盲逆断层震后变形耦合机制研究——以2017年伊朗M_(W)7.3地震为例  

Coupled mechanism of the postseismic deformation of blind thrust fault:Case study of the 2017 Iran/Iraq M_(W)7.3 earthquake

作　　者：王洵 王卫民[2] 何建坤[2] 周云 WANG Xun;WANG WeiMin;HE JianKun;ZHOU Yun(Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;Key Laboratory of Continental Collision and Plateau Uplift,Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地震预测研究所,北京100036 [2]中国科学院青藏高原研究所大陆碰撞与高原隆升重点实验室,北京100101 [3]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2024年第2期571-586,共16页Chinese Journal of Geophysics

基　　金：中国地震局地震预测研究所基本科研业务专项项目(CEAIEF2022030202);国家自然科学基金项目(41904094,42174112);中国科学院战略性先导科技专项(XDA20070302)共同资助.

摘　　要：震后变形是地震周期中一个重要阶段,深入研究其产生机制有助于提高对地震演化过程、断层性质及地震危险性评估的认识.2017年伊朗M_(W)7.3地震InSAR观测资料丰富,为研究扎格罗斯造山带山前褶皱带盲逆冲断层震后变形机制提供了切入点.合理详细的震源模型及高精度的形变观测是开展震后余滑或黏弹松弛研究的首要前提,本文采用多视角InSAR资料联合远场波形数据反演该地震的破裂滑动分布,并解算得到伪三维地表位移,利用InSAR时序分析提取震源区主震后一年半内变形特征,显示震源区震后形变特征与同震位移场类似,LOS向形变速率最大值约8 cm·a^(-1),震后变形预示震源区可能存在明显的震后应力调整现象.利用震后半年内形变资料约束的纯运动学余滑模型表明同时期释放能量为矩震级M_(W)6.7,进一步探讨应力驱动震后余滑及下地壳黏弹性松弛对震后变形的贡献,基于分层黏弹模型的模拟计算表明震后余滑和黏弹松弛效应的耦合模型可以更好地解释地表震后变形特征,其中震后余滑主要分布在同震破裂区的上方浅部,对主震后一年半内震后地表变形起主导作用,震源区壳下黏滞系数量级下限约为10^(19)Pa·s,震后变形对扎格罗斯褶皱带的生长有一定的促进作用,更长周期的震后变形机制研究还需长期高精度观测和顾及岩石圈流变结构的横向不均一性.The phase of postseismic deformation constitutes a pivotal component within the seismic cycle,and a comprehensive exploration of its underlying mechanistic origins serves to elevate our comprehension of not only the intricate trajectory of seismic evolution but also the inherent characteristics of faults and the evaluative discernment of seismic risk.The abundant InSAR observational data from the 2017 M_(W)7.3 earthquake in Iran presents a substantial resource,affording an entry point for the investigation of the postseismic deformation mechanisms along blind thrust faults within the piedmont fold belt of the Zagros orogenic belt.A prerequisite for investigating post-earthquake afterslip or viscoelastic relaxation is the development of a detailed seismic source model and precise deformation observations.In this study,we combine multi-perspective InSAR data with far-field waveform information to invert the slip distribution of the 2017 M_(W)7.3 earthquake in Iran,and obtain the pseudo-3D surface displacement in the source area.Utilizing InSAR time series analysis,we extract post-earthquake deformation characteristics within the epicentral area over a year and a half following the main shock.The results reveal similarities between postseismic deformation and coseismic displacement fields.Along the LOS profile,the maximum LOS deformation rate reaches around 8 cm·a^(-1),suggesting significant postseismic stress adjustment within the source area.Constraining the purely kinematic afterslip model with deformation data obtained within six months post-earthquake reveals an energy release equivalent to that of a moment magnitude M_(W)6.7 seismic event during the same period.Further investigation into the respective contributions of stress-driven afterslip and viscoelastic relaxation within the lower crust to the ensuing postseismic deformation is undertaken.Through simulation employing a layered viscoelastic model,it is demonstrated that a coupled model encompassing both afterslip and viscoelastic relaxation effects yield

关 键 词：伊朗M_(W)7.3地震 InSAR 联合反演 震后形变 震后余滑 

分 类 号：P315[天文地球—地震学] P313[天文地球—固体地球物理学]