基于LURR的前震分析方法及其在川滇地区的应用  

The foreshock analysis technique based on the LURR method and its application in Sichuan—Yunnan region

作　　者：李泽平 余怀忠[2] 晏锐[2] 刘杰[2] 陈界宏 张小涛[2] 苑争一 郭菲 马玉川[2] 杨文[2] 贾东辉 赵彬彬[4] 李盛乐 张致伟[6] 洪敏[7] LI ZePing;YU HuaiZhong;YAN Rui;LIU Jie;CHEN Chieh-Hung;ZHANG XiaoTao;YUAN ZhengYi;GUO Fei;MA YuChuan;YANG Wen;JIA DongHui;ZHAO BinBin;LI ShengLe;ZHANG Zhiwei;HONG Min(Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;China Earthquake Networks Center,Beijing 100045,China;Chengdu University of Technology,Chengdu 610059,China;Earthquake Agency of Xinjiang Uygur Autonomous Region,Urumqi 830011,China;Hubei Earthquake Agency,Wuhan 430071,China;Sichuan Earthquake Agency,Chengdu 610041,China;Yunnan Earthquake Agency,Kunming 650224,China)

机构地区：[1]中国地震局地震预测研究所,北京100036 [2]中国地震台网中心,北京100045 [3]成都理工大学,成都610059 [4]新疆维吾尔自治区地震局,乌鲁木齐830011 [5]湖北省地震局,武汉430071 [6]四川省地震局,成都610041 [7]云南省地震局,昆明650224

出　　处：《地球物理学报》2024年第6期2248-2271,共24页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2018YFE0109700);国家自然科学基金地震联合基金(U2039205)资助。

摘　　要：加卸载响应比(Load-Unload Response Ratio,LURR)是基于岩石介质本构关系动态变化提出的一种中短期地震预测方法,然而,在实践应用中存在构造剪应力方向难以确定的问题.本文以前震为研究对象,发展了一种确定构造剪切应力方向的新思路.当4级以上地震发生后,通过沿该地震滑动方向计算库仑破坏应力(CFS)的变化,判断其固体潮加卸载状态,探测后续强震发生的可能性.以川滇地区(20°N—35°N,96°E—106°E)为研究区域,分析2000年以来所有6级以上地震的4级以上前震的加卸载状态发现,大部分4级以上前震发生在加载阶段.进一步分析近10年来所有4级以上地震的加卸载状态发现,非前震则更易发生在卸载阶段.结合概率增益分析可知,(1)若原震区连续发生至少2个4级以上地震,且均位于固体潮加载过程,后续发生强震的可能性较大;(2)当地震位于卸载过程,原震区发生更强地震的可能性要低于平时的背景地震活动水平.此外,对2022年11月以来的4级以上地震加卸载状态分析推测,川东南、滇南、滇西北地区应力积累水平较高,需要重点关注强震危险性.The Load-Unload Response Ratio(LURR)theory is a medium-to-short-term earthquake prediction method that relies on the dynamic changes in rock constitutive relationships.However,determining the direction of tectonic shear stress in practice can be challenging.This study focuses on foreshocks and proposes a new approach to determine the direction of tectonic shear stress.When an earthquake with a magnitude 4 or higher occurs,the changes in Coulomb Failure Stress(CFS)along the slip direction of the earthquake are calculated to assess its loading/unloading states induced by the earth tide.This information can then be utilized to detect the possibility of subsequent strong earthquakes.In the study area of the Sichuan—Yunnan region(20°N—35°N,96°E—106°E),the loading/unloading states of M4.0+foreshocks for all M6.0+earthquakes since 2000 were analyzed.It was discovered that most foreshocks occurred during the loading process.Further analysis of the loading/unloading states of all M4.0+earthquakes in the past 10 years revealed that non-foreshocks are more likely to occur during the unloading process.By combining this information with probability gain analysis,the following conclusions are drawn:(1)If there are at least two consecutive earthquakes of magnitude 4.0 or above occurring in the seismogenic area and all of them are in the loading process,the probability of a strong earthquake occurring in the following days is higher;(2)If an earthquake occurs during the unloading process,there is little likelihood of a strong earthquake occurring in the following days.Additionally,the analysis of the loading/unloading states of M4.0+earthquakes since November 2022 suggests higher stress accumulation levels in the southeastern Sichuan,southern Yunnan,and northwestern Yunnan regions.This indicates a need for increased attention to the risk of strong earthquakes in these areas.

关 键 词：加卸载响应比 4级以上显著地震 震源机制解 潮汐应力 加卸载状态 

分 类 号：P315[天文地球—地震学]