Preface to the 2nd Edition .................................. xi
Acknowledgements .......................................... xiii
1 Introduction ................................................. 1
1.1 What are 'applied' and 'environmental' geophysics? ...... 1
1.2 Geophysical methods ..................................... 3
1.3 Matching geophysical methods to applications ............ 5
1.4 Planning a geophysical survey ........................... 5
1.4.1 General philosophy ............................... 5
1.4.2 Planning strategy ................................ 5
1.4.3 Survey constraints ............................... 7
1.5 Geophysical survey design ............................... 9
1.5.1 Target identification ............................ 9
1.5.2 Optimum line configuration and survey
dimensions ....................................... 9
1.5.3 Selection of station intervals .................. 11
1.5.4 Noise ........................................... 13
1.5.5 Position fixing ................................. 15
1.5.6 Data analysis ................................... 16
2 Gravity Methods ............................................. 19
2.1 Introduction ........................................... 19
2.2 Physical basis ......................................... 19
2.2.1 Theory .......................................... 19
2.2.2 Gravity units ................................... 20
2.2.3 Variation of gravity with latitude .............. 20
2.2.4 Geological factors affecting density ............ 22
2.3 Measurement of gravity ................................. 24
2.3.1 Absolute gravity ................................ 24
2.3.2 Relative gravity ................................ 25
2.4 Gravity meters ......................................... 26
2.4.1 Stable (static) gravimeters ..................... 27
2.4.2 UnstabLe (astatic) gravimeters .................. 27
2.4.3 Marine and airborne gravity systems ............. 31
2.5 Corrections to gravity observations .................... 34
2.5.1 Instrumental drift .............................. 34
2.5.2 Tides ........................................... 34
2.5.3 Latitude ........................................ 35
2.5.4 Free-air correction ............................. 35
2.5.5 Bouguer correction .............................. 36
2.5.6 Terrain correction .............................. 38
2.5.7 Building corrections ............................ 41
2.5.8 Eütvüs correction ............................... 41
2.5.9 Isostatic correction ............................ 44
2.5.10 Miscellaneous factors ........................... 45
2.5.11 Bouguer anomaly ................................. 45
2.6 Interpretation methods ................................. 45
2.6.1 Regionals and residuals ......................... 46
2.6.2 Anomalies due to different geometric forms ...... 47
2.6.3 Depth determinations ............................ 51
2.6.4 Mass determination .............................. 52
2.6.5 Second derivatives .............................. 53
2.6.6 Sedimentary basin or granite pluton? ............ 55
2.7 Applications and case histories ........................ 59
2.7.1 Mineral exploration ............................. 59
2.7.2 Engineering applications ........................ 59
2.7.3 Archaeological investigations ................... 66
2.7.4 Hydrogeological applications .................... 67
2.7.5 Volcanic hazards ................................ 71
2.7.6 Glaciological applications ...................... 78
3 Geomagnetic Methods ......................................... 83
3.1 Introduction ........................................... 83
3.2 Basic concepts and units of geomagnetism ............... 83
3.2.1 Flux density, field strength and permeability ... 83
3.2.2 Susceptibility .................................. 84
3.2.3 Intensity of magnetisation ...................... 84
3.2.4 Induced and remanent magnetisation .............. 85
3.2.5 Diamagnetism, paramagnetism, and ferri- and
ferro-magnetism ................................. 85
3.3 Magnetic properties of rocks ........................... 87
3.3.1 Susceptibility of rocks and minerals ............ 87
3.3.2 Remanent magnetisation and Kiinigsberger
ratios .......................................... 88
3.4 The Earth's magnetic field ............................. 89
3.4.1 Components of the Earth's magnetic field ........ 89
3.4.2 Time variable field ............................. 94
3.5 Magnetic instruments ................................... 95
3.5.1 Torsion and balance magnetometers ............... 95
3.5.2 Fluxgate magnetometers .......................... 95
3.5.3 Resonance magnetometers ......................... 97
3.5.4 Cryogenic (SQUID) magnetometers ................. 99
3.5.5 Gradiometers .................................... 99
3.5.6 Airborne magnetometer systems .................. 100
3.6 Magnetic surveying .................................... 100
3.6.1 Field survey procedures ........................ 100
