Some theoretical aspects of the two-level magnetovariational method

Abstract

We discuss some theoretical aspects of the two-level magnetovariational method for the determination of the underground electrical structure. The properties of two new apparent resistivity functions, respectively depending on gain and phase of the transfer function of the horizontal magnetic field variations between the Earth's surface and a given depth, are examined for two-layer Earth models. The effects of a finite wavelength of the source field are also investigated. It is shown that the measurement of the attenuation of the magnetic vertical component generated by an inhomogeneous source field can provide further information on the vertical distribution of the Earth's conductivity. In particular, it is shown that the measurement of the transfer function of both vertical and horizontal components between two levels can be used to estimate the average conductivity of the interlying medium.