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  • 1
    Book
    Book
    PACOMAR 91/92 - Fahrtbericht SONNE 76 : 20. Dezember 1991 bis 25 Januar 1992 (1992)
    Kiel
    Details Availability
    Keywords: Fahrtbericht ; Sonne ; Plattentektonik ; Costa Rica
    Type of Medium: Book
    Pages: 59 S. , graph. Darst., Kt. , 1 Kt.
    Language: German
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  • 2
    Online Resource
    Online Resource
    Das Konzept der Polarisationsmethode und seine Anwendungen auf das seismische Vektorwellenfeld im Weitwinkelbereich (1993)
    Kiel
    Details Availability
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 127Seiten = 15MB) , Ill., graph. Darst
    Edition: 2022
    URL: https://oceanrep.geomar.de/id/eprint/29258/
    Language: German
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  • 3
    Online Resource
    Online Resource
    Crustal structure of the Mid-Atlantic Ridge at 5° South : two contrasting spreading segments (2006)
    Kiel
    Details Availability
    Keywords: Hochschulschrift ; Mittelatlantischer Rücken ; Ozeanische Erdkruste
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 217Seiten = 36MB) , Ill., graph. Darst., Kt.
    URL: https://oceanrep.geomar.de/id/eprint/5802/
    Language: English
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  • 4
    Online Resource
    Online Resource
    Seismic structure off- and onshore Maule, constraints for megathrust earthquakes in central Chile (2011)
    Kiel
    Details Availability
    Keywords: Hochschulschrift ; Maule-Gebiet ; Subduktion ; Seismik
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 147Seiten = 42MB) , graph. Darst.
    URL: https://oceanrep.geomar.de/id/eprint/13529/
    DDC: 551.8098335
    Language: English
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  • 5
    Electronic Resource
    Electronic Resource
    NIZUSE: a deep seismic reflection line in north-eastern Germany (1994)
    Springer
    International journal of earth sciences 83 (1994), S. 161-169 
    Details
    ISSN: 1437-3262
    Keywords: Deep seismic reflection profiling ; Northeast German Basin ; External Variscides ; North German Massif ; Rugen-Pomorze Terrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Out of a dense network of seismic reflection lines for hydrocarbon exploration in the North-east German Basin, several lines were recorded to 12 s TWT to obtain information about the structure of the crust and the crust-mantle transition. One of these profiles is presented here. This stretches for 110 km in a NNE direction between Neustrelitz and the island of Usedom. It reaches from the External Variscides in the south across the North German Massif into the Rügen-Pomorze Terrane in the Baltic Sea. Below Cenozoic-Mesozoic-Paleozoic cover with clear reflections down to base Zechstein, the reflectivity varies considerably with depth and also laterally. The Paleozoic and Precambrian sediments and basement are generally void of reflections, but the lower crust and the Moho show strong reflections. To the north the reflectivity decreases, and the Moho depth increases to beyond the bottom of the record section at 12 s. There are no direct indications for deep-reaching faults such as the Trans-European Fault in the north. The North German Massif acted as a ramp towards the Variscan Orogeny, similar to the London-Brabant Massif further west.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211899
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    Paper (German National Licenses)
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  • 6
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    Lower slope morphology of the Sumatra trench system (2008)
    Wiley
    In:  Basin Research, 20 (4). pp. 519-529.
    Details
    Publication Date: 2019-01-21
    Description: At convergent margins, the structure of the subducting oceanic plate is one of the key factors controlling the morphology of the upper plate. We use high-resolution seafloor mapping and multichannel seismic reflection data along the accretionary Sumatra trench system to investigate the morphotectonic response of the upper plate to the subduction of lower plate fabric. Upper plate segmentation is reflected in varying modes of mass transfer. The deformation front in the southern Enggano segment is characterized by neotectonic formation of a broad and shallow fold-and-thrust belt consistent with the resumption of frontal sediment accretion in the wake of oceanic relief subduction. Conversely, surface erosion increasingly shapes the morphology of the lower slope and accretionary prism towards the north where significant oceanic relief is subducted. Subduction of the Investigator Fracture Zone and the fossil Wharton spreading centre in the Siberut segment exemplifies this. Such features also correlate with an irregularly trending deformation front suggesting active frontal erosion of the upper plate. Lower plate fabric extensively modulates upper plate morphology and the large-scale morphotectonic segmentation of the Sumatra trench system is linked to the subduction of reactivated fracture zones and aseismic ridges of the Wharton Basin. In general, increasing intensity of mass-wasting processes, from south to north, correlates with the extent of oversteepening of the lower slope (lower slope angle of 3.8 degrees in the south compared with 7.6 degrees in the north), probably in response to alternating phases of frontal accretion and sediment underthrusting. Accretionary mechanics thus pose a second-order factor in shaping upper plate morphology near the trench.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1365-2117.2008.00381.x
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  • 7
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    Ocean bottom seismics (2011)
    Springer
    In:  In: Encyclopedia of Solid Earth Geophysics, Vol. 1-2. , ed. by Gupta, H. K. Encyclopedia of Earth Sciences Series . Springer, Heidelberg, Germany, pp. 901-918. 1. ed. ISBN 978-90-481-8701-0
    Details
    Publication Date: 2020-08-03
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 8
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    The seismogenic zone in the Central Costa Rican Pacific margin: high-quality hypocenters from an amphibious network (2014)
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 1747-1764.
