HR: 0800h
AN: T11E-1325    [Abstracts]
TI: Geodynamic Implications of Convection-Related Surface Observables: The Role of Lateral Variations in Mantle Rheology
AU: * Moucha, R
EM: moucha@physics.utoronto.ca
AF: University of Toronto, Department of Physics, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AU: Forte, A M
EM: forte.alessandro@uqam.ca
AF: Universite du Quebec a Montreal, GEOTOP - Departement des Sciences de la Terre et de l'Atmosphere, CP 8888, succursale Centre-Ville, Montreal, QUE H3C 3P8 Canada
AU: Mitrovica, J X
EM: jxm@terra.physics.utoronto.ca
AF: University of Toronto, Department of Physics, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AU: Daradich, A L
EM: adaradich@physics.utoronto.ca
AF: University of Toronto, Department of Physics, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AB: Over the past decade numerous analyses of convection-related observables, such as geoid or gravity anomalies and dynamic surface topography, have been carried out in the context of tomography-based mantle flow models in an effort to better understand the 3-D density and thermo-chemical structure of the mantle as well as the rheology of this region. With few exceptions, most of the studies have been conducted in the framework of a viscous flow theory which assumes that the mantle rheology may be represented in terms of an effective viscosity which varies with depth only. An ongoing effort to simultaneously invert both shorter time-scale glacial isostatic adjustment data, and much longer time-scale convection data, has recently yielded a new series of radial viscosity profiles which provide good fits to both sets of data. The reconciliation of regional and global constraints on mantle rheology, spanning such wide time spans, suggests that we are able to effectively resolve the mean or horizontally averaged value of viscosity as a function of depth. However, apart from some limited investigations, we have yet to carry out a detailed assessment of the impact of lateral variations in viscosity on our inferences of viscosity and deep mantle thermo-chemical structure. To this end, we present a new series of calculations which explicitly incorporate lateral viscosity variations in the viscous flow theory using both a semi-analytical variational approach and a purely numerical finite-element method. We will report here on results pertaining to the "primary" signatures of convection, such as the mantle flow and strain rate fields, as well as "secondary" or indirect signatures such as the dynamic topography and gravity fields. We also consider the impact of this rheological complexity on studies connecting backward-convection flow simulations with the geological record.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8162 Rheology--mantle
DE: 3210 Modeling
DE: 1213 Earth's interior--dynamics (8115, 8120)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting