Constraints on grain size and stable iron phases in the uppermost Inner Core from multiple scattering modeling of seismic velocity and attenuation - Physics > GeophysicsReport as inadecuate




Constraints on grain size and stable iron phases in the uppermost Inner Core from multiple scattering modeling of seismic velocity and attenuation - Physics > Geophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We propose to model the uppermost inner core as an aggregate of randomlyoriented anisotropic ``patches-. A patch is defined as an assemblage of apossibly large number of crystals with identically oriented crystallographicaxes. This simple model accounts for the observed velocity isotropy of shortperiod body waves, and offers a reasonable physical interpretation for thescatterers detected at the top of the inner core. From rigorous multiplescattering modeling of seismic wave propagation through the aggregate, weobtain strong constraints on both the size and the elastic constants of ironpatches. We perform a systematic search for iron models compatible withmeasured seismic velocities and attenuations. An iron model is characterized byits symmetry cubic or hexagonal, elastic constants, and patch size.Independent of the crystal symmetry, we infer a most likely size of patch ofthe order of 400 m. Recent {\it bcc} iron models from the literature are invery good agreement with the most probable elastic constants of cubic crystalsfound in our inversion. Our study 1 suggests that the presence of melt maynot be required to explain the low shear wavespeeds in the inner core and 2supports the recent experimental results on the stability of cubic iron in theinner core, at least in its upper part.



Author: Marie Calvet DTP, Ludovic Margerin CEREGE

Source: https://arxiv.org/







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