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  • 1
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    Phase distortion due to absorption in seismograms and Vertical seismic profiling (1984)
    In:  Geophys. Prosp., Luxembourg, EGS-Gauthier-Villars, vol. 32, no. 2, pp. 406-424, pp. L23303
    Details
    Publication Date: 1984
    Keywords: Absorption ; Inelastic ; Seismics (controlled source seismology)
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Offset continuation of seismic sections (1982)
    In:  Geophys. Prospecting, Warszawa, Elsevier, vol. 30, no. 1, pp. 813-828, pp. 2091, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1982
    Keywords: Applied geophysics ; Seismics (controlled source seismology)
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
    Electronic Resource
    Electronic Resource
    REPLY TO COMMENT BY A. L. LUCAS (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 31 (1983), 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.1365-2478.1983.tb01091.x
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    OFFSET CONTINUATION OF SEISMIC SECTIONS (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 30 (1982), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Geometrical acoustic and wave theory lead to a second-order partial differential equation that links seismic sections with different offsets. In this equation a time-shift term appears that corresponds to normal moveout; a second term, dependent on offset and time only, corrects the moveout of dipping events.The zero-offset stacked section can thus be obtained by continuing the section with maximum offset towards zero, and stacking along the way the other common-offset sections.Without the correction for dip moveout, the spatial resolution of the section is noticeably impaired, thus limiting the advantages that could be obtained with expensive migration procedures. Trade-offs exist between multiplicity of coverage, spatial resolution, and signal-to-noise; in some cases the spatial resolution on the surface can be doubled and the aliasing noise averaged out.Velocity analyses carried out on data continued to zero offset show a better resolution and improved discrimination against multiples. For instance, sea-floor multiples always appear at water velocity, so that their removal is simplified.This offset continuation can be carried out either in the time-space domain or in the time-wave number domain. The methods are applied both to synthetic and real data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1982.tb01340.x
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    PHASE DISTORTION DUE TO ABSORPTION IN SEISMOGRAMS AND VSP (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 32 (1984), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Absorption of seismic energy in the earth reduces amplitudes and changes phases of the propagating seismic waves. Amplitudes are usually recovered according to an estimated exponential decay curve, while phase distortions are generally disregarded. Therefore, accurate processing of seismic data requires a careful investigation of the relationship between absorption and phases.In this paper a procedure is suggested to achieve this goal, and some related topics are worked out. A method is outlined for computing synthetic seismograms and vertical seismic profiles with phase distortion due to absorption.The algorithm works in the frequency domain, and it provides for absorption according to the usual model of exponential decay of amplitude with distance. The absorption coefficient is a linear function of frequency and is related to the quality factor Q of the rocks. Complex seismic velocities are introduced and minimum-phase delay due to absorption is assumed for all cases considered.Methods for estimating Q profiles from seismic well surveys and seismic data are described. Comparison between field and synthetic data shows the effectiveness and benefits of the procedure. Some applications of the method to phase distortion recovery and wavelet processing are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1984.tb01108.x
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  • 6
    Electronic Resource
    Electronic Resource
    A LINEAR MODEL FOR VELOCITY ANOMALIES (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 31 (1983), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Variations of seismic interval velocities within the cable length cause anomalies in the stacking velocity analyses. Utilizing the approximation of rectilinear ray propagation, i.e. supposing that the velocity changes cause time delays only, it is shown that the stacking velocity anomalies are linearly related to the interval velocity variations. In particular, the stacking velocity anomaly is calculated when the interval velocity of an intermediate layer undergoes a stepwise variation. The amplitude of the anomaly increases with the ratio between horizon depth and cable length.From the forward model, a program for the inversion is derived in order to identify lateral changes of interval velocities from unsmoothed stacking velocity analyses.Some examples of the application of this technique to synthetic and real data are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1983.tb01044.x
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    OFFSET CONTINUATION IN THEORY AND PRACTICE (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 32 (1984), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Offset continuation is a technique that was recently proposed for the dip moveout correction. This correction can be carried out in the time-wavenumber domain using a proper partial differential equation that links sections with different offset.It has been shown that a single spike in a common-offset section—corresponds to a semi-elliptically shaped reflector with foci located at the source and receiver in the section migrated after dip moveout correction.The sections that result after offset continuation, stack, and migration are thus a superposition not only of semicircles, but also of semi-ellipses with different lengths of axes. This effect smears the migration alias-noise which, without offset continuation, would appear as migration circles not close enough together to interfere destructively.Offset continuation can improve the quality of seismic sections in several ways:—the velocity analyses are more readable, less dispersed and dip independent; diffraction tails arrive with the same normal moveout velocity as the apex and thus diffraction-noise can be “stacked out”;—noise produced by aliasing in the migrated section is reduced.In this paper we give a practical and conceptual interpretation of the offset continuation method, with a generalization to three-dimensional volumes of data. A critical examination of several synthetic and field data examples shows the actual possibilities and advantages of offset continuation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1984.tb00754.x
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  • 8
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    A finite element approach to a quasi-variational inequality (1980)
    Springer
    Details
    Publication Date: 1980-09-01
    Print ISSN: 0008-0624
    Electronic ISSN: 1126-5434
    Topics: Mathematics
    Published by Springer
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    PAPER CURRENT
  • 9
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    Sur L'approximation d'une I. Q. V. Liee a des Problemes D'infiltration en Milieu Poreux (1982)
    Springer
    Details
    Publication Date: 1982-06-01
    Print ISSN: 0008-0624
    Electronic ISSN: 1126-5434
    Topics: Mathematics
    Published by Springer
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    PAPER CURRENT
  • 10
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    The cross‐shooting methodology: Design, acquisition, and processing (1998)
    Society of Exploration Geophysicists
    Details
    Publication Date: 1998-11-01
    Print ISSN: 1070-485X
    Electronic ISSN: 1938-3789
    Topics: Geosciences
    Published by Society of Exploration Geophysicists
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