Advances In Geophysical Data Processing: Vertical Seismic Profiles

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Book reviews

The materiai, new in 1963, on underground nuclear explosions and extra-terrestrial seismology have been much reduced. On the other hand, the sections on earthquake statistics and prediction have been greatly extended and a new chapter on strong-motion seismology introduced, all of this in line with progress and change of emphasis in the world of seismology. One further welcome introduction has been a selection of exercises at the end of most chapters. There is of course some considerable competition for this book on its fourth appearance, both in the area of seismology and in elastodynamics. However, I feel confident that it will maintain its reputation. J. A. HUDSON,DAMTP, Cambridge

Advances in Geophysical Data Processing:Vertical Seismic Profiles Marwan Simaan (ed.), JAIPress, Greenwich, USA, 1984

$57.50 (institutions), $28.75 (individuals) This is the first in a series of annual research monographs under the general title of ‘Advances in Geophysical Data Processing’. The first volume published in 1984 by JAI Press, Inc. under the editorship of Marwan Simaan is subtitled ‘Vertical Seismic Profiles’. It contains nine chapters contributed by a total of 1 4 authors. Vertical Seismic Profile (VSP) has now become a generic name applied to seismic data sets recorded with a vertical or near vertical distribution of seismic sensors (or equivalently but less commonly, a vertical array of sources). Although the Russians have used VSPs for a t least 30 years, only in the last decade has the technique been widely used in the West. At the recent annual meeting of the Society of Exploration Geophysicists (1985 October, Washington, DC) three sessions were devoted to VSP and a total of over 20 papers presented on VSP case-studies, processing, interpretation. etc. The optic of this volume is thus both timely and inevitably over-ambitious. The subject is developing and expanding too fast to expect a comprehensive or definitive monograph and some articles will already appear dated. The short introductory chapter by P. C. Wuenschel entitled ‘Vertical seismic profiling: the future’ becomes as much a useful review of the present a s a view of the future. The vertical distribution of seismic sensors in approximately the direction of wave propagation introduces new processing requirements and advantages. Compared with conventional reflection seismology, both up- and downgoing wavetrains are recorded. Identification of upand downgoing waves and multiples is facilitated and velocity filtering is particularly effective. Two articles in this volume are devoted to the processing of VSP data. M. W. Lee discusses the processing of near-offset and far-offset VSP data. Compared with conventional processing, two new features are particularly important. Multichannel velocity filtering is used to separate the up- and downgoing waves. For far-offset data, the dynamic time correction is more complicated as the geometry of up- and downgoing waves is different. Lee introduces this complex subject and gives some simple examples. Already, since the publication of this monograph, the rewards from far-offset VSP have been great in exploring subtle and complex stratigraphical features around wells. In a second chapter about processing, J. W. Wiggins and A. R. Levander investigate migration of multiple offset synthetic VSP data in complex structures. Not surprisingly, they find that the success of the migration depends strongly on the geometries of the survey and structure. The extra control available in VSP data make them ideal for studying attenuation. Three

Book reviews 217 of the chapters discuss different aspects of this problem. D. Moos presents an interesting case study of VSP in fractured crystalline rock. The importance of both scattering and anelasticity is emphasized. M. Simaan and P. L. Love discuss the synthesis of VSP including the effects of absorption, dispersion and frequency-dependent reflection coefficients. E. Strick in a significant chapter occupying almost a third of the book provides a thorough review of anelasticity and P-wave distortion. In comparing well log sonic data and VSPs it is essential that dispersion and distortion are accounted for properly. In this excellent article, Strick considers the various mathematical models for attenuation and dispersion and compares the predicted waveforms with observations. It might be argued that too much emphasis is placed on analytic models. Mathematical methods and final results are often sensitive to analytic details not necessarily required by the data nor predicted by physics. Perhaps a more general, numerical approach would be preferable and more flexible as available data expand. Nevertheless, this article is to be highly recommended. Three chapters in the book consider synthetic VSP data. The article by Simaan and Love in which the normal recursive transfer model is used connecting up- and downgoing wave in successive layers, has already been mentioned. J. M. Mendel extends this method using the so-called ‘state variable’ models. The Bremmer series decomposition is used to separate primaries and multiple seismograms. These two chapters are restricted to plane wave seismograms. In the other chapter on modelling, D. Khosla and G . H. F. Gardner use both scale laboratory models and finite difference solutions to model realistic structures. Unfortunately, the book contains no mention of modelling techniques intermediate between plane wave and finite difference methods. The final chapter of the book by E. R. Kanasewich, D. Bingham and C. Gold is outside the main scope of the book as its title suggests: ‘Continuous monitoring of rnicrotremors using a digital seismic nrray’. mis book natLlraily suffers fronl the rapid growth of its subject. The main emphasis is on near-offset VSP data while many recent developments have been with far-offset and hole-tohole tomography. Most seismologists will be happy to use library copies of this book rather than buy their own. Nevertheless, much is useful as introductory reading for VSP techniques and the chapter by E. Strick is highly recommended.

C . H. CHAPMAN, Bullard Laboratories, Cambridge

Imaging the Earth‘s Interior J . F. Claerbout, Blackwell Scientific Publications, Oxford, I 9 8 5 4!4pp., E42.00

Fundamentals of Geophysical Data Processing, 2nd e dn J . F. Claerbout, Blackwell Scientific Publications, OxJi,rd, I985 274 pp., .~ 242.00 The interpretative techniques that are being used in the seismic exploration industry have changed considerably in the past, and continue t o d o so a t present. A major breakthrough occurred around 1970 when Claerbout introduced wavc equation migration with finite difference met.hods, soon to he followed by Kirchhoff summation and a variety of methods,