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Zur Parametrisierung radialsymmetrischer Dichtemodelle für die Erde / H. Wziontek (2005)

Public Titre : Zur Parametrisierung radialsymmetrischer Dichtemodelle für die Erde Titre original : [Pour la paramétrisation de modèles denses symétriques pour la Terre] Type de document : Thèse/HDR Auteurs : H. Wziontek, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2005 Collection : DGK - C Sous-collection : Dissertationen num. 587 Importance : 102 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-5026-6 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] croute terrestre [Termes IGN] densité [Termes IGN] équation de Poisson [Termes IGN] masse de la Terre [Termes IGN] potentiel de pesanteur terrestre [Termes IGN] vitesse Résumé : (Auteur) Even in the frame of a spherical symmetric, non-rotating, linear elastic and isotropic model an independent description of the Earth's density and elastic properties, as usual in most existing models, has no unique solution and thus leads to an over-parametrisation. Whereas the elastic properties can be verified well with the help of seismic traveltimes, the density remains much less determinate. With this work, an adequate description of a normal density distribution based on a physically meaningful, non-empirical parametrisation and an abstraction to the essential physical properties will be presented. Beside the postulate on homogeneity of the chemical composition and phase inside each shell and an adiabatic gradient of temperature, the main assumption is hydrostatic equilibrium, which must be fulfilled in a global sense for the widest parts of the Earth's interior. Under these circumstances the Williamson-Adams-equation holds as a fundamental relation between density and seismic velocities. Deviations from the underlying suppositions can be described, if necessary and appropriate information exists, a priori by the Bullen-Parameter. By the physical relation between density and seismic velocities alone a parametrisation is not given. With the help of a postulate on a pressure-density-relation in historical density laws it is possible to develop a suitable function. A differential equation follows from the Poisson equation for the inner gravitational potential in conjunction with that postulate and the assumption of hydrostatic equilibrium. Its special solutions lead in consistence with seismic data to a parametrisation of the density. Extensive investigations show that only functions in even powers of the radius allow a best and stable fit to the seismic data, while ordinary polynomials most common in use are less eligible for a description of the density. Furthermore, to obtain a stable determination of the density a strict separation of the data-types is unavoidable. From the seismic velocities it is only possible to infer the shape of the density-function within the shells, additional data as the density below the crust-mantle-boundary, the geodetic values for mean mass and mean moment of inertia and the frequencies of the free oscillations are necessary to fix the absolute level in each shell. Under consideration of the aforementioned aspects it is possible to obtain a unique and stable description of a normal density distribution in accordance with seismic and geodetic information. Thus the presented parametrisation can serve as a basis for anomaly analysis in geodesy and geophysics. Numéro de notice : 13274 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54953

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