Evidence for a Kilometer-Scale Seismically Slow Layer Atop the Core-Mantle Boundary From Normal Modes

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Abstract

jats:titleAbstract</jats:title>jats:pGeodynamic modeling and seismic studies have highlighted the possibility that a thin layer of low seismic velocities, potentially molten, may sit atop the core‐mantle boundary but has thus far eluded detection. In this study we employ normal modes, an independent data type to body waves, to assess the visibility of a seismically slow layer atop the core‐mantle boundary to normal mode center frequencies. Using forward modeling and a data set of 353 normal mode observations we find that some center frequencies are sensitive to one‐dimensional kilometer‐scale structure at the core‐mantle boundary. Furthermore, a global slow and dense layer 1–3 km thick is better‐fitting than no layer. The well‐fitting parameter space is broad with a wide range of possible seismic parameters, which precludes inferring a possible composition or phase. Our methodology cannot uniquely detect a layer in the Earth but one should be considered possible and accounted for in future studies.</jats:p>

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Publication status: Published

Keywords
37 Earth Sciences, 3705 Geology, 3706 Geophysics
Journal Title
Geophysical Research Letters
Conference Name
Journal ISSN
0094-8276
1944-8007
Volume Title
50
Publisher
American Geophysical Union (AGU)
Sponsorship
European Research Council (804071)