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  • 1
    Publication Date: 2018-07-04
    Description: Multichannel seismic (MCS) data from the Yaquina forearc basin off Peru reveal a complex distribution of gas and gas hydrate related reflections. Lateral variations of the reflection pattern at the assumed base of the gas hydrate stability zone in terms of continuity, amplitude, and signal attenuation underneath are observed, as well as the possible occurrence of paleo-bottom simulating reflectors (BSRs). Phase reversed reflections above the bottom simulating reflector point to free gas within the gas hydrate stability zone (GHSZ). To constrain the interpretation of the observed reflection pattern we calculated the velocity distribution along the MCS line from high-resolution ocean bottom hydrophone recordings with two independent methods. Heat flux values estimated on the basis of the velocity-depth functions increase with decreasing amplitude of the BSR and peak near chemoherms. These results suggest a model of the Yaquina Basin where free gas is trapped under parts of the BSR, and within the GHSZ, particularly under the seafloor and under an erosional unconformity. The hypothesis of a paleo-BSR that reflects the uplift of the base of the hydrate stability zone caused by the deposition of a particular sediment sequence is supported by the estimated heat flux values.
    Type: Article , PeerReviewed
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  • 2
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    Society of Exploration Geophysicists
    In:  SEG Technical Program Expanded Abstracts, 2018 . pp. 5133-5136.
    Publication Date: 2018-10-17
    Description: P-cable data often do not allow model building by conventional methods because of an insufficient offset to target ratio. Diffractions, however, provide a tool for model building, even for Zero-Offset data. Here, we introduce a diffraction-based velocity analysis that provides seismic velocity information without the need of acquiring ocean bottom seismometer data. The diffraction based processing uses a multiparameter stacking operator which naturally enhances diffractions and at the same time generate kinematic wavefield attributes. These attributes together with the stack serve as input for a wavefront tomography and generate a depth velocity model in an automated fashion. An additional advantage of diffraction tomography is the scatter potential which yields a large area of illumination in the tomography compared to a pure reflection processing. The illuminated area is two to three times larger and more velocity information can be calculated from the same amount of data.
    Type: Article , NonPeerReviewed
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  • 3
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    In:  [Paper] In: 81. EAGE Annual Conference + Exhibition 2019, 03.-06.06.2019, London, United Kingdom .
    Publication Date: 2019-10-28
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 4
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    In:  Geophysics, 76 (5). S187-S195.
    Publication Date: 2015-12-17
    Description: Imaging of diffractions is a challenge in seismic processing. Standard seismic processing is tuned to enhance reflections. Separation of diffracted from reflected events is frequently used to achieve an optimized image of diffractions. We present a method to effectively separate and image diffracted events in the time domain. The method is based on the common-reflection-surface-based diffraction stacking and the application of a diffraction-filter. The diffractionfilter uses kinematic wavefield attributes determined by the common-reflection-surface approach. After the separation of seismic events, poststack time-migration velocity analysis is applied to obtain migration velocities. The velocity analysis uses a semblance based method of diffraction traveltimes. The procedure is incorporated into the conventional common-reflection-surface workflow. We apply the procedure to 2D synthetic data. The application of the method to simple and complex synthetic data shows promising results.
    Type: Article , PeerReviewed
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  • 5
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    Society of Exploration Geophysicists
    In:  Geophysics, 74 (3). V49-V58.
    Publication Date: 2016-07-28
    Description: We developed a new partial common-reflection-surface (CRS) stacking method to enhance the quality of sparse lowfold seismic data. For this purpose, we use kinematic wavefield attributes computed during the automatic CRS stack. We apply a multiparameter CRS traveltime formula to compute partial stacked CRS supergathers. Our algorithm allows us to generate NMO-uncorrected gathers without the application of inverse NMO/DMO. Gathers obtained by this approach are regularized and have better signal-to-noise ratio compared with original common-midpoint gathers. Instead of the original data, these improved prestack data can be used in many conventional processing steps, e.g., velocity analysis or prestack depth migration, providing enhanced images and better quality control.We verified the method on 2D synthetic data and applied it to low-fold land data from northern Germany. The synthetic examples show the robustness of the partial CRS stack in the presence of noise. Sparse land data became regularized, and the signal-to-noise ratio of the seismograms increased as a result of the partial CRS stack. Prestack depth migration of the generated partially stacked CRS supergathers produced significantly improved common- image gathers as well as depth-migrated sections.
    Type: Article , PeerReviewed
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