基于三维应变格林函数反演中小震震源机制  

Inversion of Focal Mechanisms of Small and Moderate Earthquakes Based on a Three-dimensional Strain Green Tensor Database

作　　者：周立 林强[1,2,3] 范涛 ZHOU Li;LIN Qiang;FAN Tao(Hubei Key Laboratory of Earthquake Early Warning,Institute of Seismology,China Earthquake Agency,Wuhan 430071,Hubei,China;Wuhan Institute of Seismologic Instrument Co.,Ltd,Wuhan 430071,Hubei,China;Engineering Technology Research Center for Earthquake Monitoring and Early Warning Disposal of Major Projects in Hubei Province,Wuhan 430071,Hubei,China)

机构地区：[1]中国地震局地震研究所地震预警湖北省重点实验室,湖北武汉430071 [2]武汉地震科学仪器研究院有限公司,湖北武汉430071 [3]湖北省重大工程地震监测与预警处置工程技术研究中心,湖北武汉430071

出　　处：《地震工程学报》2019年第6期1553-1559,共7页China Earthquake Engineering Journal

基　　金：国家重点研发计划项目(2017YFC1500804);中国地震局地震研究所基本科研业务费专项资助项目;中国地震局地壳应力研究所基本科研业务费专项资助项目(项目批准号:IS201726160)

摘　　要：随着复杂速度结构反演的发展和高性能计算能力的提升,基于高精度3D介质模型计算格林函数反演震源机制更具可行性。中小地震因具有更好的覆盖和近似点源效应,在区域结构成像中有着广泛的应用。基于波形类的反演方法如波动方程层析成像\,全波形反演都需要震源机制解,而传统的震源机制反演方法不能很好地应用于中小地震。采用有限差分法构建应变格林张量(Strain Green Tensor,SGT)数据库,将合成波形和实际波形按震相截窗并滤波到不同的频带范围,先通过最小化互相关走时差来进行震源重定位,再通过最小化波形残差反演震源机制。通过合成数据测试验证方法的正确性,随后将该方法应用于青藏高原东部边缘龙门山地区,反演一系列M W3.4~5.7的中小地震震源机制。由于应变格林张量数据库可预先构建,该方法可以应用于(近)实时震源机制解反演。With the development of complex velocity structure inversion and improvements in high-performance computational power,it has become possible to calculate accurate 3D strain Green tensors(SGT)by means of high-resolution 3D earth models.Due to more uniform distribution and better point source effects,small-to-moderate earthquakes are widely used in local-scale waveform-based tomography.As it is known,waveform-based tomography methods like wave-equation tomography and full waveform inversion(FWI)require focal mechanism solutions during the whole inversion procedure.However,traditional focal mechanism inversion methods are not very suitable to small-to-moderate earthquakes.In this study,we first used the finite differential method to construct a strain Green tensor(SGT)database and filtered the synthetic and actual waveforms in different frequency band ranges.We then relocated the earthquakes by minimizing the cross-correlation travel time differences,and,next,inverted the focal mechanism by minimizing the waveform residuals.Finally,we used this SGT database method to inverse the focal mechanisms of a series of M W 3.4-5.7 earthquakes in the Longmenshan fault zone,between the eastern margin of the Tibetan plateau and the western part of Sichuan basin.The results indicated that the proposed method can be applied in(near)real-time inversions of focal mechanism solutions since the database can be pre-constructed.

关 键 词：震源机制反演 应变格林函数 青藏高原 有限差分法 波形反演 

分 类 号：P315[天文地球—地震学]