2012年彝良M_S5.7和M_S5.6地震序列重定位和震源机制解特征  

Relocations and focal mechanism solutions characteristics of 2012 Yiliang M_S5.7 and M_S5.6 earthquake sequence

作　　者：吕苗苗[1,2] 丁志峰[1,2] 徐小明[1,2] 李大虎[1,2,3] 叶庆东[4] 郑晨[1,2] 

机构地区：[1]中国地震局地震观测与地球物理成像重点实验室,中国北京100081 [2]中国地震局地球物理研究所,中国北京100081 [3]四川省地震局,中国成都610041 [4]中国地震局第一监测中心,中国天津300180

出　　处：《地震学报》2015年第6期885-898,1,共14页Acta Seismologica Sinica

基　　金：国家公益性地震行业科研专项(201308011;201008001)资助

摘　　要：利用地震科学探测台阵在云南、贵州地区的17个流动台站的地震记录,采用双差定位法对2012年9月7日云南彝良MS5.7和MS5.6地震及其余震序列(ML≥1.0)进行重定位.在获得精确的震源位置后,采用CAP法反演了MS≥4.0地震的震源机制解.结果显示,彝良MS5.7主震位于(27.509°N,103.971°E),震源深度为9.7km,震源机制解节面Ⅰ走向251°、倾角66°、滑动角150°,节面Ⅱ走向354°、倾角63°、滑动角27°;彝良MS5.6主震位于(27.563°N,104.034°E),震源深度为10.0km,震源机制解节面Ⅰ走向235°、倾角39°、滑动角147°,节面Ⅱ走向352°、倾角70°、滑动角56°.反演结果显示断层的几何形态、余震分布特征、震源机制解特征及构造应力场等均有很好的一致性.综合断层的运动学特征、地震活动规律和地质构造背景,推测彝良地震的发震断裂为昭通断裂带的前缘断裂,即NE走向的石门断裂.导致震区受灾严重的主要原因是由于彝良地震震源深度较浅,能量释放多发生在地壳浅部所致.Based on the recordings of 17 portable seismographs of ChinArray deployed in Yunnan-Guizhou region,the Yiliang MS5.7and MS5.6earthquakes happened on September 7,2012 and the aftershocks with ML≥1.0were relocated by double-difference hypocenter location algorithm（hypoDD）,and then the focal mechanism solutions of earthquakes（MS≥4.0）were determined by CAP（cut and paste）method.Our results show that the Yiliang MS5.7mainshock is located at（27.509°N,103.971°E）with initial rupture depth of 9.7km.The best double-couple solutions for the Yiliang MS5.7earthquake have one nodal plane with strike 251°,dip 66°,rake 150°,and another plane with strike 354°,dip 63°and rake 27°.The Yiliang MS5.6mainshock is relocated at（27.563°N,104.034°E）with initial rupture depth of 10.0km,and the mechanism solutions of two nodal planes are 235°,39°,147°and 352°,70°,56°,respectively.The fault geometry,aftershock distribution characteristics,focal mechanism solutions and the tectonic stress field are in good consistency.Combining with the characteristic of fault kinematic,seismicity and the geological structure,we infer that Yiliang MS5.7and MS5.6earthquakes occurred on the NE-striking Shimen fault which is the leading edge of Zhaotong fracture.The shallow focal depth of Yiliang earthquake and the energy release occurred in shallow crust are the major reasons for serious damage in the hypocentral region.

关 键 词：彝良MS5.7和MS5.6地震 双差定位法 CAP法 震源机制解 

分 类 号：P315.31[天文地球—地震学]