华北平原GB大地电磁剖面的二维解释

大地电磁测深资料的二维解释主要有两种方法，即二维反演拟合和二维数值模拟。作者参考二维三次样条快速反演方法的思路，在一维样条插值的基础上作形式推广，建立了三维三次样条插值的一般表达式及其计算过程，给出了三维三次样条插值的反演方法。二维数值模拟是在一维形式化解释的基础上构制二维初始模型，然后计算各测点上的MT响应，与实测值拟合，以便求得最佳拟合结果。所谓一维化解释是把剖面上各测点测得的纵向视电阻率ρ_⊥和横向视电阻率ρ₁₁分别按一维模型曲线作解释，求得地电剖面的二维模型和参数。用所述方法对华北地区的GB剖面的大地电磁测深资料进行试算，获得了地下导电率分布的基本情况。

The 2-D interpretation of GB magnetotelluric sounding profile on North China Plain

The 2-D interpretation of magnetotelluric sounding data is main1y made using two methods: 2-D inversion fitting and 2-D numerical modeling. Referring to the principle of fast inversion of 2-D cubic spline function, the authors extend 1-D spline interpolation expression into the expression of 3-D cubic spline interpolation, and also give the algorithm and the inversion method for 3-D cubic spline interpolation. 2-D numerical modeling is accomplished in two steps: (1) constructing the 2-D initial model on the basis of generalized 1-D interpretation, (2)computing the MT responses at all stations, which are then fitted to their real responses to get optimum fitting result. The so-called generalized 1-D interpretation is that the vertical and lateral apparent resistivities(ρ_⊥and ρ₁₁) observed at all stations of the profile are respectively interpreted according to 1-D model curves so as to get 2-D model and parameters of the geoclectric profile. Trial computation of the magnetotelluric sounding data of GB profile in North China is made using this method, and the basic distribution of underground conductivity is ascertamed.