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- Volume 10, Issue 4, 1962
Geophysical Prospecting - Volume 10, Issue 4, 1962
Volume 10, Issue 4, 1962
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TOOLS FOR TOMORROW'S GEOPHYSICS *
Authors MILTON B. DOBRIN and STANLEY H. WARDAbstractThe introduction of methods for recording and processing field data in digital form on magnetic tape for subsequent processing on electronic computers will result in major improvements in geophysical prospecting techniques. This offers great advantages over analogue recording such as increased dynamic range, greater filter flexibility, more convenience in processing by correlation techniques, freedom from distortion and noise, better adaptability to automatic plotting and contouring, and greater suitability for inverse convolution procedures. Digitally recorded seismic signals can be reliably transmitted long distances by telephone circuits to central data processing centers. Electronic computers facilitate processing of gravity, magnetic, and other potential field data. Smoothing, residual, correlation, and derivative techniques for handling data in digital form can enhance speed and flexibility of processing.
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CONTRIBUTION A L'ETUDE DE LA DEFORMATION DU SIGNAL SISMIQUE. ANALOGIES. FILTRAGE EQUIVALENT *
By J. CHAUVEAUAbstractThis paper begins with a synthesis of previous studies on the deformation of a seismic signal due to its propagation in surface layers and enterface zones and to reverberations in a layer of water. We show how a suitable analog model enables us to derive directly the reflections and transmissions of a non‐uniform‐velocity layer. The results are compared with the exact solutions of the equations of propagation and with the solutions resulting from a sampling of the velocity distribution in the layer. The filters equivalent to propagation and sampling are deduced from these comparisons.
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EXPERIENCE WITH THE REFLECTION SEISMOGRAPH IN A MINE WITHIN A SALT‐PLUG *
Authors GÜNTHER WACHSMUTH and EDGAR SCHMIDTAbstractTechnical development and the introduction of new construction procedures has increased the number of seismic surveys carried out underground. Interesting seismic records in three components are shown and discussed. A vertical section containing results of seismic research investigations and of drilling is shown.
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LA “COUPE SISMIQUE VECTORIELLE”*
Authors CLAUDE PICOU and RENE UTZMANNAbstractThe coefficient of resemblance is defined in the following way:
Consider a group of four traces on a seismic record. For a given time t add the six products that can be formed by multiplication of the signal strengths recorded on two of these four traces. By doing this for all values of t, a new signal is obtained that can be smoothed by having it pass through an appropriate filter. The result of this smoothing procedure is called the smoothed coefficient of resemblance Γ.
Instead of multiplying the signals of two traces at the same time t, the signal of the first trace can be taken at time t‐3θ/2, of the second trace at t‐θ/2, of the third trace at t+θ/2 and finally of the fourth trace at t+ 3θ/2. Thus coefficients of resemblance are obtained that depend on the dip θ.
For each value of θ a plotting system is triggered when Γ has a maximum with respect to time. Then a vector is plotted having a thickness proportional to Γ and a dip determined by θ. If no optical mixing takes place, the vector covers just one trace of the new vectorial registration; in case of optical mixing the vector covers a number of these traces. All vectors belonging to a certain group of traces of the seismic record appear on one trace of the vectorial presentation, so one trace includes all values of θ.
Alternatively the plotting can be triggered when the corresponding sum of the signals of the four traces passes through a maximum. In this latter case the triggering can be conditioned by the maxima of Γ.
The article discusses the influence of:
— the optical mixing,
— the integration time determined by the band width of the smoothing filter,
— the method of triggering,
— the way the seismic traces that have to form a group are selected (electrical mixing).
A consequence of the method is that both phase alignments and energy bursts have an influence on the vectorial registration.
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REFLECTION AND REFRACTION OF SPHERICAL COMPRESSIONAL WAVES AT ARBITRARY PLANE INTERFACES *
By R. BORTFELDAbstractThe exact expressions for the reflection and refraction of homogeneous spherical compressional waves at the plane contact between two semi‐infinite media are obtained by a new simple method. Whilst its general ideas were outlined in a previous paper (Bortfeld 1962) dealing with some special interfaces, this method is now applied to all kinds of contact (solid‐solid, solid‐fluid, fluid‐solid, solid‐free, fluid‐fluid, fluid‐free). By some improvements, the treatment of the general case is even more simple than the previous one of the special cases.
