3D Step-by-step inversion strategy for audio magnetotellurics data based on unstructured mesh  

作　　者：Cheng San Zhang Zhi-Yong Zhou Feng Li Man Chen Hui Shi Fu-Sheng Huang Lin-Pin Li Yong 

机构地区：[1]School of Geophysics and Measurement-control Technology,East China University of Technology,Nanchang 330013,China [2]State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China [3]Key Laboratory of Geophysical Electromagnetic Probing Technologies of Ministry of Natural Resources,Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang,065000,China

出　　处：《Applied Geophysics》2021年第3期375-385,433,共12页应用地球物理（英文版）

摘　　要：A three-dimensional(3D)step-by-step inversion strategy for audio magnetotellurics(AMT)is investigated in this study.The objective function is minimized by iteratively solving the Gauss-Newton normal equation,and the inversion region is discretized with unstructured tetrahedral elements.The inversion proceeds step-by-step from a coarse mesh to a fine mesh.In the inversion iteration process,a mesh is adaptively optimized according to the spatial gradient information about the model resistivity to fine delineate the boundaries of abnormal bodies.In the early stage of inversion execution,a coarse mesh is used for inversion,and the inversion stability is improved by reducing the number of inversion elements.In addition,mesh refinement is performed in the iterative inversion process.The inversion results obtained from the previous mesh are used as the reference and initial models for the next mesh iterative inversion.The step-by-step inversion strategy can ensure that the inversion is performed in the correct direction,improving the inversion stability and results gradually.Synthetic results show that the step-by-step inversion strategy with a Gauss-Newton method for 3D AMT inversion is stable and reliable,which lays a foundation for further practical 3D AMT data inversion.

关 键 词：Audio magnetotellurics 3D inversion step-by-step inversion Gauss-Newton unstructured gird 

分 类 号：P631.325[天文地球—地质矿产勘探]