Chapter 2 Magnetovariational Method in Deep Geoelectrics

Abstract

Publisher Summary This chapter discusses the magnetovariational method in deep geoelectrics. Deep geoelectrics studies of the Earth's crust and upper mantle include two methods: (1) The magnetotelluric (MT) method using the electric and magnetic fields and (2) the magnetovariational (MV) method using only the magnetic field. The MT–MV geoelectric complex is widely and rather successfully used throughout the world. It provides an unique information on the Earth's interior (porosity, permeability, graphitization, sulfidizing, dehydration, melting, fluid regime, ground-water mineralization, rheological characteristics, thermodynamic, and geodynamic processes). The inverse problem of MV and MT soundings is unstable. An arbitrarily small error in the measurement data can give rise to an arbitrarily large error in the conductivity distribution. The weak point of deep geoelectrics with MT priority is that inhomogeneities in the uppermost layers may severely distort the electric field and consequently the impedance tensor along with the apparent resistivity. It is commonly supposed that ‘‘MV studies determine only horizontal conductivity gradients, while the vertical conductivity distribution is not resolved.’’