HR: 1340h
AN: G43B-1207    [Abstracts]
TI: Response of Hydrated Crust to Tidal Loading: Theoretical Predictions for Comparison With GPS-inferred Displacements.
AU: * Rouleau, P M
EM: prouleau@swgc.mun.ca
AF: Division of Science, Sir Wilfred Grenfell College, Memorial University of Newfoundland, University Drive, Corner Brook, NL A2H 6P9, Canada
AB: In recent years, deformation of the Earth surface due to ocean-tide loading has been measured by both ground- and space-based techniques in several coastal regions. In particular, displacements inferred from the Global Positioning System (GPS) have been reported for regions of high tidal ranges (e. g. British Isles; Bay of Fundy). As the database of such measurements lengthens, the displacement amplitudes and phase lags of the main tidal constituents improve, thereby providing better constraints on possible ocean tide loading displacement (OTLD) models. Available OTLD models, however, are all based on the assumption that the response of the solid Earth at tidal frequencies is perfectly elastic. This assumption is questionable at the regional scale, especially where the earth structure is predominately deformed by the higher harmonics in the loading function. Under such conditions, ground-based geophysical constraints indicate an earth structure which is heterogeneous, fractured, dissipative and often fluid-saturated. A data-constrained structural model that reflects these complexities is presented; it is used to predict the anelastic earth-response to ocean tide loading at the primary semi-diurnal period (12.25 h). Central to this model is an absorption mechanism by which elastic energy is lost to heat via viscous flow of interstitial nanofluids. The scaling of this microscopic mechanism to observational scales is done using an effective-medium scheme and the theory of viscoelasticity. The anelastic response is quantified by a quality factor (Q) which, in turn, quantifies the phase lag of response behind loading. Predictions from such modeling are compared to calculations from currently used OTLD models, and to recent GPS-derived tidal displacements. Thus, demands on the precision required of GPS data for significantly improving OTLD models can be assessed.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1835 Hydrogeophysics
DE: 3021 Marine hydrogeology
DE: 3909 Elasticity and anelasticity
DE: 5114 Permeability and porosity
SC: Geodesy [G]
MN: 2007 Fall Meeting