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Multiscale model of global inner-core anisotropy induced by hcp alloy plasticity

Abstract : The Earth's solid inner core exhibits a global seismic anisotropy of several percents. It results from a coherent alignment of anisotropic Fe alloy crystals through the inner-core history that can be sampled by present-day seismic observations. By combining self-consistent polycrystal plasticity, inner-core formation models, Monte-Carlo search for elastic moduli, and simulations of seismic measurements, we introduce a multiscale model that can reproduce a global seismic anisotropy of several percents aligned with the Earth's rotation axis. Conditions for a successful model are an hexagonal close packed structure for the inner-core Fe alloy, plastic deformation by pyramidal ⟨c + a⟩ slip, and large-scale flow induced by a low-degree inner-core formation model. For global anisotropies ranging between 1 and 3%, the elastic anisotropy in the single crystal ranges from 5 to 20% with larger velocities along the c axis.
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A. Lincot, Ph. Cardin, R. Deguen, S. Merkel. Multiscale model of global inner-core anisotropy induced by hcp alloy plasticity. Geophysical Research Letters, American Geophysical Union, 2016, 43 (3), pp.1084 - 1091. ⟨10.1002/2015GL067019⟩. ⟨insu-01899915⟩

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