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  • 1
    Electronic Resource
    Electronic Resource
    Gravity interpretation of a unified 2-D acoustic image of the central Alpine collision zone (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 111 (1992), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Four individual deep seismic reflection profiles across the eastern and southern Swiss Alps have been combined along the trend of the Bouguer gravity anomalies onto the European Geotraverse. The profiles were migrated ray theoretically with the migration velocity model derived from a smoothed reinterpretation of the seismic wide-angle profiles running parallel to the strike of the Alpine arc. The contours of this velocity model were ray theoretically depth migrated together with the combined digitized line drawings of the seismic reflection profiles. The resulting acoustic image depicts the subduction of parts of the lower crust of the European plate beneath the Adriatic promontory of the African plate at a low angle of 15°. Based on the interpretation of the seismic data, orogenic crustal thickening is attributed to the stacking of crystalline nappes onto the upper crust of the European plate and wedging of the European and Adriatic middle and lower crusts the latter being ill-constrained by the seismic evidence alone. The south-vergent thrusting of the Southern Alps can be accounted for by the observed downbending of the Adriatic Moho and the lower crust in conjunction with the inferred wedging at mid-crustal levels. Using the geometric constraints provided by seismic data, gravity modelling of the Alpine lithosphere/asthenosphere system relative to stable central European platform clearly favours a gently inclined subduction zone reaching down to at least 200 km depth. Such a gently dipping subduction zone is at odds with prominent models on Alpine geodynamics which favour a near-vertical orientation of the subducting lithosphere (‘Verschluckung’). In agreement with the wedging hypothesis indirectly inferred from the seismic data the short wavelength part of the Alpine gravity anomaly requires a middle crust of anomalously high density in the axial zone of the orogen. Both seismic and gravimetric evidence therefore suggest that late-orogenic lithospheric shortening and crustal thickening was governed by the mechanical decoupling of the upper, middle and lower parts of the crust. The amount of subducted lower crustal material cannot be constrained by gravity modelling since its gravity effect cannot be separated from the effect of the subducting slab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1992.tb00571.x
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    Paper (German National Licenses)
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  • 2
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    The AlpArray Seismic Network: A Large-Scale European Experiment to Image the Alpine Orogen (2018)
    Springer
    In:  Surveys in Geophysics, 39 (5). pp. 1009-1033.
    Details
    Publication Date: 2021-02-08
    Description: The AlpArray programme is a multinational, European consortium to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps–Apennines–Carpathians–Dinarides orogenic system. The AlpArray Seismic Network has been deployed with contributions from 36 institutions from 11 countries to map physical properties of the lithosphere and asthenosphere in 3D and thus to obtain new, high-resolution geophysical images of structures from the surface down to the base of the mantle transition zone. With over 600 broadband stations operated for 2 years, this seismic experiment is one of the largest simultaneously operated seismological networks in the academic domain, employing hexagonal coverage with station spacing at less than 52 km. This dense and regularly spaced experiment is made possible by the coordinated coeval deployment of temporary stations from numerous national pools, including ocean-bottom seismometers, which were funded by different national agencies. They combine with permanent networks, which also required the cooperation of many different operators. Together these stations ultimately fill coverage gaps. Following a short overview of previous large-scale seismological experiments in the Alpine region, we here present the goals, construction, deployment, characteristics and data management of the AlpArray Seismic Network, which will provide data that is expected to be unprecedented in quality to image the complex Alpine mountains at depth.
    Type: Article , PeerReviewed
    Format: text
    Format: video
    Format: other
    Format: other
    Format: other
    Format: text
    DOI: 10.1007/s10712-018-9472-4
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Approach to submerged fore-arc subductions in the Lesser Antilles and Hellenic arcs: integrated marine MCS, refraction, and OBS seismic activity and noise recording (2011)
    In:  [Invited talk] In: EGU General Assembly 2011, 03.-06.04.2011, Vienna, Austria .
    Details
    Publication Date: 2012-07-06
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 4
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    A 80 OBS and and 30 Land 3-component seismometers array encompassing the 280 km segment of the Lesser Antilles subduction megathrust seismogenic zone : view of current seismicity (2010)
    In:  [Talk] In: EGU General Assembly, 02.05.-07.05, Vienna, Austria .
