ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 154 (1999), S. 575-591 
    ISSN: 1420-9136
    Keywords: Key words: Alaska earthquakes, tectonics, earthquake segmentation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —Tectonic studies of the great 1964 Alaska earthquake have underappreciated the nature of the subducted plate in influencing seismicity. We compare seismological observations in the Prince William and Kodiak areas that ruptured during this earthquake with the corresponding morphology and structure of the subducting plate. The upper plate geology (Prince William Terrane) and velocity structure are the same in both areas. In the Prince William area where the Yakutat Terrane subducted, the energy released and coupling were stronger than above the Kodiak subduction zone where thick trench sediment subducts. The conjecture that lower plate character or the amount of subducted sediment affects coupling helps explain variability in seismology, geodetic inversions and the horizontal velocity of GPS stations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Within the DEKORP project (DEKORP: Deutsches Kontinentales Reflexionsseismisches Programm) a joint deep seismic reflection venture with the BELCORP (Belgian Continental Reflection Seismic Programme) group of the Belgian Geological Survey was carried out in 1987 across the Rhenish Massif, a part of the mid-European Variscides. This orogenic belt developed in the Upper Devonian/Carboniferous. Mostly Devonian rocks crop out at the surface. The Rhenish Massif is bordered by two sedimentary troughs: the sub-Variscan Foredeep in the north and the Permo-Carboniferous Saar-Nahe Basin in the south. In the east-west direction it is subdivided by the axial depression of the Eifel Nord-Süd Zone.The aim of the survey which totals almost 220 km of seismic profiling, was to investigate the crustal structure of the western part of the Rhenish Massif and to compare it with the line DEKORP 2-N which crosses the eastern portion of the massif. The results indicate the presence of NW-vergent tectonics of various styles that can often be traced down to deep parts of the crust. Horizontal Variscan compression plays a dominant role in the northern part while post-Variscan extension seems to dominate in the Saar-Nahe Basin, although even there traces of Variscan compression seem to be preserved in the middle crust. Common characteristics of the pre-Palaeozoic basement, differences between the western and eastern parts of the Rhenish Massif, and the deep extension of the Aachen Thrust (Faille du Midi) have been clearly observed. This prominent thrust in the north with its characteristic ramp and flat structure has been followed over 100 km length down
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-0581
    Keywords: passive continental margin ; continent-ocean transition ; crustal structure ; active ridge ; deep seismic sounding ; airgun ; explosives ; gravity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Results are presented from a deep seismic sounding experiment with the research vessel POLARSTERN in the Scoresby Sund area, East Greenland. For this continental margin study 9 seismic recording landstations were placed in Scoresby Sund and at the southeast end of Kong Oscars Fjord, and ocean bottom seismographs (OBS) were deployed at 26 positions in and out of Scoresby Sund offshore East Greenland between 70° and 72° N and on the west flank of the Kolbeinsey Ridge. The landstations were established using helicopters from RV POLARSTERN. Explosives, a 321 airgun and 81 airguns were used as seismic sources in the open sea. Gravity data were recorded in addition to the seismic measurements. A free-air gravity map is presented. The sea operations — shooting and OBS recording — were strongly influenced by varying ice conditions. Crustal structure 2-D models have been calculated from the deep seismic sounding results. Free-air gravity anomalies have been calculated from these models and compared to the observed gravity. In the inner Scoresby Sund — the Caledonian fold belt region — the crustal thickness is about 35 km, and thins seaward to 10 km. Sediments more than 10 km thick on Jameson Land are of mainly Mesozoic age. In the outer shelf region and deep sea a ‘Moho’ cannot clearly be identified by our data. There are only weak indications for the existence of a ‘Moho’ west of the Kolbeinsey Ridge. Inside and offshore Scoresby Sund there is clear evidence for a lower crust refractor characterised byp-velocities of 6.8–7.3 km s−1 at depths between 6 and 10 km. We believe these velocities are related to magmatic processes of rifting and first drifting controlled by different scale mantle updoming during Paleocene to Eocene and Late Oligocene to Miocene times: the separation of Greenland/Norway and the separation of the Jan Mayen Ridge/Greenland, respectively. A thin igneous upper crust, interpreted to be of oceanic origin, begins about 50 km seaward of the Liverpool Land Escarpment and thickens oceanward. In the escarpment zone the crustal composition is not clear. Probably it is stretched and attenuated continental crust interspersed with basaltic intrusions. The great depth of the basement (about 5000 m) points to a high subsidence rate of about 0.25 mm yr−1 due to sediment loading and cooling of the crust and upper mantle, mainly since Miocene time. The igneous upper crust thickens eastward under the Kolbeinsey Ridge to about 2.5 km; the thickening is likely caused by higher production of extrusives. The basementp-velocity of 5.8–6.0 km s−1 is rather high. Such velocities are associated with young basalts and may also be caused by a higher percentage of dykes. Tertiary to recent sediments, about 5000 m thick, form most of the shelf east of Scoresby Sund, Liverpool Land and Kong Oscars Fjord. This points to a high sedimentation rate mainly since the Miocene. The deeper sediments have a rather high meanp-velocity of 4.5 km s−1, perhaps due to pre-Cambrian to Caledonian deposits of continental origin. The upper sediments offshore Scoresby Sund are thick and have a rather low velocity. They are interpreted as eroded material transported from inside the Sund into the shelf region. Offshore Kong Oscars Fjord the upper sediments, likely Jurassic to Devonian deposits, are thin in the shelf region but thicken to more than 3000 m in the slope area. The crust and upper mantle structure in the ocean-continent transition zone is interpreted to be the result of the superposition of the activities of three rifting phases related to mantle plumes of different dimensions: 1. the ‘Greenland/Norway separation phase’ of high volcanic activity, 2. the ‘Jan Mayen Ridge/Greenland separation phase’ and 3. the ‘Kolbeinsey Ridge phase’ of ‘normal’ volcanic activity related to a more or less normal mantle temperature. During period 2 and 3 only a few masses of extrusives were produced, but large volumes of intrusives were emplaced. So the margin between Scoresby Sund and Jan Mayen Fracture Zone is interpreted to be a stretched margin with low volcanic activity.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 1990
    Keywords: Rhenish Massif, DEKORP 1, Western Germany, refraction seismics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    facet.materialart.
