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  • 1
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    Geodynamical implications from the correlation of surface geology and seismic tomographic structure (1995)
    In:  Earth planet. Sci. Lett., Potsdam, ZIPE, vol. 136, no. 4, pp. 615-627, pp. 2156, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1995
    Keywords: GeodesyY ; Geol. aspects ; Tomography ; Deep seismic sounding (espec. cont. crust) ; Cadek ; Kyalova
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Lower mantle thermal structure deduced from seismic tomography, mineral physics and numerical modelling (1994)
    In:  Earth planet. Sci. Lett., Potsdam, ZIPE, vol. 121, no. 4, pp. 385-403, pp. 2156, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1994
    Keywords: Geothermics ; earth mantle ; Tomography ; Seismology ; Mineralogy ; Modelling ; Cadek
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    New perspectives on mantle dynamics from high-resolution seismic tomographic model P1200 (1998)
    In:  Pure and Applied Geophysics, Potsdam, ZIPE, vol. 151, no. 2-4, pp. 503-525, pp. 2156, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1998
    Keywords: Tomography ; GeodesyY ; ConvolutionE ; Teleseismic events ; Seismology ; Earth model, also for more shallow analyses ! ; Cadek ; Cizkova ; PAG
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Structure and tectonics of convergent plate margins (2004)
    In:  Physics of the Earth and Planetary Interiors, Hannover, Polish Geothermal Association, vol. 141, no. 4, pp. 241, pp. 1051, (ISSN: 1340-4202)
    Details
    Publication Date: 2004
    Keywords: Plate tectonics ; Velocity depth profile ; Subduction zone ; Spicak ; Cadek ; PEPI
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    European Variscan orogenic evolution as an analogue of Tibetan-Himalayan orogen - Insights from petrology and numerical modeling (2016)
    Wiley
    In: Tectonics
    Details
    Publication Date: 2016-07-05
    Description: The European Variscan orogeny can be compared to the Tibetan–Himalayan system for three main reasons: 1) The Variscan belt originated through progressive amalgamation of Gondwanan blocks that were subsequently squeezed between the Laurussia and Gondwana continents. Similarly, the Tibetan–Himalayan orogen results from amalgamated Gondwanan blocks squeezed between Asia and India. 2) The duration of the collisional period and the scale of the two orogens are comparable. 3) In both cases the collisional process resulted in formation of a thick crustal root and long lasting high-pressure granulite-facies metamorphism. Recent petrological data allow a more detailed comparison pointing to similarities also in the mid-crustal re-equilibration of the granulites and their association with specific (ultra-)potassic magmatic rocks. In both orogens, the origin of the granulites was attributed to relamination and thermal maturation of lower-crustal allochthon below upper-plate crust. Later evolution was explained by mid-crustal flow eventually leading to extrusion of the high-grade rocks. We propose that the lower and middle crustal processes in hot orogens are connected by gravity overturns. Such laterally-forced gravity-driven exchanges of material in the orogenic root were already documented in the Variscides, but the recent data from Tibet and Himalaya show that this process may have occurred also elsewhere. Using numerical models we show that the exchange of the lower and middle crust can be efficient even for a minor density inversion and various characteristics of the crustal layers. The modeled pressure–temperature paths are compatible with two-stage metamorphism documented in Tibet and Himalaya.
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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    PAPER CURRENT
  • 6
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    Topography and geoid induced by a convecting mantle beneath an elastic lithosphere (2012)
    Oxford University Press
    Details
    Publication Date: 2012-02-22
    Description: SUMMARY In the absence of seismological measurements, observations of the topography and gravity fields of solid planets are the primary constraints on their internal structure. To compute the synthetic geoid and topography induced by the dynamics of planetary interiors, we introduce a 3-D numerical tool describing mantle convection beneath an elastic lithosphere. Although the energy conservation is treated in the whole spherical domain, the deformation aspect is solved using a hybrid technique (finite volume method for the viscous flow, spectral method for elastic deformation). The mechanical coupling is achieved via the imposition of the traction at the surface of the viscous flow as a basal boundary condition for the elastic deformation. We present both response functions and full thermal convection cases computed with our new method for planetary bodies of varying dimensions: the filtering effect of the lithosphere on the dynamic topography and geoid is specific for each planetary body, justifying the importance of such a tool. Furthermore, since our approach specifically focuses on the mechanical coupling at the base of the lithosphere, it will permit future, more elaborate, rheological treatments. It also enables to discriminate between the radial and tangential components of the viscous traction. The latter is found to have a significant influence on the elastic deformation. The effect on geoid is prominent. More specifically, while a thin elastic lithosphere is usually considered to play little role on the dynamic topography and geoid of Venus, a ∼35 per cent reduction is obtained for geoid height in the numerical example we propose. On a planet with thicker elastic lithosphere such as Mars, the consequence of this filtering effect is to rule out the possibility of a dynamical support for the Tharsis Rise, even for the lowest admissible values of elastic thickness in this region.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 7
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    Deformation of an elastic shell with variable thickness: a comparison of different methods (2012)
    Oxford University Press
    Details
    Publication Date: 2012-06-14
