多源数据联合反演权比确定及玉树地震同震断层滑动分布反演研究

温扬茂++许才军++何平++江国焰++刘洋

摘 要：为了更好地研究重力场对地壳形变、活动断层、地震等动力学过程的时变响应，需要建立动态地壳形变模型，研究重力、形变与地震波数据联合反演活动断层参数的相关理论及方法，进行活动断层潜在地震的危险性评估，探讨强震发生的动力学背景。该报告主要介绍两个方面的研究内容：一方面是如何表述反演数据中多源数据的权矩阵，通过引入虚拟观测方程将断层滑动的连续性约束一并纳入观察方程，采用Helmert方差分量估计确定各类观测数据的权比，推导了相关理论公式。另一方面，利用InSAR和GPS资料提取了Iwaki和Kita-Ibarake两个余震区典型余震的同震形变场，以及结合InSAR干涉图形状和方位向偏移量法对发震断层的几何参数进行约束。在此基础上，采用弹性半空间矩形位错模型对这两个强余震的同震滑动分布进行反演，得到的最大滑动量分别为3.28 m和0.98 m。最后利用余震的断层作为接收断层，计算了Mw 9.0 Tohoku-Oki静态库仑应力对余震作用的大小，结果显示Iwaki和Kita-Ibarake研究区的余震近似为纯正断层类型的浅源地震，静态库仑应力在两个研究区的最大值分别为1.1 MPa和0.7 MPa，表明Mw 9.0 Tohoku-Oki地震对研究区的余震触发是有促进作用的。

关键词：多源数据 反演 活动断层 地震波数据 同震形变场

Abstract：In order to understand the time-dependent gravity response from crustal deformation， active fault， earthquakes and other dynamic processes， we need to estimate the kinematic crustal deformation model， to study theory and method of active fault parameters joint inversion from gravity， deformation and seismic data， to do the potential earthquake hazard assessment of active faults and to explore the dynamic background of strong earthquakes. This report focuses on the following two aspects： on one hand， we introduce the fault slip continuity constraint as a virtual observation function to observation functions， and determine the relative weight of various kinds of observation using Helmert variance component estimation. On the other hand， we derive the coseismic deformation of Iwaki and Kita-Ibarake aftershocks from InSAR and GPS data， and obtain the preliminary location of the fault traces combing InSAR deformation pattern with azimuth-offset measurements. The fault location and geometry of these two earthquakes are constrained by a rectangular dislocation model in a multilayered elastic half-space， which indicates that the maximum slips for the two earthquakes are 3.28 m and 0.98 m， respectively. The Coulomb stress changes are calculated for the faults following the 2011 Mw 9.0 Tohoku-Oki earthquake based on the modeled slip along the fault planes. The resulting Coulomb stress changes indicate that the stresses on the faults increased by up to 1.1 MPa and 0.7 MPa in the Iwaki and Kita-Ibarake regions， respectively， suggesting that the Tohoku-Oki earthquake triggered the two aftershocks， supporting the results of seismic tomography.

Key Words：Multi-source data；Inversion；Weight ratio；Dislocaiton model；Earthquake；InSAR

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