Kilometer-scale structure on the core–mantle boundary near Hawaii

Li, Zhi; Leng, Kuangdai; Jenkins, Jennifer; Cottaar, Sanne

Abstract

The lowermost mantle right above the core-mantle boundary is highly heterogeneous containing multiple poorly understood seismic features. The smallest but most extreme heterogeneities yet observed are ‘Ultra-Low Velocity Zones’ (ULVZ). We exploit seismic shear waves that diffract along the core-mantle boundary to provide new insight into these enigmatic structures. We measure a rare core-diffracted signal refracted by a ULVZ at the base of the Hawaiian mantle plume at unprecedentedly high frequencies. This signal shows remarkably longer time delays at higher compared to lower frequencies, indicating a pronounced internal variability inside the ULVZ. Utilizing the latest computational advances in 3D waveform modeling, here we show that we are able to model this high-frequency signal and constrain high-resolution ULVZ structure on the scale of kilometers, for the first time. This new observation suggests a chemically distinct ULVZ with increasing iron content towards the core-mantle boundary, which has implications for Earth’s early evolutionary history and core-mantle interaction.

Citation

Li, Z., Leng, K., Jenkins, J., & Cottaar, S. (2022). Kilometer-scale structure on the core–mantle boundary near Hawaii. Nature Communications, 13(1), https://doi.org/10.1038/s41467-022-30502-5

• Journal Article Type: Article
• Acceptance Date: Apr 28, 2022
• Online Publication Date: May 19, 2022
• Publication Date: 2022
• Deposit Date: Aug 1, 2022
• Publicly Available Date: Aug 1, 2022
• Journal: Nature Communications
• Electronic ISSN: 2041-1723
• Publisher: Nature Research
• Peer Reviewed: Peer Reviewed
• Volume: 13
• Issue: 1
• DOI: https://doi.org/10.1038/s41467-022-30502-5
• Public URL: https://durham-repository.worktribe.com/output/1198207