地震辐射能量测定方法研究及其在汶川8.0级地震中的应用  

Research on the method to determine the seismic radiated energy and its application in Wenchuan M 8.0 earthquake

作　　者：孔韩东 刘瑞丰[1] 边银菊[1] 李赞 王子博 胡岩松 KONG HanDong;LIU RuiFeng;BIAN YinJu;LI Zan;WANG ZiBo;HU YanSong(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2022年第12期4775-4788,共14页Chinese Journal of Geophysics

基　　金：中国地震局地球物理研究所基本科研业务专项(DQJB22B18,DQJB21X28)共同资助.

摘　　要：地震辐射能量是关于震源定量的特征量,地震辐射能量的测定是地震定量化研究中一个重要的基本问题.本文基于点源震源模型,开展了地震辐射能量测定方法的研究,推导了计算地震辐射能量的理论公式,自主研发了一套利用远场垂直向P波记录测定地震辐射能量的软件系统,能够快速测定全球范围内5.5级以上浅源地震的地震辐射能量.以2008年5月12日汶川8.0级地震为例,检验了地震辐射能量测定方法和软件系统的科学性和准确性,研究结果表明:(1)汶川地震的地震辐射能量为2.84×10^(16) J,各台站地震辐射能量的分布与震中距和方位角都没有明显的依赖关系,说明使用理论格林函数法消除路径效应对地震辐射能量测定的约束效果较好;(2)汶川地震的能量震级M_(e)为8.04,震源机制校正可以使能量震级测定结果的标准差更小,结果更稳定;(3)反演得到汶川地震的地震矩为8.97×10^(20) N·m,转化为矩震级M_(W)为7.9,M_(e)比M_(W)高0.14,说明汶川地震的地震辐射能量偏高.(4)汶川地震的能矩比为3.17×10^(-5),约为全球浅源地震平均能矩比的2.6倍,约为全球逆冲型地震平均能矩比的4倍,地震辐射能量释放效率明显偏高;能矩比取对数可得慢度系数为-4.50,慢度系数可以更直观地显示地震辐射能量释放效率的高低,更适合在普通群众中推广.(5)地震辐射能量、能量震级、能矩比、慢度系数和等效震级差这些新的地震参数,能够定量表示震源的动态特性,对于地震灾害快速评估具有重要意义.The radiated seismic energy is a characteristic quantity about quantification of the source,and its determination is an important fundamental problem in the quantitative study of the earthquake.In this study,based on the point source model,we carried out a research on the determination method of radiated seismic energy,derived the theoretical formulas,and developed a software system for measuring it using far-field vertical P-wave records independently,which can quickly determine the radiated seismic energy of shallow earthquakes of M≥5.5 worldwide.The scientificity and accuracy of the method and software are verified by using the example of the Wenchuan M 8.0 earthquake.The results show that:(1)The radiated seismic energy of the Wenchuan earthquake is 2.84×10^(16) J,and the distribution of radiated seismic energy of each station has no obvious dependence on the epicenter distance and azimuth,indicating that theoretical Green′s function has an important impact on eliminating the path effect.(2)The energy magnitude M_(e) of the Wenchuan earthquake is 8.04.The correction of the focal mechanism can make the standard deviation of M_(e) smaller and the result more stable.(3)The seismic moment of the Wenchuan earthquake obtained by inversion is 8.97×10^(20) N·m,which is converted into a moment magnitude M_(W) of 7.9,and M_(e) is 0.14 higher than M_(W),indicating that the seismic radiated energy of the Wenchuan earthquake is high.(4)The energy-moment ratio of the Wenchuan earthquake is 3.17×10^(-5),which is about 2.6 times the average energy-moment ratio of global shallow earthquakes and about 4 times the average of the global thrust earthquakes.It shows that the release efficiency of seismic radiated energy of the Wenchuan earthquake is high.Taking the logarithm of the energy-moment ratio,the slowness coefficient can be obtained as-4.50.The slowness coefficient is more direct perceived to show the release efficiency of the seismic radiated energy,which is more suitable for promotion among the general public.(5)

关 键 词：地震辐射能量 汶川地震 能量震级 能矩比 慢度系数 等效震级差 

分 类 号：P315[天文地球—地震学]