Integrating the potentials for sinusoidal excitation over the circular frequency and adding the static potentials yields expressions for the step‐response which consist of (infinite) single integrals of elementary functions. By a single application of Cauchy's theorem, the complete set of wavefronts is obtained and the step‐response is put into forms suitable as a basis for numerical calculations. The responses for arbitrary source excitations are given in the usual way by superposition integrals.
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MESURES D'AMPLITUDE DANS LES SONDAGES: LE LOG D'ATTENUATION *
Authors J. MORLET and T. SCHWAETZERAbstractAmong the different factors that affect the amplitude of the acoustic signals measured by continous velocity logs (“V logs”) in bore holes, the coefficient of attenuation appears to be of considerable interest in the determination of some of the mechanical qualities of the formations. In particular, the attenuation seems to relate to the continuity of the matrix, thus, to a certain extent, to the permeability.
In order to eliminate the secondary factors affecting the amplitudes (such as variations of the velocity) we have found it necessary to measure the ratio of the amplitudes logged at the first and second receiver of the C.V.L. The “continous attenuation logger” developed by the C.E.P. allows us to make a continous measurement not only of the amplitudes of the first arrivals at the two receivers, but also directly of the ratio of these amplitudes.
We present here the first results obtained by the continous attenuation log (C.A.L.) in different types of formations. Comparisons are made with Velocity, Electric and Radioactivity logs.
The Continous Attenuation Log correlates well with the lithology and, in particular, gives a very good localisation of fractured and permeable zones. Although we have, as yet, but little experience with this new type of log, it seems that the first results obtained are quite promising.
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BOOK REVIEWS
Book reviews in this article
G. H. Darwin, The Tides, and Kindred Phenomena in the Solar System
L. Cagniard, Reflection and Refraction of Progressive Seismic Waves, Translated and revised by Edward A. Flinn and C. Hewitt Dix
A. V. H. Masket and William C. Rodgers, Tables of Solid Angles
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Volumes & issues
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Volume 72 (2023 - 2024)
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Volume 70 (2021 - 2022)
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Volume 69 (2021)
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Volume 65 (2017)
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Volume 64 (2015 - 2016)
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Volume 63 (2015)
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Volume 62 (2014)
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Volume 61 (2013)
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Volume 60 (2012)
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Volume 59 (2011)
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Volume 58 (2010)
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Volume 57 (2009)
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Volume 56 (2008)
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Volume 55 (2007)
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Volume 54 (2006)
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Volume 53 (2005)
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Volume 52 (2004)
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Volume 51 (2003)
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Volume 50 (2002)
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Volume 49 (2001)
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Volume 48 (2000)
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Volume 47 (1999)
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Volume 46 (1998)
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Volume 45 (1997)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1994)
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Volume 41 (1993)
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Volume 40 (1992)
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Volume 39 (1991)
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Volume 38 (1990)
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Volume 37 (1989)
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Volume 36 (1988)
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Volume 35 (1987)
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Volume 34 (1986)
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Volume 33 (1985)
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Volume 32 (1984)
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Volume 31 (1983)
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Volume 30 (1982)
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Volume 29 (1981)
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Volume 28 (1980)
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Volume 27 (1979)
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Volume 26 (1978)
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Volume 25 (1977)
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Volume 24 (1976)
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Volume 23 (1975)
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Volume 22 (1974)
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Volume 21 (1973)
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Volume 20 (1972)
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Volume 19 (1971)
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Volume 18 (1970)
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Volume 17 (1969)
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Volume 16 (1968)
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Volume 15 (1967)
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Volume 14 (1966)
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Volume 13 (1965)
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Volume 12 (1964)
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Volume 11 (1963)
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Volume 10 (1962)
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Volume 9 (1961)
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Volume 8 (1960)
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Volume 7 (1959)
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Volume 6 (1958)
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Volume 5 (1957)
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Volume 4 (1956)
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Volume 3 (1955)
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Volume 2 (1954)
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Volume 1 (1953)