2015年尼泊尔地震破裂过程的统一模型  

A unified source model of the 2015 Gorkha earthquake

作　　者：刘刚[1,2] 杨少敏[2] 师宏波 聂兆生[2] 熊维[2] 王迪晋[2] 李恒[2] 周宇[2] 乔学军[2] 谭凯[2] 王琪[1] 

机构地区：[1]中国地质大学地球物理与空间信息学院,武汉430074 [2]中国地震局地震研究所中国地震局地震大地测量重点实验室,武汉430071 [3]地壳运动监测工程研究中心,北京100036

出　　处：《地球物理学报》2017年第7期2663-2679,共17页Chinese Journal of Geophysics

基　　金：中国地震局地震研究所所长基金(IS201326127;IS201506204);国家自然科学基金(41541029;41404016;41504011;41574017;41304046);湖北省技术创新专项(2016AHB012)联合资助

摘　　要：模拟2015年尼泊尔地震(主震M_w7.8及最大余震M_w7.3)GPS/InSAR同震位移、远震体波、高频GPS位移波形和强震加速度记录,构建统一震源模型.统一模型分布特征主要由InSAR观测决定,地震矩释放过程则与P波模型相似,静态与高频GPS观测增加了对破裂时空特征的约束强度;各种比对表明,该模型对各基于单一类型反演模型具有很好的兼容性,棋盘测试展现其具有更优空间分辨率,最小可恢复20 km×20 km尺度的空间特征,压缩了非同震信号或误差导致的零散瑕疵,主、余震破裂具有更好的空间对应关系.主震展布范围为140 km×80 km;4 m以上破裂集中在加德满都以北30 km、深度15 km的狭长区域内,最大滑动量为7.4 m;破裂持续总时长为60 s,破裂速度为3.3 km·s^(-1),子断层上升时间在10 s内.M_w7.3余震破裂区域位于主震东侧边缘,滑动量围绕震中扩散,扩展范围为30 km×20 km,最大滑动量约为4.4 m,总破裂持续时间为35 s.本次地震中静态和高频的GPS观测亦具备独立约束主震破裂扩展过程的能力.Abstract On 25 April 2015, the Gorkha earthquake struck the central Nepal, for which diverse data sets including the surface displacements field derived by both InSAR and static GPS, and especially strong ground motions recorded by high-rate GPS are available to depict its rupture process, providing an unprecedented opportunity to assess their contributions to the inversion of the source parameters of the large megathrust earthquake. We investigate the space-time history of fault slip during the Gorkha earthquake mainshock （Mw = 7.8） and its largest aftershock （Mw = 7.3, happened 12 days later） using separate and joint inversions of high-rate GPS, static GPS,InSAR data, teleseismic waveform and strong-motion data to pursue a self-consistent and compatible rupture model. After obtaining the preferred rupture velocity and subfault rise time by using the tradeoff line between the cross correlation coefficients of observed and synthetic waveforms of HRGPS versus rupture velocity and subfault rise time, we performed separate inversions of the individual datasets. Separately inverted models present different slip patterns due to the intrinsic resolution of different datasets. Finally, two joint inversions of the near-field datasets and all datasets have been carried out. The joint model from near-field datasets improves the resolution of GPS model, but is not better than InSAR model. However, the scattered slip patches due to the non- coseismic deformation or observation errors have been depressed in the joint models. The optimal joint model of all datasets, supplemented by far-field observation, can be regarded as a unified model for preserving the common features of all separate inversions and yielding good combined resolution of slip. The Checkerboard tests also show that the unified model has the best spatial resolution for almost recovering the 20 km M 20 km slip patch and is more stable to rupture velocity variance. The slip pattern is mainly constrained by InSAR and the temporal process agrees well with

关 键 词：尼泊尔地震 联合反演 时空分布模型 高频GPS 

分 类 号：P541[天文地球—构造地质学]