2021年青海玛多M_(W)7.5地震的同震变形及断层滑动模型研究  

An analysis of the co-seismic deformations and fault slip models of the 2021 Qinghai Madoi M_(W)7.5 earthquake

作　　者：张岚 李琦[3] 唐河 孙文科 ZHANG Lan;LI Qi;TANG He;SUN WenKe(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;Institute of Seismology,China Earthquake Administration,Wuhan 430071,China)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]中国地震局地震预测研究所,北京100036 [3]中国地震局地震研究所,武汉430071

出　　处：《地球物理学报》2022年第3期1044-1056,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金(42174097,41974093,41774088);武汉引力与固体潮国家野外科学观测研究站开放研究基金(WHYWZ202112)资助。

摘　　要：2021年5月22日,中国青海玛多县发生了M_(W)7.5地震.针对此次地震,国内外多家机构发布的震源机制解和有限断层滑动模型结果大都是基于半无限空间地球模型的位错理论反演得到的,未考虑地球曲率和层状效应的影响.该影响的量级以及其是否可以忽略目前仍是一个未知问题,值得研究.为此,本文利用美国地质调查局(USGS)、中国科学院青藏高原研究所以及中国地震局地球物理研究所提供的三个断层模型,基于弹性半无限空间、均质球、PREM三种地球模型的位错理论,分别计算了地表同震位移场和应变场,并对比分析了这些结果的差异.我们发现基于PREM位错理论的同震位移场与半无限空间模型的对应值差异约为3~28 cm,占PREM位错理论值的10%~30%,应变场差异更大,表明地球曲率和层状效应的影响不可忽略.此外,理论同震形变结果与GNSS和InSAR形变观测数据对比发现,基于PREM模型的理论位移场最接近于观测值.利用InSAR数据和三种地球模型反演得到的有限断层滑动模型存在差异,说明了地球模型的选择对断层模型的反演具有一定影响.本文的结果为今后对此次地震的观测数据物理解释和断层滑动反演提供了理论参考.On May 22,2021,the M_(W)7.5 earthquake occurred in Madoi County,Qinghai Province,China.For this event,different focal mechanism solutions and finite fault slip models published by many domestic and foreign institutions are mostly based on the inversion of the dislocation theory of the semi-infinite space Earth model.The effects of the Earth curvature and stratification were not considered.It is still unknown that the magnitudes of the effects of the Earth curvature and stratification and whether they can be omitted,which is worth studying.In this paper,three fault models provided by the United States Geological Survey(USGS),the Institute of Tibetan Plateau Research,Chinese Academy of Sciences(ITPCAS)and the Institute of Geophysics of China Earthquake Administration(IGPCEA)were used to calculate the surface co-seismic displacement and strain fields based on the dislocation theory of elastic half-space,homogeneous sphere and PREM earth models,respectively.The differences between these results were compared and analyzed.It is found that the discrepancies between co-seismic displacement fields based on the PREM and the semi-infinite space dislocation theories are about 3~28 cm,which accounts for about 10%~30%of the results based on the dislocation theory of PREM,and the strain fields have larger discrepancies,indicating that the influence of the Earth curvature and stratification cannot be ignored.In addition,the comparison between theoretical co-seismic deformation and Global Navigation Satellite System(GNSS)and Interferometric Synthetic Aperture Radar(InSAR)observations suggests that the theoretical seismic displacement field based on PREM is the closest to the observed ones.The differences among three finite slip models constrained by InSAR data and three Earth models show that the choice of the Earth model has a certain degree of influence to the finite slip fault model inversion.The results of this paper provide theoretical reference for the physical interpretation of observational data and fault slip inversion

关 键 词：同震变形 2021青海玛多地震 位错理论 PREM 半无限空间地球模型 

分 类 号：P315[天文地球—地震学]