基于非结构化六面体网格矢量有限元的大地电磁测深三维反演  

Three-dimensional magnetotelluric inversion based on unstructured hexahedral mesh edge-base finite element method

作　　者：李阳铭 郭长安 陈楚桐 王堃鹏[1] LI YangMing;GUO ChangAn;CHEN ChuTong;WANG KunPeng(Key Laboratory of Earth Exploration and Information Technology of Ministry of Education(Chengdu University of Technology),Chengdu 610059,China;Center for Geophysical Survey,China Geological Survey,Langfang 065000,China)

机构地区：[1]成都理工大学地球勘探与信息技术教育部重点实验室,成都610059 [2]中国地质调查局地球物理调查中心,廊坊065000

出　　处：《地球物理学进展》2024年第5期1901-1910,共10页Progress in Geophysics

基　　金：中国地质调查局“北山及邻区区域地球物理调查”项目(DD20230254);国家自然科学基金项目(42004057)联合资助。

摘　　要：结构化六面体网格对地形起伏的模拟效果不好,并且会对网格外延区域进行不必要的加密.有限元法在对区域剖分的网格选择上比较灵活,可以采用非结构化网格对研究区域进行划分,更适合对起伏地形和复杂的地质构造进行模拟.因此,本文基于矢量有限元算法,采用非结构化变形六面体网格来实现大地电磁三维正演,既能较好的模拟地形起伏,也能对局部重点区域进行加密,减少外扩区域的网格划分数量,减轻计算量.通过对理论模型的正演试算,验证了程序的正确性.对于反演,采用高斯-牛顿算法,分别对平地、双峰和双谷地形的理论模型进行了反演试算,对比了带地形反演和不带地形反演的结果差异,最后对日本Kayabe地区的阻抗张量数据进行了反演.理论模型和实测数据的反演结果表明本文算法能够用于三维大地电磁反演.Structured hexahedral grids are not effective in simulating undulating terrain,and they unnecessarily encrypt the mesh extents.The Finite Element Method(FEM)is more flexible in the selection of the mesh for area segmentation,and can be used to divide the study area with an unstructured mesh,which is more suitable for the simulation of undulating terrain and complex geological formations.Therefore,based on the edge-base finite element algorithm,this paper adopts unstructured deformed hexahedral mesh to realize the three-dimensional magne-totelluric forward,which can not only simulate the terrain undulation better,but also encrypt the local key areas,reduce the number of mesh delineation of the expanding area,and alleviate the computational quantity.The correctness of the procedure is verified by forward simulation of the theoretical model.For the inversion,Gaussian-Newton algorithm was used to invert the theoretical models for flat,bimodal and bivariate terrains for trial calculations,comparing the differences in the results between the inversion with and without terrain,and finally the inversion of the impedance tensor data for the Kayabe area in Japan.Inversion results from theoretical models and measured data show that the algorithm in this paper can be used for three-dimensional magnetotelluric inversion.

关 键 词：大地电磁 非结构化网格 矢量有限元 三维反演 

分 类 号：P631[天文地球—地质矿产勘探]