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Dobrin, M.B. & Savit, C.H. () Introduction to Geophysical. Prospecting (4th edn). McGraw-Hill, New York. Kanasewich, E.R. () Time Sequence Analysis . INTRODUCTION. TO GEOPHYSICAL. PROSPECTING. FOURTH EDITION. Milton B. Dobrin. Late Professor of Geology. University of Houston. Carl H. Savit. Milton Dobrin. Read Online ↠ Introduction to Geophysical. Prospecting [PDF] by Milton Dobrin. Title: Introduction to Geophysical Prospecting. Author: Milton.
Kearey, P. An Introduction to Geophysical Exploration, 3rd Ed. Borehole Geophysics 3 Credit hours Introduction. Basic theory of Geophysical methods. Petrophysics and Formation evaluation.
Different types of logging techniques, Instrumentation and their field application. Log analysis and Interpretation. Application of borehole geophysics for lithological, environmental, water resources, geotechnical, mineral and hydrocarbon studies. Case histories. Sharma, P. Also, any comments or corrections that readers might have would also be gratefully received.
I would particularly like to thank Professor Don Tarling for his Preface continual encouragement to complete this book and for having commented on substantial parts of the manuscript. Thanks are also due to companies that have very kindly supplied material, and to colleagues around the world for permitting extracts of their work to be reproduced. I must also thank Richard Baggaley formerly of the Open University Press for commissioning me to write the book in the first place, and to Helen Bailey, Abi Hudlass and Louise Portsmouth at John Wiley for their patience in waiting so long for the final manuscript.
My final acknowledgement must be to my wife, Moira, and sons, Steven and David, for their support, encouragement and longsuffering patience while I have been closeted with 'The Book', Without their help and forbearance, this project would have been abandoned long ago.
John M. Geophysical methods Matching geophysical methods to applications Planning a geophysical survey 1. In the broadest sense, the science of Geophysics is the application of physics to investigations ofthe Earth, Moon and planets.
The subject is thus related to astronomy.
Normally, however, the definition of 'Geophysics' is used in a more restricted way, being applied solely to the Earth. Even then, the term includes such subjects as meteorology and ionospheric physics, and other aspects of atmospheric sciences.
To avoid confusion, the use of physics to study the interior of the Earth, from land surface to the inner core, is known as Solid Earth Geophysics. This can be subdivided further into Global Geophysics, or alternatively Pure Geophysics, which is the study of the whole or 2 An introduction to applied and environmental geophysics substantial parts of the planet, and Applied Geophysics which is concerned with investigating the Earth's crust and near-surface to achieve a practical and, more often than not, an economic aim.
The same scientific principles and technical challenges apply as much to shallow geophysical investigations as to pure geophysics.
Sheriff ; p. This can be defined as being: 'The application of geophysical methods to thc investigation of near-surface physico-chemical phenomena which are likely to have significant implications for the management of the local environment.
Chemical effects are equally as important as physical phenomena. Since the mids in the UK, geophysical methods have been used increasingly to investigate derelict and contaminated land, with a specific objective of locating polluted areas prior to direct observations using trial pits and boreholes e.
Reynolds and Taylor Geophysics is also being used much more extensively over landfills and other waste repositories e. Reynolds and McCann One ofthe advantages of using geophysical methods is that they are largely environmentally 4 An introduction to applied and environmental geophysics geophysics in glaciology. The last one is the least well known, despite the fact that it has been in existence for far longer than either archaeoor environmental geophysics, and is particularly well established within the polar scientific communities and has been since the s.
The general orthodox education of geophysicists to give them a strong bias towards the hydrocarbon industry has largely ignored these other areas of our science.
It may be said that this restricted view has delayed the application of geophysics more widely to other disciplines. Geophysics has been taught principally in Earth Science departments of universities.
