鲁甸M_(S)6.5地震前巧家台阵观测到的中小地震应变释放加速现象  

The Accelerating Seismic Strain Release Observed by the Qiaojia Seismic Array Prior to the Ludian M_(S)6.5 Mainshock

作　　者：陈学忠[1] 李艳娥[1] 陈丽娟 CHEN Xue-zhong;LI Yan-e;CHEN Li-juan(Institute of Geophysics,CEA,Beijing 100081,China;Chongqing Earthquake Administration,Chongqing 401147,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]重庆市地震局,重庆401147

出　　处：《地震》2021年第3期32-41,共10页Earthquake

基　　金：中国地震局地球物理研究所基本科研业务专项(DQJB19B31)。

摘　　要：本文利用2012年3月-2019年12月巧家台阵观测到的地震活动资料,基于累积应变释放曲线的斜率K随时间的变化,分析了鲁甸地震前地震活动的应变释放加速现象。结果显示:(1)鲁甸MS6.5地震前,深部(震源深度h≥10 km)地震K值出现了明显的逐渐上升过程,而浅部(震源深度在10 km以内)地震K值则没有明显变化,保持平稳。表明深部地震活动应变释放存在显著的加速过程,而浅部地震活动则保持平稳;(2)鲁甸地震之后,深部地震K值迅速下降,于2016年年初达到最低值,直到2019年年底,一直处于较低水平,期间巧家台阵邻近地区没有发生过较强的地震;(3)根据应变释放理论模型估计了幂指数m,在K值上升过程前期m=0.177,后期m=0.902,表明在K值上升过程前期应变释放加速是很快的。上述观测结果对地震孕育过程的认识和地震预测研究拟或具有一定的启示意义。On the basis of earthquakes observed by the Qiaojia array from March,2012 to December,2019,we investigated the temporal evolution of seismic strain release.We considered the slope K of cumulative seismic strain release curve as a function of time.The results show that before the Ludian M_(S)6.5 mainshock,the slope K increased rapidly for the deep earthquakes(focal depth h≥10 km),and remained stable for the shallow earthquakes(focal depth h<10 km),i.e.,there was a significant accelerating seismic strain release in the deeper crust,but no significant accelerating seismic strain release nor significant decelerating one in the shallower crust.After the Ludian earthquake occurred,in the deeper crust k value dropped rapidly,corresponding to the decelerating seismic strain release,and approached the lowest value in early 2016,and then maintained at low values up to the end of 2019.In this period no strong earthquake occurred in and around the Qiaojia array.The power index m estimated by the seismic strain release theoretical model is 0.177 during the early stage of k value rising process,and 0.902 during the later one for deep earthquakes before the Ludian MS6.5 mainshock,indicating that the strain release accelerated very rapidly in the deeper crust in the early stage of k value rising process.The above observations may avail to take a deeper insight about the earthquake gestation process and earthquake prediction.

关 键 词：鲁甸地震 巧家台阵 应变释放 加速 

分 类 号：P315.7[天文地球—地震学]