Effective-Medium Models of Inner-Core Anisotropy

Xin Song, & Thomas H. Jordan

Published July 20, 2018, SCEC Contribution #7934

We investigate the consistency between the seismological observations and the mineralogical models derived from ab initio calculations of the elasticity tensors for hcp-Fe. We get the best estimates and uncertainties for current normal-mode observations [Mäkinen et al., 2014; Beghein and Trampert, 2003; Ishii et al., 2002; Tromp, 1993] and the direct body wave observations [Creager, 1992; Irving and Deuss, 2011]. Two transversely isotropic stochastic rotation effective-medium models are presented: the J model from Jordan’s [2015] effective-medium theory and the F model based on von Mises-Fisher distribution. The fine-scale local stiffness hcp-Fe tensor is up-scaled to large-scale effective tensors by the stochastic models that are comparable to the seismological observations. With Gaussian-Bayesian inversion technique, we show the difficulty to fit both normal-mode and body-wave observations that estimate the average anisotropy in the outer half of the inner core using an original or modified local stiffness tensor at 7250K and 360GPa [Martorell et al., 2013], so trade-off must be involved.

Song, X., & Jordan, T. H. (2018). Effective-Medium Models of Inner-Core Anisotropy. Journal of Geophysical Research: Solid Earth, 123(7), 5793-5813. doi: 10.1029/2017JB015089.