川滇地区活动块体边界断裂现今运动和应力分布  

PRESENT SLIP AND STRESS DISTRIBUTION OF BLOCK BOUNDARY FAULTS IN THE SICHUAN-YUNNAN REGION

作　　者：万永魁 沈小七[2] 刘瑞丰[1] 刘峡[2] 郑智江[2] 李媛[2,3] 张扬 王雷 WAN Yong-kui;SHEN Xiao-qi;LIU Rui-feng;LIU Xia;ZHENG Zhi-jiang;LI Yuan;ZHANG Yang;WANG Lei(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;The First Monitoring and Application Center,China Earthquake Administration,Tianjin 300180,China;Institute of Geology,China Earthquake Administration,Beijing 100029,China;Shandong Earthquake Agency,Jinan 250014,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局第一监测中心,天津300180 [3]中国地震局地质研究所,北京100029 [4]山东省地震局,济南250014

出　　处：《地震地质》2021年第6期1614-1637,共24页Seismology and Geology

基　　金：国家重点研发计划项目(2018YFC150330506);国家自然科学基金(41472180)共同资助。

摘　　要：基于川滇地区活动块体划分及断裂构造现有认知,文中构建了包含块体主要边界断裂的二维有限元接触模型,利用1991—2015年长期GPS观测结果,采用"块体加载"方法模拟块体边界带现今的运动,得到了断裂滑动速率和应力分布。结合震源机制解、地震活动性等资料,对川滇地区大型左旋走滑断裂带滑动速率分配、传递与应力转换的关联,局部区域正断型震源机制解的构造机制以及红河断裂南、北段地震活动性差异的可能成因进行了初步探讨。主要结论包括:1)东昆仑断裂带和鲜水河-小江断裂带的左旋走滑由NW向转变为近SN向,断裂强烈转折区吸收了部分走滑分量并转化为应变积累,呈高应力分布特征。2)受小江断裂左旋剪切的影响,红河断裂中南段以右旋走滑兼微弱挤压运动为主,并牵引断裂北段右旋走滑,与金沙江和德钦-中甸断裂共同构成右阶斜列右旋剪切变形带,正断型震源机制解多分布于该变形带的构造拉分区内。3)红河断裂中南段为弱压性,北段呈弱张性,更易破裂,地震活动明显强于中南段。Previous studies have shown that M≥8 earthquakes and more than 80% M≥7 earthquakes occurred in the boundary zones of active blocks. Therefore, studies on the slip rate and stress distribution of the boundary faults can provide the basis for assessing the risk of strong earthquake. It also can help us understand the regional tectonic deformation, motion and dynamic process. Based on current cognition of the division of active block and fault system in the Sichuan-Yunnan region, we build a two-dimensional finite-element contact model, which includes ten small blocks and the primary block boundary faults, such as East Kunlun Fault, Minjiang Fault, Huya Fault, Xianshuihe-Xiaojiang Fault and Red River Fault. Slip rate and stress distribution of the primary block boundary faults are obtained by using long-term GPS observation data from 1991 to 2015 and “block-loading” method. This loading method can reflect interaction between the block and the boundary. Compared with the direct loading of GPS results, it can avoid local distortion caused by the large single-point error. Comparing GPS observation results with simulation results, the residual error less than 1 mm accounts for 66%, and the error less than 2 mm accounts for 86%. The direction angle residual error less than 5° accounts for~56%, and that less than 10° accounts for 82%, which means that simulation results of this study are reasonable. In addition, by collecting the relevant information on seismic activity and focal mechanism solutions in the Sichuan-Yunnan region, and combining with the simulation results, we discuss the relationship between slip rate distribution, transfer and stress transformation in large left-lateral strike-slip fault zones, the tectonic mechanism with normal fault type, as well as the probable cause of the seismic discrepancy between the northern and southern segments of the Red River Fault. The main conclusions are as follows:(1)As the strike of the left-lateral strike-slip East Kunlun and Xianshuihe-Xiaojiang fault zones tur

关 键 词：川滇地区 活动块体边界断裂 滑动速率 应力分布 

分 类 号：P315.2[天文地球—地震学]