带地形的可控源电磁法2.5维各向异性介质正演研究  

Forward modeling of the 2.5D controlled-source electromagnetic method in anisotropic media with topography

作　　者：赵东东[1,2] 戴世坤[1,2] 张钱江[1,2] 陈龙伟[3] 李昆[1,2] ZHAO Dong-Dong DAI Shi-Kun ZHANG Qian-Jiang CHEN Long-Wei LI Kun(Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, Central South University, Changsha 410083, China School of Geosciences and Info-physics, Central Sounth University, Changsha 410083, China College of Earth Sciences, Guilin University of Technology, Guilin 541004, China)

机构地区：[1]中南大学地球科学与信息物理学院,长沙410083 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,长沙410083 [3]桂林理工大学地球科学学院,桂林541004

出　　处：《地球物理学报》2017年第10期4005-4017,共13页Chinese Journal of Geophysics

基　　金：国家重大科研仪器设备研制专项资助项目(41227803);国家自然科学基金项目(41574127);中南大学研究生自主探索创新项目(重点项目:2017zzts008)联合资助

摘　　要：目前,对于可控源电磁法各向异性介质2.5维问题,主要采用一次场、二次场分离的方法消除场源奇异性并降低截断边界对计算区域的影响.该方法数值计算精度高,但是很难适用于复杂地形条件下的数值模拟.针对复杂地形问题,基于总场的有限元方法表现出一定的优越性,然而,这种方法存在场源奇异性问题和截断边界问题.本文采用基于总场计算的方法对带地形的可控源电磁法2.5维各向异性介质进行模拟研究,推导了考虑电导率和介电常数各向异性的2.5维控制方程;引入网格加密-收缩算法降低场源奇异性的影响范围,提升数值计算效率;引入行波分解边界条件降低截断边界的影响;提出任意采样反傅里叶变换方法,快速、高精度地计算出空间域电磁场分量.理论模型数值算例中:首先,验证了本文算法的有效性;其次,对任意各向异性倾角产生的可控源电磁响应规律进行研究;最后,采用山丘模型对各向异性介质电磁场的响应规律进行了模拟和分析.At present, to solve the controlled source electromagnetic field in the 2.5-dimentional anisotropic media, the method of separation of the primary and secondary fields is often exploited to eliminate the singularity source and to reduce the influence of the truncated boundary on the computation region. The method is able to achieve high numerical accuracy; however, there is a serious limitation when complex terrain is considered. In order to deal with the problem of complex terrain, the method based on the numerical simulation of the total field basis of finite element method can be applied, but this method has the problems of the singularity source and the truncated boundary. This paper has studied the numerical simulation based on the total controlled source electromagnetic field in 2.5-dimensional anisotropic media. The 2.5-dimensional governing equations have been derived which consider the conductivity and dielectric constant; the grid refinement/contraction method is also introduced, which improves the precision of near-field source and the efficiency of the numerical calculation; the traveling wave decomposition on the boundary is used to reduce the truncated boundary effects. In addition, an arbitrary sampling method for the inverse Fourier transform is proposed to calculate the electromagnetic field components in the spatial domain, which has the advantages of high accuracy and efficiency property. In this paper, firstly, a group of synthetic tests have been performed and they have demonstrated the validity of the proposed method; secondly, the controlled source electromagnetic response for arbitrary anisotropic dip angles has been analyzed; finally, the hill model has been adopted to simulate and to analyze the response of electromagnetic field.

关 键 词：各向异性 可控源电磁法 2.5维 数值模拟 

分 类 号：P631[天文地球—地质矿产勘探]