2017年四川九寨沟M_(S)7.0地震前地电场优势方位角与小震震源机制解异常一致性分析  

Analysis of consistency with anomalous focal mechanisms of small earthquakes and the dominant azimuth of the geoelectric field before the 2017 Jiuzhaigou M_(S) 7.0 earthquake in Sichuan Province

作　　者：鲍海英[1] 夏忠[1] 杨云[1] 李锋[1] BAO Haiying;XIA Zhong;YANG Yun;LI Feng(Jiangsu Earthquake Agency,Nanjing 241000,China)

机构地区：[1]江苏省地震局,南京241000

出　　处：《地震地磁观测与研究》2025年第1期78-84,共7页Seismological and Geomagnetic Observation and Research

基　　金：地震科技星火计划(项目编号:XH24017YC);震情跟踪定向工作任务(项目编号:2023010406)。

摘　　要：地电场优势方位角和小震震源机制解均可反映区域应力场方向变化,本文以2017年8月8日四川九寨沟M_(S)7.0地震为例,采用大地电场潮汐波岩体裂隙水(电荷)渗流(移动)模型,选取2017年震中300 km范围内5个地电场台站记录数据,计算其优势方位角,并收集研究区2010—2018年发生的1294个M≥3.0中小地震的震源机制解,通过区域应力张量阻尼反演方法进行区域应力场反演,对比分析地电场优势方位角异常和区域应力场时空变化的相关性。研究结果表明:在此次M_(S)7.0地震发生前,汉王、玛曲、成都和天水地震台大地电场优势方位角均具有变化范围明显变小、增大及阶变等现象;该区域小震震源机制解在震前表现出较好的一致性,而震后则一致性较差,即小震震源机制一致性异常在时间上与地电场优势方位角异常具有较高的一致性。该研究结果对于提升地电场优势方位角异常判断的可靠性具有一定促进作用。Since both the dominant azimuth of the geoelectric field and the focal mechanism solution of small earthquakes can reflect the direction change of the regional stress field,this paper uses the seepage(movement)model of the geoelectric field tidal wave rock fissure water(charge)to calculate the dominant azimuth of the electric field observation data within 300 km before the 2017 Jiuzhaigou M_(S)7.0 earthquake in Sichuan,collects the focal mechanism solutions of small and medium-sized earthquakes in the same period in the study area to invert for the regional stress field by the regional stress tensor damping inversion method.The spatial and temporal variation characteristics of the regional stress field inverted by the dominant azimuth anomaly of the geoelectric field and the focal mechanism solution are compared and analyzed.The research results show that before the 2017 Jiuzhaigou M_(S) 7.0 earthquake in Sichuan,the dominant azimuth angle of the electric field in Hanwang,Maqu,Chengdu,and Tianshuitai showed significant changes such as a smaller range,an increase,and a step change.At the same time,the focal mechanism solution of small earthquakes in the study region showed good consistency before the Jiuzhaigou earthquake,but poor consistency afterward.That is,the consistency anomaly of the focal mechanism solution of small earthquakes is consistent with the dominant azimuth anomaly of the geoelectric field in time.This research result has a certain promoting effect on the reliability improvement of the dominant azimuth anomaly of the geoelectric field.

关 键 词：地电场 优势方位角 可靠性 震源机制异常 九寨沟M_(S)7.0地震 

分 类 号：P315.7[天文地球—地震学]