TRANSIENT ELECTRIC-FIELD RESPONSE TO A UNIFORM, MAGNETICALLY VISCOUS EARTH EXCITED BY A GROUNDED LINE SOURCE
E.Yu. Antonov1, N.O. Kozhevnikov1,2
1A.A. Trofimuk 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 2, Novosibirsk, 630090, Russia
Keywords: Grounded line, equatorial array, transient response, magnetic viscosity, superparamagnetism, uniform earth
Abstract
A new method is suggested for calculation of transient electric-field response to conducting magnetically viscous earth excited by a grounded line source. Calculation algorithms are implemented in the computer program FwLL_MV. Using a conducting uniform, magnetically viscous half-space as an earth model, we have shown that magnetic relaxation affects the TEM response of equatorial and in-line arrays. As in the case of loop arrays, apparent resistivity steadily decreases with time. The higher the half-space resistivity and the shorter the offset, the earlier the voltage and the apparent resistivity begin to decrease as 1/ t . Magnetic relaxation and decay of eddy currents are independent processes within the range of resistivities typical of rocks.
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