2021年5月21日云南漾濞M_(S)6.4地震震区地壳结构特征与孕震背景  

The characteristics of crustal structure and seismogenic background of Yangbi M_(S)6.4 earthquake on May 21,2021 in Yunnan Province,China

作　　者：李大虎[1,2] 丁志峰[3] 吴萍萍[3] 刘韶[2] 邓菲[3] 张旭[3] 赵航 LI DaHu;DING ZhiFeng;WU PingPing;LIU Shao;DENG Fei;ZHANG Xu;ZHAO Hang(Chengdu Institute of the Tibetan Plateau Earthquake Research,China Earthquake Administration(Chengdu Base of China Seismic Experimental Site),Chengdu 610039,China;Earthquake Administration of Sichuan Province,Chengdu 610039,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局成都青藏高原地震研究所(中国地震科学实验场成都基地),成都610039 [2]四川省地震局,成都610039 [3]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2021年第9期3083-3100,共18页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41974066);国家重点研发计划(2020YFA0710600);中国地震局地震科技星火计划攻关项目(XH20051);四川省地震局地震科技创新团队专项(201804)共同资助.

摘　　要：本文基于“中国地震科学台阵探测——南北地震带南段”密集布设的流动地震台阵和川滇区域数字测震台网等共计634个台站所记录的观测资料,先采用地震体波层析成像(TOMO3D)方法反演获得川滇区域的地壳速度结构特征,在此基础上,重点剖析云南漾濞M_(S)6.4地震震区及周边的三维P波速度结构;再采用三维视密度反演方法,获得漾濞震区壳内视密度的横向变化特征,最后综合分析漾濞M_(S)6.4地震震区地壳结构特征与地震活动关系、深部孕震背景等科学问题.研究结果表明:漾濞震区P波速度结构与视密度展布特征在深度和分区特征上均具有较好的联系和可比性,震区三维速度结构和视密度反演结果均表现出明显的横向不均匀分布特征,漾濞M_(S)6.4地震位于高低异常值的过渡带附近,震区南、北两侧速度结构和视密度分布特征各异,综合说明了震区地壳物质存在显著的横向差异.漾濞M_(S)6.4地震序列集中分布在主震的SE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,主震震源深度为8.6 km,序列震源深度优势分布层位在5~15 km,漾濞M_(S)6.4地震序列处于高低速异常过渡带附近,震区壳内介质结构的非均匀分布是控制漾濞地震及其序列展布形态的深部构造因素.我们的研究结果还揭示了漾濞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,该结果与该部位地表温泉较发育、大地热流值显著偏高等地热分布高度一致,这些均暗示着漾濞地震机制除了与青藏高原东缘深部物质SE向逃逸有关外,可能还与来自上地幔的热异常和深部过程密切相关.We have fully collected the observational data of 634 stations(arrays)including Sichuan-Yunnan Regional Digital Seismic Network and“ChinArray Exploration-Southern Segment of the South-North Seismic Belt”,and obtained the crustal velocity structure characteristics in Sichuan-Yunnan region by using body wave tomography method.On this basis,the 3D P-wave velocity structure in and around Yangbi M_(S)6.4 earthquake region is analyzed and studied.Then,the 3D apparent density inversion of gravity data in Yangbi earthquake region and its surrounding area is carried out,and the lateral variation characteristics of apparent density in different depths of the crust are obtained.Finally,the relationship between crustal structure and seismicity,and the background of deep seismogenesis in Yangbi M_(S)6.4 earthquake region are analyzed.The results show that:the P-wave velocity structure and apparent density distribution characteristics of Yangbi earthquake region have good relationship and comparability in depth and zoning characteristics,and the inversion results of 3D velocity structure and apparent density show obvious lateral uneven distribution characteristics.The Yangbi M_(S)6.4 earthquake is located near the transition zone with high and low abnormal values.The distribution characteristics of velocity structure and apparent density are different on the north and south sides of the earthquake region,which indicates that there are significant lateral differences in the crust medium in the earthquake region.The Yangbi M_(S)6.4 earthquake sequence is mainly distributed in the southeast direction of the mainshock,it is a strip distribution in northwest-southeast direction along the Weixi-Qiaohou fault,with a length of about 20 km,and the dominant distribution layer of focal depth is 5~15 km.The Yangbi M_(S)6.4 earthquake and its sequence are located near the transition zone of high and low velocity anomalies.The inhomogeneous distribution of medium structure in the crust of the earthquake region is the deep structural fac

关 键 词：漾濞M_(S)6.4地震 地壳速度结构 地震活动 深部孕震背景 

分 类 号：P315[天文地球—地震学]