Gross Earth Data and Mantle Convection: New Inferences of Mantle Viscosity
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We introduce a theory for calculation of the buoyancy-induced flow expected on the basis of seismic tomographic inferences of lateral heterogeneity in the mantle, for a compressible mantle possessing an arbitrary radial viscosity stratification. This theory includes the first fully consistent treatment of all gravitationally-induced loads arising from the effects of self-gravitation. We employ this theory to calculate the nonhydrostatic geoid and surface horizontal divergence and, by matching these predicted surface observables to the corresponding observational data, we constrain the depth variation of mantle viscosity. We also introduce a new formalism for calculating the flow that is consistent with the existence of rigid tectonic plates at the Earth’s surface. This predicted plate-like surface flow is sensitive to the absolute value of the mantle viscosity and, by matching it to the observed plate velocities, we infer mantle viscosities that are compatible with those inferred from glacial isostatic adjustment data.
KeywordsPlate Motion Mantle Convection Horizontal Divergence Mantle Flow Density Heterogeneity
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- Cathles, L.M., 1975. The Viscosity of the Earth’s Mantle, Princeton University Press, Princeton, J.J.Google Scholar
- Clayton, R.W. and Comer, R.P., 1984. A tomographic analysis of mantle heterogeneities, (abstract) Terra Cognita, 4, 282–283.Google Scholar
- Forte, A.M., 1989. Mantle Convection and Global Geophysical Observables, Ph.D. thesis, Department of Physics, University of Toronto.Google Scholar
- Forte, A.M. and Peltier, W.R., 1989. Mantle convection and core-mantle boundary topography: explanations and implications, Tectonophysics, in press.Google Scholar
- Forte, A.M. and Peltier, W.R., 1990. Viscous flow models of global geophysical observables. I. Forward problems, submitted to J. Geophvs. Res. Google Scholar
- Hager, B.H. and Clayton, R.W., 1989. Constraints on the structure of mantle convection using seismic observations, flow models, and the geoid, in W.R. Peltier (ed.), Mantle Convection, Gordon and Breach Science Publishers, New York, 657–763.Google Scholar
- Nicolas, A. and Poirier, J.P., 1976. Crystalline Plasticity and Solid State Flow in Metamorphic Rocks, John Wiley and Sons, London, 444 pp.Google Scholar
- Ricard, Y., Fleitout, L. and Froidevaux, C., 1984. Geoid heights and lithospheric stresses for a dynamic Earth, Ann. Geophys., 2, 267–286.Google Scholar
- Ricard, Y. and Vigny, C., 1989. Mantle dynamics with induced plate tectonics, J. Geophvs. Res., 94, 17,543–17,559.Google Scholar
- Tarantola, A. and Valette, B., 1982. Inverse problems = Quest for information, J. Geophvs., 50, 159–170.Google Scholar
- Wong, Y.K. and Woodhouse, J.H., 1990. Upper mantle heterogeneity consistent with phase and amplitude data of mantle waves, submitted to Geophys. J. Int. Google Scholar