3.6.2 Noise and corrections .......................... 101
3.6.3 Data reduction ................................. 103
3.7 Qualitative interpretation ............................ 103
3.7.1 Profiles ....................................... 105
3.7.2 Pattern analysis on aeromagnetic maps .......... 105
3.8 Quantitative interpretation ........................... 107
3.8.1 Anomalies due to different geometric forms ..... 110
3.8.2 Simple depth determinations .................... 112
3.8.3 Reduction to the Pole (RTP) .................... 115
3.8.4 Modelling in two and three dimensions .......... 115
3.8.5 Depth determinations and Euler deconvolution ... 118
3.9 Applications and case histories ....................... 123
3.9.1 Regional aeromagnetic investigations ........... 123
3.9.2 Mineral exploration ............................ 125
3.9.3 Detection of underground pipes ................. 126
3.9.4 Detection of buried containers ................. 127
3.9.5 Landfill investigations ........................ 128
3.9.6 Acid tar lagoon survey ......................... 133
3.9.7 UneXploded Ordnance (UXO) ...................... 136
4 Applied Seismology: Introduction and Principles ............ 143
4.1 Introduction .......................................... 143
4.2 Seismic waves ......................................... 144
4.2.1 Stress and strain .............................. 144
4.2.2 Types of seismic waves ......................... 145
4.2.3 Seismic wave velocities ........................ 147
4.3 Raypath geometry in layered ground .................... 149
4.3.1 Reflection and transmission of normally
incident rays .................................. 149
4.3.2 Reflection and refraction of obliquely
incident rays .................................. 150
4.3.3 Critical refraction ............................ 151
4.3.4 Diffractions ................................... 151
4.4 Loss of seismic energy ................................ 152
4.4.1 Spherical divergence or geometrical
spreading ...................................... 152
4.4.2 Intrinsic attenuation .......................... 153
4.4.3 Scattering ..................................... 154
4.5 Seismic energy sources ................................ 154
4.5.1 Impact devices ................................. 155
4.5.2 ImpuLsive sources .............................. 157
4.5.3 Explosive sources .............................. 159
4.5.4 Non-explosive sources .......................... 159
4.5.5 High-resolution waterborne sources ............. 162
4.5.6 Vibrators ...................................... 163
4.5.7 Animals ........................................ 166
4.6 Detection and recording of seismic waves .............. 169
4.6.1 Geophones and accelerometers ................... 170
4.6.2 Hydrophones and streamers ...................... 171
4.6.3 Seismographs ................................... 177
5 Seismic Refraction Surveying ............................... 179
5.1 Introduction .......................................... 179
5.2 General principles of refraction surveying ............ 179
5.2.1 Critical refraction ............................ 179
5.2.2 Field survey arrangements ...................... 181
5.3 Geometry of refracted raypaths ........................ 182
5.3.1 Planar interfaces .............................. 182
5.3.2 Irregular (non-planar) interfaces .............. 185
5.4 Interpretational methods .............................. 186
5.4.1 Phantoming ..................................... 187
5.4.2 Hagedoorn plus-minus method .................... 188
5.4.3 Generalised reciprocal method (GRM) ............ 190
5.4.4 Hidden-layer problem ........................... 191
5.4.5 Effects of continuous velocity change .......... 192
5.4.6 Seismic refraction software .................... 193
5.5 Applications and case histories ....................... 193
5.5.1 Rockhead determination for a proposed waste
disposal site .................................. 193
5.5.2 Location of a buried doline .................... 197
5.5.3 Assessment of rock quality ..................... 199
5.5.4 Landfill investigations ........................ 201
5.5.5 Acid-tar lagoons ............................... 203
5.5.6 Static corrections ............................. 205
5.5.7 Locating buried miners ......................... 207
5.6 Shear wave methods .................................... 208
5.6.1 Ground stiffness profiling ..................... 208
5.6.2 Multichannel Analysis of Shear Waves (MASW) .... 211
5.6.3 Earthquake hazard studies ...................... 215
6 Seismic Reflection Surveying ............................... 217
6.1 Introduction .......................................... 217
6.2 Reflection surveys .................................... 217
6.2.1 General considerations ......................... 217
6.2.2 General reflection principles .................. 218
6.2.3 Two-dimensional survey methods ................. 219
6.2.4 Three-dimensional surveys ...................... 221
