Core-Mantle Interface - Thermodynamics and chemistry

A 5-year multidisciplinary project funded by the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC Grant agreement 240473.

CoMITAC models

Elastic models of D″ from global flow

We (Walker et al., G3, 2011) use a global model of mantle flow to derive the predicted elastic anisotropy in D″. We seek to test the hypothesis that post-perovskite (the mineral phase believed to be present at the base of the mantle) can cause the observed seismic anisotropy in the lowermost mantle by aligning in response to flow; specifically, by forming a lattice preferred orientation by dislocation glide.

We test three different models of slip in post-perovskite and compare the predicted P and S wave anisotropy to global observations (Panning & Romanowicz, 2006, GJI; Panning et al., JGR, 2010; Kustowski et al., JGR, 2008). We find that formation of texture in post-perovskite by slip on (010) or (100) planes best matches observations.

Shear wave radial anisotropy predicted by two models for dislocation glide in post-perovskite (left and right), compared to a global inversion from observations by Kustowski et al. (2008) (centre). Blue regions indicate VSH > VSV; red regions show VSH < VSV. There is a strong anti-correlation between observations and the predictions for the (001) case, but the other two models ((100) and (010), not shown) correlate positively with observations up to spherical harmonic degree l = 6.

Accompanying models to the paper can be downloaded as a tarball here. See the included README file for details. For MATLAB tools for handling seismic anisotropy data, see MSAT.

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