Environmental Geophysics (EET 7)

Everything you ever wanted (needed!) to know but were afraid to ask!

image of Environmental Geophysics (EET 7)
  • By Peter Styles
  • Format: EPUB
  • Publication Year: 2012
  • Number of Pages: 220
  • Language: English
  • Ebook ISBN: 9789462820128

This is an outward facing book for people who need to understand Geophysics because it can solve the problems they regularly encounter and help to deliver their optimal geotechnical solution, proved by the essential, but last to be applied, intrusive investigation. It may, of course, be of significant use to students and geophysical practitioners as it contains a wealth of case studies kindly provided by friends, colleagues and collaborators.
The people to whom this book is addressed do not require a great understanding of the mathematical basis of geophysics but do need to understand the physical principles, what information can be gleaned, the limitations and boundaries of interpretation and especially how we can combine techniques in an integrated way to solve subtle, complex and critical problems which one technique alone cannot solve.

Table of Contents



1 Introduction

1.1 Problems which arise now and then
1.2 The probability of detecting and proving something you suspect is, but don’t know, may or may not be underground!
1.2.1 Economic considerations
1.3 Why is site investigation tricky and why does it often end in litigation?
1.3.1 When does site investigation not work? The jaundiced view of a geophysicist!
1.3.2 When does site investigation work well? The Holy Grail
1.4 Framework

2 Gravity
2.1 What is it that we are measuring?
2.2 Units of gravity
2.3 What are we actually going to see?
2.4 Measuring gravity
2.4.1 Instrumentation
2.5 Planning and survey procedures: How will I know it will/might/won’t work? 2.5.1 Sample interval
2.6 Acquisition along a profile
2.6.1 Acquisition using a square grid
2.6.2 Station selection
2.7 Survey point accuracy requirements
2.8 Acquisition of microgravity data
2.9 Data reduction
2.9.1 Drift and tidal correction
2.9.2 Latitude correction
2.9.3 The combined elevation correction
2.9.4 Errors in the combined elevation correction
2.9.5 The terrain correction
2.9.6 Data verification and quality control
2.9.7 Isolation of gravity anomalies of interest
2.10 Modelling and interpretation of gravity anomalies
2.10.1 Depth estimates
2.10.2 Analytical methods
2.10.3 Euler deconvolution
2.10.4 Neural network and fuzzy logic methods
2.11 2.5D modelling
2.12 Inversion of gravity data and other geophysical data
2.12.1 Gravity inversion
2.13 Estimation of total anomalous mass
2.14 Some examples
2.14.1 Microgravity techniques in cavity detection
2.14.2 Applications of microgravity: Case studies
2.14.3 Detection of tunnels
2.14.4 Mining Voids Kalgoorlie Superpit, Western Australia
2.14.5 Monitoring underground gas storage
2.15 Summary

3 Magnetic Surveying
3.1 Environmental magnetic “surveying
3.2 Target features
3.3 Measuring the magnetic field
3.4 Units
3.5 Diurnal changes and the main field
3.6 Magnetic anomalies
3.7 Instrumentation
3.7.1 Fluxgate magnetometers (Usually used as gradiometers)
3.7.2 Proton precession magnetometer
3.7.3 Optically pumped magnetometers
3.8 Dipoles and virtual monopoles
3.9 Data acquisition and reduction
3.10 Interpretation of magnetic data
3.11 Recognising and Interpreting magnetic anomalies by comparison with known features
3.12 Depth estimation
3.12.1 Slope method for magnetic data
3.12.2 Peter’s method
3.12.3 Total field method from gradiometer data
3.13 Semi-automated methods
3.13.1 Werner deconvolution
3.13.2 Euler deconvolution
3.13.3 Power spectral methods
3.14 Beautiful curves
3.15 Pseudogravity
3.16 Modelling
3.17 Summary

4 Ground Penetrating Radar
4.1 Permittivity (ε R) or dielectric constant
4.2 Magnetic permeability (μ)
4.3 Electrical conductivity (σ)
4.4 Velocity
4.5 Field data acquisition
4.6 Basic GPR signal processing and image processing
4.6.1 Post processing gain
4.6.2 DC bias removal
4.6.3 Debanding through background removal
4.6.4 Migration
4.6.5 Hilbert transform
4.6.6 Borehole radar
4.7 Is GPR the perfect solution to all engineering problems?

5 Electrical Techniques
5.1 Brief history
5.2 Self-potential
5.2.1 Where does this voltage come from?
5.2.2 Self-potential tomography
5.3 Electrical Resistivity
5.3.1 Data acquisition in the field
5.3.2 Practical resistivity interpretation
5.4 CST - Constant Separation Traversing 5.4.1 Electrical Resistivity Imaging (ERI)
5.5 Problems and complexities
5.6 Main limitations of resistivity
5.7 Landfill monitoring
5.8 Hydrocarbon and other organic liquid spills
5.9 Cavity detection
5.10 Fracture detection
5.11 Mapping stratigraphy
5.12 Cross borehole electrical resistance tomography
5.13 Induced polarisation
5.14 Time scales
5.15 Indicative costs

6 Electromagnetic Imaging
6.1 Examples of EM applications in environmental geophysics
6.2 Airborne EM
6.3 TDEM (Time-domain EM) or TEM (Transient Electromagnetics)
6.4 Difficulties

7 Seismic Waves
7.1 Materials can be deformed in a number of ways
7.2 Waves
7.3 Amplitude decay
7.4 How do we generate seismic waves?
7.4.1 Explosives
7.4.2 Ambient noise
7.4.3 Vibroseis
7.5 How do we detect seismic waves?
7.5.1 Recording the signals
7.6 How does the Earth affect seismic signals and what can we learn from that?
7.6.1 Shallow seismic reflection
7.6.2 Seismic refraction
7.7 A case study of a detailed high resolution seismic refraction survey in the East Midlands of the UK
7.7.1 MASW: Multichannel Analysis of Surface Waves Method
7.8 The Galligu and other strange engineering materials
7.9 Multi-component seismic microtremor
7.9.1 Determining engineering parameters from microtremor data
7.10 Borehole seismic methods
7.11 Conclusions

8 Quo Vadis Environmental Geophysics?
8.1 Noise
8.2 Seismic interferometry
8.3 GPR interferometry
8.4 Nuclear Magnetic Resonance (NMR)
8.4.1 Data acquisition
8.4.2 Data interpretation
8.4.3 Limitations
8.5 Seismoelectric and electroseismic potentials
8.6 Coupled geophysical inversion
8.7 Every good thing must come to an end


Appendix A. The Tricky Bits
A.1. More trickier stuff! But it applies to magnetic anomalies too
A.2. Continuation
A.2.1 Upward continuation provides separation & qualitative depth estimation



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