Principles of Applied Geophysics

1 Introduction.- 2 Magnetic methods.- 2.1 Short history.- 2.2 Basic concepts and units.- 2.3 Magnetic properties of rocks.- 2.4 The geomagnetic field.- 2.5 Instruments of magnetic surveying.- 2.6 Survey layout and field procedure.- 2.7 Relative merits of horizontal, vertical and total-field measurements.- 2.8 Qualitative interpretation of magnetic anomalies.- 2.9 Quantitative interpretation.- 2.10 Effect of demagnetization.- 2.11 Some examples of magnetic investigations.- Problems.- 3 Gravitational methods.- 3.1 Introduction.- 3.2 Gravitational field of the earth.- 3.3 Measurement of gravity: absolute and relative measurements.- 3.4 Gravimeters.- 3.5 Field procedure.- 3.6 Corrections to gravity observations.- 3.7 The Bouguer anomaly.- 3.8 Density determinations.- 3.9 Interpretation.- 3.10 Depth determinations.- 3.11 Some theoretical aspects of gravity interpretation.- 3.12 Determination of total anomalous mass.- 3.13 Vertical derivatives of gravity.- 3.14 Illustrations of gravity surveys and interpretation.- 3.15 Note on marine gravity measurements.- Problems.- 4 Electrical methods.- 4.1 Introduction.- 4.2 Self-potential method.- 4.3 Earth resistivity.- 4.4 Some practical aspects of resistivity work.- 4.5 Vertical electrical sounding (VES).- 4.6 Electrical mapping.- 4.7 Anisotropic earth.- Problems.- 5 Induced polarization.- 5.1 Introduction.- 5.2 Measures of IP.- 5.3 Origin of IP.- 5.4 Electromagnetic coupling.- 5.5 Example of an IP survey.- Problems.- 6 Electromagnetic continuous wave, transient-field and telluric methods.- 6.1 Introduction.- 6.2 Electromagnetic induction.- 6.3 Elliptic polarization.- 6.4 Free-space magnetic fields of low-frequency sources.- 6.5 Near and far fields.- 6.6 Classification of artificial source, continuous wave methods.- 6.7 Near-field CW methods.- 6.8 Far-field methods.- 6.9 Interpretational aids in EM prospecting.- 6.10 Depth penetration.- 6.11 Influence of overburden conductivity.- 6.12 Transient-field methods (time-domain EM).- 6.13 Influence of magnetic permeability.- 6.14 Controlled-source electromagnetic sounding.- 6.15 Natural-field methods.- 6.16 Airborne measurements.- 6.17 Note on the design of electromagnetic coils.- Problems.- 7 Seismic methods.- 7.1 Introduction.- 7.2 Elastic constants and waves.- 7.3 The reflection method.- 7.4 The refraction method.- Problems.- 8 Radioactivity methods.- 8.1 Introduction.- 8.2 Theoretical background.- 8.3 Radioactivity of rocks.- 8.4 Radiation detectors and field procedure.- 8.5 Radon measurements.- 8.6 Radioactive density determinations.- 8.7 Airborne radioactivity measurements.- 9 Well logging in oil fields.- 9.1 Introduction.- 9.2 Permeable zones.- 9.3Archie's law.- 9.4 Permeability-zone logs.- 9.5 Resistivity and conductivity logs.- 9.6 Porosity logs.- 9.7 Auxiliary logs and measurements.- 9.8 Basic log interpretation procedure.- 10 Miscellaneous methods and topics.- 10.1 Borehole magnetometer.- 10.2 Mise-a-la-masse method.- 10.3 Logging in crystalline rocks and coal fields.- 10.4 Geothermal methods.- 10.5 Geochemical prospecting.- 10.6 Optimum point and line spacing.- 10.7 Position location in airborne surveying.- 10.8 Composite surveys.- Appendices.- Appendix 1 The magnetic potential.- Appendix 2 Magnetized sphere and a magnetic dipole.- Appendix 3 Magnetic anomaly of a sphere.- Appendix 4 Measurement of susceptibility and remanence.- Appendix 5 Magnetic potential of a linear dipole and the anomalies of thin and thick sheets 362 Appendix 6 Demagnetization 'factors' for a rectangular parallelepiped.- Appendix 7 Electric potential.- Appendix 8 Apparent resistivities for dipole-diople configurations.- Appendix 9 Potential of a point current electrode on the surface of a horizontally-layered earth.- Appendix 10 Homogeneous, anisotropic earth (derivation of Eq. (4.73)).- Appendix 11 Single-turn loop and other topics in electromagnetic methods.- Appendix 12 Acoustic impedance.- Appendix 13 Fourier transforms and convolution.- References.- Answers and hints.