Results of magnetotelluric sounding (MTS) in Gornyi Altai are interpreted on the basis of a numerical model of MTS curve distortions in a 3D earth. The distortions are modeled using the Trefftz method permitting the application of models of different degrees of similarity to the test medium (depending on available computational resources). The main advantages of this approach are demonstrated. There is no need to choose between different MTS curves (transverse and longitudinal, minimum and maximum, undistorted and distorted). Procedures of normalizing these curves become unnecessary. All recorded curves are fully used as input data for their inversion. Optimization of the model of the medium taking into account the distortions of MTS curves caused by surface and depth inhomogeneities improves the reliability of geoelectric sections.