6.2.5 Vertical seismic profiling (VSP) ............... 224
6.2.6 Cross-hole seismology: tomographic imaging ..... 225
6.3 Reflection data processing ............................ 228
6.3.1 Preprocessing .................................. 229
6.3.2 Static corrections (field statics) ............. 230
6.3.3 Convolution and deconvolution .................. 233
6.3.4 Dynamic corrections, velocity analyses and
stacking ....................................... 236
6.3.5 Filtering ...................................... 241
6.3.6 Migration ...................................... 243
6.4 Correlating seismic data with borehole logs and
cones ................................................. 246
6.4.1 Sonic and density logs, and synthetic
seismograms .................................... 246
6.4.2 Correlation with cone penetration testing ...... 247
6.5 Interpretation ........................................ 250
6.5.1 Vertical and horizontal resolution ............. 250
6.5.2 Identification of primary and secondary
events ......................................... 252
6.5.3 Potential interpretational pitfalls ............ 256
6.6 Applications .......................................... 257
6.6.1 High-resolution seismic profiling on land ...... 257
6.6.2 Seismic reflection surveys for earthquake
prediction studies ............................. 265
6.6.3 High-resolution seismic profiling over water ... 266
6.6.4 Geophysical diffraction tomography in
palaeontology .................................. 283
6.6.5 Forensic seismology ............................ 286
7 Electrical Resistivity Methods ............................. 289
7.1 Introduction .......................................... 289
7.2 Basic principles ...................................... 289
7.2.1 True resistivity ............................... 289
7.2.2 Current flow in a homogeneous earth ............ 292
7.3 Electrode configurations and geometric factors ........ 293
7.3.1 General case ................................... 293
7.3.2 Electrode configurations ....................... 294
7.3.3 Media with contrasting resistivities ........... 298
7.4 Modes of deployment ................................... 301
7.4.1 Vertical electrical sounding (VES) ............. 301
7.4.2 Automated array scanning ....................... 303
7.4.3 Electrical resistivity tomography (ERT) ........ 306
7.4.4 Constant separation traversing (CST) ........... 307
7.4.5 Field problems ................................. 308
7.5 Interpretation methods ................................ 311
7.5.1 Qualitative approach ........................... 311
7.5.2 Master curves .................................. 313
7.5.3 Curve matching by computer ..................... 314
7.5.4 Equivalence and suppression .................... 317
7.5.5 Inversion and deconvolution .................... 318
7.5.6 Modelling in 2D and 3D ......................... 321
7.6 ERT applications and case histories ................... 326
7.6.1 Engineering site investigations ................ 326
7.6.2 Groundwater and landfill surveys ............... 330
7.6.3 Mineral exploration ............................ 333
7.6.4 Glaciological applications ..................... 333
7.7 Mise-a-la-masse (MALM) method ......................... 336
7.7.1 Mineral exploration ............................ 338
7.7.2 Civil engineering pile testing ................. 341
7.7.3 Study of tree roots ............................ 344
7.7.4 Groundwater flow ............................... 344
7.8 Leak detection through artificial membranes ........... 346
8 Spontaneous (Self) Potential Methods ....................... 349
8.1 Introduction .......................................... 349
8.2 Occurrence of self-potentials ......................... 349
8.3 Origin of self-potentials ............................. 349
8.3.1 Electrokinetic potentials ...................... 350
8.3.2 Electrochemical potentials ..................... 351
8.3.3 Mineral potentials ............................. 352
8.4 Measurement of self-potentials ........................ 353
8.5 Corrections to SP data ................................ 354
8.6 Interpretation of self-potential anomalies ............ 354
8.6.1 Qualitative interpretation ..................... 354
8.6.2 Quantitative interpretation .................... 355
8.7 Applications and case histories ....................... 357
8.7.1 Geothermal exploration ......................... 357
8.7.2 Mineral exploration ............................ 359
8.7.3 Hydrogeology ................................... 361
8.7.4 Landfills and contaminant plumes ............... 363
8.7.5 Leak detection ................................. 364
8.7.6 Mapping mine shafts ............................ 370
8.8 Electrokinetic (EK) surveying ......................... 371
9 Induced Polarisation ....................................... 373
9.1 Introduction .......................................... 373
9.2 Origin of induced polarisation effects ................ 374
