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

• Published in: arXiv.org
• Main Authors: Lincot, A, Cardin, Ph, Deguen, R, Merkel, Sébastien
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 21.01.2016
• Subjects: Anisotropy; Computer simulation; Crystallization; Earth axis; Earth rotation; Elastic anisotropy; Elastic deformation; Modulus of elasticity; Monte Carlo simulation; Physics - Geophysics; Plastic deformation; Plastic properties; Polycrystals; Single crystals; Slip
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1601.05674

\(\bullet\) Multiscale model of inner-core anisotropy produced by hcp alloy deformation\(\bullet\) 5 to 20% single-crystal elastic anisotropy and plastic deformation by pyramidal slip \(\bullet\) Low-degree inner-core formation model with faster crystallization at the equatorThe 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 \textless{}c+a\textgreater{} 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.