杜广宝^1,2,,
吴庆举^1,,,
张雪梅²,
张瑞青¹
1. 中国地震局地球物理研究所, 北京 100081
2. 中国地震台网中心, 北京 100045

基金项目: 国家重点研发计划（2020YFA0710601），中国地震局地球物理研究所基本科研业务专项（DQJB19A0113，DQJB19A0111），国家重点研发计划（2017YFC1500304）共同资助


详细信息

作者简介: 杜广宝, 男, 1984年生, 高级工程师, 主要从事地震监测和地震层析成像研究工作.E-mail: dgb@seis.ac.cn

通讯作者: 吴庆举, 男, 1966年生, 研究员, 主要从事地震学、地球内部结构以及地球动力学研究工作.E-mail: wuqj@cea-igp.ac.cn

中图分类号: P315

收稿日期:2020-11-24
修回日期:2021-05-13
上线日期:2021-11-10

Activity characteristics of moderate and small earthquakes and fine crustal feature beneath Weiyuan, Sichuan and adjacent areas

DU GuangBao^1,2,,
WU QingJu^1,,,
ZHANG XueMei²,
ZHANG RuiQing¹
1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China
2. China Earthquake Networks Center, Beijing 100045, China


More Information

Corresponding author: WU QingJu,E-mail:wuqj@cea-igp.ac.cn

MSC: P315

--> Received Date: 24 November 2020
Revised Date: 13 May 2021
Available Online: 10 November 2021


摘要
摘要:利用2019年以来在四川荣县-威远布设的密集地震台站，以及部分固定台站记录到的近震资料，采用双差层析成像方法获得了高分辨率的浅层地壳三维速度结构和震源位置.重定位结果显示，研究区内中小地震多数呈南北向条带状分布，与已知地表断层的分布无明显关联.地震震源深度主要集中在2~5 km深度之间.研究区中小地震活动与速度结构变化具有相关性，在5 km以浅，地震多分布在S波高速异常区；在7~10 km深度范围，地震多发生在P波和S波的高、低速异常转换带.综合重定位和速度剖面结果，推测研究区内沉积层厚度约4~6 km，而一些中强地震多发生在结晶基底顶部.在研究区深部，黄桷坡断层以北地震区比荣县地震区具有更高的P波速度，在相似的应力状态下，力学性质更强的黄桷坡断层以北地区更难以破裂，可能是该地区更晚发生地震的缘由.
关键词: 荣县—威远地区/
双差层析成像/
地震活动/
速度结构

Abstract:In this work, we collected the seismic travel-time data from a local dense array in the Rongxian-Weiyuan area since 2019 and the seismic networks. Double-difference seismic tomography method was used to invert the high-resolution three-dimensional velocity structure and hypocentral locations. The results show that most of moderate and small earthquakes occurred in NS trending clusters, which are not associated with known faults. Their focal depths generally range 2~5 km. These events are associated with velocity anomalies, mostly occurred at the high V_S anomalies above depth 5 km, while in the high-to-low anomaly transition zones of V_P and V_S in the depth range of 7~10 km. Synthesis of the relocation and velocity profile permit to speculate that the thickness of sedimentary cap is about 4~6 km, and some moderate earthquakes took place in crystalline basement. In the deep subsurface, higher P wave velocity anomalies are present in the seismic area north of the Huangjuepo fault compared with the Rongxian seismic area. In a similar stress state, the seismic area north of the Huangjuepo fault with larger strength is more difficult to rupture, which may be the reason for later occurrence of earthquakes in this region.
Key words:Rongxian-Weiyuan area/
Double-difference tomography/
Seismic activity/
Velocity structure



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