综合InSAR和应变张量估计2016年MW7.0熊本地震同震三维形变场  

Integrated InSAR and strain tensor to estimate three-dimensional coseismic displacements associated with the 2016 MW7.0 Kumamoto earthquake

作　　者：袁霜 何平 温扬茂[2] 许才军[2] YUAN Shuang;HE Ping;WEN YangMao;XU CaiJun(Hubei Subsurface Multi-scale Imaging Key Laboratory,Institute of Geophysics and Geomatics,China University of Geosciences,Wuhan 430074,China;School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,China)

机构地区：[1]中国地质大学(武汉)地球物理与空间信息学院,湖北省近地表多尺度成像重点实验室,武汉430074 [2]武汉大学测绘学院,武汉430079

出　　处：《地球物理学报》2020年第4期1340-1356,共17页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41704005);中央高校基本科研业务费专项(CUGL180410)共同资助.

摘　　要：利用合成孔径雷达(Synthetic Aperture Radar,SAR)影像提取与地质活动相关的三维地表形变场,对深入理解地质灾害的形成机制及其潜在灾害风险评估非常重要.目前,利用SAR影像的同震三维形变场提取主要利用单个像素点的多次观测构建观测方程,然后基于加权最小二乘(Weighted Least Squares,WLS)方法分解从而获得同震三维形变场,因此该方法缺乏对相邻像素点空间相关性的约束.考虑相邻同震位移点的应力连续性,研究学者提出了顾及大地测量应变张量和卫星形变观测的SAR同震三维形变场方法(Extended Simultaneous and Integrated Strain Tensor Estimation from geodetic and satellite deformation Measurements,ESISTEM).本文以2016年MW7.0熊本地震为例,收集了覆盖此次地震的ALOS-2卫星升降轨影像,利用传统差分InSAR(DInSAR)方法和子孔径雷达干涉测量(Multiple Aperture InSAR,MAI)方法分别对升降轨SAR影像对进行处理,得到视线向(LOS)形变和方位向形变,最后利用ESISTEM方法获取此次地震的三维同震形变场.此外,利用GPS和野外考察观测对本文的三维形变场结果进行结果精度分析.研究结果表明,与传统WLS方法相比,ESISTEM方法不仅能有效抑制奇异像素点对形变结果的干扰,同时对近断层的失相干信号能进行较好的恢复,更有助于解释地表破裂区的地震形变特征和掌握地震发生机制.本文确定的三维同震形变场结果显示主形变区发生在Futagawa断层中部和Hinagu断层最北端,最大水平位移为2m,抬升为0.55m.断层破裂以NE-SW走向的右旋走滑为主兼有部分正断成分.应变张量分析表明发震断层处受到了明显的收缩力和剪切力的作用.The three-dimensional(3D)surface displacements associated with different geohazardphenomenon derived from Synthetic Aperture Radar(SAR)images significantly improve our ability to understand their formation mechanisms and assess the potential disaster risk.At present,the most common approach for 3D coseismic deformation field derived from SAR images is using the Weighted Least Squares(WLS)method to resolve the 3D components based on more than three observations at each pixel point.However,this approach will be no constraints on the spatial correlation between the adjacent pixel points.Therefore,a new approach,i.e.,the Extended Simultaneous and Integrated Strain Tensor Estimation from geodetic and satellite deformation Measurements(ESISTEM),has been proposed to reveal the 3D coseismic displacement by adding a constraint equation of stress continuity between the adjacent pixel points.In this study,we collect both the ascending and descending ALOS-2 images for the 2016 Kumamoto earthquake sequence,and then generate the displacement both in line of sight(LOS)and azimuth direction by using the traditional differential InSAR(DInSAR)method and the Multiple Aperture InSAR(MAI)method,respectively.After that,we utilize the ESISTEM method to recover 3D coseismic deformation field for this event.In addition,we verify the uncertainty of the 3D displacements with GPS and field work observations,respectively.In compare to the traditional WLS approach,our results show the ESISTEM approach can not only effectively reduce the disturbance of singular displacement,and recover the displacement in incoherence region,which is helpful to the coseismic 3D displacement characteristics analyzed.Our final 3D displacement map demonstrates that the main deformation zone occurs in the central section of the Futagawa fault and the northernmost part of the Hinagu fault,and the maximum horizontal and uplift displacement are 2 m and 0.55 m,respectively.The subsurface rupture is dominated by NE-SW-trending dextral strike-slip with minor normal-slip

关 键 词：INSAR 同震三维形变场 应变张量 熊本地震 

分 类 号：P227[天文地球—大地测量学与测量工程]