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Geo-Electromagnetism - 1st Edition - ISBN: 9780127308807, 9780323158091


1st Edition

Author: James Wait
eBook ISBN: 9780323158091
Imprint: Academic Press
Published Date: 28th July 1982
Page Count: 278
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Geo-Electromagnetism surveys the theoretical concepts and applications of electrical prospecting methods. This book is divided into seven chapters that specifically tackle the basic electromagnetic concepts and the special mathematical functions. This text deals first with the numerical and analytical approaches to delineate earth resistivity principles, followed by a description of the three-layer model. These topics are followed by a discussion on the theory of induced electrical polarization. The subsequent chapters are devoted to relevant electromagnetic theory of low-frequency current flow in conducting with varying fields. The discussion then shifts to the geophysical problems associated with vertical electric dipole sources, with an emphasis on the quasi-static range in which all significant distances are small compared with the free-space wavelength. The last chapters outline the relevant analytical development of the magnetotelluric theory and the theoretical principles of the transient electromagnetic methods used in geophysical exploration. Geophysicists, theoreticians, and undergraduate level students will find this book invaluable.

Table of Contents


Chapter I Earth Resistivity Principles


Potentials about a Single Current Electrode for a Two-Layer Earth Model

General Four-Electrode Array

Three-Layer Model Formulation

Discussion of Three-Layer Case

Numerical and Analytical Approaches

Effect of Anisotropy

Current Source Excitation of Layered Anisotropic Region

Current Source in Anisotropic Medium and Extensions

Outcropping Vertical Dike Model

Variable Resistivity with Depth—Exponential Model

Variable Resistivity with Depth—General Case and the Kernel Function

Resistivity for a Wedge Model

Limiting Case of 180° Wedge

Image Results for Acute-Angle Wedge

Sphere Problems

Response of a Homogeneous Conducting Sphere

Current Point Source and Cylinder Problems

Current Electrode on Axis of Fluid-Filled Borehole

Current Electrode in Wall of Layered Tunnel

Limiting Case for External Current Excitation of a Cable

Cable Located in Resistive Half-Space

Spheroidal Problems

Resistance of Grounded Electrodes


Chapter II Theory of Induced Electrical Polarization (Quasi-Static Approach)


Basic Transient Response

Other Parameter Descriptions

Induced Polarization Model Based on Coated Spherical Particles

Response of a Layered Polarizable Earth Model

General Formulation for Heterogeneous Media

Resistivity and IP Analysis for a Thin Conductive Sheet

Response of a Polarizable Sphere

Multiregion Polarizable Models


Chapter III Electromagnetic Induction and Loop-Loop Coupling


Magnetic Field of a Circular Loop of Current

Circular Loop over Two-Layer Earth

Extension to M-Layer Medium

General Orientation of Source Dipole

Explicit Field Expressions for Vertical and Horizontal Magnetic Dipole Sources

Analog with dc Resistivity

Low-Frequency Response

Asymptotic Limiting Forms

Mutual Impedance Formulation

Homogeneous Half-Space Model

Inclusion of Displacement Currents

General Solution for a Horizontal Magnetic Dipole

Electromagnetic Induction in a Conducting and Permeable Sphere

Boundary Conditions at Conducting Shell and Core Boundary


Chapter IV Electromagnetic Coupling for Grounded Sources


Some General Considerations

Anisotropic Media Considerations

Horizontal Electric Dipole Excitation

Horizontal Electric Dipole over N-Layer Anisotropic Medium

Mutual Impedance Formulation


Chapter V Earth Conduction Induced by Vertical Current Sources


Exact Integral Solution for Raised Dipole

Quasi-Static Limit and Fields within Half-Space

Vertical Grounded Line Source

Current Source in Borehole

Transient Coupling between Grounded Finite Circuits


Chapter VI Magnetotelluric Theory


Basic Plane-Wave Model

Current Sheet Source

Line Source Model Results

Segmented Overburden Model

Variable Subsurface Interface

Concluding Remarks


Chapter VII Inductive Transients


Pulse-Excited Loop over Layered Ground

Limit of Thin Conductive Sheet

Homogeneous Earth or Half-Space

Guided Wave Effects

Buried Source Problem

Scattering from Buried Target

Buried Sphere in Half-Space

Final Comment on IP and EM


Appendix A Electromagnetic TM and TE Spherical Waves


The Debye Potentials

General Surface Impedance

External Excitation of Sphere

Concentrically Layered Model

The Iterative Solution

Dipole Excitation

The Quasi-Static Limit

A Further Extension


Appendix B

Note on Bessel Functions Integrals



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© Academic Press 1982
28th July 1982
Academic Press
eBook ISBN:

About the Author

James Wait

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