2020年云南巧家M 5.0地震重定位及地质构造探索  

Relocation and geological structure exploration of the 2020 Qiaojia M 5.0 earthquake

作　　者：王祖东 尹欣欣 梁坤 陈晓龙 蒲举 WANG ZuDong;YIN XinXin;LIANG Kun;CHEN XiaoLong;PU Ju(Earthquake Agency of Gansu Province,Lanzhou 730000,China;Kunming Southern Geophysical Technology Development Co.,Ltd.,Kunming 650000,China)

机构地区：[1]甘肃省地震局,兰州730000 [2]昆明南方地球物理技术开发有限公司,昆明650000

出　　处：《地球物理学进展》2022年第4期1500-1511,共12页Progress in Geophysics

基　　金：中国地震局地震预测研究所基本科研业务费专项(2020IESLZ01,2019IESLZ07)资助。

摘　　要：本文使用云南、四川、贵州区域数字台网所观测到的巧家、东川地区P波和S波震相数据,利用双差层析成像方法反演得到了小江断裂中北段、莲峰断裂、昭通—鲁甸断裂、包谷垴—小河断裂及周边区域P波、S波三维速度结构.结果显示,研究区上地壳速度结构与地质构造变化及相应的断裂有较好对应关系,速度结构整体呈低速状态,泊松比偏低,表现出呈酸性的长英质介质属性;中下地壳(15~30 km)包谷垴—小河断裂西侧区域大量地震事件位于高速异常体,推测该高速异常区可能表现出较为明显的脆性特征;重定位后地震深度主要分布在15~35 km,呈现出与断层位置相关的两条平行条带状分布,推测其断层面倾向SW,倾角大约75°,整体较深,位于中下地壳;通过多维度比较发现,研究区地震的发生随着时间推移在空间上有SW方向扩展趋势,且逐渐变浅.This paper using the seismic phase data of P-waves and S-waves that recorded from Yunnan, Sichuan and Guizhou Regional Digital Network, the three-dimensional(3 D) velocity structures of P-waves and S-waves that middle-north section of Xiaojiang fault, Lianfeng fault, Shaotong-Ludian fault, Baogunao-Xiaohe fault and their surrounding region are obtained by double-differential tomography method. The results show that the velocity structure of the upper crust in the research area has a good correspondence with the geological structure changes and the corresponding faults, the velocity structure is in a low speed state overall, and has a lower Poisson’s ratio, it shows acidic felsic medium property. The western region of Baogunao-Xiaohe fault in the mid-lower crust(15~30 km), a great quantity of seismic events located in high velocity abnormal material, we inferred that the high-speed anomaly areas may exhibit obvious brittleness characteristics. After relocation, the seismic depth is mainly distributed in the range of 15~35 km, showing two parallel strip distribution related to the fault location. In this paper, it is inferred that the fault plane tends to SW, dip angle is about 75°, and is located in the deeper mid-lower crust as a whole. Moreover, through the multi-dimensional comparison, it is found that the occurrence of earthquakes in the study area has a SW direction expansion trend with the passage of time, and gradually becomes shallower.

关 键 词：巧家地震 包谷垴—小河断裂 双差层析成像 速度结构 泊松比 

分 类 号：P315[天文地球—地震学]