Free wobble/nutation of the Earth : a new approach for hydroAppalachian Mountainsstatic Earth models

Zhang, Yuli (1998) Free wobble/nutation of the Earth : a new approach for hydroAppalachian Mountainsstatic Earth models. Masters thesis, Memorial University of Newfoundland.

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    Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
    (Original Version)

Abstract

One of the two conventional approaches to formulate a theory to describe the Earth's wobble/nutations is to regard these as among the set of free oscillations of a rotating oblate Earth model. This theory, now standard, predicts the eigenperiods of the Chandler wobble and free core nutation (FCN). Very-long-baseline interferometry and superconducting gravimetry data indicate a significant discrepancy between the inferred and theoretically-predicted values of FCN period. The widely-accepted explanation for this discrepancy is that the core-mantle boundary's ellipticity departs from its hydrostatic equilibrium value. However the standard theory for a hydrostatic Earth model has two mathematical shortcomings, which should be removed before abandoning hydrostatic equilibrium as the reference state. These shortcomings are: (1) the treatment of the governing equations in interior regions is not consistent with the treatment of the boundary conditions at surfaces of discontinuity in material properties; (2) formulation of the boundary conditions does not treat material properties properly. To remove these shortcomings, in this thesis spherical polar coordinates are replaced by a non-orthogonal coordinate system (ro,θ,ø), named after Clairaut. A set of new variables in Clairaut coordinates is introduced, generalizing the conventional notation for a spherical-layered Earth model. The governing equations and boundary conditions, written in these new variables, give a consistent description of free wobble/nutation accurate to first order in ellipticity. A program to compute wobble/nutation eigenperiods has been written, and preliminary numerical results obtained, but either the program still contains errors or truncation is too severe.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/6541
Item ID: 6541
Additional Information: Bibliography: leaves 84-87.
Department(s): Science, Faculty of > Earth Sciences
Date: 1998
Date Type: Submission
Geographic Location: Earth
Library of Congress Subject Heading: Nutation; Earth (Planet)--Rotation--Mathematical models

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