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  • 1
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    Estimation of the primary seismic pulse (1974)
    In:  Geophys. Pros, Kunming, China, D. Reidel Publishing Company, vol. 22, no. 30, pp. 627-651, pp. L09303, (ISSN: 1340-4202)
    Details
    Publication Date: 1974
    Keywords: Inversion
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Model Seismology, Vol. 2, Data Processing and Interpretation (1971)
    Cambridge University Press
    In:  Cambridge, Cambridge University Press, vol. IUGG Volume 18, no. 85, pp. 175, (3-7723-6434-9)
    Details
    Publication Date: 1971
    Keywords: Seismics (controlled source seismology) ; Textbook of geophysics ; SEModelling ; Data analysis / ~ processing
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Seismic reflection interpretation (1985)
    Gebrüder Bornträger
    In:  Bull., Polar Proj. OP-O3A4, Geoexploration Monographs, Berlin, Gebrüder Bornträger, vol. 14, no. XVI:, pp. 95-104, (ISBN: 3-540-23712-7)
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    Publication Date: 1985
    Keywords: Seismics (controlled source seismology) ; Reflection seismics ; Review article
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
    Electronic Resource
    Electronic Resource
    Absorption and Dispersion of Elastic Energy in Rocks (1962)
    [s.l.] : Nature Publishing Group
    Nature 193 (1962), S. 764-765 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Absorption and dispersion in a single rock sample have usually been measured at frequencies higher than those observed in seismology and over a range of only one or two decades1'2. Because different samples measured over different frequency ranges generally show a constant Q and constant moduli, it ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/193764a0
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  • 5
    Electronic Resource
    Electronic Resource
    VELOCITY DISPERSION OF SEISMIC WAVES (1971)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 19 (1971), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: In well velocity surveys made to calibrate Sonic (CV) Logs the calibration survey uses frequencies around 50 Hz whereas the Sonic Logging tool uses frequencies around 20 kHz. There thus exists the possibility of making a direct measure of velocity dispersion. In any one survey the disturbing factors, both instrumental and operational, will often mask any dispersive effect that might exist. Consequently this paper reports on a statistical analysis of the velocity differences resulting from calibration surveys and Sonic logs. Only Borehole Compensated Sonic Logs were used. Four areas were investigated: the North Sea, Abu Dhabi, Libya and Alaska. After rejecting logs and calibration records which were obviously in error there remained 424000 feet (about 130 km) of usable log distributed throughout 66 wells. The four areas were analysed separately and in no case was the estimated dispersion significantly different from zero. However, the mean values did correlate with lithology from (− 0.17 ± 0.18)% for the essentially carbonate section in Abu Dhabi to (+ 0.45 ± 0.25)% for the sand-shale section in Alaska, a positive sign meaning that the higher frequencies travelled faster. Except for Alaska the calibration surveys were made with a wall-clamp geophone, and for these areas amplitude measurements were made. After suitable corrections estimates of the absorption parameter Q were obtained. These varied from 20 to 200 with mean values of 63 for Libya, 70 for Abu Dhabi and 88 for the North Sea (excluding the Tertiary). If, as is usually assumed, the absorption mechanism is linear and is described by a Q which is independent of frequency, then these values would necessarily imply dispersion of several percent. As instanced above no such dispersion was observed. It is possible that the expected dispersion was compensated for by invasion of the mud filtrate into the borehole walls, but it is more likely that the absorption mechanism was substantially non-linear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1971.tb00583.x
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  • 6
    Electronic Resource
    Electronic Resource
    A DISCUSSION ON THE NATURE AND MAGNITUDE OF ELASTIC ABSORBTION IN SEISMIC PROSPECTING (1961)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 9 (1961), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Laboratory measurements indicate that seismic absorbtion in sedimentary rocks lies in the range 0.1 to 1.0 decibel per wavelength. Field measurements on the amplitude attenuation of direct, reflected and refracted pulses give values consistent with this.If the absorption is linear, dispersion must occur. If it occurs field measurements show that it must be less than 1% over the frequency range 20 c/s to 20 kc/s.Seismic pulses broaden so slowly with distance that, if the absorbtion is linear it must be less than that measured in the laboratory by a factor of at least ten. This is inconsistent with the amplitude measurements and would mean that emplaced rocks are more perfectly elastic than steel.Seismic absorbtion must therefore be non-linear. It is assumed that, for large values of Q, the non-linear equation of motion may be linearised (Knopoff and MacDonald, 1958) and Fourier synthesis used. If this is valid, then the attenuation per unit distance must be practically independent of frequency and dispersion must be negligible.Whatever mechanism is acting it must produce an attenuation of roughly one decibel per 1000 feet and a pulse broadening of about 1–2% in the same distance.It is extremely desirable to make more field and laboratory experiments to determine the physical mechanism by which absorbtion takes place.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1961.tb01510.x
