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  • 1
    In: Geophysical Prospecting, Wiley, Vol. 60, No. 5 ( 2012-09), p. 855-869
    Type of Medium: Online Resource
    ISSN: 0016-8025
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 2020311-1
    detail.hit.zdb_id: 799178-2
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 2008
    In:  GEOPHYSICS Vol. 73, No. 3 ( 2008-05), p. Q19-Q27
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 73, No. 3 ( 2008-05), p. Q19-Q27
    Abstract: A time-coded sequence of source pulses has been designed to allow for increased range to the target and reduced side-lobe energy with correlation. The method was designed for a new type of marine-combustion seismic source that can be fired repeatedly, but the method also can be applied to other acoustic-pulsed sources. The basic concept is that one can reduce autocorrelation side lobes by using semiperiodic sequences to concentrate much of the side-lobe noise into time intervals corresponding to the semiperiod. Signals can then be detected with better sensitivity in the time interval after the first autocorrelation peak and before the first periodic side lobe, because this interval contains only lower-level crosscorrelations between the sequence components. Compared with a source which fires pulses randomly, an 8-dB reduction of autocorrelation side lobes has been simulated for sequences of [Formula: see text] duration.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2008
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    Elsevier BV ; 1995
    In:  Journal of Applied Geophysics Vol. 34, No. 2 ( 1995-12), p. 142-143
    In: Journal of Applied Geophysics, Elsevier BV, Vol. 34, No. 2 ( 1995-12), p. 142-143
    Type of Medium: Online Resource
    ISSN: 0926-9851
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 1995
    detail.hit.zdb_id: 1496997-X
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Elsevier BV ; 2009
    In:  Journal of Applied Geophysics Vol. 67, No. 1 ( 2009-1), p. 66-73
    In: Journal of Applied Geophysics, Elsevier BV, Vol. 67, No. 1 ( 2009-1), p. 66-73
    Type of Medium: Online Resource
    ISSN: 0926-9851
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2009
    detail.hit.zdb_id: 1496997-X
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 2012
    In:  GEOPHYSICS Vol. 77, No. 6 ( 2012-11-01), p. T211-T220
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 77, No. 6 ( 2012-11-01), p. T211-T220
    Abstract: Seismic experiments in which the number of sources is considerably larger than the number of receivers occur regularly. An important example is the collection of crustal scale seismic data using ocean bottom seismometers and marine sources. We describe a method to accurately and efficiently compute synthetic seismograms for such experiments by using finite differences and reciprocity. We show numerically how to decompose an explosive source into its equivalent body force components using the staggered-grid finite-difference technique with a fourth-order approximation for the spatial derivative and a second-order approximation for the temporal derivative. This decomposition results in a source configuration where the equivalent body forces are defined in 12 points around the point where the ex-plosive source is applied. We then use the derived equivalent body forces for the explosive source and seismic reciprocity theorems to convert the common receiver gather to a common shot gather. The method is tested on a structurally complex elastic model of the crust and the results show that it is accurate within floating point precision. The synthetic data are compared to data from a real ocean bottom seismometer experiment conducted across a continent-ocean transition zone. A good fit in terms of traveltime is observed for many of the prominent seismic phases. The amplitude fit of these arrivals is not always as good as the traveltime fit. This indicates that full-waveform modeling of such data can provide useful information about the subsurface that cannot be obtained from traveltime modeling. If enough data are available, the modeling method can be used in full-waveform inversion.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2012
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 2014
    In:  GEOPHYSICS Vol. 79, No. 6 ( 2014-11-01), p. P9-P19
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 79, No. 6 ( 2014-11-01), p. P9-P19
    Abstract: This paper reports a comparison of three different rheological models used to characterize receiver coupling to the seafloor. We used a finite-element simulation tool to simulate the mechanical receiver coupling to the seafloor as a viscoelastic system with a combination of linear elastic springs and linear viscous dashpots, known as rheological models. Three models cover most of all mechanic coupling systems, the most commonly applied Kelvin-Voigt model (KVM), the Maxwell model (MM), and the standard linear solid (SLS) model. The models differ in behavior for different coupling aspects such as oscillation, creeping, stress relaxation, and their combinations. We tested these models’ ability and relevance for use in modeling seismic receiver coupling to the seafloor. For that purpose, we used an optimized mathematical approach to simulate coupling behavior under various coupling conditions. We found how receiver coupling will affect P- and S-waves for all three models and provided some insight into which model is most suitable to describe coupling under different circumstances. We found that the SLS model represents a general description of most of the coupling effects to the seafloor and should be used when the coupling acts as a viscoelastic system. The KVM and MM are applicable in extreme cases, such as for elastic waves in consolidated sediments (KVM) and dominant creeping effects, as in very soft biosediment (MM).
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2014
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 2014
    In:  GEOPHYSICS Vol. 79, No. 6 ( 2014-11-01), p. P21-P29
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 79, No. 6 ( 2014-11-01), p. P21-P29
    Abstract: Inconsistent horizontal receiver coupling to the seafloor causes measured signal differences on both horizontal receiver components. To explain this inconsistency, we considered distinct coupling parameters, the damping ratio and resonance frequency, for the receiver inline and crossline directions. Our approach combined these coupling parameters with the azimuth angle between an airgun shot and the receiver geometrically and used two visualization methods to show spatially dependent receiver coupling, based on correlation and root-mean-square amplitudes. We developed finite-element method simulation results together with field data from one ocean bottom cable (OBC) in very soft biosediment. The simulations provided an insight to the difference between perfectly coupled ideal receiver response and poor coupling. From the field data, we compared OBC receiver coupling for trenched and untrenched cable. Our results revealed that the field data had an azimuth-dependent response pattern with amplitude decay and time shift on the untrenched inline component, which we can reproduce with our simulations. Azimuth-dependent receiver coupling indicated that the inline and crossline receiver components were connected by the direction of the traveling wave, and trenching the cable will reduce the azimuth-dependent coupling effects.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2014
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Location Call Number Limitation Availability
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