2012年9月7日彝良地震震源区横波分裂变化特征分析  

A Study on Variation Characteristics of Shear-wave Splitting in the September 7, 2012 Yiliang Earthquake Region

作　　者：刘希康[1,2] 李媛[1] 丁志峰[2] 常利军[2] 王跃东[1] LIU Xi-kang;LI Yuan;DING Zhi-feng;CHANG Li-jun;WANG Yue-dong(First Crust Monitoring and Application Center,China Earthquake Administration,Tianjin 300180,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局第一监测中心,天津300180 [2]中国地震局地球物理研究所,北京100081

出　　处：《地震》2020年第1期73-83,共11页Earthquake

基　　金：地震科技星火计划项目(XH18068Y,XH17057Y);中国地震局震情跟踪项目(2017010122)

摘　　要：为探究2012年9月7日彝良地震前后横波分裂参数的时空变化特征,利用研究区内中国地震科学台阵--南北地震带南段2011年8月至2013年9月的19个流动地震台观测资料进行了横波分裂计算。结果显示,位于断裂带上方及其附近台站的快波偏振方向显示为NE方向,与断裂带走向基本一致,而断裂带不发育的局部区域快波偏振方向为NW向,与区域主应力场方向较为一致,说明快波偏振方向能够很好反映上地壳的应力分布状态;慢波时间延迟则在地震前后表现出明显的变化,在地震发生前,整体表现为逐渐增加的趋势,且分布较为离散,表明该地区地壳应力逐渐积累,在地震发生后慢波时间延迟开始急剧下降,分布也较为收敛,说明地壳应力随地震的发生迅速得到释放。In order to study the spatial and temporal change of shear-wave splitting before and after September 72012 Yiliang earthquake,the study uses data obtained from temporary stations in the south part of North-South Seismic Belt setting up under the project ChinArray Phase one from August 2011 to September 2013,to compute the seismic anisotropy.The result shows that the stations in the area of fault belt and nearby reveal the NE polarization directions of fast shear waves,which are consistent with the strike of faults.However,the stations in the area have no or little faults reveal the NW polarization,which are consistent with the directions of regional principal compressive stress.The result demonstrates polarization directions of fast shear waves can clearly reveal the stress states of upper crust.There is a visible change in the delay time of slow shear-wave during the observational times,especially before and after earthquake.Before the earthquake,the delay time of slow wave slowly increased,and the distribution was discrete,suggesting the stress accumulation.After the earthquake occurred,the delay time of the slow shear-wave decreased rapidly,indicating the stress in the crust releases rapidly with the earthquake occurrence,which meaned this method can be used to monitor crustal stress changes.

关 键 词：彝良地震 横波分裂 地壳各向异性 地壳应力 

分 类 号：P315.7[天文地球—地震学]