    Details
    Publication Date: 2017-05-23
    Description: Transition from subduction of normal to thickened oceanic crust occurs in the central portion of the Costa Rican margin, where large interplate earthquakes (M * 7) and abundant interseismic seismicity have been associated with subduction of bathymetric highs. We relocated *1,300 earthquakes recorded for 6 months by a combined on- and offshore seismological network using probabilistic earthquake relocation in a 3D P-wave velocity model. Most of the seismicity originated at the seismogenic zone of the plate boundary, appearing as an 18° dipping, planar cluster from 15 to 25–30 km depth, beneath the continental shelf. Several reverse focal mechanisms were resolved within the cluster. The upper limit of this interseismic interplate seismicity seems to be controlled primarily by the overlying-plate thickness and coherency, which in turn is governed by the erosional processes and fluid release and escape at temperatures lower than *100 to 120° C along the plate boundary. The downdip limit of the stick–slip behaviour collocates with relative low temperatures of *150 to 200° C, suggesting that it is controlled by serpentinization of the mantle wedge. The distribution of the interseismic interplate seismicity is locally modified by the presence of subducted seamounts at different depths. Unlike in northern Costa Rica, rupture of large earthquakes in the last two decades seems to coincide with the area defined by the interseismic interplate seismicity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-013-0955-8
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Seismic investigation of a bottom simulating reflector and quantification of gas hydrate in the Black Sea (2005)
    Wiley
    In:  Geophysical Journal International, 161 (3). pp. 662-678.
    Details
    Publication Date: 2018-07-16
    Description: A bottom simulating reflector (BSR), which marks the base of the gas hydrate stability zone, has been detected for the first time in seismic data of the Black Sea. The survey area is in the northwestern Black Sea at 44°–45°N and 31.5°–32.5°E. In this paper, seismic wide-angle ocean bottom hydrophone (OBH) and ocean bottom seismometer (OBS) data are investigated with the goal to quantify the gas hydrate and free gas saturation in the sediment. An image of the subsurface is computed from wide-angle data by using Kirchhoff depth migration. The image shows the BSR at 205–270 m depth below the seafloor and six to eight discrete layer boundaries between the seafloor and the BSR. The top of the hydrate layer and the bottom of the gas layer cannot be identified by seismic reflection signals. An analysis of traveltimes and reflection amplitudes leads to 1-D P-wave velocity–depth and density–depth models. An average S-wave velocity of 160 m s−1 between the seafloor and the BSR is determined from the traveltime of the P to S converted wave. The normal incidence PP reflection coefficient at the BSR is −0.11, where the P-wave velocity decreases from 1840 to 1475 m s−1. Velocities and density are used to compute the porosity and the system bulk modulus as a function of depth. The Gassmann equation for porous media is used to derive explicit formulae for the gas hydrate and free gas saturation, which depend on porosity and on the bulk moduli of the dry and saturated sediment. A gas hydrate saturation–depth profile is obtained, which shows that there is 38 ± 10 per cent hydrate in the pore space at the BSR depth, where the porosity is 57 per cent (OBS 24). This value is derived for the case that the gas hydrate does not cement the sediment grains, a model that is supported by the low S-wave velocities. There is 0.9 or 0.1 per cent free gas in the sediment below the BSR, depending on the model for the gas distribution in the sediment. The free gas layer may be more than 100 m thick as a result of a zone of enhanced reflectivity, which can be identified in the subsurface image.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1365-246X.2005.02635.x
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  • 10
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    Mantle wedge hydration in Nicaragua from Local Earthquake Tomography (2011)
    Wiley
    In:  Geophysical Journal International, 186 (1). pp. 92-112.
    Details
    Publication Date: 2019-09-23
    Description: The continental margin of Nicaragua and Costa Rica is characterized by significant lateral changes from north to south such as a decreasing dip of the slab, a decreasing magma production and a shift in the volcanic front. To investigate this transition, a joint on- and offshore local earthquake tomography was performed. Low P-wave velocities and high Vp/Vs ratios, indicative for hydration, were found in the upper-mantle and lowermost crust beneath the Sandino Basin. The mantle wedge hydration can be estimated to 2.5 wt. per cent beneath south Nicaragua. In contrast, the mantle wedge beneath north Costa Rica is weakly or not hydrated. The hydration leads to a local gap in the seismicity in Nicaragua. The lateral transition between the hydrated and non-hydrated areas occurs within a distance of about 10 km. This transition coincides with a change in the crustal thickness in the order of 5–10 km, thickening to the south, and in the tectonic regimes. The change in the tectonic regimes towards a stronger extension along the margin of Nicaragua could be the key for understanding the observations: the extension may support the opening of pathways for a wide zone of fluid migration and hydration through the overriding plate which are identified with areas of low Vp, high Vp/Vs and low seismicity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1365-246X.2011.05041.x
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