2021年5月21日云南漾濞M_(S)6.4地震序列重新定位与深部孕震环境浅析  

Relocation of the Yangbi M_(S)6.4 Earthquake Sequence on May 21,2021,Yunnan and its Implications for Deep Seismogenic Environment

作　　者：赵航 李大虎[1] 吴微微[1] 廖华[1] 梁宏 黄雪影[1] 陈学芬[1] ZHAO Hang;LI Dahu;WU Weiwei;LIAO Hua;LIANG Hong;HUANG Xueying;CHEN Xuefen(Sichuan Earthquake Agency,Sichuan Chengdu 610041,China)

机构地区：[1]四川省地震局中国地震局成都青藏高原地震研究所,四川成都610041

出　　处：《四川地震》2021年第4期1-6,共6页Earthquake Research in Sichuan

基　　金：四川省地震局地震科技创新团队“川滇地区强震孕育深部结构与动力环境研究”(201804)项目资助.

摘　　要：为了研究漾濞M_(S)6.4地震序列空间分布特征和探讨震区深部孕震环境,本文利用云南省地震台网和震后流动台站观测资料,采用双差定位方法对2021年5月21日震后3天发生的M_(L)≥1.0余震序列进行重新定位,获得415个事件的定位结果,结合震区深部结构反演资料进行分析,结果表明:漾濞M_(S)6.4地震序列集中分布在主震的南东侧,并沿着NW-SE向呈条带状与维西—乔后断裂近似平行展布,长约20 km,纵剖面图揭示了震源深度优势分布为5~15 km,地震震源深度较浅,说明地震大多发生在脆性上地壳范围内。考虑到漾濞震区北侧洱源等地的地表温泉较发育、大地热流值显著偏高等地热分布以及滇西北地区多数地震活动都在一定程度受地热流体影响,并结合漾濞M_(S)6.4地震震区北侧洱源附近存在地壳尺度的低速、低密度异常这一最显著特征等研究成果,我们认为本次漾濞M_(S)6.4地震序列与深部流体密切相关,流体活动导致漾濞震区热状态的改变以及触发地震。In order to study the spatial distribution characteristics of the Yangbi M_(S)6.4 earthquake sequence and to explore the deep seismogenic environment in the earthquake area,we use the observation data of Yunnan fixed seismic network and post-earthquake mobile stations to relocate the aftershock sequence with M_(L)≥1.0 three days after the earthquake on May 21,2021 by the double difference positioning method.We obtain the relocation results of 415 events and combine with the deep structure data of the earthquake area.The results show that the Yangbi M_(S)6.4 earthquake sequence is concentrated on the southeast side of the main earthquake and distributed in a strip with a length of about 20 km along the NW-SE direction that is approximately paralleled to the Weixi-Qiaohou fault.The longitudinal profile shows that the dominant range of focal depth distribution is located at 5~15 km at depth indicating a shallow characteristic and most earthquakes occurred in a brittle upper crust.Considering that hot springs at surface in Eryuan and other places to north side of the Yangbi earthquake area are widely developed,the geothermal distribution such as significantly high earth heat flow value,most seismic activities in Northwest Yunnan are affected by geothermal fluid to a certain extent,and combined with the most significant feature of low-speed and low-density anomaly at the crustal scale near Eryuan to north side of the Yangbi M_(S)6.4 earthquake area revealed by previous research results,we suggest that the Yangbi M_(S)6.4 earthquake sequence is closely related to the deep fluid.The fluid activity leading to the change of thermal state in Yanghe earthquake area is the key factor in triggering the earthquake.

关 键 词：漾濞M_(S)6.4地震 双差定位 地震序列 深部孕震环境 

分 类 号：P315.7[天文地球—地震学]