2022年四川泸定MS6.8地震前重力场变化及其孕震机理分析

(1.中国地震局第二监测中心,陕西 西安 710054; 2.中国科学院精密测量科学与技术创新研究院,湖北 武汉 430071; 3.中国科学院大学,北京 100049; 4.河南城建学院测绘与城市空间信息学院,河南 平顶山 467036; 5.中国地震局第一监测中心,天津 300180; 6.四川省地震局地壳形变观测中心,四川 雅安 625000)

泸定MS6.8地震; 重力场变化; 布格重力异常; 深部孕震背景

Gravity Filed Variation before the Luding,Sichuan MS6.8 Earthquake in 2022 and Its Seismogenic Mechanism
WEI Shouchun1,ZHU Yiqing1,ZHAO Yunfeng1,2,3,LIU Fang1,JIANG Yongtao4,LIU Jinzhao5,ZHENG Bing6

(1.The Second Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,Shaanxi,China)(2.Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430071,Hubei,China)(3.University of Chinese Academy of Sciences,Beijing 100049,China)(4.School of Surveying and Urban Spatial Information,Henan University of Urban Construction,Pingdingshan 467036,Henan,China)(5.The First Monitoring and Application Center,China Earthquake Administration,Tianjin 300180,China)(6.Crustal Deformation Monitoring Center of Sichuan Earthquake Agency,Ya'an 625000,Sichuan,China)

the Luding MS6.8 earthquake; gravity field variation; Bouguer gravity anomaly; deep seismogenic background

DOI: 10.20015/j.cnki.ISSN1000-0666.2025.0058

备注

利用全球重力场模型grav.img.23.1和全球DEM模型topo_18.1.img研究了川西地区的布格重力异常特征,利用小波多尺度分析方法对重力异常信号进行分离,研究了该地区的深部物质迁移特征和强震孕育背景; 并基于2017—2022年的区域流动重力观测资料,研究了2022年9月5日泸定MS6.8地震前的区域重力场变化特征。结果表明:①小波多尺度分解得到的不同深度重力异常特征图像,均在三岔口—石棉一带存在显著的重力异常梯度带和四象限分布特征,表明了该地区深部强烈的物质迁移和密度变化,泸定MS6.8地震震源区处于不同密度地质体的交会区域,具备发生强震的孕震背景; ②地震前出现了较好的中期前兆性重力变化图像,前期沿鲜水河断裂及玉龙希断裂形成了重力变化高梯度带,泸定MS6.8地震发生在重力变化高梯度带的拐弯处附近,临震前重力场出现了反向变化,并在三岔口地区出现重力异常四象限变化特征,地震发生在重力场反向变化过程中; ③依据震质源和震质中模型,分析认为震中南侧的九龙、石棉、冕宁一带的正重力变化可能是导致此次地震发生的主要诱因,引起该重力变化的深部场源可能是主导此次地震的孕震体。
In this paper,the global gravity field model grav.img.23.1 and global DEM model topo_18.1.img are used to study the characteristics of Bouguer gravity anomaly in the western region of Sichuan province.The method of wavelet multi-scale decomposition is used to separate the gravity anomaly signals at different depths,and the characteristics of deep material migration and the seismogenic background of strong earthquakes in this region are studied.Based on the mobile gravity observation data during 2017-2022,the characteristics of regional gravity changes before the Luding MS6.8 earthquake on September 5,2022 were studied.The results show that:(1)All the gravity anomaly signals at different depths obtained by wavelet multi-scale decomposition show that there is a significant gradient zone and four-quadrant distribution feature of gravity anomaly in divergence area,indicating strong material migration and density change in the deep part of the area.The focal area is located in the interface area of geological bodies with different densities,which has the seismogenic background of strong earthquakes.(2)Before the earthquake,there were good images of medium-term precursor gravity change.In the early stage,a high gradient zone of gravity change was formed along the Xianshuihe fault and the Yulongxi fault.The Luding MS6.8 earthquake occurred near the bend of the high gradient zone of gravity change.Earthquakes occur in the process of reverse change of gravity field;(3)According to the “hypocentroid and epicentroid” model,this paper concludes that the positive gravity changes in Jiulong,Shimian and Mianning areas on the south side of the epicenter may be the main inducement of the earthquake,and the deep field source that caused the gravity changes may be the seismogenic body leading the earthquake.
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