There is an obvious need for it to be introduced to engineers and archaeologists much more widely than at present. Similarly, the discipline of environmental geophysics needs to be brought to the attention of policy-makers and planners, to the insurance and finance industries Doll The term 'environmental geophysics' has been interpreted by some to mean geophysical surveys undertaken with environmental sensitivity - that is, ensuring that, for example, marine seismic surveys are undertaken sympathetically with respect to the marine environment Bowles With growing public awareness of the environment and the pressures upon it, the geophysical community has had to be able to demonstrate clearly its intentions to minimise environmental impact Marsh By virtue of scale, the greatest likely impact on the environment is from hydrocarbon and some mineral exploration, and the main institutions involved in these activities are well aware of their responsibilities.
In small-scale surveys the risk of damage is much lower; but all the same, it is still important that those undertaking geophysical surveys should be mindful of their responsibilities to the environment and to others whose livelihoods depend upon it.
While the term 'applied geophysics' covers a wide range of applications, the importance of 'environmental' geophysics is particularly highlighted within this book. The growth of the discipline, which appears to be expanding exponentially, is such that this subject may outstrip the use of geophysics in hydrocarbon exploration during the early part of the next century and provide the principal area of employment for geophysicists.
The geophysicist needs to translate the velocity data into a rippability index with which the engineer would be familiar. Few, if any, geophysical methods provide a unique solution to a particular geological situation.
It is possible to obtain a very large number of geophysical solutions to some problems, some of which may be geologically nonsensical. It is necessary, therefore, always to ask the question: "Is the geophysical model geologically plausible? Conversely, if the geological model proves to be inconsistent with the geophysical interpretation, then it may require the geological information to be re-evaluated.
It is of paramount importance that geophysical data are inter- preted within a physically constrained or geological framework. While the model with the form of a question mark satisfies a statistical fit to the observed data, the model is clearly and quite deliberately geological nonsense in order to demonstrate the point.
However, geophysical observations can also place stringent restrictions on the interpretation of geological models. While the importance of understanding the basic principles cannot be over-emphasised, it is also necessary to consider other factors that affect the quality and usefulness of any geophysical survey, or for that matter of any type of survey whether it is geophysical, geochemical or geotechnical. This is done in the following few sections. The constraints on a commercial survey will have emphases different from those on an academic research investigation and, in many cases, there may be no ideal method.
The techniques employed and the subsequent interpretation of the resultant data tend to be compromises, practically and scientifically. There is no short-cut to developing a good survey style; only by careful survey planning backed by a sound knowledge of the geophysical methods and their operating principles, can cost-effective and efficient surveys be undertaken within the prevalent constraints.
However, there have been only a few published guidelines - e.
Scant attention has been paid to survey design, yet a badly thought-out survey rarely produces worthwhile results. Indeed, Darracott and McCann , p. Introduction 1. The mere acquisition of data does not guarantee the success of the survey. Knowledge by way of masses of data does not automatically increase our understanding of a site; it is the latter we are seeking, and knowledge is the means to this.
One less-than-ideal approach is the 'blunderbus' approach - take along a sufficient number of different methods and try them all out usually inadequately owing to insufficient testing time per technique to see which ones produce something interesting. Whichever method yields an anomaly, then use that technique. This is a crude statistical approach, such that if enough techniques are tried then at least one must work!
This is hardly scientific or cost-effective. The success of geophysical methods can be very site-specific and scientifically-designed trials of adequate duration may be very worthwhile to provide confidence that the techniques chosen will work or that the survey design needs modifying in order to optimise the main survey.
It is in the interests of the client that suitably experienced geophysical consultants are employed for the vital survey design, site supervision and final reporting. So what are the constraints that need to be considered by both clients and geophysical survey designers? An outline plan of the various stages in designing a survey is given in Figure 1.
The remainder of this chapter discusses the relationships between the various components. How much is the survey going to cost and how much money is available? The cost will depend on where the survey is to take place, how accessible the proposed field site is, and on what scale the survey is to operate. An airborne regional survey is a very different proposition to, say, a local, small-scale ground-based investigation.
The more complex the survey in terms of equipment and logistics, the greater the cost is likely to be. It is important to remember that the geophysics component of a survey is usually only a small part of an exploration programme and thus the costs of the geophysics should be viewed in relation to those of the whole project. Indeed, the judicious use of geophysics can save large amounts of money by enabling the effective use of resources Reynolds a.