郯庐断裂中南段地壳速度结构与地震活动性研究  

Crustal Velocity Structure of the Middle-Southern Segment of the Tanlu Fault Zone (China) and its Correlation with the Seismic Activity in the Region

作　　者：夏心茹 江国明 赵大鹏[3] XIA Xinru;JIANG Guoming;ZHAO Dapeng(Key Laboratory of Intraplate Volcanoes and Earthquakes(China University of Geosciences,Beijing),Ministry of Education,Beijing 100083,China;School of Geophysics and Information Technology,China University of Geosciences(Beijing),Beijing 100083,China;Department of Geophysics,Graduate School of Science,Tohoku University,Sendai,9808578,Japan)

机构地区：[1]陆内火山与地震教育部重点实验室(中国地质大学,北京),北京100083 [2]中国地质大学(北京)地球物理与信息技术学院,北京100083 [3]日本东北大学理学部地球物理系,日本仙台9808578

出　　处：《CT理论与应用研究(中英文)》2025年第2期163-174,共12页Computerized Tomography Theory and Applications

基　　金：深地国家科技重大专项(郯-庐断裂带大震孕育成灾规律研究(2024ZD1000405))。

摘　　要：郯庐断裂带中南段为中国东部规模最大且第四纪活动性最为显著的活动断裂,该断裂带不仅存在地震频发区,还存在地震空区,在南段的郯城1668年曾发生过8.5级大地震。为揭示该断裂带地壳速度结构,探讨速度结构与地震活动性之间的关系,本研究利用郯庐断裂中南段附近的121个固定地震台的P波和S波震相数据,采用天然地震层析成像方法(TOMOG3D),对研究区内8 886个地震事件进行重定位,获得研究区下方地壳内三维P波速度(V_(P))、S波速度(V_(S))及纵横波速比(V_(P)/V_(S))结构。层析成像结果表明,(1)郯庐断裂带中南段表现出显著的速度分段特征,可分为郯城以北段、郯城-明光段、明光-武穴段;(2)大地震主要分布在高、低速交界处;(3)速度结构与地震活动分布具有较好的空间对应关系,宿迁地震空区下方存在明显的低速异常。本研究结果为深入理解郯庐断裂中南段的地质构造动力学过程以及地震活动分布的关联性提供地震学证据。The Tanlu fault zone is the largest and most active Quaternary fault in eastern China.An M8.5 earthquake occurred in 1 668in Tancheng City located on the southern segment of the Tanlu fault.In this study,we analyzed the crustal velocity structure of the Tanlu fault zone and assessed its relationship with the regional seismic activity,using a large dataset of the arrival times of the primary(P) and secondary(S) waves recorded at 121 permanent seismic stations in and around the middle-southern segments of the Tanlu fault;in total,we used the data of 8 528 local earthquakes.We developed three-dimensional(3D) images of the P-wave(V_(P)) and Swave(V_(S)) velocities and the V_(P)/V_(S) ratio,using the TOMOG3D(a seismic tomography method).The tomography results revealed the following features:(1) a significant velocity segmentation feature exists in the middle-southern segments of the Tanlu fault zone;this feature can be divided into Section A(located in the north of Tancheng),Section B(extending from Tancheng to Mingguang),and Section C(extending from Mingguang to Wuxue).(2) Large earthquakes are mainly distributed at the junction of the high-and low-velocity anomalies.(3) A strong correlation was noted between the velocity structure and seismic activity,especially in Suqian(where a clear low-velocity anomaly that corresponded to a seismic gap was observed).Our study provides new insights into the crustal heterogeneity and seismic activity in the middle-southern segments of the Tanlu fault zone.

关 键 词：地震层析成像 郯庐断裂带中南段 地壳速度结构 地震活动性 

分 类 号：P315[天文地球—地震学]