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  • 1
    Call number: M 12.0316
    Type of Medium: Monograph available for loan
    Pages: 209 S. : z.T. farb. Ill. und graph. Darst.
    ISBN: 9783034804592
    Series Statement: Pageoph topical volumes
    Classification:
    Gravimetry
    Location: Upper compact magazine
    Branch Library: GFZ Library
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 3 (1991), S. 0 
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We consider an isochemical, isentropic, incompressible fluid half-space and study quasistatic viscoelastic perturbations, induced by two-dimensional (2D) surface loads, of a hydrostatic initial state. In view of the regional or local scale required for deformations of planets to be amenable to the half-space approximation, the model is assumed to be externally gravitating. We derive analytic solutions for the displacement and incremental stress components and study several approximations to the expressions. Particular emphasis is placed on discriminating between the material and local incremental stresses. Based on this distinction, deeper insight is gained into the physical significance of the solution.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 104 (1991), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We consider a chemically and entropically stratified, compressible, rotating fluid planet and study gravitational-viscoelastic perturbations of a hydrostatic initial state. Using the Lagrangian formulation, we first derive the incremental field equations and continuity conditions governing the perturbations. Following this, we deduce the asymptotes to the equations for short and long times after the onset of the perturbations. the short-time asymptotic equations are referred to as the incremental field equations and continuity conditions of generalized elastodynamics. They include the equations of conventional elastodynamics as zeroth-order approximations. the long-time asymptotic equations agree with the incremental field equations and continuity conditions of Newtonian-viscous fluid dynamics. In particular, the incremental thermodynamic pressure appearing in the long-time asymptote to the incremental constitutive equation satisfies the appropriate incremental state equation. Finally, we introduce the generalized incremental incom-pressibility condition. Based on it, we derive approximate incremental field equations for gravitational-viscoelastic perturbations of isochemical, isentropic and compressible regions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 121 (1995), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The glacial-isostatic adjustment following the removal of the Pleistocene ice sheets furnishes basic information on the thickness of the Earth's lithosphere and the viscosity of the subjacent mantle. Paper I is concerned with an elementary interpretation of the post-glacial land emergence observed at a restricted set of six locations in the Svalbard Archipelago.The interpretation is based on a three-layer, incompressible Maxwell-viscoelastic earth model, which is forced by a time-dependent load distribution simulating the deglaciation history of the Svalbard Archipelago and the Barents Sea. In view of inconclusive geomorphological evidence suggesting either total or partial glaciation of the area at glacial maximum, two simple load models, BARENTS-T1 and BARENTS-P1, are considered in the first instance.A comparison between the calculated and observed values of land emergence suggests increases in lithosphere thickness and asthenosphere viscosity with increasing distance of the location from the continental margin. The trends are qualitatively insensitive to the load model, load thickness or load cross-section used. For load model BARENTS-T1 with parabolic cross-section, an initial load thickness of 1.50 km and a relaxed fitting criterion, the lateral variations are only weak. If a more restrictive fitting criterion is employed, the variations become more prominent and suggest increasing values of lithosphere thickness from below 80 km to above 140 km and of asthenosphere viscosity from below 3 × 1018 Pa s to above 2 × 1019 Pa s over a distance of about 300 km.In Paper II (Kaufmann & Wolf 1995), a high-resolution load model and an extended set of land-emergence observations are used to study further the possibility of resolving lateral heterogeneity in the upper mantle below the Svalbard Archipelago.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 127 (1996), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: For more than 30 years, Sauramo's (1958) shoreline diagram of the Fennoscandian uplift has been used in geophysical studies for estimates of the glacial-isostatic decay spectrum in order to infer from it the viscosity stratification in the Earth's mantle below Fennoscandia. The intent of the present note is to point out that more recent geological studies suggest that Sauramo's shoreline diagram is an incorrect representation of the Fennoscandian uplift. Geophysical interpretations based on the diagram may therefore require revision.