The Murman-2018 experiment on remote sensing in order to study the boundary of “impenetrability” at the transition between the brittle and plastic states of the crystalline earth's crust

The article describes the experiment “Murman-2018” on remote electromagnetic sounding in combination with frequency and audio magnetotelluric soundings. The current from 29 kW power car-generator was fed into the ground using two mutually orthogonal grounded electric dipoles 1.6 and 1.9 km long. The measurements were carried out along three traces with maximum distances from the source up to 105 km in the mode of frequency sounding (in the range of 4-1000 Hz) and up to 56 km in the mode of remote sensing at direct current. The data processing was performed in the spectral mode and in the accumulation mode. The results of the experiment made it possible to quantify for the first time in the scientific literature the position of the boundary of a sharp increase in rock resistance at a depth of 10-15 km. The nature of the established boundary (the boundary of the “impenetrability” for direct current) is associated with the transition of the properties of the rocks of the Earth's crust from the fragile state in the upper crust to a plastic state at depths of 10-15 km and more. In foreign literature, this boundary is defined as the BDT-zone (brittle-ductile transition zone).