    Description: SUMMARY Deformation of the outermost parts of single-plate planetary bodies is often modelled in terms of the response of a spherical elastic shell to surface or basal loading. As the thickness of such elastic lithosphere is usually much smaller than the radius of the body, the deformation is commonly approximated by that obtained for a thin elastic shell of uniform thickness. The main advantage of the thin shell approximation is its simplicity—the solution can be expressed analytically if the thickness of the shell is uniform, but even in the case of a thin shell of variable thickness, when the problem must be solved numerically, the computational costs are much lower than in a fully 3-D case. Here we analyse the error of the thin shell approximation by comparing it with the solution obtained for a shell of finite thickness using finite element methods. Special attention is paid to a shell of variable thickness and, in general, to the effect of elastic thickness variations on local deformation. For a shell of uniform thickness with the outer radius corresponding to Mars, we find that the error in radial displacement at low harmonic degrees (ℓ≤ 20) does not exceed 5 per cent for small shell thicknesses ( d ≤ 50 km) and 10 per cent for thick shells ( d ∼ 250 km). Similar accuracy is also found for a shell of variable thickness if the thin shell approximation is used. Our numerical tests indicate that local deformation of a shell is mostly sensitive to the average thickness of the shell in the near zone while the effect of thickness variations in the far zone can be neglected in the first approximation. Consequently, the extremely simple thin shell method, designed for shells of uniform thickness, can be effectively used to obtain a reasonably accurate estimate of deflection even in the case of a shell with varying thickness. Finally, we investigate the deformation of an elastic lithosphere due to viscous flow beneath the shell, and we propose an extension of the concept, recently developed to correct dynamic topography for the effect of an elastic lithosphere, to the case of a shell of variable thickness.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 8
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    The effect of variable thermal diffusivity on kinematic models of subduction (2012)
    Wiley
    Details
    Publication Date: 2012-07-11
    Description: We examine the influence of variable thermal properties on the thermal state of a subducting slab in the upper mantle and the transition zone by combining a kinematic slab model with models of thermal conductivity. Thermal diffusivity and conductivity models for major mantle minerals in the MgO-SiO2 system are developed based on experimental measurements on these minerals at high pressure and temperature. The models show significantly higher thermal conductivity for stishovite and clinopyroxene compared to the Mg2SiO4 polymorphs and majorite garnet. In our subduction model we consider scenarios with a differentiated slab (basalt–harzburgite–pyrolite) in a pyrolite mantle and uniform composition for both the slab and the mantle (pyrolite or a pure Mg2SiO4-based system). The role of highly conductive pyroxene is examined by taking it into account in some models and replacing it in others with majorite garnet. This choice has a strong influence on the thermal state of the slab, shifting the depth of the −1000 K temperature anomaly by as much as 100 km. This is caused by faster cooling of the plate at the surface and thermal insulating effects once subducted. Temperature differences between models with variable thermal diffusivity and those with constant parameters can reach ∼125 K, i.e. 10% of total thermal anomalies of the slab relative to an average geotherm. Taking into account the stable mineral phases we evaluate density variations between different models and find that variable thermal diffusivity results in a modest increase of negative buoyancy of the slab.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Mercury's low-degree geoid and topography controlled by insolation-driven elastic deformation (2015)
    Wiley
    Details
    Publication Date: 2015-09-02
    Description: Mercury experiences an uneven insolation that leads to significant latitudinal and longitudinal variations of its surface temperature. These variations, which are predominantly of spherical harmonic degree 2 and 4, propagate to depth, imposing a long-wavelength thermal perturbation throughout the mantle. We computed the accompanying density distribution and used it to calculate the mechanical and gravitational response of a spherical elastic shell overlying a quasi-hydrostatic mantle. We then compared the resulting geoid and surface deformation at degree-2 and 4 with Mercury's geoid and topography derived from MESSENGER data. More than 95% of the data can be accounted for if the thickness of the elastic lithosphere were between 110 and 180 km when the thermal anomaly was imposed. The obtained elastic thickness implies that Mercury became locked into its present 3:2 spin-orbit resonance later than about 1 Gyr after planetary formation.
    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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  • 10
    Electronic Resource
    Electronic Resource
    Regional Correlation Analysis between Seismic Heterogeneity in the Lower Mantle and Subduction in the Last 180 Myr: Implications for Mantle Dynamics and Rheology (1998)
    Springer
    Pure and applied geophysics 151 (1998), S. 527-537 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Correlation analysis, seismic velocity heterogeneities, subduction history.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. —We have carried out a regional correlation analysis between the seismic structure of the lower mantle and the reconstructions of subduction sites in the past 180 Myr with the aim of estimating individual styles of slab motion over different parts of the earth. The correlation patterns obtained for three subduction branches (West Pacific, East Pacific and Alpine-Himalayan) are remarkably different. In the West Pacific, the subducting slabs tend to be stagnant beneath the 660-km discontinuity, while basically no subducted lithosphere has been detected below the depth of 1000 km. In contrast, the lithosphere subducted beneath the Americas seems to penetrate through the lower mantle continuously, showing correlation peaks at depth intervals of 800–1100 km and 1900–2500 km. In the Alpine-Hi malayan region, significant correlation has been found below the 660-km discontinuity for recent subduction and in the mid-mantle for subduction younger than 120 Myr. An increase in the correlation close to the core-mantle boundary nevertheless indicates that, under certain circumstances, the slabs can reach the bottom of the mantle in the West Pacific and in the Alpine-Himalayan regions as well. The correlation peak at a depth of around 1000 km is common to all the subduction branches. However, its depth rather varies for different subduction zones and, thus, it is not clear whether this correlation maximum may be associated with a global mid-mantle discontinuity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050127
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