Magnetotelluric Responses of an Anisotropic 1-D Earth with a Layer of Exponentially Varying Conductivity

Abstract

The magnetotelluric (MT) sounding of a layered Earth model involving a transitional layer has been widely studied, and MT responses of the model with dipping anisotropic conductivity have also been treated. However, a model incorporating both a transitional layer and dipping anisotropy has seldom been considered. The analytical solution of such a geoelectrical model including three layers was derived in this study. The middle layer was a transitional layer with conductivity exponentially varying with depth, which was covered by a homogeneous layer and underlaid by a dipping anisotropic half-space. The electromagnetic (EM) fields in the transitional layer were explicitly solved with modified Bessel functions. The surface impedance was calculated recursively. The dependence of the apparent resistivity and impedance phase as well as the EM fields on different model parameters were investigated in detail. We believe that our analytical solution provides a useful complement to the theory of the one-dimensional (1D) inversion and interpretation based on the layered model with fixed conductivity.

Nature-inspired stochastic hybrid technique for joint and individual inversion of DC and MT data

“…Although both strategies are inherently ambiguous, their combined interpretation is more rational and produces superior outcomes 54 , 55 . These techniques provide more consistent and trustworthy subsurface models and variations than those derived by individual inversions 33 , 56 . The DC and MT datasets were obtained in the period range of 0.02 to 1995s from a site near Broken Hill in South Central Australia, where Schlumberger sounding data was received over a spreading of 20 km 57 , 58 .…”

“…The impedance Z for a multi-layered earth surface is described as a function of frequency that provides the impedance for the first to ( )th layer as follows 33 : …”

Analysis of two-dimensional magnetotelluric inversion for the delineation of the petroleum system in the Kutai basin, East Kalimantan, Indonesia

“…In the 1-dimensional medium, there are EM field components in the horizontal direction (Ex, Ey, and Hy, Hx) that vary only with depth (not varying with x-axis and y-axis) and there are no vertical EM field components [30]. Based on the orthogonal nature of induction between the electric field and the magnetic field and the same properties in Ex and Ey as well as in Hx and Hy, the discussion of EM components in this medium is one of them in Ex and Hy [31].…”

Editorial for the Special Issue “Electromagnetic Exploration: Theory, Methods and Applications”

“…Two modeling papers are presented in this Special Issue. Qin et al [6] studied the analytical solutions of MT fields of a three-layered model with an isotropic top layer, a transition layer of exponentially varying conductivity with depth and a dipping anisotropic layer. They recursively computed the surface apparent resistivity and impedance phase, as well as the EM fields for different model parameters.…”