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Seismically determined elastic parameters for Earth’s outer core

Author(s): Irving, Jessica CE; Cottaar, Sanne; Lekić, Vedran

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dc.contributor.authorIrving, Jessica CE-
dc.contributor.authorCottaar, Sanne-
dc.contributor.authorLekić, Vedran-
dc.date.accessioned2022-01-25T14:58:37Z-
dc.date.available2022-01-25T14:58:37Z-
dc.date.issued2018-06-27en_US
dc.identifier.citationIrving, Jessica CE, Sanne Cottaar, and Vedran Lekić. "Seismically determined elastic parameters for Earth’s outer core." Science Advances 4, no. 6 (2018): eaar2538. DOI: 10.1126/sciadv.aar2538.en_US
dc.identifier.urihttp://arks.princeton.edu/ark:/88435/pr10r9m36d-
dc.description.abstractTurbulent convection of the liquid iron alloy outer core generates Earth’s magnetic field and supplies heat to the mantle. The exact composition of the iron alloy is fundamentally linked to the processes powering the convection and can be constrained by its seismic properties. Discrepancies between seismic models determined using body waves and normal modes show that these properties are not yet fully agreed upon. In addition, technical challenges in experimentally measuring the equation-of-state (EoS) parameters of liquid iron alloys at high pressures and temperatures further complicate compositional inferences. We directly infer EoS parameters describing Earth’s outer core from normal mode center frequency observations and present the resulting Elastic Parameters of the Outer Core (EPOC) seismic model. Unlike alternative seismic models, ours requires only three parameters and guarantees physically realistic behavior with increasing pressure for a well-mixed homogeneous material along an isentrope, consistent with the outer core’s condition. We show that EPOC predicts available normal mode frequencies better than the Preliminary Reference Earth Model (PREM) while also being more consistent with body wave–derived models, eliminating a long-standing discrepancy. The velocity at the top of the outer core is lower, and increases with depth more steeply, in EPOC than in PREM, while the density in EPOC is higher than that in PREM across the outer core. The steeper profiles and higher density imply that the outer core comprises a lighter but more compressible alloy than that inferred for PREM. Furthermore, EPOC’s steeper velocity gradient explains differential SmKS body wave travel times better than previous one-dimensional global models, without requiring an anomalously slow ~90- to 450-km-thick layer at the top of the outer core.en_US
dc.languageengen_US
dc.language.isoen_USen_US
dc.relation.ispartofScience Advancesen_US
dc.rightsFinal published version. Article is made available in OAR by the publisher's permission or policy.en_US
dc.titleSeismically determined elastic parameters for Earth’s outer coreen_US
dc.typeJournal Articleen_US
dc.identifier.doidoi:10.1126/sciadv.aar2538-
dc.identifier.eissn2375-2548-
pu.type.symplectichttp://www.symplectic.co.uk/publications/atom-terms/1.0/journal-articleen_US

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