介绍了有限差分算法在大地电磁测深法中的应用，推导了一维层状介质和连续介质模型下的有限差分算法，提出了一种新的网格剖分方法，并通过两层和三层介质模型的正演计算，验证了算法的正确性以及网格剖分方法的合理性。设计了一种连续介质模型，与两种不同程度近似的多层层状介质模型进行了正演结果的对比，指出了研究连续介质模型正演的必要性。对于连续介质模型，计算中剖分得越详细，其结果越接近真实值，而随着误差的逐渐减小，精确度的提高不再明显，但资源与时间的消耗将大幅增加。因此，无限制地减小网格步长是不必要的。同时，为了兼顾误差大小与网格步长的关系，采用了一种将一次网格剖分进行二次差分计算的方法得到新的结果，使计算结果明显得到了改善。%This paper describes the application of finite difference algorithms in MT method, deduces the algorithms of 1D layered and continuous medium, and proposes a new mesh generation method. Meanwhile, with two-layer or three-layer medium model inversion calculation, the paper demonstrates the correctness of the algorithms and rationality of the grid subdivision method. The authors also de⁃signed a kind of continuous medium and made a comparison of the inversion result between two kinds of multiple layered medium mod⁃els which have different layer approximations, and indicated the necessity of continuous medium model inversion research. For continu⁃ous medium model, the fine the grid, the better the approach result. Nevertheless, with the gradual decreasing of the error, the im⁃provement of accuracy becomes not so distinct. However, resource and time consumption will dramatically increase. So decreasing grid spacing without restriction is not necessary. What's more, taking both the error and grid spacing into consideration, the authors conduc⁃ted second difference calculation in first mesh generation and achieved a new conclusion, which can distinctly improve the calculation result.
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