基于二次场的可控源电磁法三维有限元-无限元数值模拟  

Forward modeling of 3D CSEM with the coupled finite-infinite element method based on the second field

作　　者：张林成[1,2] 汤井田[1,2] 任政勇[1,2] 肖晓[1,2] ZHANG Lin-Cheng TANG Jing-Tian REN Zheng-Yong XIAO Xiao(School of Geosciences and Info-Physics, Central South University, Changsha 410083, China Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, Changsha 410083, 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]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

出　　处：《地球物理学报》2017年第9期3655-3666,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41574120;41174105);湖南省自然科学基金(2016JJ2139);国家高技术研究发展计划(863计划)(2014AA06A602);国家自然科学基金(41404111;41474103);国家重点基础研究发展计划(973计划)青年科学家专题(2015CB060200);中南大学创新驱动项目(2016CX005);中南大学猎英人才计划共同资助

摘　　要：本文提出了一种新的混合有限元-无限元三维可控源电磁法(CSEM)问题快速高精度正演模拟算法.首先从电场双旋度方程出发,推导了水平电偶极子源的二次场边值问题,采用无限元代替截断边界条件和有限元离散内部计算区域的新策略,达到减小计算区域的目的,基于并行直接求解技术,实现多源CSEM问题的快速精确求解.其次,通过层状解析模型测试,一方面验证了新算法的正确性,另一方面通过与其他三种已知CSEM问题求解策略进行对比,表明了本文提出的基于二次场有限元-无限元算法具有离散区域小、求解速度快和计算精度高等优点.最后,通过3D模型计算,清晰直观地模拟了场源阴影效应,为野外数据的处理与解释提供指导.In this work, we developed a new fast and accurate forward modeling algorithm for the three-dimensional CSEM, named the coupled finite-infinite element method. Firstly, on the base of the double curl equation, we derived the boundary value problem of the second field with a horizontal electric dipole source. In order to reduce the calculation domain, we used the finite elements to discrete the target domain, and used the infinite element instead of the Dirichlet boundary condition. At the same time, the parallel direct solution technique was applied to solve the multi-source CSEM problem quickly and accurately. Secondly, the new algorithm was tested by a layered model. The results showed that the new algorithm is correct. Comparing with other three forward methods of CSEM showed that the new algorithm has the advantages of small discrete regions, fast calculation speed and high accuracy. Lastly, the source shadow effect was simulated clearly and intuitively by the three-dimensional models, which could provide guidance for processing and interpretation of field data.

关 键 词：边界条件 有限元-无限元 并行求解器 场源阴影效应 

分 类 号：P631[天文地球—地质矿产勘探]