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  • 1
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    Global azimuthal seismic anisotropy and the unique plate-motion deformation of Australia (2005)
    In:  Nature, London, Army Corps of Engineers, Woodward-Clyde Consultants, vol. 433, no. 7025, pp. 509-512, pp. B12307, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 2005
    Description: ... We infer that the fast-moving Australian plate contains the only continental region with a sufficiently large deformation at its base to be transformed into azimuthal anisotropy. Simple shear leading to anisotropy with a plunging axis of symmetry may explain the smaller azimuthal anisotropy beneath other continents.
    Keywords: Anisotropy ; Plate tectonics ; earth mantle ; Seismology
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Seismic evidence for a change in the large scale tomographic pattern across the D” layer (2016)
    Wiley
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    Publication Date: 2016-07-24
    Description: We present SEISGLOB1, a pure SV tomographic model of Earth's mantle based on Rayleigh phase velocities and normal mode self- and cross-coupling data. SEISGLOB1 is the first model that incorporates the cross-coupling of normal modes since the pioneering work of Resovsky & Ritzwoller [1999]. The simultaneous inversion of new cross-coupling normal modes and self-coupling of high order normal modes measured by Deuss et al. [2013] and Stoneley modes measured by Koelemeijer et al. [2013] allows us to show that the velocity structure at the base of the mantle is more complex than that expected from a dominant spherical hamonic degree 2 and that the relative strength of odd degrees has previously been underestimated. Near the CMB, the LLSVPs are less homogeneous than in previous studies, and various local maxima, often potentially associated with hotspots sources, are observed.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Rayleigh wave phase velocity and error maps up to the fifth overtone (2015)
    Wiley
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    Publication Date: 2015-04-19
    Description: We present a global dataset of phase velocity maps for Rayleigh waves, with their errors. These maps are obtained from the tomographic inversion of phase velocity curves measured in the period range 40-250 s by Debayle and Ricard [2012], completed with new measurements at longer periods, between 150 and 360 s. The full dataset includes ~ 22,000,000 phase velocity measurements combined to build 60 phase velocity maps covering the period range 40-360 s for the fundamental mode and up to the fifth overtone.Each phase velocity map is provided with its a posteriori error, resulting in a unique dataset which can be combined with other seismic measurements (surface waves, normal modes, body waves) in regional and global tomographic studies. A preliminary inversion of this dataset shows that it provides constraints on the shear velocity structure down to 1,000 km depth.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    An evolutionary S-wave model of the Earth upper mantle and transition zone (2016)
    Wiley
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    Publication Date: 2016-01-06
    Description: We present 3D2015_07Sv, an S-wave model of the upper mantle based on the waveform modeling of 1,359,470 Rayleigh waves recorded since 1976. The use of approximate forward theory and modeling allows updating the model with new data on a regular basis. 3D2015_07Sv contains azimuthal anisotropy, achieves a lateral resolution of ∼600 km, and is consistent with other recent models up to degree 60 in the uppermost 200 km and degree 15 in the transition zone. Although radial anisotropy has been found to extend deeper beneath continents than beneath oceans, we find no such difference for azimuthal anisotropy, suggesting that beneath most continents, the alignment of olivine crystal is preferentially horizontal, and azimuthally random at large scale. As most continents are located on slow moving plates, this supports the idea that azimuthal anisotropy aligns at large scale with the present plate motion only for plates faster than ∼4 cm yr −1 .
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Depth-variant azimuthal anisotropy in Tibet revealed by surface wave tomography (2015)
    Wiley
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    Publication Date: 2015-05-19
    Description: Azimuthal anisotropy derived from multi-mode Rayleigh wave tomography in China exhibits depth-dependent variations in Tibet, which can be explained as induced by the Cenozoic India-Eurasian collision. In west Tibet, the E-W fast polarization direction at depths 〈100 km is consistent with the accumulated shear strain in the Tibetan lithosphere, whereas the N-S fast direction at greater depths is aligned with Indian plate motion. In northeast Tibet, depth-consistent NW-SE directions imply coupled deformation throughout the whole lithosphere, possibly also involving the underlying asthenosphere. Significant anisotropy at depths of 225 km in southeast Tibet reflects sublithospheric deformation induced by northward and eastward lithospheric subduction beneath the Himalaya and Burma, respectively. The multi-layer anisotropic surface wave model can explain some features of SKS splitting measurements in Tibet, with differences probably attributable to the limited backazimuthal coverage of most SKS studies in Tibet and the limited horizontal resolution of the surface wave results.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    A global shear velocity model of the upper mantle from fundamental and higher Rayleigh mode measurements (2012)
    Wiley
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    Publication Date: 2012-10-24
    Description: We present DR2012, a global SV-wave tomographic model of the upper mantle. We use an extension of the automated waveform inversion approach of Debayle (1999) which improves our mapping of the transition zone with extraction of fundamental and higher-mode information. The new approach is fully automated and has been successfully used to match approximately 375,000 Rayleigh waveforms. For each seismogram, we obtain a path average shear velocity and quality factor model, and a set of fundamental and higher-mode dispersion and attenuation curves. We incorporate the resulting set of path average shear velocity models into a tomographic inversion. In the uppermost 200 km of the mantle, SV wave heterogeneities correlate with surface tectonics. The high velocity signature of cratons is slightly shallower (≈200 km) than in other seismic models. Thicker continental roots are not required by our data, but can be produced by imposing a priori a smoother model in the vertical direction. Regions deeper than 200 km show no velocity contrasts larger than ±1% at large scale, except for high velocity slabs within the transition zone. Comparisons with other seismic models show that current surface wave datasets allow to build consistent models up to degrees 40 in the upper 200 km of the mantle. The agreement is poorer in the transition zone and confined to low harmonic degrees (≤10).
