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Numerical models of convection in a rheologically stratified oceanic upper mantle: Early results

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Abstract

Recent seismological evidences imply that the boundary between the lithosphere and asthenosphere is a compositional boundary in the oceanic upper mantle, and a rapid increase of viscosity at this boundary is suggested. We modeled a thermal convection in the oceanic mantle numerically using the finite element method, and investigated geodynamical consequences of such a rheological layering. Early results from both quasi-steady state flows and time-dependent flows are presented in this report. We assumed a temperature- and depth-dependent viscosity law so that both the thermal effects and those of layering are taken into account. The effect of a high-viscosity layer (HVL) is small on the flow and the temperature field. Velocity gradients in the HVL are small in both directions, and the velocity field is well approximated by a one-dimensional channel flow. The HVL acts as a low-pass filter of the dynamic topography.

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Correspondence to Mamoru Kato.

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Kato, M. Numerical models of convection in a rheologically stratified oceanic upper mantle: Early results. Earth Planet Sp 50, 1047–1054 (1998) doi:10.1186/BF03352199

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Keywords

  • Rayleigh Number
  • Asthenosphere
  • Quasi Steady State
  • Seismic Anisotropy
  • Uppermost Mantle