2018年9月8日墨江5.9级地震云南普洱大寨流体异常特征及机理  

THE CHARACTERISTICS AND MECHANISM OF FLUID ANOMALIES IN THE DAZHAI OBSERVATION WELL OF PU ER,YUNNAN PROVINCE BEFORE THE M 5.9 MOJIANG EARTHQUAKE ON SEPTEMBER 8,2018

作　　者：胡小静[1] 付虹[1] 张翔 李利波[1] 黄江培 李琼[1] 高文斐 HU Xiao-jing;FU Hong;ZHANG Xiang;LI Li-bo;HUANG Jiang-pei;LI Qiong;GAO Wen-fei(Yunnan Earthquake Agency,Kunming 650224,China)

机构地区：[1]云南省地震局,昆明650224

出　　处：《地震地质》2024年第2期477-491,共15页Seismology and Geology

基　　金：中国地震局地震科技星火计划项目(XH21030Y);地震预测开放基金(XH24011D);2023年度震情跟踪定向工作任务(2023020303)共同资助。

摘　　要：文中梳理了2004年以来普洱大寨井连续观测的水化学离子和井-含水层渗透性异常特征。研究发现,在观测井周边250km范围内5.5级以上地震发生前,多次出现过可重复、可类比的异常变化,对地震具有较好的异常指示和预测意义。但相比以往震例,墨江5.9级地震发生前,无论是化学离子还是物理参数均出现了观测以来幅度最大的变化,异常状态较以往强烈很多,但发震的震级只有5.9级。为了研究这一现象产生的原因和机理,文中尝试从区域深部物质活动和区域应力水平2个方面对墨江5.9级地震前的异常演化过程开展讨论,得到以下认识:墨江5.9级地震前,流体异常整体呈现出较为显著的从深部到浅部、从背景到短期微观异常再到临震宏观异常的演化过程;墨江5.9级地震前,普洱大寨连续观测的水化学离子浓度异常和井-含水层渗透性的改变是由于区域内垂向剪切应力持续增强引起的含水层受挤压,从而形成了垂向的流体补给,最终引起不同含水层水体发生交替混合而产生的结果;本次异常形成初期还伴随深部物质剧烈活动的现象,较为显著的由深部到浅部的耦合作用过程可能是导致墨江5.9级地震前出现自观测以来地下流体异常幅度最显著的原因。因此,流体活动从深部开始,随着区域应力不断积累,不断向地表传递的演变过程是墨江5.9级地震前流体异常演化的本质特征;区域应力的作用方式和深部物质活动程度不同,是引起墨江5.9级地震前异常特征与研究区其他历史震例前明显不同的根本原因。文中研究为全面认识普洱大寨井地下流体异常的预测意义和地震前流体异常的深浅耦合演化过程提供了一定参考。The precursors before earthquakes are very useful to earthquake prediction,and fluid anomalies before earthquakes are very important to precursory observations.This paper reviews the characteristics of hydrochemical ions and well-aquifer permeability anomalies of the Dazhai observation Well in Pu er,which is in the Yunnan-Southwestern region of China,for all M≥5.5 earthquakes since 2004.We find that both the chemical ions and physical parameters before the Mojiang M 5.9 earthquake exhibited the largest magnitude of changes since observation,and the abnormal state was much stronger than that of previous historical earthquakes,but the magnitude of the earthquake was below 6.About 1.5-2a before the M 5.9 Mojiang earthquake,the composition of hydrogen and oxygen isotopes of the water samples in the Dazhai observation Well showed a significant deviation,accompanied by a continuously increasing concentration of fluoride ions from sources at deeper depths.This might suggest that the deep material in the earthquake source area began to be active.At the same time,starting one year before the earthquake,the phase lag of the water level in the wellhole changed from negative to positive,indicating that the source and pathway of well water recharge have been changed.In addition,around half a year before the earthquake,the continuously observed water chemical ions at shallow depths in the wellhole began to show a dramatic change.Moreover,macroscopic anomalies of hot spring water volume increased sharply before the earthquake,showing a remarkable evolution process from deep to shallow,from background to short-term,and from micro anomalies to macro anomalies before the earthquake.To investigate the causes and mechanisms of this phenomenon,we attempt to discuss the abnormal evolution process before the M 5.9 Mojiang earthquake from the aspects of regional deep material activity and regional stress level.The abnormal concentration of the hydrochemical ions and the change of aquifer permeability observed continuously at the Dazha

关 键 词：地下流体异常 深浅耦合 普洱大寨井 墨江5.9级地震 

分 类 号：P315.723[天文地球—地震学]