ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • Articles  (59)
Collection
Source
Keywords
Publisher
Years
Journal
Topic
  • 1
    Electronic Resource
    Electronic Resource
    Structure of a Volcanic Continental Margin Derived from Ocean-bottom Seismographic Data: The Northern Vøring Margin, off Norway (1998)
    Springer
    Pure and applied geophysics 152 (1998), S. 1-21 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Vøring margin, Ocean-Bottom Seismograph, crustal structure, volcanic continental margin.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —This paper presents a crustal model derived from an Ocean Bottom Seismograph (OBS) study along the northern Vøring margin off Norway. The profile was acquired to map the crustal structure in the northernmost part of the Vøring Basin, and to link crustal models of the Lofoten and central Vøring Basin obtained by previous OBS studies. The Vøring margin, as well as the Lofoten margin to the north, was created by continental breakup between Norway and Greenland in late Paleocene-early Eocene. The rifting and continental breakup process were accompanied by intense extrusive and intrusive magmatic activities. The OBS data provide the whole crustal structure along the northern Vøring margin, in the area where the deep crustal structure cannot be resolved by conventional multichannel reflection data due to sill intrusions in the sedimentary sequence. The shallow part of the crustal model is characterized by up to 10 km thick sediments, a sequence of flood basalts and sill intrusions. The P-wave velocities in the flood basalts and sill intrusions are estimated to 5.0 km/s and 4.7–5.8 km/s, respectively. The model indicates an abrupt thickening of the upper crystalline crust from approx.3 km in the NE, to about 10 km towards the SE, with velocities of 6.0–6.2 km/s. The lower crustal velocities are not well resolved due to lack of clear refraction arrivals from the lower crust. However, the observed amplitude versus offsets are best explained by a model with a change in lower crustal velocities from 6.8 to 7.2 km/s beneath the Bivrost lineament. The modelling infers the presence of a lower crustal reflector beneath the lineament, which represents the landward continuation of the Bivrost lineament. Reflection arrivals from the Moho reveal a Moho depth of 23 km in the middle of the profile and 18– 20 km in the northeastern part of the profile. A 370 km long crustal section from the central part of the Vøring Basin to the Lofoten margin, obtained by the results of this study and previous OBS studies, shows a simple thinned continental crust on the Lofoten margin, and a high velocity lower crust underlying an upper crust of varying thickness in the Vøring Basin. The transition between these structures is situated beneath the Bivrost lineament in the lower crust, and beneath the basement high about 40 km south of the lineament in the upper crust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050138
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Comparison between a Regional and Semi-regional Crustal OBS Model in the Vøring Basin, Mid-Norway Margin (1997)
    Springer
    Pure and applied geophysics 149 (1997), S. 641-665 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Vøring Basin, crustal structure, 3-component OBSs.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —Semi-regional Ocean Bottom Seismograph (OBS) data acquired in the central and northern part of the Vøring Basin, mid-Norway margin, have been modeled by use of 2-D ray-tracing. The semi-regional model, derived from the study of twenty-five OBSs deployed along a 120-km long profile, is compared with a regional model consisting of five OBSs from the same profile. The semi-regional model is somewhat more detailed than the regional model, due to the considerably closer receiver spacing. The overall geometry and velocity distribution of the two models are remarkably similar, however, proving that the regional procedure with large OBS spacing provides a reliable regional model.¶Intrusions of sills, related to early Tertiary continental rifting and break up, are important at intermediate and deep sedimentary levels (2–10 km below sea floor) in most parts of the area. The semi-regional modeling suggests that one of the deepest sills extends much further east and is substantially thicker (locally more than 500 m) than indicated in the regional model. Another important difference is a high-velocity body within the upper crystalline crust at 11–12 km depth in the NW part of the area, indicating that the closer OBS spacing in the semi-regional modeling allows detection of local intra-crustal intrusions. Local differences are also inferred in the lower crust; at about 20 km depth a structure is inferred within the lower crust from wide-angle reflections. This might suggest that the high-velocity lower crustal layer, interpreted as magmatic underplating, consists of a mixture of underplated/intruded magmatic material and blocks of continental lower crust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050045
