Table Of ContentPrinciples
of
Applied Geophysics
'This is called practice, but remember to first set forth
the theory.'
Leonardo da Vinci
Codex Madrid I (1493-1497)
Principles
of
Applied Geophysics
D.S. PARASNIS
Professor of Applied Geophysics
University of Luled. Luled. Sweden
Fellow of the Royal Swedish Academy
of Engineering Sciences
Fourth edition
London New York
CHAPMAN AND HALL
First published in 1962 by
Methuen & Co. Ltd
Reprinted once
Reprint 1971
published by
Chapman and Hall Ltd.
11 New Fetter Lane. London EC4P 4EE
Second edition 1972
Reprinted once
Third edition 1979
Reprinted 1982
Fourth edition 1986
Published in the USA by
Chapman and Hall.
29 West 35th Street. New York. NY 10001
© 1962, 1972, 1979, 1986, D.S. Parasnis
This title is available in both hardbound and paperback editions.
The paperback edition is sold subject to the condition that it shall
not, by way of trade or otherwise, be lent, resold, hired out, or
otherwise circulated without the publisher's prior consent in any
form of binding or cover other than that in which it is published and
without a similar condition including this condition being imposed
on the subsequent purchaser.
All rights reserved. No part of this book may be reprinted, or
reproduced or utilized in any form or by any electronic, mechanical
or other means, now known or hereafter invented, including
photocopying and recording, or in any information storage and
retrieval system, without permission in writing from the publisher.
British Library Cataloguing in Publication Data
Parasnis, D.S.
Principles of applied geophysics.-4th ed.
1. Prospecting-Geophysical methods
I. Title
622'.15 TN269
Library of Congress Cataloging in Publication Data
Parasnis, D.S.
Principles of applied geophysics.
Bibliography: p.
Includes index.
1. Prospecting-Geophysical methods. I. Title.
TN269.P32 1986 622'.15 85-32570
ISBN-l3: 978-0-412-28330-7 e-ISBN-13: 978-94-009-4113-7
DOl: 10.1007/978-94-009-4113-7
Contents
Preface to the fourth edition ix
1 Introduction 1
2 Magnetic methods 3
2.1 Short history 3
2.2 Basic concepts and units 3
2.3 Magnetic properties of rocks 6
2.4 The geomagnetic field 12
2.5 Instruments of magnetic surveying 14
2.6 Survey layout and field procedure 20
2.7 Relative merits of horizontal, vertical and total-field
measurements 22
2.8 Qualitative interpretation of magnetic anomalies 24
2.9 Quantitative interpretation 28
2.10 Effect of demagnetization 53
2.11 Some examples of magnetic investigations 55
Problems 60
3 Gravitational methods 61
3.1 Introduction 61
3.2 Gravitational field of the earth 64
3.3 Measurement of gravity: absolute and relative
measurements 65
3.4 Gravimeters 66
3.5 Field procedure 70
3.6 Corrections to gravity observations 71
3.7 The Bouguer anomaly 74
vi Contents
3.8 Density determinations 75
3.9 Interpretation 76
3.10 Depth determinations 84
3.11 Some theoretical aspects of gravity interpretation 86
3.12 Determination of total anomalous mass 93
3.13 Vertical derivatives of gravity 94
3.14 Illustrations of gravity surveys and interpretation 95
3.15 Note on marine gravity measurements 101
Problems 102
4 Electrical methods 104
4.1 Introduction 104
4.2 Self-potential method 104
4.3 Earth resistivity 115
4.4 Some practical aspects of resistivity work 119
4.5 Vertical electrical sounding (VES) 125
4.6 Electrical mapping 155
4.7 Anisotropic earth 166
Problems 169
5 Induced polarization 173
5.1 Introduction 173
5.2 Measures of IP 174
5.3 Origin of IP 175
5.4 Electromagnetic coupling 178
5.5 Example of an IP survey 180
Problems 180
6 Electromagnetic continuous wave, transient-field and telluric
methods 182
6.1 Introduction 182
6.2 Electromagnetic induction 183
6.3 Elliptic polarization 187
6.4 Free~space magnetic fields of low-frequency sources 189
6.5 Near and far fields 193
6.6 Classification of artificial source, continuous wave methods 194
6.7 Near-field CW methods 195
6.8 Far-field methods 210
6.9 Interpretational aids in EM prospecting 218
6.10 Depth penetration 221
6.11 Influence of overburden conductivity 222
6.12 Transient-field methods (time-domain EM) 224
Contents vii
6.13 Influence of magnetic permeability 231
6.14 Controlled-source electromagnetic sounding 232
6.15 Natural-field methods 237
6.16 Airborne measurements 242
6.17 Note on the design of electromagnetic coils 247
Problems 248
7 Seismic methods 250
7.1 Introduction 250
7.2 Elastic constants and waves 250
7.3 The reflection method 259
7.4 The refraction method 304
Problems 316
8 Radioactivity methods 318
8.1 Introduction 318
8.2 Theoretical background 318
8.3 Radioactivity of rocks 321
8.4 Radiation detectors and field procedure 321
8.5 Radon measurements 324
8.6 Radioactive density determinations 324
8.7 Airborne radioactivity measurements 325
9 Well logging in oil fields 327
9.l Introduction 327
9.2 Permeable zones 327
9.3 Archie's law 328
9.4 Permeability-zone logs 329
9.5 Resistivity and conductivity logs 332
9.6 Porosity logs 335
9.7 Auxiliary logs and measurements 340
