大地电磁测深二维地形影响及其校正方法研究

采用有限元法实现ＭＴ二维模型的正演模拟，将地形条件下的二维地电模型的ＭＴ响应分解为地形引起的畸变场和与测点高程位置有关的稳定场两部分进行分析。用有限元法模拟二维地形条件下地电结构的ＭＴ 响应和纯地形的ＭＴ响应，采用比值法消除地形引起的干扰场，然后，将消除地形影响后的视电阻率值通过延拓方法获水平地形条件下二维地电结构的视电阻率分布，完善大地电磁测深视电阻率曲线的地形校正。

TWO DIMENSIONAL TOPOGRAPHIC RESPONSES IN MAGNETO-TELLURIC SOUNDING AND ITS CORRECTION METHODS

Using finite element method, the apparent resistivity and phase of the magnetotelluric response are calculated for two-dimensional inhomogeneities and topographic models, and corresponding quasi-section maps are presented. Through the analysis and study of distortion curves of simulating models, a number of useful conclusions have been obtained. Firstly, we have discussed about the characteristics of distortion responses coursed by the topography and deep lateral inhomogeneities. Secondly, The abnormality from the complex terrain condition might be divided into two components. One is the distortion due to the topographic undulation and another is the function of position. Then, the distortion part could be separated from the MT response by a so-called "ratio method" borrowing from electrical topographic correcting methods, after reality terrain undulation are simulated. Finally, we use a field regularization continuation technique to correct the retained part, which make the result perfect.