利用区域宽频带数据反演鲁甸M_s6.5级地震震源破裂过程  

Rupture process of M_s6.5 Ludian earthquake constrained by regional broadband seismograms

作　　者：刘成利[1] 郑勇[1] 熊熊[1] 付芮[1,2] 单斌[1] 刁法启[1] 

机构地区：[1]中国科学院测量与地球物理研究所,大地测量与地球动力学国家重点实验室,武汉430077 [2]中国科学院大学,北京100049

出　　处：《地球物理学报》2014年第9期3028-3037,共10页Chinese Journal of Geophysics

基　　金：中国地震科学台阵探测(201308011);中国地震局行业专项项目(201308013);国家自然科学基金委优秀青年基金(41422401);面上基金(41174086;41274104)联合资助

摘　　要：基于有限断层模型反演方法,我们利用区域宽频带数据反演得到了2014年8月3日鲁甸M_s6.5级地震的震源破裂过程.反演结果显示:此次地震的发震断层走向为北北西向,破裂主要以左旋走滑为主,位移主要发生在震源左上方,最大滑动量为0.7 m,模型显示断层破裂可能接近地表,破裂长度约10 km.此次地震释放的标量地震矩为1.97×10^(18)N·m,相当于矩震级为M_w 6.1,地震能量主要在前15 s释放.鲁甸地震有四个显著的特点:(1)位移主要集中在浅部,从11 km起破点开始迅速向上传播,大部分位于10 km以上且最大位移位于深度3 km处,从模型来看,破裂可能接近地表,因此地表震动较为强烈;(2)应力降比较大,计算显示释放的同震静态应力降约为2.8 MPa;(3)破裂速度较快,在地表附近超过了2.5 km·s^(-1);(4)主震可能发生在一个共轭断层系上.这四个特点可能是导致此次地震造成如此重大人员伤亡和财产损失的最重要的原因.Based on the finite fault inversion method,we investigated the rupture process of the 3August 2014 Ludian Ms6.5 earthquake by regional broadband data provided by China Earthquake Administration.The inversion results indicate that the Ludian earthquake occurred on NNW oriented sinistral strike-slip fault,and most of the rupture slips concentrated in the upper left side of the hypocenter with the peak slip of about 0.7 m.The results show that the rupture slip of this earthquake initiated from 11 km and propagated quickly to the shallower depth,and probably could touch the ground surface with a rupture length of 10 km.The total seismic moment released by the whole fault is 1.97×10^18N·m,which is equivalent to magnitude of Mw6.1,and most energy released at the first 15 s.Comparing with ordinary earthquakes,four obvious characteristics can be observed from the Ludian earthquake：（1）The majority of the rupture slips concentrated in the shallow depth（less than 10 km）and the maximum slip occurred at the depth of 3 km,and the rupture could be close to the ground surface,thus the shaking of the ground is very strong.（2）The stress drop is very high.Based on our model,the magnitude of the associated static stress drop of the Ludian earthquake is - 2.8 MPa.（3） The fault rupture of the earthquake propagated with a higher velocity,and expands to the surface at a speed of more than2.5 km·s-1.（4） The mainshock may ruptured a conjugate fault system.These four characteristics might be the main reasons why this earthquake caused massive human casualties and property losses.

关 键 词：鲁甸地震 区域宽频带数据 有限断层 破裂过程 

分 类 号：P315[天文地球—地震学]