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  • 1
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    DFG-Forschungsprojekt "Krustensplitter" : 3D-Makro-Geschwindigkeitsbestimmungen und 3D-Tiefenmigration des seismischen 3D-Costa-Rica-Datensatzes (1999)
    GEOMAR
    In:  GEOMAR-Report, 091 . GEOMAR, Kiel, 101 pp.
    Details
    Publication Date: 2015-02-23
    Description: Thema des Gemeinschaftsprojektes: Dreidimensionale Detailabbildungen prominenter reflexionsseismischer Strukturen am aktiven Kontinentalrand vor Costa Rica Förderungszeitraum insgesamt vom 01.07.1996 bis 31.12.1998
    Type: Report , NonPeerReviewed
    Format: text
    DOI: 10.3289/GEOMAR_Report_91_1999
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    OceanRep: Report - other report
  • 2
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    Three-dimensional seismic refraction tomography of the crustal structure at the ION site on the Ninetyeast Ridge, Indian Ocean (2003)
    Wiley
    In:  Geophysical Journal International, 152 (1). pp. 171-184.
    Details
    Publication Date: 2018-07-17
    Description: We have performed a 3-D seismic refraction tomography of a 48 × 48 km2 area surrounding ODP site 757, which is planned to host an International Ocean Network (ION) permanent seismological observatory, called the Ninetyeast Ridge Observatory (NERO). The study area is located in the southern part of the Ninetyeast Ridge, the trail left by the Kerguelen hotspot on the Indian plate. The GEOMAR Research Centre for Marine Geosciences and the Federal Institute for Geosciences and Natural Resources acquired 18 wide-angle profiles recorded by 23 ocean bottom hydrophones during cruise SO131 of R/V Sonne in spring 1998. We apply a first arrival traveltime tomography technique using regularized inversion to recover the 3-D velocity structure relative to a 1-D background model that was constructed from a priori information and averaged traveltime data. The final velocity model revealed the crustal structure down to approximately 8 km depth. Resolution tests showed that structures with approximately 6 km horizontal extent can reliably be resolved down to that depth. The survey imaged the extrusive layer of the upper crust of the Ninetyeast Ridge, which varies in thickness between 3 and 4 km. A high-velocity anomaly coinciding with a positive magnetic anomaly represents a volcanic centre from which crust in this area is thought to have formed. A pronounced low-velocity anomaly is located underneath a thick sedimentary cover in a bathymetric depression. However, poor ray coverage of the uppermost kilometre of the crust in this area resulted in smearing of the shallow structure to a larger depth. Tests explicitly including the shallow low-velocity layer confirmed the existence of the deeper structure. The heterogeneity of the upper crust as observed by our study will have consequences for the waveforms of earthquake signals to be recorded by the future seismic observatory.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1046/j.1365-246X.2003.01838.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
    Electronic Resource
    Electronic Resource
    Enhancement of Deep Seismic Reflections in Pre-stack Data by Adaptive Filtering (1999)
    Springer
    Pure and applied geophysics 156 (1999), S. 253-278 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Prestack signal enhancement, adaptive filtering, deep reflection seismics.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —Adaptive filters offer advantages over Wiener filters for time-varying processes. They are used for deconvolution of seismic data which exhibit non-stationary behavior, and seldom for noise reduction. Different algorithms for adaptive filtering exist. The least-mean-squares (LMS) algorithm, because of its simplicity, has been widely applied to data from different fields that fall outside geophysics. The application of the LMS algorithm to improve the signal-to-noise ratio in deep reflection seismic pre-stack data is studied in this paper. Synthetic data models and field data from the DEKORP project are used to this end.¶Three adaptive filter techniques, one-trace technique, two-trace technique and time-slice technique, are examined closely to establish the merits and demerits of each technique. The one-trace technique does not improve the signal-to-noise ratio in deep reflection seismic data where signal and noise cover the same frequency range. With the two-trace technique, the strongest noise reduction is achieved for small noise on the data. The filter efficiency decreases rapidly with increasing noise. Furthermore, the filter performance is poor upon application to common-midpoint (CMP) gathers with no normal-moveout (NMO) corrections. Application of the two-trace method to seismic traces before dynamic correction results in gaps in the signal along the reflection hyperbolas. The time-slice technique, introduced in this paper, offers the best answer. In this case, the one-trace technique is applied to the NMO-corrected gathers across all traces in each gather at each time to separate the low-wavenumber component of the signal in offset direction from the high-wavenumber noise component. The stacking velocities used for the dynamic correction do not need to be known very accurately because in deep reflection seismics, residual moveouts are small and have only a minor influence on the results of the adaptive time-slice technique. Noise reduction is more significant with the time-slice technique than with the two-trace technique. The superiority of the adaptive time-slice technique is demonstrated with the DEKORP data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050299
