Geoexploration, 14 (1976) 151-154 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

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Book Reviews

Spectral Analysis in Geophysics. Marcus Bith. Elsevier, Amsterdam, 1974, 563 pp., U.S.$46.50.

This is an introductory text book which could be used at an undergraduate level by any student with a background course in integral calculus. Much of the mathematical background is developed in a selfcontained presentation. The book’s major asset is the large number of detailed examples discussed in chapters 7 to 9. Including all chapters, over half the book is devoted to a discussion of actual geophysical case histories. As a consequence, the list of references is the most comprehensive one that is available for papers up to about 1972 and a part of 1973. The emphasis is on pure geophysics and very little is included on exploration geophysics.

The first two chapters are introductory with Chapter 2 being a review of Fourier series and transforms. Autocorrelation and power spectra are intro- duced in Chapter 3. The maximum entropy and maximum likelihood spectral methods are mentioned in a few lines at several points in the book. Errors in digitization as well as techniques and reliability of spectral estimates are dis- cussed thoroughly in chapters 4 and 5. The treatment on filtering in Chapter 6 is disappointing since it is brief and with very little assistance to the novice in setting up algorithms.

The second half of the book is a comprehensive discussion on the applica- tion of spectral studies to geophysics. There are abundant examples from geomagnetism, gravity, oceanography and seismology. This portion of the book will be of benefit to interpreters of geophysical data who wish to examine the range of problems which may be undertaken by transforming into the frequency or wave number domain.

In summary, this book gives a sound background on various phases of time series analysis as applied to pure geophysics. The author does not treat the material in depth nor does he give comprehensive details on writing computer algorithms. The book is well illustrated with diagrams and tables and the bibliography is excellent.

E.R. KANASEWICH (Edmonton, Alta.)

Applied Geophysics - Introduction to Geophysical Prospecting. Gerhard Dohr. Ferdinand Enke Verlag, Stuttgart, 1974, 272 pp., DM 16.80.

This book is the first of a series, under the general editorial direction of Prof. Heinz Beckmann, on the Geology of Petroleum. The book is a transla- tion of the original German text. The translator is G.H. Kirby. In Applied Geophysics, Dohr sets out to provide in one convenient volume, a contempo-

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rary account of the geophysical methods that are used in the search for petroleum oil. The book does not adopt an historical approach to the subject. Dohr does not include methods solely on their former or historical impor- tance. Consequently, a useful account of contemporary applied geophysical practice used in the search for petroleum oil has been presented within the 272 pages of one book.

With this approach in mind, it is obvious that half of the book will deal with seismic reflection, and a substantial proportion of this will deal with digital data processing. However, let us look at the organization of the book!

Chapter 1 (pp. I-14) skims over the various geophysical methods which can give information about the terrestrial environment and in particular the basic types of seismic waves.

Chapter 2 (pp. 15-45) discusses refraction seismics in a way similar to that in the usual undergraduate text-book on refraction seismology.

In Chapter 3 (pp. 46-103) we find the main thrust of the book. Reflec- tion coefficients are discussed8 and their relationship to the recorded monitor record provides an engaging introduction to the chapter. The effect of depth and dip on the record is clearly presented with self-explanatory diagrams. The problems associated with uncertainties in the velocities of the layers are pointed out and the methods of determining the velocities are given. Like- wise the corrections to the seismic traces are discussed. The problem of mul- tiples and ghosting are explained and the effect on the record given. The ef- fect on the seismic record of faulting of the layers is presented. The chapter is concluded with a qualitative discussion of filtering and multiple coverage possible with magnetic recording, and the advantages provided by play-back followed by digital processing.

Chapter 4 (pp. 104-154) was a disappointment. It dealt in too much detail with the internal workings of a digital computer - ferrite cores, number sys- tems, storage devices and programming languages. It was very superficial in its discussion of sampling, cross- and auto-correlation and deconvolution. If the reader was not familiar with these operations before reading the book, he would come away with the feeling that they were magical processes whereby poor reflections are inexplicably enhanced.

Chapter 5 (pp. 155-161) discusses the special procedures of offshore-work and Vibroseis and Dinoseis. There is a need in this chapter for references so that those who wish to read further about the methods, can do so. Chapter 6 (two pages, 162 and 163) has a few words to say about the make-up and jobs in a field party.

