四川芦山M_s7.0级强烈地震震源运动学特征  

Kinematic characteristics of the source process of the Lushan, Sichuan M_s7.0 earthquake on 20 April 2013

作　　者：赵旭[1] 黄志斌[1] 房立华[2] 李强 赵博[1] 苗春兰[1] 

机构地区：[1]中国地震台网中心,北京100045 [2]中国地震局地球物理研究所,北京100081 [3]地壳运动监测网络工程研究中心,北京100037

出　　处：《地球物理学报》2014年第2期419-429,共11页Chinese Journal of Geophysics

基　　金：地震科技星火计划项目(XH12060Y);地震行业科研专项(201208003);海洋局行业科研专项(201405026)共同资助

摘　　要：使用中国数字地震台网记录的区域宽频带波形,通过频率域和时间域多步反演,研究了2013年四川芦山"4·20"7.0级强烈地震的震源运动学特征.基于点源的震源机制解揭示:地震发震断层面参数分别为走向214°/倾角47°/滑动角96°,表现为一次高倾角的逆冲型事件.矩心在水平方向上位于震中(30.303°N/102.988°E)西南向约4.5km,矩心深度约17km.平均总标量地震矩M0为1.16×1019 N·m,矩震级Mw约6.6.进一步模拟高达0.5Hz高频波形,获得了芦山地震破裂过程图像,结果显示:此地震为一次不对称双侧破裂事件.破裂半径约15km,整个破裂面积为706.7km2,平均滑动量约0.231m.破裂在8s内释放了大多数能量.震后0～3s内,破裂以孕震点为中心向四周同时扩展,3s后,破裂表现出明显的方向性,主要向北北东扩展,导致位于震中北东向多数台站视破裂持续时间总体偏小,最小值为4s.破裂约8s后基本停止.We employ multistep inversions in the frequency or time domain to infer the kinematic characteristics of the source process of the 2013April 20Lushan,Sichuan Ms7.0earthquake,mainly using regional broadband waves recorded by the China Digital Seismic Network.The focal mechanism solution based on the point-source model indicates that this event occurred on a rupture plane（strike 214°,dip 47°,and rake 96°）,showing a high-angle thrust faulting.The centroid in the horizontal direction is located 4.5km southwest of the epicenter（30.303°N/102.988°E）,and the best-fitting centroid depth is around 17km.The total scalar moment,M0,is retrieved with an average value of 1.16×1019 N·m（or moment magnitude Mw6.6）.We make use of the highfrequency（up to 0.5Hz）data to reconstruct the rupture process,which is not detailed enough but robust.The event is considered as an asymmetric bilateral rupturing with a radius of 15km.The total rupture area is about 706.7km2 with an average slip of nearly 0.231m.Most of theenergy is released within about 8s.From 0sto 3s,the energetic rupture starts at the nucleation center,then propagates bilaterally along the fault plane.After 3s,the rupture mainly extends north-north-east,showing obvious rupture directivity.As a result,the apparent durations at majority of the stations,which lie northeast of the epicenter,become much smaller,and the smallest value is 4s.Finally,the rupturing ends at about 8s.

关 键 词：4·20四川芦山地震 Eikonal震源模型 震源机制解 破裂过程 

分 类 号：P315[天文地球—地震学]