2010年4月玉树M_S7.3地震序列的断层结构  

Fault structure of M_S7.3 Yushu earthquake sequence in April,2010

作　　者：王勤彩[1] 王中平[2] 张金川[3] 李君[1] 陈章立[1] 

机构地区：[1]中国地震局地震预测研究所,北京100036 [2]中国地震台网中心,北京100045 [3]江苏省地震局,南京210014

出　　处：《地球物理学报》2015年第6期1931-1940,共10页Chinese Journal of Geophysics

基　　金：中国地震局地震预测研究所基本科研业务费专项重点项目(2014IES0102);国家自然科学基金(41404047);地震行业专项(201208003和201508010)联合资助

摘　　要：利用双差定位方法对玉树地震序列2010年4月14日至10月31日间发生的ML≥1.0地震进行双差定位,得到1545个地震的重定位结果.综合分析地震双差定位结果和玉树地震序列中强地震震源机制解,发现玉树MS7.3地震发震构造由北西向和北东东向两条相交断层组成,主震发生在北西走向的甘孜—玉树断裂带上,5月29日的MS5.9余震序列发生在北东东走向的一条隐伏断裂上,两条断裂均接近直立.甘孜—玉树断裂是羌塘地块和巴彦喀拉地块的构造边界,由于羌塘地块和巴颜喀拉地块的差异运动使甘孜—玉树断裂强耦合段应力高度积累,在应变能超过岩石强度时破裂失稳发生了MS7.3地震.主震断层的左旋滑动导致北东东向断层的正应力减小,库伦应力增加,45天后触发了MS5.9余震序列的活动.The object of this paper is to investigate the seismogenic fault structures and stress field where MS7.3 Yushu earthquake sequence occurred in April 2010,and then tentatively discuss the triggering mechanism for the Yushu MS7.3mainshock and MS5.9strong aftershock sequences.We adopted double difference algorithm for earthquake hypocenter relocation by using different seismic velocity models,and chose the outcome with the maximal proportion of relocated earthquakes in total events as our final result.With the combination of focal mechanism solutions and earthquake relocation,the fault structures and stress field for Yushu earthquake sequences were comprehensively analyzed.After the relocation of ML≥1.0earthquakes among Yushu earthquake sequence from April14 to October 31,2010,we obtained precise locations of 1545 earthquakes.Relocation results show that Yushu earthquake sequence was mainly composed of two intersecting seismic strips with NW trending and NEE trending respectively.The MS7.3mainshock occurred in the north-west trending seismic zone along Ganzi-Yushu fault.This seismic strip extended for about 80 kilometers with 300 degree trending and indicated a high-angle fault plane that is close to upright.The MS5.9aftershock on May 29 occurred in a wide NEE rectangular strip,which extended approximately 40 kilometers with a width of 18 kilometers,indicating apossible buried fault.The relocated Yushu earthquake sequences occurred from ground surface to around 15 kilometer in depth,but were mainly concentrated in the depth range of 8to 12 kilometers.Combined analysis of double difference and focal mechanism leads to the conclusion that the NW fault plane in the focal mechanism solution for mainshock is most likely the seismogenic fault of mainshock sequence.The mainshock fault is a NW trending,nearly vertical,and sinistral strike-slip fault.The seismogenic fault plane for MS5.9aftershock is an NEE,almost upright sinistral strike-slip fault.The maximum principal stress direction in mainshock seismic zone is consis

关 键 词：玉树地震序列 双差定位 矩张量解 断层结构 

分 类 号：P315[天文地球—地震学]