    Details
    Publication Date: 2012-07-06
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 5
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    An integrated approach to the seismic activity and structure of the central Lesser Antilles subduction megathrust seismogenic zone (2010)
    In:  [Talk] In: EGU General Assembly, 02.05.-07.05, Vienna, Austria .
    Details
    Publication Date: 2012-07-06
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 6
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    Methoni Mw 6.8 rupture and aftershocks distribution from a dense array of OBS and land seismometers, offshore SW Hellenic subduction (2020)
    Elsevier
    Details
    Publication Date: 2023-02-08
    Description: Highlights • Spatio-temporal distribution of the Mw 6.8 Methoni aftershocks by OBS • Aftershocks driven by afterslip • Post-seismic deformation spread within the forearc crust • Bending-related normal faulting of the subducting crust Abstract Along the south-western offshore Hellenic subduction zone, the overriding Aegean upper plate above the Mediterranean oceanic lithosphere generates uncommon large earthquakes on the offshore megathrust fault. The largest subduction thrust event, for half a century, has been the 14 February 2008 Methoni earthquake (Mw = 6.8) that occurred offshore of the southwest coast of Peloponnesus. We conducted micro-seismicity experiments around the rupture area and forearc domain -between Peloponnesus and Crete- using ocean bottom seismometers (OBS) jointly with land-based seismological stations. Our first experiment in 2006, had revealed an association of the Matapan Trough, a 400-km-long forearc basin, with local seismicity clustering and a possible gap in activity over the later Methoni rupture area. Here we present new data of post-Methoni seismic activity, recorded during a time-span of 11 months, beginning in October 2008 within the period of proposed afterslip on the megathrust, by an extended and dense seismic array consisting of up to 33 OBS. A minimum 1D velocity model was constructed for the region to provide better constraints on absolute locations and double-difference relocation was applied to produce an enhanced image of the spatial distribution of hypocenters. The high resolution earthquake locations confirm correlation of the Matapan Trough with local seismicity as a regional feature, also filling up the previously observed gap. Over the Methoni rupture area, we constrain seismicity to be located mainly within the upper plate. Hypocenters are also resolved above the updip and downdip edges of the rupture area, respectively. Seismic activity provides hints of upper plate structures which were activated in response to post-seismic deformation spreading within the forearc crust. Our findings highlight the characteristics of a megathrust domain which is related with a highly deformable overriding plate and controlled by a segmented lower plate topography.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Arrival angles of teleseismic fundamental mode Rayleigh waves across the AlpArray (2019)
    Wiley
    In:  Geophysical Journal International, 218 (1). pp. 115-144.
    Details
    Publication Date: 2022-01-31
    Description: The dense AlpArray network allows studying seismic wave propagation with high spatial resolution. Here we introduce an array approach to measure arrival angles of teleseismic Rayleigh waves. The approach combines the advantages of phase correlation as in the two-station method with array beamforming to obtain the phase-velocity vector. 20 earthquakes from the first two years of the AlpArray project are selected, and spatial patterns of arrival-angle deviations across the AlpArray are shown in maps, depending on period and earthquake location. The cause of these intriguing spatial patterns is discussed. A simple wave-propagation modelling example using an isolated anomaly and a Gaussian beam solution suggests that much of the complexity can be explained as a result of wave interference after passing a structural anomaly along the wave paths. This indicates that arrival-angle information constitutes useful additional information on the Earth structure, beyond what is currently used in inversions.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1093/gji/ggz081
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Ambient-noise tomography of the wider Vienna Basin region (2018)
    Wiley
    In:  Geophysical Journal International, 215 (1). pp. 102-117.
