ELECTROMAGNETIC RESPONSE OF VERTICAL ELECTRIC DIPOLE OVER VERTICALLY INHOMOGENEOUS EARTH MODELS

摘要

A theoretical analysis of the electromagnetic field response of a vertical electric dipole placed over the surface of vertically inhomogeneous earth model is presented. The problem is formulated for a general multi-layered earth model, with the assumption that the electrical conductivity of an intermediate-inhomogeneous layer varies in accordance with the linear or exponential variation with depth. Analytical expressions for the various electric and magnetic field components and the computational results are obtained for a three layer earth model with the transition layer possessing the described conductivity variation. Conduction currents are assumed to dominate over displacement currents. Computations are performed for the absolute-amplitude ratio of the E_(ρ1) component and are expressed as a function of numerical distance d_1. The results for the absolute-amplitude of the E_(z1) and E_(φ1) components are presented as a function of the distance between the dipole and the observation point. The nature of response curves depicting characteristic variations of the models are discussed.