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Large-scale structure at the core–mantle boundary from diffracted waves

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Abstract

AT the base of the Earth's mantle is a region, called D″, which serves as a thermal and chemical boundary layer between the silicate mantle and the liquid-iron outer core1,2. Tomographic models of mantle compressional-wave velocity (vp) have their worst resolution in D″, owing to limited ray sampling3–5, but have hinted at large-scale lateral variations there. Here I use a new technique, which has its greatest resolution within D″, to produce a map of the large-scale vp variations within D″. The technique compares the arrival times of waves that have been refracted across and diffracted around the core–mantle boundary (CMB). The diffracted waves travel a long way in D″, making them excellent probes of this layer, and the differential technique removes many effects arising from ray paths outside of D″ (ref. 6). The new map provides an image of the continent-sized variations at the CMB that is complementary to existing shear-wave data7,8, and similarities between the map and projections of ancient subducted lithosphere9 verify previous suggestions10 of a strong coupling between surface plate tectonics and the base of the mantle.

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Authors and Affiliations

  1. Department of Earth and Planetary Sciences, Washington University, St Louis, Missouri, 63130, USA

    Michael E. Wysession

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Wysession, M. Large-scale structure at the core–mantle boundary from diffracted waves. Nature 382, 244–248 (1996). https://doi.org/10.1038/382244a0

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