2021年5月21日云南漾濞M_(S)6.4地震序列地震矩张量及发震构造  

Seismic moment tensor and seismogenic structure of the Yangbi M_(S)6.4 earthquake sequence on May 21,2021 in Yunnan

作　　者：刘俊清 甘卫军[3] 王光明 王忠礼[1] 张宇[5] 蔡宏雷[5] 李仲巍 LIU JunQing;GAN WeiJun;WANG GuangMing;WANG ZhongLi;ZHANG Yu;CAI HongLei;LI ZhongWei(School of Geomatics and Prospecting Engineering,Jilin Jianzhu University,Changchun 130118,China;Key Laboratory of Songliao Aquatic Environment,Ministry of Education,Jilin Jianzhu University,Changchun 130118,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Yunnan Earthquake Agency,Kunming 650224,China;Jilin Earthquake Agency,Changchun 130117,China;Longgang Volcanic Observatory,Jilin Earthquake Agency,Jilin Fusong 134528,China)

机构地区：[1]吉林建筑大学测绘与勘查工程学院,长春130118 [2]吉林建筑大学松辽流域水环境教育部重点实验室,长春130118 [3]中国地震局地质研究所地震动力学国家重点实验室,北京100029 [4]云南省地震局,昆明650224 [5]吉林省地震局,长春130117 [6]吉林省地震局龙岗火山监测站,吉林抚松134528

出　　处：《地球物理学报》2021年第12期4475-4487,共13页Chinese Journal of Geophysics

基　　金：国家重点研发计划项目(2018YFC1503300);吉林建筑大学博士科研启动基金(202180010);住房和城乡建设部科学技术项目(2014-K8-063)共同资助.

摘　　要：2021年5月21日云南大理州漾濞县发生了M_(S)6.4地震.我们利用区域地震台网记录的地震波形资料,首先采用多点源地震矩张量反演方法确定了漾濞地震序列中3次M_(S)≥5.0地震的矩心矩张量解,分析研究了地震矩释放的最佳模型;然后对序列中较大地震进行了绝对定位,结合余震序列重新定位结果研究了地震矩心在断层面上的位置.结果显示M_(S)5.6前震可用2点源模型模拟,矩震级分别为M_(W)5.3、M_(W)5.1,矩心时间相隔约30 s,矩心位置相距约2 km.M_(S)6.4主震可用单点源模型模拟,矩心与起始破裂点平面距离约5 km.前震和主震的矩心均位于地表以下6 km处,矩心与起始破裂点的位置关系显示两地震向南东方向单侧破裂,断层以“前震\|主震”型地震序列典型的“撤退式”方式破裂,M_(S)5.6前震的发生降低了断层面的抗剪强度,从而发生了更大的M_(S)6.4主震.M_(S)5.2余震可用单点源模型模拟,起始破裂点与矩心空间位置相近,在地表以下约10 km处.余震区构造应力场反演结果显示漾濞6.4级地震序列属于区域应力场触发的地震活动,地震序列震源机制解符合走滑断裂伴生的负花状构造系统内部断裂的运动特征,余震的空间分布图像显示花状构造系统内部的两条断裂发生了地震活动.The Yangbi M_(S)6.4 earthquake occurred on May 21,2021 in Dali of Yunnan Province,China.Using the seismic waveform data recorded by regional seismic networks,and based on multi-point source seismic moment tensor inversion method,we obtained the moment tensor solutions of the M_(S)5.6 foreshock,M_(S)6.4 mainshock,and M_(S)5.2 aftershock in the earthquake sequence,and further studied the optimal model of seismic moment release.We also performed absolute location for the larger earthquakes in the sequence,and studied the location of the centroids on the fault plane by combining the relocation results of the aftershock sequence.The results show that the M_(S)5.6 foreshock can be simulated by a two-point source model with moment magnitudes of M_(W)5.3 and M_(W)5.1,respectively,and the centroids were separated by 30 s in time and 2 km in space.The M_(S)6.4 mainshock can be simulated by a single point source model,and the distance between the moment centroid and the hypocenter was about 5 km.The centroids of the foreshock and mainshock were both located at 6 km below the ground surface.The fault ruptured unilaterally in the south-east direction,with a typical“retreating”rupture mode of the“foreshock-mainshock”seismic sequence.The M_(S)5.2 aftershock can be simulated with a single point source model,and the hypocenter was close to the location of the centroid,about 10 km in depth.The inversion results of the tectonic stress field in the aftershock area show that the Yangbi 6.4 seismic sequence was a result of the regional stress field,and the focal mechanism solutions of the earthquake sequence were consistent with the motion of the internal faults of the negative flower structure associated with the strike-slip fault,and the spatial distribution of aftershocks showed the seismicity was triggered on two faults within the flower structure.

关 键 词：多点源地震矩张量反演 地震矩张量 花状构造 漾濞6.4级地震 

分 类 号：P315[天文地球—地震学]