利用GRACE重力和重力梯度变化估计2012年苏门答腊地震断层参数  

Fault parameters of the 2012 Sumatra earthquake estimated from GRACE gravity and gravity gradient changes

作　　者：郑增记 金双根 范丽红 ZHENG ZengJi;JIN ShuangGen;FAN LiHong(Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai200030, China;University of Chinese Academy of Sciences, Beijing 100049, China;Shaanxi Earthquake Agency, Xi′an 710068, China;School of Remote Sensing and Geomatics Engineering, Nanjing University of Information Science and Technology,Nanjing 210044, China;National Time Service Center, Chinese Academy of Science, Xi′an 710600, China)

机构地区：[1]中国科学院上海天文台,上海200030 [2]中国科学院大学,北京100049 [3]陕西省地震局,西安710068 [4]南京信息工程大学遥感与测绘工程学院,南京210044 [5]中国科学院国家授时中心,西安710600

出　　处：《地球物理学报》2019年第11期4129-4141,共13页Chinese Journal of Geophysics

基　　金：国家重点研发计划项目课题(2018YFC0603502);中国地震局监测、预报、科研三结合课题(3JH-201901088);中国科学院西部青年学者项目(Y916YRa701)联合资助

摘　　要：2012年4月11日苏门答腊北部附近海域发生MW=8.6地震,国际上采用不同数据获得了该地震的断层滑动模型,但断层走滑性质存在较大差异.卫星重力GRACE(Gravity Recovery and Climate Experiment)观测覆盖震中区域,可以提供很好的断层参数估计约束.本文采用GRACE月重力场模型数据提取了此次地震同震重力和重力梯度变化,表明了北向分量的优越性.并与断层模型理论计算结果进行了比较,分析了Txx(北-北向重力梯度)分量对断层参数的敏感性,以及基于粒子群算法以及Okubo位错模型反演了该地震断层参数.结果表明GRACE观测到的同震重力梯度变化在空间形态分布上与断层模型模拟结果符合较好,但振幅差异较大.重力和重力梯度的北向分量可以很好地压制条带误差,其中gN(北向重力变化)和Txx的误差最小,其次是Txz(北-上向重力梯度),误差最大和对条带误差抑制效果最差的是Txy(北-东向重力梯度).Txx对断层的深度不敏感,对其余断层参数较敏感.基于GRACE反演得到的断层的走向角为113.63°,倾角为89.99°,滑移角为175.26°,平均滑移量为28.18m,相应的矩震为8.71级,且此次地震的走滑性质为右旋走滑.The M W=8.6 earthquakes occurred on11.April2012.and ruptured off the west coast of northern Sumatra. The fault slip models of the earthquake were estimated from different data, but have large differences in the strike-slip nature of faults. GRACE-derived co-seismic gravity changes cover the epicenter area, which can provide good constraint on the fault parameters inversion. In this paper, co-seismic gravity and gradient changes of the 2012 Sumatra earthquake are extracted from GRACE time-variable gravity field and the superiority of the northward component is presented. The theoretical calculation results of the fault model are compared with the GRACE and the sensitivity of the T xx (north-to-north gravity gradient) to the fault parameters is analyzed. Finally, the fault parameters of the earthquake are retrieved based on the particle swarm optimization (PSO) algorithm and the Okubo dislocation model. The results show that the GRACE-observed co-seismic gravity and gravity gradient changes are in good agreement with the model-estimated results in spatial pattern, but have difference in amplitudes. The strip errors can be substantially suppressed by the north components of gravity and gravity gradients changes, where the noise level of g N (north gravity change) and T xx are the lowest, followed by T xz (north-to-up gravity gradient) and the worst is the T xy (north-to-east gravity gradient). The T xx is not sensitive to the depth of the fault, but sensitive to other fault parameters. The GRACE-inverted strike angle, dip angle, rake angle and average slip magnitude of the earthquake are113.63°, 89.99°,175.26° and28.18 m, respectively, indicating a moment-magnitude M W=8.71. In addition, the GRACE-inverted rake angle shows that the earthquake is dominated by the right-lateral strike-slip.

关 键 词：GRACE 粒子群算法 苏门答腊地震 断层参数 

分 类 号：P228[天文地球—大地测量学与测量工程]