A geodynamic and mineral physics model of a solid-state ultralow-velocity zone

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.epsl.2010.12.035.

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Authors

Dan J. Bower , June K. Wicks, Michael Gurnis, Jennifer M. Jackson

Abstract

Recent results (Wicks et al., 2010) suggest that a mixture of iron-enriched (Mg,Fe)O and ambient mantle is consistent with wavespeed reductions and density increases inferred for ultralow-velocity zones (ULVZs). We explore this hypothesis by simulating convection to deduce the stability and morphology of such chemically-distinct structures. The buoyancy number, or chemical density anomaly, largely dictates ULVZ shape, and the prescribed initial thickness (proxy for volume) of the chemically-distinct layer controls its size. We synthesize our dynamic results with a Voigt–Reuss–Hill mixing model to provide insight into the inherent seismic tradeoff between ULVZ thickness and wavespeed reduction. Seismic data are compatible with a solid-state origin for ULVZs, and a suite of these structures may scatter seismic energy to produce broadband PKP precursors.

DOI

https://doi.org/10.31223/osf.io/x24qc

Subjects

Earth Sciences, Geophysics and Seismology, Mineral Physics, Physical Sciences and Mathematics

Keywords

mantle convection, core-mantle boundary, (MgFe)O, PKP waves, ultralow-velocity zone

Dates

Published: 2019-09-06 13:59

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License

CC BY Attribution 4.0 International

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