基于改进的高分辨率时序InSAR技术研究Khash Mw7.7地震震后形变机制

Postseismic motion is aseismic transient deformation that occurs following a major earthquake in response to stress changes in the crust and upper mantle caused by the earthquake. It is very effective to solve the indistinct question of postseismic mechanism using time-series vertical displacement with high spatial resolution. Interferometric Synthetic Aperture Radar (InSAR) is very sensitive to vertical displacement. In this project, we have integrated the advantages of PS, SBAS, and IPTA to research InSAR time-series analysis algorithm based on coherent target of high resolution SAR images. We focus on solving some key technical problems such as compensation of terrain phase of coherent target, separation of long wavelength phase from displacement signal, correction of layered tropospheric phase, and then establish the flow of InSAR time-series analysis algorithm with high resolution images. Finally, postseismic displacement of Khash earthquake is analyzed using the improved InSAR time-series analysis technique, and postseismic mechanism is also investigated with multi-track integrated InSAR results. The research project will be to the exemplary role for investigating postseismic motion with high resolution InSAR , which has an important scientific significance for solving the the indistinct question of postseismic mechanism.

震后形变是地震发生后的一种无震瞬态形变过程，是对地震引起的地壳和上地幔应力释放的响应，利用高空间采样的垂向形变时间序列约束可以有效的解决大地震震后形变机制模糊问题。雷达干涉测量技术（InSAR）对垂向形变非常敏感，本项目综合PS、SBAS和IPTA等InSAR时序分析算法优势，开展基于相干点目标的高分辨率InSAR震后形变时序分析技术研究。重点解决相干点目标地形相位补偿、差分干涉图残余长波相位与形变相位分离、对流层垂直分层延迟相位校正等关键技术问题，在此基础上，研究建立高分辨率InSAR震后形变时序分析流程。利用改进的基于相干点目标的InSAR形变时序分析技术研究Khash地震震后形变时间序列，以多条带的InSAR集成结果作为约束，研究Khash地震震后形变的驱动机制问题。本项目研究将为高分辨率InSAR研究大地震震后形变过程起到示范作用，对于解决震后形变机制模糊问题具有重要的科学意义。

2013年4月16日在伊朗和巴基斯坦交界的Khash Mw7.7地震是一次发生在俯冲带板内中深部（>50km）的正断层地震，俯冲地壳中脱水脆化导致的摩擦失稳以及地幔内板块弯曲引起的伸展俯冲之前形成的正断层可能是此次地震的驱动机制。本项目在研究实现COSMO-Skymed原始数据的自动聚焦成像、基于DEM的SAR影像高精度配准、基于地形数据的对流层垂直分层大气延迟相位校正、距离向频谱分割估计电离层相位等方法的基础上，研究了一种无需引入外部DEM进行地形相位补偿的高分辨率InSAR震后形变时序分析方法。基于COSMO-Skymed条带模式数据，利用改进的高分辨率InSAR形变时序分析方法提取了Khash地震震后形变场，结果显示震中附近以及同震最大形变区域的震后形变量在-2.5mm-2.5mm之间。剪切加热导致的粘滑不稳主要发生在600-800℃深度位置，板块从伸展到收缩的深度转换可能起到了滑动屏障作用，阻碍了震后断层滑动向地壳上层传播。