基于连续重力台观测的玛多M_(S)7.4地震的同震重力变化特征  

STUDY ON THE CHARACTERISTICS OF CO-SEISMIC GRAVITY CHANGE INDUCED BY MADUO M_(S)7.4 EARTHQUAKE BASED ON OBSERVATIONS OF CONTINUOUS GRAVITY STATIONS

作　　者：韦进[1,2,4] 郝洪涛 韩宇飞[3] 胡敏章 江颖 刘子维[1,2,4] WEI Jin;HAO Hong-tao;HAN Yu-fei;HU Min-zhang;JIANG Ying;LIU Zi-wei(Institute of Seismology,CEA,Wuhan 430071,China;Key Laboratory of Earthquake Geodesy,China Earthquake Administration,Wuhan 430071,China;China Earthquake Networks Center,Beijing 100045,China;Hubei Earthquake Agency,Wuhan 430071,China)

机构地区：[1]中国地震局地震研究所,武汉430071 [2]中国地震局地震大地测量重点实验室,武汉430071 [3]中国地震台网中心,北京100045 [4]湖北省地震局,武汉430071

出　　处：《地震地质》2021年第4期984-998,共15页Seismology and Geology

基　　金：国家自然科学基金项目(41204058)资助。

摘　　要：同震重力变化可为位错模型的检验和约束提供新数据。文中利用指数函数和阶跃函数法分析了玛多M_(S)7.4地震震中距≤800km的5个重力台的同震重力信号。结果显示:观测和位错模型模拟结果的方向一致性好,只是量级存在差异。通过对同震重力变化精度的讨论,同震重力变化和GNSS垂直位移的比较,九寨沟M_(S)7.0、玛多M_(S)7.4同震重力变化空间分布的分析,以及漾濞M_(S)6.4地震对同震重力变化影响的改正,分析认为:震中距为175km的玛沁台记录到(2.9~4.0)×10^(-8)m·s^(-2)的同震重力变化;震中距为763km的中甸台在改正了漾濞地震的影响后记录到1.09×10^(-8)m·s^(-2)的同震重力变化;松潘台记录的9.1×10^(-8)m·s^(-2)的重力变化信号中应包含其他因素的影响;林芝台的负变化规律和位错模型模拟结果方向一致。综合文中的观测结果认为,玛多M_(S)7.4地震能够在175~800km的远场范围内产生约(0.5~4.0)×10^(-8)m·s^(-2)的同震重力变化信号。该结果可为未来中强地震远场产生的同震重力变化量级的判定提供参考。The Bayan Kara block is a secondary block in the Qinghai-Tibet Plateau interior with the strongest seismic activity occurring in the recent years.Unlike the 8 earthquakes above M 7.0 occurring on the block boundary in the past 20 years,the Maduo M_(S)7.4 earthquake occurred inside the block,thus providing a new research perspective for the composition of coseismic gravity change observations.At the same time,China Earthquake Administration set up 5 gPhone continuous gravity stations,which operated normally before and after the earthquake,about 800km away from the epicenter,near the northeast edge of the Qinghai Tibet Plateau and the adjacent areas.Among them,the Maqin gravity station is inside the block and the Songpan gravity station is on the block boundary.The location of this earthquake and the distribution characteristics of the gravity stations provide natural experimental sites and samples for studying the coseismic gravity change in the stations at different locations in and around the block.In order to check the dislocation theory based on surface deformation observation,accumulate coseismic gravity change data by strong earthquakes,and analyze the features of the coseismic gravity change by surface gravity observation from different perspectives,the gravity earth tide and barometric observation data measured by gPhone gravimeters and sampled at 1Hz in these 5 continuous gravity stations from May 10 to 25,2021 are collected.In this paper,firstly,exponential and step function methods are used to extract the coseismic gravity change in these 5 gravity stations,so as to analyze whether the post-seismic gravity signals contain relaxation signal.The relaxation time observed by gravimeter is very short compared to the near-field results of Lushan M_(S)7.0 earthquake,only about 11 minutes.And the step method result is more consistent with the model one.Comparing with the coseismic dislocation theory by Okubo and Sun model,it is found that the difference between the observation results of the two methods and the

关 键 词：玛多M_(S)7.4地震 gPhone重力仪 同震重力变化 位错模型 

分 类 号：P315.726[天文地球—地震学]