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

By A. Lincot, Ph. Cardin, R. Deguen and S. Merkel

Abstract

International audienceThe 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

Topics: [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]
Publisher: 'Wiley'
Year: 2016
DOI identifier: 10.1002/2015GL067019
OAI identifier: oai:HAL:insu-01899915v1
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