不同类型地震震级与重力变化异常的统计特征及其机理分析  

Statistic relationship between earthquake magnitude and gravity changes and their mechanism analysis of different categories of earthquakes

作　　者：李树鹏 胡敏章[2,3] 祝意青 朱成林[1] 崔华伟[1] 陆汉鹏[1] 张刚[1] 王锋吉[1] LI ShuPeng;HU MinZhang;ZHU YiQing;ZHU ChengLin;CUI HuaWei;LU HanPeng;ZHANG Gang;WANG FengJi(Earthquake Administration of Shandong Province,Jinan 250014,China;Key Laboratory of Earthquake Geodesy,Institute of Seismology,China Earthquake Administration,Wuhan 430071,China;Gravitation and Earth Tide,National Observation and Research Station,Wuhan 430071,China;The Second Monitoring Center,China Earthquake Administration,Xi'an 710054,China)

机构地区：[1]山东省地震局,济南250014 [2]中国地震局地震研究所地震大地测量重点实验室,武汉430071 [3]武汉引力与固体潮国家野外科学观测研究站,武汉430071 [4]中国地震局第二监测中心,西安710054

出　　处：《地球物理学报》2024年第8期3032-3059,共28页Chinese Journal of Geophysics

基　　金：山东省海洋地震观测研究团队(TD202401);山东郯城巨震区低速率挤压逆冲构造野外科学观测研究站;中国地震局地震科技星火计划攻关项目(XH20039);中国地震局震情跟踪定向工作任务(2023010203)共同资助。

摘　　要：依据收集到的107个4.0级以上地震震例,研究中国陆区中强地震震前重力变化异常统计特征,探讨地震震级与震前重力变化异常各要素及地震性质之间的统计关系,给出了5、6、7、8级地震震级判定的重力变化异常时变距S、量级G和时间T参考指标,并对比、分析了逆冲型、走滑型和正断型地震的重力变化特点,进而结合流体物质运移假说及岩石物理实验结果,探讨了震前重力变化异常的物理机制,以及其与亚失稳阶段、地震孕育能量的联系.得到的主要结论有:(1)震前重力变化异常参量与震级之间更符合非线性关系,5、6、7、8级地震的震前重力变化异常时变距参考指标分别为67、111、185、305 km,重力变化异常量级参考指标分别为49、67、92、125μGal,重力变化异常时间参考指标分别为1.6、2.5、3.7、5.2 a.(2)地震类型对震前重力变化参量有一定影响,尤其是7级以上强震的差异更加明显,逆冲型地震的重力变化量级及时变距可能更大;重力变化异常时间方面,正断型地震可能对应更长的重力变化时间,逆冲型次之,走滑型最短.(3)震前重力变化异常的物理机制可能是,在孕震晚期、亚失稳阶段,震中周边区域岩石裂隙增多、扩展、贯通,引起流变性的深部幔源物质向地壳运移,同时地壳内先存的流体物质由于应力分布不均而大规模迁移,最终在地表引起重力场变化响应.(4)目前流动重力观测受到时空密度的制约,地震预报主要针对5级以上地震,且震级越大预报效能越好.Based on the 107 earthquakes of M_(S)≥4.0 collected,the statistical characteristics of the gravity changes anomaly before earthquakes in Chinese continent were studied.The statistical relationship between earthquake magnitude M_(S) and the gravity changes and the nature of the earthquake was explored.Reference indicators for the scale parameter S,magnitude parameter G,and time parameter T of gravity changes for M_(S)5.0,M_(S)6.0,M_(S)7.0,and M_(S)8.0 earthquakes have been given.The gravity changes before thrust,strike-slip,and normal earthquakes were compared and analyzed.Furthermore,by integrating the hypothesis of fluid-matter migration and the results of petrophysical experiments,the physical mechanisms of gravity changes before earthquakes and their connection with the meta-instability stage and the energy for earthquake gestation were discussed.The main conclusions are:(1)The relationship between gravity change parameters before earthquakes and earthquake magnitude appears to be nonlinear across all studied cases.Specifically,for earthquakes of magnitudes M_(S)5.0,M_(S)6.0,M_(S)7.0,and M_(S)8.0,the reference indicators for scale parameter S are 67,111,185,and 305 km;for magnitude parameter G,they are 49,67,92,and 125μGal;and for time parameter T,they are 1.6 year,2.5 year,3.7 year,and 5.2 year,respectively.(2)The type of earthquake has some influence on the gravity changes before the earthquake,and the difference is especially obvious for earthquakes with M_(S)≥7.0.In terms of the scale parameter S of gravity change,the largest is for strike-slip earthquakes with M_(S)≤6.0,followed by normal earthquakes and then thrust earthquakes;thrust earthquakes are the largest with M_(S)>7.0,followed by strike-slip earthquakes.In terms of the magnitude parameter G of gravity change,for magnitude M_(S)<7.0,slip-type earthquakes are the largest,with thrust and normal earthquakes slightly lower;for magnitude M_(S)≥7.0,thrust earthquakes are the largest,followed by strike-slip earthquakes.In terms of the time param

关 键 词：地震预报 重力变化异常 震级 震源机制解 

分 类 号：P312[天文地球—固体地球物理学]