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Introduction to digital filtering in geophysics. Developments in solid earth geophysics, 8
Physics of the Earth and Planetary Interiors, 16(1978) 393 © Elsevjer Scientific Publishing Company, Amsterdam
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393
Printed in The Netherlands
BOOK REVIEW Introduction to Digital Filtering in Geophysics. Developments in Solid Earth Geophysics, 8. 0.
Kulhánek. Elsevier Scientific Publishing Company, Amsterdam—Oxford--New York, N.Y., 1976, 168 pp., Dfl. 60. 00/US $ 23.95. This book addresses one of the data analyses techniques of great importance in geophysical research today. The expansion of the number of geophysical observing stations (recording, for example, seismic waves, magnetic field variations, and atmospheric parameters) made chart recording an unsatisfactory means of acquiring and analyzing large amounts of such data. Kilometers of analog chart records are, of course, incompatible with sophisticated digital cornputation systems. In the past, the construction of sophisticated digitizing machines permitted the production of digital time series of the chart records. However, initial digital acquisition of the data, in a computer-compatible format, is most desired. The field of seismology has probably been the most progressive in instituting the digital acquisition of timeseries data. The combination of such digital data with large computing facilities allows the implementation of many new analysis and interpretation techniques. More recently, other areas of geophysics, including geomagnetism and ionospheric studies have adapted techniques from the space program and have begun to implement digital, computer-compatible techniques for the acquisition of data. For the first time, large amounts of data can be manipulated and signals separated from the noise on a routine basis. This book, in essence, discusses the use of digital filtering on geophysical data to separate wanted signals from unwanted noise and wanted signals in certain frequency regimes from unwanted signals in other frequency regimes. These techniques are necessary in a wide range of geophysical research problems. The background and interests of the author are stressed, in that most of the applications that are
discussed in detail are devoted to seismological problems. However, the author is careful to frequently point out that the techniques under discussion are quite applicable to other branches of geophysics, including gravity, geomagnetism, and ionospheric studies. For students just entering a specific field of geophysics,however, it would be more comforting to have a wider variety of examples from a wider range of fields. From a filtering viewpoint the book is good and could be recommended in areas other than geophysics. The use of extensive references provides both a broad historical perspective and also allows the author to concentrate on the main topics without having the presentation continuously interrupted by the introduction of details which are available in the literature. The emphasis in the book is more on specific techniques and examples rather than on broad principles and, as such, it is well complimented by the Kailath (1974) review paper. The filter methods presented are more applicable for use on large general purpose computers than on the special purpose hardware that is becoming more prevalent. Thus, discussions of analysis problems resulting from roundoff, etc., are brief. The main weakness of the book is perhaps that it is too classical and omits discussion of ladder forms and similar topics used in modern filtering computations. Also, the book is in a sense incomplete in that it omits discussion of the discrete Fourier transform, the fast Fourier transformalgorithm, and computational procedures derived from them. For those having a need for them these techniques will have to be obtained from other reference sources. Reference Kailath, T., 1974. A view of three decades on linear filtering theory. I.E.E.E. Trans. ml. Theory, 20: 146—180. D.J. THOMSON (Whippany, NJ.) U. LANZEROTTI (Murray Hill, NJ.)
—
393
Printed in The Netherlands
BOOK REVIEW Introduction to Digital Filtering in Geophysics. Developments in Solid Earth Geophysics, 8. 0.
Kulhánek. Elsevier Scientific Publishing Company, Amsterdam—Oxford--New York, N.Y., 1976, 168 pp., Dfl. 60. 00/US $ 23.95. This book addresses one of the data analyses techniques of great importance in geophysical research today. The expansion of the number of geophysical observing stations (recording, for example, seismic waves, magnetic field variations, and atmospheric parameters) made chart recording an unsatisfactory means of acquiring and analyzing large amounts of such data. Kilometers of analog chart records are, of course, incompatible with sophisticated digital cornputation systems. In the past, the construction of sophisticated digitizing machines permitted the production of digital time series of the chart records. However, initial digital acquisition of the data, in a computer-compatible format, is most desired. The field of seismology has probably been the most progressive in instituting the digital acquisition of timeseries data. The combination of such digital data with large computing facilities allows the implementation of many new analysis and interpretation techniques. More recently, other areas of geophysics, including geomagnetism and ionospheric studies have adapted techniques from the space program and have begun to implement digital, computer-compatible techniques for the acquisition of data. For the first time, large amounts of data can be manipulated and signals separated from the noise on a routine basis. This book, in essence, discusses the use of digital filtering on geophysical data to separate wanted signals from unwanted noise and wanted signals in certain frequency regimes from unwanted signals in other frequency regimes. These techniques are necessary in a wide range of geophysical research problems. The background and interests of the author are stressed, in that most of the applications that are
discussed in detail are devoted to seismological problems. However, the author is careful to frequently point out that the techniques under discussion are quite applicable to other branches of geophysics, including gravity, geomagnetism, and ionospheric studies. For students just entering a specific field of geophysics,however, it would be more comforting to have a wider variety of examples from a wider range of fields. From a filtering viewpoint the book is good and could be recommended in areas other than geophysics. The use of extensive references provides both a broad historical perspective and also allows the author to concentrate on the main topics without having the presentation continuously interrupted by the introduction of details which are available in the literature. The emphasis in the book is more on specific techniques and examples rather than on broad principles and, as such, it is well complimented by the Kailath (1974) review paper. The filter methods presented are more applicable for use on large general purpose computers than on the special purpose hardware that is becoming more prevalent. Thus, discussions of analysis problems resulting from roundoff, etc., are brief. The main weakness of the book is perhaps that it is too classical and omits discussion of ladder forms and similar topics used in modern filtering computations. Also, the book is in a sense incomplete in that it omits discussion of the discrete Fourier transform, the fast Fourier transformalgorithm, and computational procedures derived from them. For those having a need for them these techniques will have to be obtained from other reference sources. Reference Kailath, T., 1974. A view of three decades on linear filtering theory. I.E.E.E. Trans. ml. Theory, 20: 146—180. D.J. THOMSON (Whippany, NJ.) U. LANZEROTTI (Murray Hill, NJ.)