【作者】 赵晓博；

【导师】 朱自强；

【作者基本信息】 中南大学 ， 地球探测与信息技术， 2011， 硕士

【摘要】 瞬变电磁法(简称TEM)属于时间域电磁法,是近年来迅速发展的地球物理勘探方法之一。目前,瞬变电磁法资料解释水平较低,基本上停留在一维阶段,二维和三维反演解释技术离真正实用阶段仍有相当大的距离。在地球物理学中,正演是资料处理和数据反演的基础,因此我们有必要首先研究正演计算。2.5维瞬变电磁法数值模拟问题尚未妥善解决,但其具有很大的实用价值,因此很有必要进一步研究。本文从麦克斯韦方程组出发,详细推导了瞬变电磁法2.5维问题中异常场偏微分定解问题、边界条件、变分问题等；着重分析了对程序实现有重要影响的几个关键问题：拉普拉斯逆变换、傅里叶逆变换以及非走向分量的计算。利用matlab语言编写了2.5维有限元程序；并通过对水平层状模型的数值模拟验证了算法的正确性。除此之外,本文还计算了矩形回线在水平层状地电模型表面激励的瞬变电磁响应,分析比较了几种层状结构介质的瞬变电磁异常场和总场响应特征。针对前人在瞬变电磁2.5维正演中采用结构化网格剖分所存在的不足,本文采取非结构化策略来实现网格剖分。通过非结构化中常用的Delaunay三角剖分方法,实现了对复杂地质模型的剖分,使现有瞬变电磁2.5维正演算法应用范围得到了扩展。与传统的结构化网格剖分方式相比,本文所采用的非结构化网格剖分方式在取得相同计算精度的情况下其网格节点数和单元数得到了大幅的降低,可以减少了不必要的节点计算量。更多还原

【Abstract】 Transient Electromagnetic Method (referred to as TEM) belong to the time domain electromagnetic method,it’s a new geophysical exploration method developed in recent years. Currently, TEM is low levels of data interpretation, basically stuck in one-dimensional stage, two-dimensional and three-dimensional inversion interpretation techniques for the real practical use is still a considerable distance. In geophysics, forward modeling is the basis of data processing and data inversion, we need to first study the forward problem.2.5-dimensional numerical simulation of transient electromagnetic method that is one of difficult problems in geophysical calculation and not yet properly solved, but is valuable in practical.This article from the Maxwell equations and deduced transient electromagnetic anomaly field in the 2.5-dimensional problem set solutions of partial differential of the problem, boundary conditions, functional extrema, etc.; and focus on implementation of several key Question that’s have a major impact on the program:Laplace inverse transform, inverse Fourier transform and the calculation of non-direction component. Language using program matlab accomplish 2.5 dimensional finite element program, and examined the algorithm through horizontal layered models’ numerical simulation, the paper calculated the rectangular back to the line in the horizontal surface layer geoelectric model of the transient electromagnetic response of incentives, analysis and comparison of the layered structure of several anomaly field of media and the total transient electromagnetic field response characteristics.For the previous use structured mesh’s shortcomings in the transient electromagnetic 2.5-D problem forward, this strategy adopted unstructured mesh to achieve the meshing. Unstructured mesh generation by using the commonly used method of Delaunay triangulation method, and realized the subdivision of complex geological model, the range of applications of existing 2.5-D transient electromagnetic forward algorithm has been expanded. With traditional structured mesh generation as compared to the unstructured grid used in this paper partition means to achieve the same accuracy in the case of the grid, the number of nodes and cells were significantly reduced, to reduce the unnecessary computation nodes.更多还原