INFLUENCES OF THE EARTH’S MAGNETIC FIELD ON THE TRANSIENT ELECTROMAGNETIC PROCESS IN THE GEOELECTRIC FIELD: AN EXPERIMENTAL STUDY
V.S. Mogilatov1,2, V.V. Potapov1,2, A.N. Shein1, V.A. Gur'ev1,2
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk 630090, Russia
Keywords: Electrical prospecting, controlled source transient electromagnetic (TEM) method, geomagnetic field, Hall effect
Abstract
A mathematical model of the influence of the Earth’s magnetic field (the Hall effect) on results of the controlled source transient electromagnetic (TEM) method has been elaborated. For identification of this effect, we propose a schematic layout of the experimental grounded system with a pulsed loop source and signals recording by radial receive lines equally spaced relative to the loop. The 2018-2019 special field experiments were conducted in the Tatar region of the West Siberian Lowland with an aim to estimate the Hall effect contributions to the TEM method. To detect the Hall effect, transient electromagnetic responses were measured mainly by four receive lines radiating from a 500×500 m square loop. Analysis of the TEM results processing aimed at improving the signal quality and reducing the interference revealed a great similarity in signals from the radial lines, which is theoretically possible only under the Hall effect. Comparison of the field signals with the theoretical ones enabled estimation of the components caused by the Hall effect, in particular, conductivity at ~0.002 S/m.
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