    Unknown
    In:  Diplomarbeit, Universität Kiel, 86 S.
    Publication Date: 1988
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2015-06-23
    Description: The upward migration of gas through marine sediments typically manifests itself as gas chimneys or pipes in seismic images and can lead to the formation of cold seeps. Gas seepage is often linked to morphological features like seabed domes, pockmarks, and carbonate build-ups. In this context, sediment doming is discussed to be a precursor of pockmark formation. Here, we present parametric echosounder, sidescan sonar, and two-dimensional seismic data from Opouawe Bank, offshore New Zealand, providing field evidence for sediment doming. Geomechanical quantification of the stresses required for doming show that the calculated gas column heights are geologically feasible and consistent with the observed geophysical data. The progression from channeled gas flow to gas trapping results in overpressure build-up in the shallow sediment. Our results suggest that by breaching of domed seafloor sediments a new seep site can develop, but contrary to ongoing discussion this does not necessarily lead to the formation of pockmarks.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2013-05-26
    Description: Extension of the continental lithosphere leads to the formation of rift basins and ultimately may create passive continental margins. The mechanisms that operate during the early-stage of crustal extension are still intensely debated. We present the results from coincident multichannel seismic and wide-angle seismic profiles that transect across the northern Tyrrhenian Sea basin. The profiles cross the Corsica Basin (France) to the Latium Margin (Italy) where the early-rift stage of the basin is well preserved. We found two domains, each with a distinct tectonic style, heat-flow and crustal thickness. One domain is the Corsica Basin in the west that formed before the main rift-phase of the northern Tyrrhenian Sea opening (~8-4 Ma). The second domain is rifted continental crust characterized by tilted blocks and half-graben structures in the central region and at the Latium Margin. These two domains are separated by a deep (~10 km) sedimentary complex of the eastern portion of the Corsica Basin. Travel-time tomography of wide-angle seismic data reveals the crustal architecture and a sub-horizontal 15-17 ± 1 km deep Moho discontinuity under the basin. To estimate the amount of horizontal extension we have identified the pre-, syn-, and post-tectonic sedimentary units and calculated the relative displacement of faults. We found that major faults initiated at angles of 45-50° and that the rifted domain is horizontally stretched by a factor of β=1.3 (~8-10 mm/a). The crust has been thinned from ~24 to 17 km indicating a similar amount of extension (~30%). The transect represents one of the best imaged early-rifts and implies that the formation of crustal-scale detachments, or long-lived low-angle normal faults, is not a general feature that controls the rift initiation of continental crust. Other young rift basins, like the Gulf of Corinth, the Suez-Rift or Lake Baikal, display features resembling the northern Tyrrhenian Basin, suggesting that half graben formations and distributed homogeneous crustal thinning are a common feature during rift initiation.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 2013-04-19
    Description: Methane seepage at south Hydrate Ridge (offshore Oregon, United States), one of the best-studied examples of gas venting through gas hydrates, is the seafloor expression of a vigorous fluid flow system at depth. The seeps host chemosynthetic ecosystems and release significant amounts of carbon into the ocean. With new three-dimensional seismic data, we image strata and structures beneath the ridge in unprecedented detail to determine the geological processes controlling the style of focused fluid flow. Numerical fluid flow simulations reveal the influence of free gas within a stratigraphic unit known as Horizon A, beneath the base of gas hydrate stability (BGHS). Free gas within Horizon A increases the total mobility of the composite water-gas fluid, resulting in high fluid flux that accumulates at the intersection between Horizon A and the BGHS. This intersection controls the development of fluid overpressure at the BGHS, and together with a well-defined network of faults, reveals the link between the gas hydrate system at depth and methane seepage at the surface.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
  • 10
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...