—The potentialities of the 3D inversion program WSINV3DMT were estimated on the model [Zm] and observed [Zob] components of the impedance tensor and its invariants during the construction of geoelectrical models for the southern part of the Altai–Sayan region characterized by a three-dimensional distribution of electrical conductivity. These components were obtained for a 3D model constructed by the method of interactive selection of the 3D model induction curves for the experimental ones. Testing of the WSINV3DMT program on the model magnetotelluric data showed the possibility of not only isolation of blocks of high electrical conductivity but also of the appearance of conductivity anomalies different from the model ones. The paper presents a 3D geoelectrical model for the southern focal zones of the region, constructed with the use of the WSINV3DMT program and the proposed method of interpretation. The isolated blocks of low electrical resistivity are correlated with the location of earthquake foci, deep faults, and regions of high absorption of earthquake exchange waves.