The paper describes theory, method and first experimental results of research on the interaction between electromagnetic waves of extremely low and ultra low frequency (0.1-200 Hz), the Earth crust and ionosphere in the field of two mutually orthogonal industrial power lines, 109 and 120 km long, in the course of FENICS experiment (Fennoscandian Electrical conductivity from Natural and Induction Control Source soundings). The main focus was on the observation results along the line of Karelia-Kola geotraverse over a distance of 700 km from the source. High horizontal homogeneity of geoelectrical lithosphere section has been detected in the eastern part of the Baltic shield at depth range from 10-15 to 50-70 km. Parameters of «regular» lithosphere section have been specified to the depth of 60-70 km. As a result of inverse problem solution for the western part of Karelia and Central Finland, a zone of decreased transverse resistivity has been detected at the depth of 50-60 km, corresponding to the area, detected by seismic methods, where Moho boundary reaches the same depth.
In 2011 and 2012 insitu electromagnetic soundings using the industrial power transmission line «Urengoy-Pangody» were taken in the Yamal-Nenets Autonomous District (YaNAD). They were conducted both in the field of the extralow frequencies (ELF) antenna «Zeus» located on the Kola Peninsula and in the fields of the natural sources (AMT-MT). Conductive layers were installed at depths of a few hundred meters and more than 1 km. These layers were linked with changes in lithology, porosity and fluid saturation of rocks. The research results showed perspectivity of complex electromagnetic sounding with natural and powerful controlled sources to find gas and oil promising horizons at a depth in the sedimentary cover of the West Siberian platform in the YaNAD.
