HR: 14:55h
AN: T22D-06    [PDF]
TI: Inverse Problem of Thermal Convection: Numerical Approach and Application to Mantle Plume Restoration
AU: * Ismail-Zadeh, A
AF: International Institute of Earthquake Prediction Theory and Mathematical Geophysics, Russian Academy of Sciences, Warshavskoye shosse 79-2, Moscow, 113556 Russian Federation
AU: Schubert, G
AF: Department of Earth and Space Sciences, UCLA, 3806 Geology Building, 595 Charles Young Drive East, Los Angeles, CA 90095-1567
AU: Tsepelev, I
AF: Institute of Mathematics and Mechanics, Ural Branch, Russian Academy of Sciences, ul. S. Kovalevskoy 16, Ekaterinburg, 620219 Russian Federation
AU: Korotkii, A
AF: Institute of Mathematics and Mechanics, Ural Branch, Russian Academy of Sciences, ul. S. Kovalevskoy 16, Ekaterinburg, 620219 Russian Federation
- AB: Modern seismic tomography images of the Earth's interior allow the complex trajectories of the present-day convective flow to be seen at least in the upper mantle. To reconstruct quantitatively both the observed mantle structure and temperature field backwards in time, we need a numerical tool for solving an inverse problem of thermal convection at infinite Prandtl number. In this paper we present a variational approach to three-dimensional numerical restoration of thermoconvective mantle flow with temperature-dependent viscosity. This approach is based on a search for the mantle temperature and flow in the geological past by minimizing differences between present-day mantle temperature derived from seismic velocities (or their anomalies) and that predicted by forward models of mantle flow for an initial temperature guess. The mantle temperatures in the past so obtained could be employed as constraints on forward models of mantle dynamics. To demonstrate the applicability of this technique, we restore numerically a fluid dynamic model of the evolution of upper mantle plumes and show that the initial shape of the plumes can be reconstructed accurately. We model then the evolution of the plumes forward in time (plume upbuilding) starting from the restored state to the state they were before the restoration and demonstrate the high accuracy of the model predictions. We show also that a neglect of the heat diffusion in the backward modeling of thermal plumes (in order to simplify the numerical procedure) results in erroneous restorations of the plumes.
DE: 8100 TECTONOPHYSICS
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting