基于非结构化网格有限元法的大地电磁测深法三维带地形数值模拟研究

项目名称： 基于非结构化网格有限元法的大地电磁测深法三维带地形数值模拟研究

项目编号： No.41504062

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 天文学、地球科学

项目作者： 董浩

作者单位： 中国地质大学（北京）

项目金额： 21万元

中文摘要： 地形效应在大地电磁测深法中一般指由近地表地形起伏引起的电流畸变现象，可能造成反演异常体的位置与形态发生畸变，甚至造成虚假异常。作为研究地形效应并消除其畸变影响最为有效的方法，带地形数值模拟一直是大地电磁测深数值方法的前沿课题之一。然而，由于三维介质电磁场数值模拟方法的复杂性，目前，考虑地形效应的三维大地电磁测深法数值模拟的研究相对较少,且多采用难以模拟自然地形的结构化网格。本项目拟针对这一研究空白，开发自适应带地形网格离散化算法，并以此为基础，利用非结构化网格有限元方法模拟复杂起伏地形，实现一种高效的大地电磁测深三维带地形正演模拟算法；最后，开发配套的三维带地形可视化建模套件与正演算法相结合，形成一个完整的带地形数值模拟系统，以研究大地电磁测深法地形畸变对勘探结果的影响，为未来大地电磁测深带地形三维反演技术的实用化奠定基础。

中文关键词： 大地电磁场；三维正演；有限单元法；起伏地形；非结构化网格

英文摘要： In magnetotellurics (MT), the term “topographic effect” is generally referred as the galvanic distortion caused by near-surface topography. Topographic effect may bring distortion to the position and geometry of target bodies, or even introduces false anomalies to MT inversion models. Being the most effective method to eliminate topographic effect, forward modelling methods considering topography have been among the forefront of MT numerical studies. However, with the complexity of the three-dimensional (3D) numerical simulation of electromagnetic field, few 3D MT modelling methods considered topography, most of which utilize structured meshes that cannot simulate natural topography smoothly. To address this topic, the project seeks to develop an automatic meshing algorithm for complex topography, and to archive a highly accuracy and efficiency 3D MT numerical simulation algorithm considering topography, using unstructured finite-element method enhanced with adaptive mesh refinement. A 3D visual model meshing and editing package is also to be developed to work with the aforementioned forward algorithm. The modelling techniques can therefore be used to study the topographic distortion effect and establish firm foundation for the future development of MT inversion considering topography.

英文关键词： magnetotellurics;3D forward modelling;finite element method;Topography;unstructed mesh