2013年四川芦山7.0级地震前后三峡库区地震活动变化

Seismicity Changes in the Three Gorges Reservoir Area Before and After the Lushan M7.0 Earthquake in Sichuan in 2013

采用地震活动性方法,在巴颜喀拉块体与三峡地区地震活动相关性分析基础上,重点研究2013年芦山7.0级地震前后三峡库首区地震活动的变化,探讨远场强震对三峡大坝的影响。研究认为,三峡地区地震活动一定程度受巴颜喀拉块体向东滑移与华南地块碰撞-俯冲动力作用影响,大震前后常伴有4级以上地震活动。大震前1~3月3级以上地震增强活动,震后活动减弱;或大震前地震活动增强一直持续到震后1~2月。芦山7.0级地震前三峡库首区微震频次上升,仙女山-九畹溪断裂深部构造运动增强;地震后库区微震频次下降,震源深度加深,高桥断层附近岩溶地区发生拉张正断型巴东5.1级地震。研究表明,远场大震引起的库区地震频次和强度的变化,对三峡大坝的安全不构成威胁,但大震前后库区4~5级地震活动可诱发滑坡、崩塌等地质灾害,防范这类灾害是库区防灾的重点。

Based on the correlation analysis between six strong earthquaks in the Bayan Har Block and M L≥3 earthquakes in the Three Gorges Reservoir area,we focused on study seismicity changes in the Three Gorges Reservoir area before and after the Lushan M 7.0 earthquake in 2013,and discussed the impact of far-field strong earthquakes on the Three Gorges Reservoir area.It shows that the seismicity in the Three Gorges area is affected by the collision-subduction dynamic action between the eastward sliding of Bayankala Block and the South China block,and M≥4.0 earthquakes often occurred before and after a strong earthquake in the study area.The frequency of M≥3.0 earthquakes increased in three months before a strong earthquake,while decreased after the earthquake,or the increasing of earthquake activities before a strong earthquake lasted to 1~2 months after the strong earthquake.Before the Lushan M 7.0 earthquake,the frequency of micro-esrthquakes increased in the Three Gorges Reservoir area,and the deep tectonic movement of Xiannvshan-Jiuwanxi Fault intensified.After the earthquake,the frequency of micro-esrthquakes decreased and the focal depth deepened,the Badong M 5.1 earthquake occurred in the karst area near the Gaoqiao Fault.The research shows that the changes of the frequency and intensity of earthquakes in the Three Gorges Reservoir area caused by far-field strong earthquakes do not threaten the safety of the Three Gorges dam,but M 4~5 earthquakes in the reservoir area before and after strong earthquakes can induce landslides,collapses etc.Therefore,it should focus on preventing such geological disasters in the reservoir area in the future.