2021年云南漾濞M_(S)6.4地震前重力变化  

GRAVITY FIELD CHANGE BEFORE THE 2021 YANGBI M_(S)6.4 EARTHQUAKE,YUNNAN

作　　者：刘东 郝洪涛[3] 王青华[2] 郑秋月 黄江培 LIU Dong;HAO Hong-tao;WANG Qing-hua;ZHENG Qiu-yue;HUANG Jiang-pei(School of Surveying and Mapping,Wuhan University,Wuhan 430079,China;Yunnan Earthquake Agency,Kunming 650224,China;Key Laboratory of Earthquake Geodesy,Institute of Seismology,CEA,Wuhan 430070,China)

机构地区：[1]武汉大学测绘学院,武汉430079 [2]云南省地震局,昆明650224 [3]中国地震局地震研究所,中国地震局大地测量重点实验室,武汉430070

出　　处：《地震地质》2021年第5期1157-1170,共14页Seismology and Geology

基　　金：中国地震局监测预报司2021年震情跟踪定向工作任务(2021010228,20210207)资助。

摘　　要：文中对云南省区域范围内的2015—2021年的相对重力数据进行了平差计算,结合区域地质构造环境和区域范围内已发生的地震震例,系统分析了区域重力场变化和地壳水平运动的时空分布特征,获得了区域重力场变化与漾濞M_(S)6.4地震之间的关系。结果表明:1)2018—2021年震中位置的重力变化较弱,以震中为中心,附近区域在短期及1a期、2a期和4a期基本呈四象限特征且重力变化较为剧烈;2)震前短期及多年期重力变化显示,重力场高梯度带集中在漾濞—下关区域,且零值线交替出现在该区域;3)震前多年期重力变化显示,发震断裂带南涧-巍山断层的西侧重力呈负变化、东侧重力呈正变化,该地震为包含走滑分量的正断型地震,与全球台网数据的计算结果一致;4)对临震1a期重力变化异常指标进行了分析,发现重力转折变化异常的量级为75×10^(-8)m·s^(-2),重力变化异常时变距约为130km。漾濞地震的实际震级M_(S)6.4稍大于重力异常指标公式的计算结果M_(S)6.2,且震后漾濞地区相继发生了42次MS>3.0地震,可判断出漾濞地区地下活动能量已完全释放,M_(S)6.4地震为此处地震序列的主震,主震后短期内无更大地震发生。Yunnan is the front area where the material of Qinghai-Tibet Plateau moves eastward and rotates southeastward.This area is subject to active crustal movement and frequent destructive earthquakes.The activity intensity of the Honghe fault zone is the strongest in the middle part of Dali and its adjacent areas.The activity sequence of the whole fault zone since the Cenozoic has also changed gradually from the north and south ends to the Dali area in the middle section.The existing research data show that,based on the current seismic gravity monitoring network covering the whole province and surrounding areas,the mobile gravity monitoring network in Yunnan and surrounding areas can identify the gravity changes related to earthquakes of magnitude 5 and above.In this paper,the relative gravity data from 2015 to 2021 in Yunnan Province is adjusted and calculated,and combined with the regional geological tectonic environment and earthquake case studies,a systematic analysis is done on the temporal and spatial distribution characteristics of the changes in the gravity field and the horizontal crustal movement of the Yangbi earthquake and its surrounding areas to obtain the relationship between the regional gravity field change and the Yangbi M_(S)6.4 earthquake,the following results are obtained:1)By analyzing the gravity observation data of seven periods since 2018,it is found that the gravity change is weak at the Yangbi survey point in the epicenter from 2018 to 2021,and the gravity change around the epicenter is relatively intense.the gravity change at the Yangbi measuring point at the epicenter is within 10×10-8m·s-2,and the gravity change at the Xiaguan measuring point at a distance of about 39.2km in a straight line is around 10×10^(-8)m·s^(-2).Considering the observation accuracy of the instrument,the epicenter area is basically in a constant state.The variation of Yongsheng survey point in the north,Tengchong survey point in the west and Jingdong survey point in the south of the epicenter are larger,with the

关 键 词：漾濞M_(S)6.4地震 重力变化 四象限 重力梯度带 重力变化异常指标 

分 类 号：P315.726[天文地球—地震学]