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Modelling shear waves in OBS data from the Vøring basin (Northern Norway) by 2-D ray-tracing (1996)
    Springer
    Pure and applied geophysics 147 (1996), S. 611-629 
    Details
    ISSN: 1420-9136
    Keywords: Vøring basin ; 3C OBS data ; shear waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Three component recordings from an array of five ocean bottom seismographs in the northwestern part of the Vøring basin have been used to obtain a 2-D shear-wave (S-wave) velocity-depth model. The shear waves are identified by means of travel-time differences compared to the compressional (P) waves, and by analyzing their particle motions. The model has been obtained by kinematic (travel-time) ray-tracing modelling of the OBS horizontal components. The shear-wave modelling indicates that mode conversions occur at several high velocity interfaces (sills) in the 4–10 km depth range, previously defined by a compressional-wave velocity-depth model using the same data set. An averageV p /V s ratio of 2.1 is inferred for the layers above the uppermost sill, indicative of both poorly consolidated sediments and a low sand/shale ratio. A significant decrease in theV p /V s ratio (1.7) below the first sill may in part be atributed to well consolidated sediments, and to a change in lithology to more sandy sediments. This layer is interpreted to lie within the lower Cretaceous sequence. At 5–10 km depthV p /V s ratios of 1.85 indicate a lower sand/shale ratio consistent with the expected lithologies. The averageV p /V s ratio inferred for the crust is 1.75, which is consistent with values obtained north of Vøring, in the Lofoten area. An eastward thinning of the crystalline basement is supported by the shear-wave modelling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01089694
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Crustal Structure Beneath Lofoten, N. Norway, From Vertical Incidence and Wide-Angle Seismic Data (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 114 (1993), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A high-quality multichannel seismic reflection line was acquired in 1987 along a 175 km long profile across the continental shelf off Lofoten, northern Norway. A seismic wide-angle experiment was performed in 1988 along the same profile, using seven three-component Ocean Bottom Seismographs (OBS) with 20-25 km spacing and shotpoint intervals of 240 m.The study of the data has shown that the combination of the multichannel reflection and the wide-angle (OBS) technique provides information about the crustal structure beneath the Lofoten shelf that could not have been achieved using only one of the techniques. the multichannel reflection data provide a detailed image of the shallow (Cretaceous) structures, which represents an important basis for inversion of the OBS data. the lower crust and the Moho are also well mapped in some parts of the area with the multichannel reflection technique.The OBS data reveal that significant amounts of pre-Cretaceous sediments exist along almost the entire profile, with a maximum thickness of about 5 km in the Vestfjorden Basin. From the OBS data the thickness of the lower crust is inferred to decrease from about 11.5 km under the Røst High to about 2 km below the Lofoten Ridge. the OBS data indicate further that the Moho position under the Vestfjorden Basin is considerably deeper than can be inferred from the reflection data.About 10km below Moho a strong dipping event is observed in the OBS data. This upper mantle reflection might be related to a possible seaward dipping master fault, and/or presence of layers of partially hydrated peridotite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1993.tb01471.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    REFLECTION AND POLARIZATION OF TUBE WAVES AS SEEN IN VSP DATA (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 40 (1992), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: P-wave and S-wave data acquired with vertical seismic profiling (VSP) often include tube waves propagating in the borehole, although considerable efforts are generally made to ensure that these waves are not recorded. However, several theoretical studies have indicated that tube waves could provide important information about the rock formation and thus should not be considered as pure noise.In order to study some of these aspects experimentally, tube waves were acquired by VSP in a well in the Paris Basin both before and after casing. A sparker was used as source inside the borehole, which ensured that the data recorded contained high-amplitude tube waves.It is shown that the casing is an obstacle which prevents the study of formation parameters, and thus further tube-wave acquisitions should be carried out in open holes only.The before-casing tube-wave reflection log is compared to a synthetic log computed from the sonic log. The high resolution of the tube waves is of particular interest, revealing layers that are too thin to be detected in body-wave surveys.It has recently been suggested that the projection of the tube-wave polarization in the horizontal plane can be used to determine directions of stress-induced anisotropy in the rock formation. Strong polarization anomalies are observed in the data sets but are attributed to tool problems rather than any rock-formation feature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1992.tb00544.