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 117 (1994), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The incremental gravitational force (IGF) arises from perturbations of the earth's gravitational potential. In glacial isostasy, its sources are the surficial and internal mass redistributions associated with the growth and decay of the continental ice sheets.We examine the errors caused by the neglect of the IGF using closed-form solutions of the equations governing surface-load induced perturbations of two types of incompressible, spherical-earth models: (1) Maxwellian-viscoelastic mantle enclosed by elastic lithosphere, and (2) Maxwellian-viscoelastic mantle enclosing inviscid core. Calculations in the Legendre domain of the radial surface displacement for these models show that neglecting the IGF causes enhancement of the elastic response and acceleration of the viscous relaxation. In the space domain, these changes entail corresponding modifications of the calculated land adjustment. The magnitude of the error caused by the neglect of the IGF strongly depends on the deglaciation history and load radius adopted. Assuming a typical deglaciation history, the error reaches a maximum of less than 20m at the end of the deglaciation phase for loads comparable in size to the Canadian or the Fennoscandian ice sheets.We also compare spherical-earth models with IGF and plane-earth models without IGF. Calculations of the radial surface displacement show that the errors due to the neglect of sphericity and the IGF partially compensate each other. Taking the uncertainties of the observational data into account, we conclude that the majority of the Canadian and Fennoscandian glacial-isostatic adjustment data can be modelled with sufficient accuracy using a plane-earth model without IGF.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 116 (1994), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We consider a spherical, isochemical, incompressible, non-rotating fluid planet and study infinitesimal, quasi-static, gravitational-viscoelastic perturbations, induced by surface loads, of a hydrostatic initial state. The analytic solution to the incremental field equations and interface conditions governing the problem is derived using a formulation in terms of the isopotential incremental pressure measuring the increment of the hydrostatic initial pressure with respect to a particular level surface of the gravitational potential. This admits the decoupling of the incremental equilibrium equation from the incremental potential equation. As result, two mutually independent (4 times 4) and (2 times 2) first-order ordinary differential systems in terms of the mechanical and gravitational quantities, respectively, are obtained, whose integration is algebraically easier than that of the conventional (6 X 6) differential system. In support of various types of application, we provide transfer functions, impulse-response functions and Green's functions for the full range of incremental field quantities of interest in studies of planetary deformations. The functional forms in the different solution domains involve explicit expressions for the Legendre degrees n= 0, n= 1 and n≥ 2, apply to any location in the interior or exterior of the planet and are valid for any type of generalized Maxwell viscoelasticity and for arbitrary surface loads.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 127 (1996), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In Paper I (Breuer & Wolf 1995), a preliminary interpretation of the postglacial land emergence observed at a restricted set of six locations in the Svalbard Archipelago was given. The study was based on a simple model of the Barents Sea ice sheet and suggested increases in lithosphere thickness and asthenosphere viscosity with increasing distance from the continental margin.In the present paper, the newly developed high-resolution load model. BARENTS-2, and land-uplift observations from an extended set of 25 locations are used to study further the possibility of resolving lateral heterogeneity in the upper mantle below the northern Barents Sea. A comparison of the calculated and observed uplift values shows that the lithosphere thickness is not well resolved by the observations, although values above 110 km are most common for this parameter. In contrast to this, there are indications of a lateral variation of asthenosphere viscosity. Whereas values in the range 1018-1020Pas are inferred for locations close to the continental margin, 1020-1021 Pa s are suggested further away from the margin.A study of the sensitivity of the values found for lithosphere thickness and asthenosphere viscosity to modifications of load model BARENTS-2 shows that such modifications can be largely accommodated by appropriate changes in lithosphere thickness, whereas the suggested lateral variation of asthenosphere viscosity is essentially unaffected. An estimate of the influence of the Fennoscandian. ice sheet leads to the conclusion that its neglect results in an underestimation of the thickness of the Barents Sea ice sheet by about 10 per cent.
    Type of Medium: Electronic Resource
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