HR: 0800h
AN: S41C-1037    [Abstracts]
TI: Geodynamic implications of lateral variations in mantle rheology on convection related observables and inferred viscosity models
AU: * Moucha, R
EM: moucha@physics.utoronto.ca
AF: GEOTOP - Départment des Sciences de la Terre et de l'Atmosphére, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, QC H3C 3P8 Canada
AU: Forte, A M
EM: forte.alessandro@uqam.ca
AF: GEOTOP - Départment des Sciences de la Terre et de l'Atmosphére, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, QC H3C 3P8 Canada
AU: Mitrovica, J X
EM: jxm@physics.utoronto.ca
AF: Department of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7 Canada
AU: Daradich, A
EM: daradich@physics.utoronto.ca
AF: Department of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7 Canada
AB: One of the major objectives of tomography-based mantle flow modelling is the inference of the rheological structure of the mantle. With few exceptions, most studies have adopted a viscous flow theory which assumes that the mantle rheology may be represented in terms of an effective viscosity which varies with depth only. Here, we present a detailed assessment of the impact of lateral variations in viscosity on global convection related observables using a variational procedure for modelling of buoyancy induced flow in a 3-D spherical shell. We find that predictions of dynamic topography at the surface and the core-mantle-boundary, as well as the gravitational response of the earth, are marginally affected by the inclusion of lateral viscosity variations (LVV) when compared with results for a purely 1-D radial viscosity model. In particular, we found that the effect of LVV on the global observables is significantly smaller than the variability due to uncertainties in the current seismic tomography models. We also quantify the effect of LVV in the context of the viscosity inverse problem using two synthetic data sets generated with a 1-D viscosity profile and with a fully 3-D viscosity distribution which is expanded laterally in spherical harmonics up to degree 32, yielding a lateral viscosity contrast of 3 orders of magnitude. We compared the 1-D viscosity profiles recovered from the inversions and found that LVV have virtually no effect on our inversion results. The synthetic viscosity inversion further revealed that the effect of LVV is small in comparison to the uncertainties arising from the seismic tomography models. Finally, the inversions demonstrate that the 1-D viscosity profiles derived from actual surface data represent the depth variation of the horizontally averaged logarithm of the 3-D viscosity distribution in the mantle.
DE: 0545 Modeling (4255)
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 8162 Rheology: mantle (8033)
SC: Seismology [S]
MN: Fall Meeting 2005