联合GNSS和InSAR观测位移反演2008年汶川大地震断层位错模型参数

Fault Slip Distribution of 2008 Wenchuan Earthquake by Jointed Coseismic Displacements from GPS and InSAR

摘要:

利用现代空间大地测量技术，尤其是卫星合成孔径雷达干涉测量，能够获取高精度、高空间分辨率的同震和孕震形变，为地震断层形变和破裂机制研究提供了前所未有的机遇。本文介绍了利用大地测量观测数据反演地震断层位错模型参数的贝叶斯反演方法。联合运用2008汶川大地震前后GNSS和InSAR技术观测获得的同震位移，反演了地震断层的几何参数和滑动位错分布。研究结果表明，汶川地震的断层滑动主要集中在倾角较陡的浅部，同时包含逆冲和右旋走滑，其中最大逆冲6.1m，最大右旋6.5m。根据断层滑动分布正演计算得到的上盘同震位移明显小于下盘，预示该断层两侧孕震形变可能存在较大的不对称性。

Abstract:

Application of modern space geodetic technology,especially satellite synthetic aperture radar interferometry,can obtain high-precision,high-spatial resolution coseismic and interseismic deformation data,providing unprecedented opportunities for the study of crustal deformation and earthquake mechanisms. This paper introduces Bayesian inversion method for inversion of parameters of fault dislocation model by using geodetic observations. Coseismic displacements obtained by GNSS and InSAR before and after the 2008 Wenchuan Earthquake were used to invert the geometric parameters of the earthquake fault and the distribution of displacements. The results of the study show that the fault slip of Wenchuan earthquake is mainly concentrated in shallow parts of the fault with steep dip angle,and includes both thrust and dextral components,with the maximum thrust slip of 6.1m and the maximum dextral slip of 6.5m respectively. The forward modelling of coseismic displacements shows that the coseismic deformation at the upper block of the fault is significantly less than that at the down block,suggesting a significantly unsymmetrical mode.