Electromagnetic Depth Soundings

Electromagnetic Sounding Methods —Introduction and History.- History of Electromagnetic Methods.- Electrical Prospecting with the Transient Magnetic Field Method.- I. Physical and Mathematical Foundation for the Transient Magnetic Field Method.- 1. Time-Domain and Frequency-Domain Methods in the Theory for Transient Magnetic Fields.- 2. Primary Magnetic Field of a Dipole.- 3. Use of the Principle of Reciprocity for Determining Transient Magnetic Fields.- II. Calculation and Analysis of Theoretical Curves.- 1. Numerical Evaluation of Transient Magnetic Fields.- 2. Asymptotic Behavior of the Vertical Component of the Transient Magnetic Field.- 3. Apparent Resistivity in the Transient Magnetic Field Method.- 4. Computation of Wave-limit Curves for Transient Magnetic Fields.- 5. Computation of Theoretical Curves for the Late Stage of the Transient Magnetic Field.- 6. Master Curves for Transient Magnetic Fields.- 7. Construction of Curves for Transient Magnetic Fields in the Far Zone.- 8. Analysis of Theoretical Curves for Transient Magnetic Fields.- 9. Maximum Resolution for Transient Magnetic Fields.- 10. Equivalent Curves for Transient Magnetic Fields.- III. Equipment.- 1. Recording Transient Magnetic Fields.- 2. Signal-to-Noise Ratio.- 3. Block Diagram for Equipment Used in the Magnetic Transient Method.- 4. Generating Equipment.- 5. Receiving Equipment.- 6. Particular Methods for Conversion.- 7. Alignment of an Amplifier.- 8. Equipment for Generating Synchronous Time Marks.- 9. Summary.- IV. Field Methods and Interpretation.- 1. Field Methods.- 2. Construction of Apparent Resistivity Curves.- 3. Topographic and Survey Control.- 4. Reduction and Presentation of Survey Results.- 5. Logistic Considerations.- 6. Basic Interpretation of the Final Stage of the Magnetic Transient.- 7. Use of Electric Log Data.- 8. Distortions of Magnetic Transient Curves.- 9. Possible Uses for the Magnetic Transient Method in Studying Structural Geology.- Appendix 1. Table of Hyperbolic and Inverse Hyperbolic Functions of Complex Arguments for Computing Wave Curves for a Transient Field.- Appendix 2. Typical Three-Layer and Four-Layer Wave Curves for Transient Fields.- Appendix 3. Nomogram for Determining the Correction for Finite Length of Source Dipole.- Appendix 4. Forms for a Field Log.- Fundamentals of Electromagnetic Sounding.- I. Geological Basis for Electromagnetic Sounding.- Field Sources and Models of the Geoelectric Section.- Maxwell’s Equations and the Vector Potential.- Vector Potential in a Homogeneous Medium.- The Electromagnetic Field in a Layered Anisotropic Medium.- Electromagnetic Fields at the Surface of a Uniform Anisotropic Half- Space.- Calculation of the Quasistatic Electromagnetic Field at the Surfaces of a Layered Anisotropic Medium.- II. Principles of Quasistatic Electromagnetic Sounding.- Determining the Resistivity of a Homogeneous Anisotropic Half-Space.- Two Principles of Electromagnetic Sounding.- Induction Sounding.- Geometric Soundings.- Equivalence for Thin Layers.- Electromagnetic Sounding in the Presence of an Insulating Screening Layer..- Two Forms of Anisotropy and Their Effect on Electromagnetic Sounding..- Conclusions.- Concerning Some Causes for the Distortion of Transient Sounding Curves.- Measuring Array Located on a Sloping Surface.- Location of Source and Receiver at Different Heights.- Insulating Hemisphere near the Observation Point.- Concerning the Factors Distorting Frequency Sounding Curves.- Four-Layer Master Curves for Frequency Electromagnetic Sounding.