9.8 Basic log interpretation procedure 340
10 Miscellaneous methods and topics 342
10.1 Borehole magnetometer 342
10.2 Mise-a-la-masse method 342
10.3 Logging in crystalline rocks and coal fields 343
10.4 Geothermal methods 344
10.5 Geochemical prospecting 344
10.6 Optimum point and line spacing 345
10.7 Position location in airborne surveying 346
10.8 Composite surveys 347
viii Contents
Appendices 351
Appendix 1 The magnetic potential 351
Appendix 2 Magnetized sphere and a magnetic dipole 355
Appendix 3 Magnetic anomaly of a sphere 357
Appendix 4 Measurement of susceptibility and remanence 359
Appendix 5 Magnetic potential of a linear dipole and the anomalies
of thin and thick sheets 362
Appendix 6 Demagnetization 'factors' for a rectangular
parallelepi ped 367
Appendix 7 Electric potential 369
Appendix 8 Apparent resistivities for dipole-diople configurations 370
Appendix 9 Potential of a point current electrode on the surface of a
horizontally-layered earth 371
Appendix 10 Homogeneous, anisotropic earth (derivation
of Eq. (4.73» 374
Appendix 11 Single-turn loop and other topics in electromagnetic
methods 374
Appendix 12 Acoustic impedance 378
Appendix 13 Fourier transforms and convolution 379
References 383
Answers and hints 390
Index 393
Preface to the fourth edition
Anyone who compares the present thoroughly revised and enlarged edition
of this book with the three previous ones, the first of which was published in
1962, may well ask whether the principles of applied geophysics have become
more numerous during the last 25 years or so. Such is not the case and the
much larger size of the present edition is due to the principles' having been
explained in greater detail than heretofore. There are major and minor
alterations, additions and emendations, too numerous to be listed here,
throughout the book but I would like to draw attention specifically to some
of them.
The chapter on seismic methods is now far more extensive than before and
so are also the chapters on electric and electromagnetic methods. There is also
a separate chapter on well logging in oil fields giving the essential ideas.
Considering the virtual plethora of available books on seismic methods and
on well logging I have not thought it necessary to extend these chapters
further. This has enabled me to keep the book to a reasonable length and at the
same time retain its fairly comprehensive character. Other features of the
present edition are solved examples in the text and the problems at the end of
all principal chapters. Answers and hints to the latter are given at the end of the
book. References (denoted in the text by numbers in square brackets) have
been brought up to date but most of the older ones have been purposely
retained in the belief that a true understanding of a subject is aided by a glance
at its history.
The emphasis is throughout on physical explanations and practical
geological applications. Algebraic details have been kept to a minimum in the
main text and even these may be skipped for the most part without loss of
continuity by readers interested mainly in the qualitative aspects ofthe various
methods. Those who may like to delve deeper into the underlying mathematics
will naturally turn to the appendices at the end of the book. However,
x Preface to the fourth edition
whatever the level of mathematical sophistication resorted to in geophysical
interpretation, the caution dealt in the preface to the first edition, that 'the
success of a geophysical survey depends almost entirely upon an intelligent
combination of physics and geology', applies as much today as it did 25 years
ago, notwithstanding (or rather because of) the progress in automatic
computer processing of geophysical data.
Like all the previous editions the present one contains many topics not to be
found in current texts in English devoted to the subject as a whole. Among
these may be mentioned a rigorous but simple, logical scheme (hitherto
unpublished as far as I know) for the complete determination of the
parameters of a thick sheet from its magnetic anomaly, rapid practical
procedures for calculating YES curves, Orellana's method of estimating the
longitudinal conductance of a stratified earth underlain by afinitely resistive
substratum, Lee's method for dipping discontinuities, design principles of
electromagnetic sensors, radioactive density determinations, statistical con
siderations in optimum line spacing and a number of others.
SI units are strictly adhered to except in nine figures reproduced from older
literature and left intact.
The chapter on seismic methods owes much to the notes of lectures
delivered at my department a few years ago by Dr Roy E. White of British
Petroleum, London. I am most grateful to him for allowing me to make liberal
use of these. Finally, my thanks are due to Irene Lundmark, Department of
Applied Geophysics, University of Luleii, for her very efficient help in the
intricate task of preparing the manuscript of this edition.
D.S. Parasnis
Lulea. Sweden