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Ocean Bottom Seismographs used in a crustal study of an area covered with flood-basalt off Lofoten, N. Norway (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 5 (1993), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Seismic refraction measurements were made in August 1988 to study the crustal structure off Lofoten, Northern Norway. Twenty-four 3-component Ocean Bottom Seismographs (OBS) were used, of which seven were deployed in the area covered by landward-flowing basalt deposited during the early Eocene break-up between Norway and Greenland. The main purpose of the OBS survey was to investigate whether this method can be used to map structures below the basalt, which is not easy to penetrate with conventional seismic reflection techniques. The records obtained showed that the OBS data contain considerable information about structures below the flood-basalt; preopening sediments up to 4.0 km thick is indicated below the 1.0–2.5 km-thick landward-flowing basalt. The success of the OBS survey indicates that such measurements can become an important tool in investigations on passive volcanic margins and, potentially, in other areas where highly reflective boundaries make the reflection technique difficult to apply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3121.1993.tb00228.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    facet.materialart.
    Unknown
    Systematic simulation of multicomponent receiver coupling to the seafloor using rheological models (2014)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2014-12-09
    Description: 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).
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
    Published by Society of Exploration Geophysicists (SEG)
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    Azimuth-dependent ocean bottom cable receiver coupling to the seafloor (2014)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2014-12-09
    Description: 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.
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
    Published by Society of Exploration Geophysicists (SEG)
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    Efficient and accurate modeling of ocean bottom seismometer data using reciprocity (2012)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2012-12-16
    Description: 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.
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
    Published by Society of Exploration Geophysicists (SEG)
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Analysis of structural trends of sub-sea-floor strata in the Isfjorden area of the West Spitsbergen Fold-and-Thrust Belt based on multichannel seismic data (2013)
    Geological Society of London
    Details
    Publication Date: 2013-07-10
    Description: A dense grid of 2D multichannel seismic data was used for the interpretation of sub-sea-floor structures in the area of Isfjorden in western Spitsbergen. West Spitsbergen underwent Eocene transpressional deformation that resulted in formation of the West Spitsbergen Fold-and-Thrust Belt. Three horizons were defined for the seismic interpretation as well-expressed and continuous reflections: (1) the top of the metamorphic basement; (2) the base of the upper Carboniferous Nordenskiöldbreen Formation; (3) the base of the Lower Cretaceous Helvetiafjellet Formation. Time–structure maps and analysis of the sub-bottom structural trends were generated for each horizon. The top of the metamorphic basement displays north–south-trending graben structures, apparently representing continuation of the Devonian grabens from northern Spitsbergen. The tectonostratigraphic unit bounded by the base of the upper Carboniferous Nordenskiöldbreen Formation and base of the Helvetiafjellet Formation encloses the fold-and-thrust belt and is affiliated with WSW–ENE shortening involving three décollement levels. Within this unit the strata between the middle (Triassic shales) and upper (Upper Jurassic shales) décollements have undergone the most intense strain, whereas sediments situated between the basal (lower Permian evaporites) and middle décollements underwent a relatively mild deformation. The strata above the base of the Helvetiafjellet Formation are characterized by minor Tertiary deformation only.
    Print ISSN: 0016-7649
    Topics: Geosciences
    Published by Geological Society of London
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...