小江断裂带东川—寻甸段大地电磁成像及深部孕震环境  

Magnetotelluric imaging and deep seismogenic environment in Dongchuan-Xundian segment of Xiaojiang fault zone

作　　者：崔腾发 陈小斌 李文军[1] 李文巧[1] 李鑫[3] 谢兴兵[4] 周磊[4] CUI TengFa;CHEN XiaoBin;LI WenJun;LI WenQiao;LI Xin;XIE XingBing;ZHOU Lei(Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;National Institute of Natural Hazards,Ministry of Emergency Management of the People's Republic of China,Beijing 100085,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Yangtze University,Wuhan 430100,China)

机构地区：[1]中国地震局地震预测研究所,北京100036 [2]应急管理部国家自然灾害防治研究院,北京100085 [3]中国科学院地质与地球物理研究所,北京100029 [4]长江大学,武汉430100

出　　处：《地球物理学报》2023年第10期4224-4240,共17页Chinese Journal of Geophysics

基　　金：中国地震局地震预测研究所基本科研业务费专项(2020IEF0505,2021IEF0104);国家自然科学基金(42174093,41874087);川滇国家地震监测预报试验场项目(20150108)资助。

摘　　要：小江断裂带是青藏高原物质向东南方向逃逸的东边界中的一段,具有较强的地震活动性.小江断裂带东川—寻甸段经历过三次6.5级以上强震,对其深部电性结构的探测,可以为研究三次历史强震的深部孕震环境提供重要依据.大地电磁成像结果显示研究区下地壳存在显著的高导结构,可能含有较高比例的熔融物质,具有较低的强度/黏度.小江断裂带在深度10 km表现为明显的结构边界,有利于断裂带的剪切变形.断裂带上的强震可能主要受上地壳高阻结构的控制.上地壳中,小江断裂带东支断裂在田坝随高阻结构向南转折;功山地区东支断裂两侧的高阻体紧靠.两个条件共同阻碍了东支断裂在局部的左旋走滑及地震破裂的传播.小江断裂带西支断裂在嵩明以北表现为上地壳三个高阻体之间的边界,坚硬的高阻体相互接触可能使断层局部存在阻碍断层走滑的构造,为强震的发生提供必要的结构条件.The Xiaojiang fault zone is one of the boundary faults where the material of the Tibet Plateau escapes in the southeast direction and has strong seismicity.The Dongchuan-Xundian segment has experienced three strong earthquakes with a magnitude greater than 6.5.The deep electrical resistivity structure of the Dongchuan-Xundian segment can provide important information for the study of the deep seismogenic environment of the three historical strong earthquakes.Magnetotelluric imaging results show that the lower crust of the study area has a significant high-conductivity structure,which may contain a high melt fraction and has a low strength/viscosity.Xiaojiang fault zone in 10 km depth is an obvious structural boundary,which is conducive to the shear deformation of the fault zone.Strong earthquakes occurred in the fault zones may be mainly limited by high-resistivity structures in the upper crust.In the upper crust,the east branch of the Xiaojiang fault zone turns southward along with the high-resistivity structure in Tianba,and the high-resistivity bodies on both sides of the East branch fault in Gongshan area are close to each other.Together,they hinder the sinistral strike-slip of the east branch fault and the propagation of the seismic rupture.The west branch of Xiaojiang fault zone is the boundary between three high-resistivity bodies in the upper crust north of Songming.The contact of rigid high-resistivity bodies may lead to the presence of local structures blocking the strike-slip of the fault and provides necessary structural conditions for strong earthquakes.

关 键 词：小江断裂带 大地电磁成像 孕震环境 三维电性结构 东川-寻甸段 

分 类 号：P318[天文地球—固体地球物理学]