    Details
    Publication Date: 2021-02-08
    Description: We present a new 3-D shear-velocity model for the top 30 km of the crust in the wider Vienna Basin region based on surface waves extracted from ambient-noise cross-correlations. We use continuous seismic records of 63 broad-band stations of the AlpArray project to retrieve interstation Green’s functions from ambient-noise cross-correlations in the period range from 5 to 25 s. From these Green’s functions, we measure Rayleigh group traveltimes, utilizing all four components of the cross-correlation tensor, which are associated with Rayleigh waves (ZZ, RR, RZ and ZR), to exploit multiple measurements per station pair. A set of selection criteria is applied to ensure that we use high-quality recordings of fundamental Rayleigh modes. We regionalize the interstation group velocities in a 5 km × 5 km grid with an average path density of ∼20 paths per cell. From the resulting group-velocity maps, we extract local 1-D dispersion curves for each cell and invert all cells independently to retrieve the crustal shear-velocity structure of the study area. The resulting model provides a previously unachieved lateral resolution of seismic velocities in the region of ∼15 km. As major features, we image the Vienna Basin and Little Hungarian Plain as low-velocity anomalies, and the Bohemian Massif with high velocities. The edges of these features are marked with prominent velocity contrasts correlated with faults, such as the Alpine Front and Vienna Basin transfer fault system. The observed structures correlate well with surface geology, gravitational anomalies and the few known crystalline basement depths from boreholes. For depths larger than those reached by boreholes, the new model allows new insight into the complex structure of the Vienna Basin and surrounding areas, including deep low-velocity zones, which we image with previously unachieved detail. This model may be used in the future to interpret the deeper structures and tectonic evolution of the wider Vienna Basin region, evaluate natural resources, model wave propagation and improve earthquake locations, among others.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/gji/ggy259
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Crustal Thinning From Orogen to Back-Arc Basin: The Structure of the Pannonian Basin Region Revealed by P-to-S Converted Seismic Waves (2021)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: We present the results of P-to-S receiver function analysis to improve the 3D image of the sedimentary layer, the upper crust, and lower crust in the Pannonian Basin area. The Pannonian Basin hosts deep sedimentary depocentres superimposed on a complex basement structure and it is surrounded by mountain belts. We processed waveforms from 221 three-component broadband seismological stations. As a result of the dense station coverage, we were able to achieve so far unprecedented spatial resolution in determining the velocity structure of the crust. We applied a three-fold quality control process; the first two being applied to the observed waveforms and the third to the calculated radial receiver functions. This work is the first comprehensive receiver function study of the entire region. To prepare the inversions, we performed station-wise H-Vp/Vs grid search, as well as Common Conversion Point migration. Our main focus was then the S-wave velocity structure of the area, which we determined by the Neighborhood Algorithm inversion method at each station, where data were sub-divided into back-azimuthal bundles based on similar Ps delay times. The 1D, nonlinear inversions provided the depth of the discontinuities, shear-wave velocities and Vp/Vs ratios of each layer per bundle, and we calculated uncertainty values for each of these parameters. We then developed a 3D interpolation method based on natural neighbor interpolation to obtain the 3D crustal structure from the local inversion results. We present the sedimentary thickness map, the first Conrad depth map and an improved, detailed Moho map, as well as the first upper and lower crustal thickness maps obtained from receiver function analysis. The velocity jump across the Conrad discontinuity is estimated at less than 0.2 km/s over most of the investigated area. We also compare the new Moho map from our approach to simple grid search results and prior knowledge from other techniques. Our Moho depth map presents local variations in the investigated area: the crust-mantle boundary is at 20–26 km beneath the sedimentary basins, while it is situated deeper below the Apuseni Mountains, Transdanubian and North Hungarian Ranges (28–33 km), and it is the deepest beneath the Eastern Alps and the Southern Carpathians (40–45 km). These values reflect well the Neogene evolution of the region, such as crustal thinning of the Pannonian Basin and orogenic thickening in the neighboring mountain belts.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    Format: archive
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Shear wave splitting in the Alpine region (2021)
    Oxford University Press
    Details
    Publication Date: 2024-02-07
    Description: To constrain seismic anisotropy under and around the Alps in Europe, we study SKS shear wave splitting from the region densely covered by the AlpArray seismic network. We apply a technique based on measuring the splitting intensity, constraining well both the fast orientation and the splitting delay. Four years of teleseismic earthquake data were processed, from 723 temporary and permanent broad-band stations of the AlpArray deployment including ocean-bottom seismometers, providing a spatial coverage that is unprecedented. The technique is applied automatically (without human intervention), and it thus provides a reproducible image of anisotropic structure in and around the Alpine region. As in earlier studies, we observe a coherent rotation of fast axes in the western part of the Alpine chain, and a region of homogeneous fast orientation in the Central Alps. The spatial variation of splitting delay times is particularly interesting though. On one hand, there is a clear positive correlation with Alpine topography, suggesting that part of the seismic anisotropy (deformation) is caused by the Alpine orogeny. On the other hand, anisotropic strength around the mountain chain shows a distinct contrast between the Western and Eastern Alps. This difference is best explained by the more active mantle flow around the Western Alps. The new observational constraints, especially the splitting delay, provide new information on Alpine geodynamics.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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