漾濞M_(S)6.4地震前后的重力变化特征及其孕震含义分析  

ANALYSIS OF GRAVITY VARIATION CHARACTERISTICS AND ITS SEIMOGENIC MEANING BEFORE AND AFTER YANGBI M_(S)6.4 EARTHQUAKE

作　　者：黄江培 曹颖[1] 刘东 郑秋月 陈政宇 王青华[1] HUANG Jiang-pei;CAO Ying;LIU Dong;ZHENG Qiu-yue;CHEN Zheng-yu;WANG Qing-hua(Yunnan Earthquake Agency,Kunming 650201,China)

机构地区：[1]云南省地震局,昆明650201

出　　处：《地震地质》2022年第6期1557-1573,共17页Seismology and Geology

基　　金：云南省地震局科技专项(2021YBZX04)资助。

摘　　要：2021年5月21日云南省漾濞县发生M_(S)6.4地震,该地震打破了云南区域自2014年以来近7a的M_(S)>6.0地震平静。文中采用基于贝叶斯原理的平差方法解算了2015—2021年的相对重力流动观测数据,获取了研究区内多年的时变重力值,分析了漾濞M_(S)6.4地震前后的重力变化特征。研究结果显示,本次地震地质活动的活跃期为2017—2018年,2018—2020年地质活动相对稳定,2020—2021年出现地下物质“逃逸”现象,地震发生于“逃逸”期;以震中为中心的200km、100km、50km、25km半径范围内,重力异常值呈四象限分布特征;震前3a重力正、负变化更加显著,达80×10-8m/s2,震前2a重力变化较小,但依然维持四象限分布特征;震后研究区内的重力场均发生反向变化,变化量级达震前3a的累计变化量;本次地震发生于重力异常四象限中心附近,且与红河断裂带北段重合,故推断红河断裂为漾濞地震的孕震构造。文中的研究方法和成果可为时变重力场变化特征研究和震前重力信号分析与解释提供震例参考;同时,可为孕震区地质构造运动的孕震含义提供有效解释,并对下一步可能发生中强震区域的探讨及预判提供参考。On May 21,2021,an earthquake with a magnitude of 6.4 occurred in Yangbi,Yunnan,China,which broke the calm of earthquakes above M_(S)6.0 in Yunnan Province for nearly seven years since2015.This paper collects the relative gravity observation data of Yunnan from 2015 to 2021,and adopts the parameters estimation method based on Bayesian principle to obtain the station-value series of multi-year time-varying gravity field.Through years of time-varying gravity data,and according to the guiding idea of“Seeking the source from the field and combining the field and the source”,the series data are divided into different“time-space domains”.The“time domain”takes the epicenter as the center to analyze the one-year difference changes of the measuring points within a radius of 200km since 2015 and the multi-year cumulative change deduced backward from the origin time of earthquakes.The“space domain”takes the epicenter as the center,collects the point value change sequence of the measuring points with the radius of 200km,100km,50km and 25km respectively,and uses the method of“layered processing and step-by-step analysis”to analyze the characteristics of gravity change before the earthquake.The research results show that the geological active period of this earthquake is 2017—2018,the geological activity is relatively stable in 2018—2020 and there was the phenomenon of“escape”of underground materials in 2020 to 2021,and the earthquake occurred in the“escape”period.The abnormal gravity near the epicenter is characterized by a fourquadrant distribution,the positive and negative changes of gravity in the three years before the earthquake were more significant,reaching 80×10-8m/s~2,the change of gravity in the two years before the earthquake was small,but the four-quadrant distribution characteristics were still maintained.After the earthquake,the gravity field in the study area changed inversely,and the magnitude of change reached the cumulative change of 3 years before the earthquake.This earthqua

关 键 词：时变重力场 漾濞地震 贝叶斯平差 时空域 

分 类 号：P315.726[天文地球—地震学]