2021年云南漾濞6.4级地震序列重定位及震源机制解特征分析  

RELOCATION AND FOCAAL MECHANISM SOLUTIONS OF THE 2021 YANGBI,YUNNAN M_(S)6.4 EARTHQUAKE SEQUENCE

作　　者：王莹[1] 赵韬[1] 胡景 刘春[1] WANG Ying;ZHAO Tao;HU Jing;LIU Chun(Shaanxi Earthquake Agency,Xi′an 710068,China;School of Geology Engineering and Geomatics,Chang′an University,Xi′an 710054,China)

机构地区：[1]陕西省地震局,西安710068 [2]长安大学,地质工程与测绘学院,西安710054

出　　处：《地震地质》2021年第4期847-863,共17页Seismology and Geology

基　　金：中国地震局监测预报司震情跟踪定向工作任务(202101024);陕西省地震局启航与创新基金(QC201931)共同资助。

摘　　要：2021年5月21日云南省大理白族自治州漾濞县发生6.4级强烈地震。为了深入研究漾濞6.4级地震序列的时空分布、震源特性以及发震构造等,文中利用双差法对漾濞地震序列中约2000个地震进行重新定位,并且利用MTINV程序包反演了地震序列中31个地震的震源机制解。结果显示:漾濞6.4级地震是一次右旋走滑型地震事件,发震断层走向NW,倾角近直立;序列震源机制与主震的一致性较好,以走滑型为主,存在少量混合类型;精定位结果显示序列呈明显的NW向展布特征,震源深度主要集中在10km以浅;与走向垂直的深度剖面显示,南、北段断层倾向均为SW,但倾角不同;P轴的优势方位为SN向,倾俯角近水平,与区域应力场特征一致。综合重定位和矩张量反演结果推测,漾濞地震的发震断层是一条整体呈NW走向、倾向SW、倾角可能具有分段性的右旋走滑活动断裂,震源区断裂破裂可能存在分段现象,且局部小区域构造形态可能较为复杂。On May 21,2021,a strong earthquake of magnitude 6.4 occurred in Yangbi County,Dali Prefecture,Yunnan Province.The focal depth of this earthquake is 8km.The earthquake broke the calm of magnitude 6 earthquake that had lasted for more than 6 years in Yunnan,and is a significant strong earthquake in the northwestern Yunnan region.Before the M_(S)6.4 Yangbi earthquake,the foreshock activity near the epicenter was frequent,and the maximum magnitude of foreshock is 5.6.After the M_(S)6.4 earthquake,another M S5.2 earthquake,and many aftershocks of magnitude 3 and 4 occurred.The earthquake sequence was very rich.In order to further study the spatio-temporal distribution,source characteristics and seismogenic structure of the magnitude 6.4 earthquake sequence in Yangbi,in this paper more than 2800 seismic events of the Yangbi earthquake sequence were relocated using the double-difference relative positioning method based on the seismic phase data from the Seismic Cataloging System of China Earthquake Networks Center,and finally 2116 precise location results were obtained.At the same time,based on the broadband digital waveform data provided by the China Earthquake Networks Center,focal mechanism solutions 31 earthquakes of the sequence were obtained by MTINV program.The results of the moment tensor inversion show that the moment magnitude of the Yangbi M_(S)6.4 earthquake is M W6.0,the centroid depth is 10km,and the optimal double-couple solution is strike 135°,dip 81°and rake 176°for nodal plane I,and strike 226°,dip 86°and rake 9°for nodal planeⅡ.It is a strike-slip earthquake.Combining the strike of the fault in the earthquake source area and the distribution of aftershocks,it is inferred that the seismogenic fault is the nodal planeⅠwhich strikes NW.Focal mechanism solutions of other 30 earthquakes of the sequence are mainly strike-slip type,which are consistent with the main shock.There are also a few events with mixed types.The focal mechanisms of several earthquakes close to the occurrence time of the M_

关 键 词：漾濞6.4级地震 震源机制解 双差定位 矩张量反演 

分 类 号：P315.2[天文地球—地震学]