Field Geophysics

Preface to the First Edition ix

Preface to the Second Edition x

Preface to the Third Edition xii

Preface to the Fourth Edition xiv

1 Introduction 1

1.1 What Geophysics Measures 1

1.2 Fields 1

1.3 Geophysical Survey Design 9

1.4 Geophysical Fieldwork 14

1.5 Geophysical Data 19

1.6 Bases and Base Networks 29

1.7 Real-Time Profiling 32

2 Gravity Method 39

2.1 Physical Basis of the Gravity Method 39

2.2 Gravity Meters 41

2.3 Gravity Reductions 49

2.4 Gravity Surveys 52

2.5 Field Interpretation 61

3 Magnetic Method 65

3.1 Magnetic Properties 65

3.2 The Magnetic Field of the Earth 67

3.3 Magnetic Instruments 72

3.4 Magnetic Surveys 75

3.5 Simple Magnetic Interpretation 81

4 Radiometric Surveys 85

4.1 Natural Radiation 85

4.2 Radiation Detectors 90

4.3 Radiometric Surveys 92

5 Electric Current Methods: General Considerations 97

5.1 Resistivity and Conductivity 97

5.2 Varying Currents 102

6 Resistivity Methods 109

6.1 DC Survey Fundamentals 109

6.2 DC Practicalities 117

6.3 Resistivity Profiling 122

6.4 Resistivity Depth-Sounding 125

6.5 Electrical Resistivity Imaging (ERI) 128

6.6 Capacitive Coupling 133

7 SP and IP 137

7.1 SP Surveys 137

7.2 Polarisation Fundamentals 140

7.3 Time-Domain IP Surveys 143

7.4 Frequency-Domain Surveys 144

7.5 IP Data 146

8 Electromagnetic Methods 149

8.1 Two-Coil CW Systems 149

8.2 CWEM Conductivity Mapping 158

8.3 Fixed-Source Methods 161

8.4 Transient Electromagnetics 165

9 Remote-Source Electromagnetics 171

9.1 Natural Electromagnetic Radiation 171

9.2 Controlled-Source Audio-Magnetotellurics (CSAMT) 180

10 Ground Penetrating Radar 185

10.1 Radar Fundamentals 185

10.2 GPR Surveys 199

10.3 Data Processing 205

11 Siesmic Methods: General Considerations 211

11.1 Seismic Waves 211

11.2 Seismic Sources 216

11.3 Detection of Seismic Waves 222

11.4 Recording Seismic Signals 226

12 Seismic Reflection 229

12.1 Reflection Theory 229

12.2 Reflection Surveys 233

13 Seismic Refraction 241

13.1 Refraction Surveys 241

13.2 Interpretation 247

13.3 Limitations of the Refraction Method 257

14 Seismic Surface Wave Methods 261

14.1 Surface Wave Surveys 261

14.2 Data Processing 266

14.3 Limitations of the Method 270

15 Maps, Mapping and GPS 273

15.1 Maps and Mapping 273

15.2 Satellite Navigation 276

Appendix: Terrain Corrections for Hammer Zones B to m 281

Index 283