9.2.1 Grain (electrode) polarisation ................. 374
9.2.2 Membrane (electrolytic) polarisation ........... 375
9.2.3 Macroscopic processes .......................... 375
9.2.4 Ionic processes ................................ 376
9.3 Measurement of induced polarisation ................... 376
9.3.1 Time-domain measurements ....................... 376
9.3.2 Frequency-domain measurements .................. 377
9.3.3 Spectral IP and complex resistivity ............ 379
9.3.4 Noise reduction and electromagnetic coupling ... 381
9.3.5 Forms of display of IP data .................... 382
9.3.6 Inversion and fitting dispersion spectra ....... 383
9.4 Applications and case histories ....................... 384
9.4.1 Base metal exploration ......................... 384
9.4.2 Hydrocarbon exploration ........................ 389
9.4.3 Geothermal surveys ............................. 390
9.4.4 Groundwaterinvestigations ...................... 391
9.4.5 Environmental applications ..................... 392
9.4.6 Geological investigations ...................... 398
10 Electromagnetic Methods: Introduction and Principles ....... 403
10.1 Introduction .......................................... 403
10.1.1 Background ..................................... 403
10.1.2 Applications ................................... 404
10.1.3 Types of EM systems ............................ 404
10.2 Principles of EM surveying ............................ 407
10.2.1 Electromagnetic waves .......................... 407
10.2.2 Polarisation ................................... 410
10.2.3 Depth of penetration of EM radiation ........... 411
10.3 Airborne EM surveying ................................. 411
10.3.1 Background ..................................... 411
10.3.2 Frequency-domain EM (FEM) ...................... 412
10.3.3 Time-domain EM (ТЕМ) ........................... 414
10.3.4 Airborne VLF-EM ................................ 418
10.4 Seaborne EM surveying ................................. 418
10.4.1 Background ..................................... 418
10.4.2 Details of marine EM systems ................... 421
10.5 Borehole EM surveying ............................ 426
11 Electromagnetic Methods: Systems and Applications .......... 431
11.1 Introduction .......................................... 431
11.2 Continuous-wave (CW) systems .......................... 431
11.2.1 Tilt-angle methods ............................. 431
11.2.2 Fixed-source systems (Sundberg, Turam) ......... 432
11.2.3 Moving-source systems .......................... 433
11.2.4 Interpretation methods ......................... 437
11.2.5 Applications and case histories ................ 441
11.3 Pulse-transient (ТЕМ) or time-domain (TDEM) EM
systems ............................................... 467
11.3.1 TDEM/TEM surveys ............................... 467
11.3.2 Data processing and interpretation of ТЕМ
surveys ........................................ 468
11.3.3 Applications and case histories ................ 470
12 Electromagnetic Methods: Systems and Applications II ....... 495
12.1 Very-low-frequency (VLF) methods ...................... 495
12.1.1 Introduction ................................... 495
12.1.2 Principles of operation ........................ 495
12.1.3 Effect of topography on VLF observations ....... 498
12.1.4 Filtering and interpretation of VLF data ....... 498
12.1.5 Applications and case histories ................ 499
12.2 The telluric method ................................... 502
12.2.1 Principles of operation ........................ 502
12.2.2 Field measurements ............................. 503
12.3 The magneto telluric (MT) method ...................... 505
12.3.1 Principles of operation ........................ 505
12.3.2 Field measurements ............................. 505
12.3.3 Interpretation methods ......................... 507
12.3.4 Applications and case histories ................ 509
12.4 Magnetic Resonance Sounding (MRS) ..................... 519
12.4.1 Principles of operation ........................ 519
12.4.2 Field measurements ............................. 522
12.4.3 Interpretation methods ......................... 525
12.4.4 Case histories ................................. 525
13 Introduction to Ground-Penetrating Radar ................... 535
13.1 Introduction .......................................... 535
13.2 Principles of operation ............................... 537
13.3 Propagation of radiowaves ............................. 539
13.3.1 Theory ......................................... 539
13.3.2 Energy loss and attenuation .................... 540
13.3.3 Horizontal and vertical resolution ............. 544
13.4 Dielectric properties of earth materials .............. 546
13.5 Modes of data acquisition ............................. 552
13.5.1 Radar reflection profiling ..................... 552
13.5.2 Wide-angle reflection and refraction (WARR)
sounding ....................................... 553
