A bite of the Earth's thin crust

Introduction to Applied Geophysics

May 25, 2007

Any encouragement of geophysics education is timely, as demand for geophysicists is extremely high. This book tackles "near-surface" geophysics - roughly, the uppermost 100m of the subsurface, and arguably as important as imaging hydrocarbons several kilometres down.

Geophysical investigations of environmental and engineering problems are growing in number and sophistication, and even being required by environmental impact legislation. Robert Burger and colleagues have written, in effect, a second edition of a book published 15 years ago and sharing the same lead author. At that time, at Leeds University at least, it found comfortable use in teaching environmental and engineering geophysics at undergraduate and - for non-geophysicists on programmes such as engineering geology - at masters level.

That's still the niche this text fills, as it covers elementary methods in each geophysical discipline, but in considerable length and depth. Few books are aimed specifically at near-surface geophysics for environmental and engineering targets: this one complements, rather than replaces, others available. Roughly half the book is dedicated to seismic methods, fundamental principles, refraction methods and reflection methods. The rest of the book covers electrical resistivity, gravity, magnetic methods, and electromagnetics and ground-penetrating radar.

The authors present a slightly different balance of methods than I would: perhaps a North American, rather than a European, view. In places, their emphasis is good - for example, seismic reflection methods are covered at length. Though they can be an expensive survey type to acquire and process, they are valuable but underused. In contrast, the preface describes magnetic methods as "the least common method... other than for metal (ore) exploration and buried iron and steel objects". Well, the latter includes virtually every brownfield site investigation, and magnetics is as common as anything in archaeological geophysics, where changes in magnetic field are generated by subtle differences in soil types. Ironically, such effects are well illustrated among the case studies with a spectacular and informative magnetic-gradient image of Bronze Age burial mounds.

More worrisome is that several prospecting methods seen as standard by many employers (and university syllabuses) are omitted or dismissed in a few paragraphs - for example, resistivity tomography, VLF, SP and IP. Chapters are formulated conventionally, beginning with descriptive and algebraic developments of basic theory and principles, moving to field procedures, analysis methods, survey planning and case studies, then closing with a good number of problems and questions, references and a reading list. I take issue with some scientific points (such as explanations of seismic wave absorption) and relevant further reading (such as Greg Baker's book and CD on shallow seismic reflection processing) that should be mentioned.

The amount and level of mathematics may prove daunting for some of the target audience in the UK. But they need not rely on interpreting equations: they can circumvent or complement them using the excellent accompanying CD. It contains spreadsheets replicating most tables and many graphs used in the text to explain the form of geophysical anomalies and interpret them.

Introduction to Applied Geophysics: Exploring the Shallow Subsurface. First Edition

Author - H. Robert Burger, Anne F. Sheehan and Craig R. Jones
Publisher - W. W. Norton
Pages - 600
Price - £38.99
ISBN - 9780393926378

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