Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 42, Issue 18, Pages 7429-7435Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015GL063727
Keywords
rheology; asthenosphere; mantle convection; high-performance computing
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Funding
- German Research Foundation (DFG) [1648]
- German Federal Ministry of Education and Research (BMBF)
- German State Ministry for Research of Baden-Wurttemberg (MWK)
- German State Ministry for Research of Bayern (StMWFK)
- German State Ministry for Research of Nordrhein-Westfalen (MIWF)
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A variety of geologic observations point to fast upper mantle flow that may exceed plate tectonic velocities by an order of magnitude. At the same time there is mounting evidence from seismology for flow-like structures in the upper 100-200km of the mantle. Here we present a set of geodynamic simulations to link these observations. In a synthetic setting, we include asthenospheric channels of varying thickness, with an extreme case of 100km, and a significant viscosity contrast of up to 4 orders of magnitude relative to the deeper mantle. Using our new global high-resolution code TERRA-NEO, we obtain an increase in velocity by a factor of 10 between a 1000km thick and the very thin channel, translating into velocities of approximate to 20cm/a within the narrow asthenosphere. We further present and verify a simple Poiseuille flow model, predicting that the upper mantle velocity scales with the inverse of the asthenosphere thickness.
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