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Estimation of Seismic Velocities from Deep Reflections in the τ-p Domain (1999)
    Springer
    Pure and applied geophysics 156 (1999), S. 279-301 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Deep seismic reflections, velocity estimation, τ-p processing, noise reduction.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —In deep reflection seismics the estimation of seismic velocities is hampered in most cases due to the low signal level with respect to noise. In the τ-p domain, it is possible to perform the velocity analysis even under such unfavorable signal conditions. This is achieved by making use of special properties of the transform, which enhance the signal-to-noise ratio. Further noise suppression is realized by incorporating filter procedures into the transform algorithm. The velocity analysis itself is also done in the τ-p domain by calculating and evaluating constant velocity gathers. The results can be directly used in the time domain. A mute algorithm, implemented into the τ-p velocity analysis procedure, further reduces noise. This velocity estimation method is discussed with synthetic data and applied to DEKORP data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050300
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Sarcoglycanopathies in Dutch patients with autosomal recessive limb girdle muscular dystrophy (2000)
    Springer
    Journal of neurology 247 (2000), S. 524-529 
    Details
    ISSN: 1432-1459
    Keywords: Key words Limb girdle muscular dystrophy ; Sarcoglycanopathy ; Mutation analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Within a group of 76 sporadic/autosomal recessive limb girdle muscular dystrophy (LGMD) patients we tried to identify those with LGMD type 2C-E. Muscle biopsy specimens of 40 index patients, who had 22 affected sibs, were analyzed immuno-histochemically for the presence of three subunits: α-, β-, and γ,-sarcoglycans. Abnormal sarcoglycan expression was established in eight patients, with six affected sibs. In one patient γ-sarcoglycan was absent, and both α- and β-sarcoglycans were reduced. In the remaining seven patients γ-sarcoglycan was (slightly) reduced, and α- and β-sarcoglycans were absent or reduced. By DNA sequencing mutations were detected in one of the three sarcoglycan genes in all eight cases. Three patients had mutations in the α-, three in the β-, and two in the γ-sarcoglycan gene. The patients with sarcoglycanopathy comprised the more severely affected cases (P=0.04). In conclusion, sarcoglycanopathy was identified in 23% (14/62) of the autosomal recessive LGMD patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150070151
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    Paper (German National Licenses)
    Fulltext
  • 6
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    Three-dimensional seismic refraction tomography of the crustal structure at the ION site on the Ninetyeast Ridge, Indian Ocean (2003)
    In:  EPIC3Geophysical journal international, 152, pp. 171-184
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
  • 7
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    SPOC-Experiment: Seismic Imaging and Bathymetry of the Central Chile Margin - First Results (2002)
    In:  27th General Assembly European Geophysical Society (EGS) (Nice, France 2002)
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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    GFZ OAI
  • 8
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    Results of the 3-D Expanding Spread Experiment (1992)
    In:  KTB Report 92-5: Integrated Seismics Oberpfalz 1989; Data evaluation and interpretation as of October 1992
    Details
    Publication Date: 2022-05-11
    Description: The 3-D expanding spread experiment, performed within ISO 89 at the KTB site, has been evaluated under two aspects. The first aspect was the estimation of velocity-depth functions. Due to the limited reflection strength, estimating NMO velocities as a function of twoway traveltime was possible in east-west direction only. Thus the calculation of interval velocities, requiring the correction of 3D effects, was not possible. The second aspect was the directional dependency of the P-wave velocity at the top of the crystalline by evaluating the direct waves. After eliminating the effects of the lithology, a least-mean-squares anisotropy-velocity ellipse was fitted to the data with WSW as the direction of the maximum velocity and a velocity contrast of about 6%.
    Language: English
    Type: info:eu-repo/semantics/bookPart
    Format: application/pdf
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