,地震数量基本恢复至蓄水前平均水平.沿水域线附近主断裂带区域,蓄水后地震活动显著增强,数量和震级增大,深度减小,蓄水前地震类型以走滑为主,蓄水后以正断层为主;主断裂带以外以及距离水域线较远的某些区域,蓄水后地震活动受到抑制.基于震源机制解,采用区域应力场阻尼反演方法计算获取了研究区应力场时空分布,结果显示主拉应力轴方向稳定,随时间波动很小,主压应力轴方向随时间波动较大,尤其位于大坝附近的主断裂带交汇区域,蓄水前应力场为走滑型,蓄水后应力场变为正断型.这些结果揭示了水库诱发地震活动和应力场改变的更多细节特征,可进一步为水库诱发地震危险性评估提供重要参考.The reservoir-induced earthquake is an important content in the study of water conservancy and hydropower projects and regional tectonic stability.The Baihetan Reservoir is located in the lower reaches of the Jinsha River,where several large faults such as the Xiaojiang fault,the Zemuhe fault and the Daliangshan fault intersect.It belongs to a high seismic intensity area.On April 6,2021,the Baihetan Reservoir began to store water.In this paper,11477 seismic events in the vicinity of the reservoir were determined by using the seismic records of Qiaojia Array in the middle and northern section of the Xiaojiang Fault Zone from January 2020 to December 2021.Using Generalized Polarity and Amplitude Technique,654 focal mechanism solutions of earthquakes with ML≥1.5 were obtained.The analysis of the distribution characteristics of seismic activity and focal mechanism solution before and after the impoundment of the reservoir shows that,overall,the seismicity in the study area is closely related to the water level of the reservoir.When the water level rises,the seismic activity increases,and when the water level remains unchanged or falls,the seismic activity decreases.After the impoundment of the Baihetan Reservoir for about 6 months,the number of earthquakes basically returns to the average level before impoundment.In the main fault zone area along the water line,the seismic activity after impoundment increased significantly with the number and magnitude increasing,and the depth decreasing.The seismic type before impoundment is mainly strike-slip,and after impoundment the normal fault earthquake dominates.Outside the main fault zone and far away from the water line,seismic activity is inhibited after impounding.Based on the focal mechanism solutions,the spatiotemporal distribution of the stress field in the study area was obtained using the regional stress field damping inversion method.The results show that the direction of the main tensile stress axis is stable with little fluctuation over time,while the direction

关 键 词：白鹤滩水库 水库蓄水 地震活动 震源机制 应力场变化 

分 类 号：P315[天文地球—地震学]