川滇地区地震危险性数值分析  

Numerical analysis of the seismic hazard in Sichuan-Yunnan region

作　　者：尹迪 董培育[2] 曹建玲[3] 石耀霖 YIN Di;DONG PeiYu;CAO JianLing;SHI YaoLin(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Earthquake Geodesy,Institute of Seismology,China Earthquake Administration,Wuhan 430071,China;Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100049,China)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]中国地震局地震研究所地震大地测量研究室,武汉430071 [3]中国地震局地震预测研究所,北京100049

出　　处：《地球物理学报》2022年第5期1612-1627,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42174113),地震数值预测联合实验室开放基金课题(2020LNEF06),国家自然科学基金-地震局地震科学联合基金(U1839207)和国家自然科学基金项目(41974111)共同资助.

摘　　要：川滇地区地处我国南北地震带南段,近百年来地震活动性持续较高,该地区未来强震预测研究备受关注.本文根据该区域百年时间内发生的30次M_(S)>6.5历史地震,结合区域地质背景及GPS观测数据等,建立区域有限元准三维弹性模型,通过反演给定区域特定时刻合理的初始应力场.在此基础上,综合考虑地震孕育阶段和震后调整阶段的动力学过程,以库仑-摩尔破裂准则作为判断地震发生的条件,模拟单次地震过程和历史地震序列的发展过程.同时,对于数值模拟中的不确定性成分,通过大量Monte Carlo随机试验得到5000种初始应力场模型,确保所有模型均能重现历史地震的发震过程,最终得到现今应力场状态,并据此计算地震危险性系数,将不同模型的计算结果进行概率统计,初步得到研究区域2017年九寨沟地震后的地震危险性概率分布.结果显示历史地震破裂区的危险性概率大幅降低,相对安全;而龙门山断裂带东北段发震概率高达30%,主要是受2008年汶川地震震后应力扰动的影响;龙门山断裂带西南段(包括汶川地震破裂区与芦山地震破裂区的中间区域)与鲜水河断裂带交界处发震概率约为15%~20%;另外滇西南龙陵瑞丽断裂带及澜沧江断裂带附近发震概率约为10%~15%,近年来滇西南地区小震频发,该地区地震危险性同样值得注意.The Sichuan-Yunnan region is located in the southern part of Chinese north-south seismic belt and has strong seismic activity.The prediction of the risk of future strong earthquakes in this region has attached more attention.In this study,firstly,we established a quasi-three-dimensional finite element elastic model,combined with the regional geological background and GPS observation data.Then,based on the information of 30 M_(S)>6.5 historical earthquakes that occurred in the region over the past 100 years,and constrained by the Coulomb-Mohr rupture criterion,we inverted a possible reasonable initial stress field at a specific time.Secondly,we simulated the development process of each historical earthquake and reproduced the 30 events orderly,by comprehensively considering the tectonic stress loading in the seismogenic stage and the stress change in the co-seismic adjustment stage.However,it is worth noting that there were some uncertainties in the numerical simulation process.We used Monte Carlo random experiments to obtain 5000 kinds of different possible initial values,which all can reproduce the development process of historical events.Then we got different current reginal stress values and calculated earthquake risk coefficient.Finally,we used mathematical methods to investigate the current seismic hazard of the different models,and assembled them into a probability distribution map of possible seismic risk in the region.The preliminary result shows that the seismic risk in the rupture zone of historical earthquakes is greatly reduced,which means relatively safe.Mainly due to the stress change caused by the 2008 Wenchuan M_(S)8.0 earthquake,the seismic probability in the northeastern segment of the Longmenshan fault is as high as 30%.At the junction of the southwestern section of the Longmenshan fault and the Xianshuihe fault zone,the seismic probability is about 15%~20%.In addition,near the Longling Ruili fault and the Lancangjiang fault in southwestern Yunnan,the value is about 10%~15%.In recent years,smal

关 键 词：川滇地区 初始应力场反演 地震序列演化 地震危险性 

分 类 号：P541[天文地球—构造地质学] P315[天文地球—地质学]