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Attenuation tomography of the upper mantle (2017)
    Wiley
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    Publication Date: 2017-07-21
    Description: We present QsADR17, a global shear wave attenuation model of the upper mantle. Synthetic tests confirm that large-scale shear-attenuation anomalies are resolved in the whole upper mantle with limited vertical smearing (≤50 km). QsADR17 shows strong correlation with surface tectonics down to 200 km depth, with low attenuation beneath continents and high attenuation beneath oceans. The attenuation signal near 250 km depth is dominated by a high quality factor along subduction zones. Attenuating anomalies are found beneath mid-ocean ridges down to 150 km and under most Pacific hotspots from the lithosphere down to the transition zone. The presence of broad attenuating anomalies at 150 km depth in the Pacific ocean suggests that several thermal plumes pond in the asthenosphere. Evidence for compositional heterogeneities is found in the lithosphere at the base of cratons, and in a number of active regions.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Seismo-acoustic coupling induced by the breakup of the 15 Feb 2013 Chelyabinsk Meteor (2013)
    Wiley
    Details
    Publication Date: 2013-06-22
    Description: [1]  On 15th Feb 2013 around 03:20:00 UTC, the largest meteor reported since the 1908 Tunguska event was observed as a fireball traveling through the Earth's atmosphere, exploding in an air burst [2]  near the city of Chelyabinsk, Russia. The rarity of such an event provides a unique window on the physics of meteoroid collision. We report the fine seismic detection of Rayleigh waves produce by the coupling of ground motion with the incident shock wave at distances up to 4000 km from the event. Combining informations from seismic beam-forming analysis, reconstructed trajectory from casual video records, and remote sensing, we identify the Rayleigh waves as being initiated by the shock wave produced by the main blast that occasioned damages and injuries in Chelyabinsk. From the Rayleigh wave observations, we report a magnitude M s  ∼ 3.7 seismic source.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    The Zagros core: Deformation of the continental lithospheric mantle (2012)
    Wiley
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    Publication Date: 2012-11-29
    Description: The Zagros of Iran form one of the youngest collisional orogenic belts on Earth. At shallow depths, shortening across the Zagros is accommodated by folding in the sediments, high-angle thrust faulting in the basement and thickening of the lower crust, but how shortening is accommodated by the lithospheric mantle has been uncertain largely because the upper mantle seismic structure has been poorly known. We map the lateral variations in upper mantle shear wave speed beneath this region using a large, multimode surface wave data set. The upper mantle is slow for most of the Middle East, but a high shear wave speed lid extending to ∼225 km depth exists beneath the Zagros. We use a T(Vs, z) relation to convert the shear wave speed profiles to temperature profiles and fit these with geotherms to identify the base of the lithosphere. The upper mantle temperatures from the seismic model are consistent with temperatures derived from geochemical modeling. The lithosphere is less than ∼120 km thick over the region except for a thick lithospheric root beneath the Zagros, implying that shortening in the mantle is accommodated by lithospheric thickening. The composition of the volcanic rocks from above the area of the thickened lithosphere has depleted magma source regions with densities ∼60 kg m−3 less than the MORB source. Elsewhere in the Middle East the volcanic source regions have compositions and densities similar to that of MORB. The shortening across the Zagros is accommodated by lithospheric thickening but the cool thickened lithosphere has been stabilized from delamination by depletion.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
    Electronic Resource
    Electronic Resource
    Global azimuthal seismic anisotropy and the unique plate-motion deformation of Australia (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 433 (2005), S. 509-512 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Differences in the thickness of the high-velocity lid underlying continents as imaged by seismic tomography, have fuelled a long debate on the origin of the ‘roots’ of continents. Some of these differences may be reconciled by observations of radial anisotropy between 250 and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03247
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    Paper (German National Licenses)
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