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  • 7
    Electronic Resource
    Electronic Resource
    THE VARIATION WITH DISTANCE OF THE AMPLITUDE OF CRITICALLY REFRACTED WAVES ) (1957)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 5 (1957), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Amplitude measurements have been made of the height of the first peak of an arrival refracted from a shallow refractor. If the amplitude is assumed to decay as the inverse mth power of the distance, the least squares value for m is found to be 2.16 ± .04. Because of this value and because of the character of the recorded event it is concluded that the arrival is a simple critical refraction. After applying the theoretical ‘spread’ factor for critical refraction there remains a residual attenuation of 1.96 ± 0.28 decibels per 1000 feet. The predominant frequency in the pulse is about 20 c.p.s. and this attenuation agrees with the losses found for such a frequency by extrapolation of the published results of other workers. Although no evidence could be seen on the records for a change of pulse frequency with distance, the quoted result would be consistent with a dependence of residual attenuation on the first power of the frequency, and would be inconsistent with a dependence on the second power of the frequency.It is concluded that studies of the amplitudes of refracted events will give useful estimates of the attenuation factors of rocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1957.tb01435.x
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  • 8
    Electronic Resource
    Electronic Resource
    PRESIDENTIAL ADDRESS (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 26 (1978), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1978.tb01610.x
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  • 9
    Electronic Resource
    Electronic Resource
    ESTIMATION OF THE PRIMARY SEISMIC PULSE (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 22 (1974), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: A seismic trace after application of suitable amplitude recovery may be treated as a stationary time-series. Such a trace, or a portion of it, is modelled by the expression 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR627:GPR_627_mu1"/〉 where j represents trace number on the record, t is time, αj is a time delay, α (t) is the seismic wavelet, s(t) is the reflection impulse response of the ground and nj is uncorrelated noise. With the common assumption that s(t) is white, random, and stationary, estimates of the energy spectrum (or auto-correlation function) of the pulse α(t) are obtained by statistical analysis of the multitrace record. The time-domain pulse itself is then reconstituted under the assumption of minimum-phase. Three techniques for obtaining the phase spectrum have been evaluated: (A) use of the Hilbert transform, (B) Use of the z-transform, (C) a fast method based on inverting the least-squares inverse of the wavelets, i.e. inverting the normal time-domain deconvolution operator. Problems associated with these three methods are most acute when the z-transform of α(t) has zeroes on or near the unit circle. Such zeroes result from oversampling or from highly resonant wavelets. The behaviour of the three methods when the energy spectra are perturbed by measurement errors is studied. It is concluded that method (A) is the best of the three. Examples of reconstituted pulses are given which illustrate the variability from trace-to-trace, from shot-to-shot, and from one shot-point medium to another. There is reasonable agreement between the minimum-phase pulses obtained by this statistical analysis of operational records and those estimated from measurements close to the source. However, this comparison incorporates a “fudge-factor” since an allowance for absorption has to be made in order to attenuate the high frequencies present in the pulse measured close to the shot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1974.tb00108.x
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  • 10
    Electronic Resource
    Electronic Resource
    A NOTE ON THE REFLECTION OF SEISMIC PULSES WITH APPLICATION TO SECOND EVENT REFRACTION SHOOTING (1963)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 11 (1963), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Richards (1961) and several others have shown that wide angle reflections may attain large amplitudes. This note extends the plane wave calculations of Richards to include the effect of the phase changes which occur at angles greater than critical. On seismic pulses this introduces a time lead of up to one half period and alters peak-to-peak amplitudes by up to 15-20 %.It is pointed out that the plane wave reflection coefficient is not applicable at angles very close to critical where the true reflection coefficient is reduced by a factor depending on (R/λ) ¼ In ultrasonic experiments this factor reduced the reflection coefficient by between ½ and ⅓.Neither does the plane wave coefficient apply at grazing incidence, when it has to be reduced by a factor depending on (R/λ)1-0.Graphs are given of the amplitudes of wide angle reflections and head waves for two cases and it is concluded that, except for shallow refractors and angles close to critical, the reflection is always significantly greater than the head wave.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1963.tb02025.x
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