13.5.3 Trans-illumination or radar tomography ......... 553
13.6 Data processing ....................................... 554
13.6.1 During data acquisition ........................ 556
13.6.2 Wide-angle reflection and refraction (WARR)
sounding ....................................... 556
13.6.3 Post-recording data processing ................. 557
13.7 Interpretation techniques ............................. 560
13.7.1 Basic interpretation ........................... 560
13.7.2 Quantitative analysis .......................... 562
13.7.3 Interpretational pitfalls ...................... 562
14 Ground-Penetrating Radar: Applications and Case
Histories .................................................. 565
14.1 Geological mapping .................................... 565
14.1.1 Sedimentary sequences .......................... 565
14.1.2 Lacustrine environments ........................ 567
14.1.3 Geological faults .............................. 570
14.2 Hydrogeology and groundwater contamination ............ 571
14.2.1 Groundwater contamination ...................... 571
14.2.2 Mapping the water table ........................ 576
14.3 Glaciological applications ............................ 578
14.3.1 Polar ice sheets ............................... 578
14.3.2 Snow stratigraphy and crevasse detection ....... 581
14.3.3 Temperate glaciers ............................. 583
14.3.4 Glacial hazards ................................ 586
14.4 Engineering applications on manmade structures ........ 587
14.4.1 Underground storage tanks (USTs), pipes and
cables ......................................... 588
14.4.2 Transportation infrastructure .................. 592
14.4.3 Dams and embankments ........................... 594
14.4.4 Golf courses ................................... 597
14.5 Voids within manmade structures ....................... 599
14.5.1 Voids behind sewer linings ..................... 600
14.5.2 Buried crypts and cellars ...................... 600
14.5.3 Coastal defences ............................... 602
14.6 Archaeological investigations ......................... 603
14.6.1 Roman roads .................................... 603
14.6.2 Historical graves .............................. 603
14.6.3 Buried Roman structures ........................ 604
14.6.4 Burial mounds .................................. 605
14.7 Forensic uses of GPR .................................. 607
14.8 Wide-aperture radar mapping and migration
processing ............................................ 607
14.9 Borehole radar ........................................ 609
14.9.1 Hydrogeological investigations ................. 612
14.9.2 Mining ......................................... 613
14.10 UXO and landmine detection ........................... 617
14.11 Animals .............................................. 618
15 Radiometrics ............................................... 625
15.1 Introduction .......................................... 625
15.2 Natural radiation ..................................... 625
15.2.1 Isotopes ....................................... 625
15.2.2 α and β particles, and γ radiation ............. 626
15.2.3 Radioactive decay series and radioactive
equilibria ..................................... 626
15.2.4 Natural gamma-ray spectra ...................... 627
15.3 Radioactivity of rocks ................................ 628
15.4 Radiation detectors ................................... 628
15.4.1 Geiger-Muller counter .......................... 628
15.4.2 Scintillometers ................................ 629
15.4.3 Gamma-ray spectrometers ........................ 630
15.4.4 Radon detectors ................................ 630
15.4.5 Seaborne systems ............................... 631
15.4.6 Borehole logging tools ......................... 632
15.5 Data correction methods ............................... 633
15.5.1 Detector calibration ........................... 633
15.5.2 Thorium source test ............................ 633
15.5.3 Dead time and live time ........................ 633
15.5.4 Geometric corrections .......................... 633
15.5.5 Environmental factors .......................... 634
15.5.6 Compton scattering ............................. 634
15.5.7 Terrain clearance corrections .................. 634
15.5.8 Radio-element ground concentrations ............ 635
15.6 Radiometric data presentation ......................... 635
15.7 Case histories ........................................ 636
15.7.1 Mineral exploration ............................ 636
15.7.2 Engineering applications ....................... 638
15.7.3 Soil mapping ................................... 639
15.7.4 Nuclear waste disposal investigations .......... 642
Appendix ................................................... 645
References ................................................. 649
Index ...................................................... 681
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