Chapter 7 (pp. 164-203) is devoted to the gravity method. If ound it inter- esting and concise, and graduate students commented favourably upon the number of diagrams and examples which illustrate the role of gravity work in a petroleum exploration programme. In this chapter, the variation of gravity with latitude is given. Instruments and gravity-reduction procedures are stan- dard. A short discussion on calculating gravity anomalies leads to the consider- ations involved in the interpretation of gravity data by automated processes

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(e.g. Linsser) and by the method of the second derivative. Chapter 8 (pp. 204-225) deals with magnetic methods. The introductory

section is not satisfactory. It is in c.g.s. units and there are errors in transla- tion. For example, “magnetic dipole moment” is called “magnetic momentum”.

Consider the following passage: “The magnetic momentum of the magnet. In a magnetic field this magnet with the momentum of M will be subjected to the force of:

F=c[HM] This vector equation means that the resulting force will stand at right angles to the direction of the vectors H and M, that means f will stand at right angles on the level that can be set by H and M.”

It is not only “not in English” but if one imagines what it is supposed to mean, then even that is scientifically incorrect.

On the positive side there are a number of maps of airborne magnetic results and profiles over type structures with a discussion of the qualitative interpretation of magnetic data in terms of geological basement.

Chapter 9 (pp. 226-248) has informative examples on geoelectrical meth- ods but it departs from the aim of the book to present geophysical methods for petroleum exploration. This chapter is a qualitative discussion of the general (water) applications of these methods. I feel that Chapter 10 (pp. 249-262) on well logging could have been expanded. This short chapter deals not only with the various electrical logs but also with seismic and syn- thetic seismograms. As a consequence it is both qualitative and short.

Finally there is Chapter 11 (pp. 263-267) which touches upon miscella- neous methods such as thermal, radio-active scintillometer and gas-probe analysis.

I feel that the book would have been more successful if it had been con- fined to its stated aim of applied geophysics in the search for petroleum. The scope of the chapters on seismic refraction (section 2), reflection (sections 3, 4, 5) were useful. Likewise, the chapters on gravity (section 7) and magnetic methods (section 8) as applied to oil exploration work could be read with profit. Basic theory given in Chapters 7 and 8 was poorly done. I feel that it would confuse the reader more than it would elucidate the subject. In general, the diagrams and examples are “good”. Readers may find this DM 16.80 book of value for the examples alone.

In looking at the book as a whole, there is much to criticize. There is the translation. The Preface begins with the quaint sentence: “This little book within the row of books concerning the geology of petrol will give a first over- look over the problems of applied geophysics.” Also in the Preface we find “differ to” instead of “differ from”. Three additional examples are to be found in the preface.

In the chapter on gravimetry there is the statement (p. 164): “We all know that objects fall to earth, that they will repose in fixed position on a table and the like; . . .” It is not English but, to be charitable, its meaning is not unknown.

However, on p. 165: “The power with which two masses will attract one

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another will be proportional to the given mass and conversely proportional to the square of distance.” Of course force not power was meant, and this is serious because both are precisely defined physical quantities not available for loose useage. Also, why is the future tense used and not the present? On the same page there is again, a “comparison to” instead of “with”.

On p. 100: instead of “voltage” the word “tension” has been used. Many readers will find it confusing. Likewise, to speak of “intrusive waves” instead of “transmitted waves” has confusing connotations.

On p. 179: “This correction takes care of gravity’s dependence on geographic parallel,” If the sentence is recast and “latitude” substituted for “parallel”, its meaning is clear. The spelling mistakes on the same page are obvious.

On p. 189, there is reference to “third derivation” and “higher derivations” whereas the “3rd derivative” and “higher derivatives” were meant. The erro- neous connotation associated with “derivation” is confusing.

The use (p. 207) of “momentum” for “moment” is also confusing. On p. 104: “Each and every, technical or scientific undertaking today has

no choice of getting around electronic data processing and solving its prob- lems through the means thus afforded.” This really says the opposite to what it is supposed to mean.

Page 105 has spelling mistakes. How critical should a reader be of non-English grammar, spelling mistakes

and elliptical expressions? We should be tolerant until a fog of uncertainty begins to creep into what we are reading.

In summary, this book could be read with profit by senior undergratuates or anyone already familiar with the subject matter. The examples are good. However, the book is not quantitative enough for someone wishing to go further in the subject. A severe oversight is the lack of references to impor- tant and very readable research papers to be found in journals such as Geo- physical Prospecting, Geoexploration, Geophysics etc. Apart from a few sec- tions, people unfamiliar with the subject matter would be well advised to start with another book.

RONALD GREEN (Armidale, N.S.W.)