Seismic visibility of melt at the core-mantle boundary from PKKP diffracted waves

Stuart Russell*, Jessica C.E. Irving, Sanne Cottaar

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

9 Citations (Scopus)
30 Downloads (Pure)

Abstract

The core-mantle boundary (CMB) is a complex and poorly understood region of the Earth. The existence of melt or partial melt at the CMB is strongly debated with evidence coming from a range of sources. While partial melt has been inferred in specific locations using seismology, often as an explanation for ultra-low velocity zones (ULVZs), no global layer of melt has been observed despite evidence that such melt should accumulate at the CMB.

Using high frequency synthetic seismograms we have systematically examined the effect of a one-dimensional melt layer at the CMB on the global seismic wavefield. We find that PKKP diffracted waves are an extremely sensitive, robust and previously underutilised seismic phase for studying the CMB and, in synthetic testing, could resolve very thin melt layers. We have constructed a global data set of PKKP diffracted observations to attempt to observe or exclude melt at the CMB. We find that within the bounds of our data, we are unable to robustly exclude or observe a melt layer at the CMB on the order of single kilometres thick. The presence of a thin layer of unobservable melt at the CMB would have profound impacts for the internal dynamics of the Earth.
Original languageEnglish
Article number117768
JournalEarth and Planetary Science Letters
Volume595
DOIs
Publication statusPublished - 1 Oct 2022

Bibliographical note

Funding Information:
The authors would like to thank past and present members of the University of Cambridge Earth Science Department, especially Carl Martin, Stephen Pugh, Florian Millet, Alistair Boyce, John Rudge and Helen Williams, as well as others including Sebastian Rost, Bruce Buffett, Harriet Lau and Richard Holme who have provided helpful and insightful scientific discussions. The authors would also like to thank the editor, Hans Thybo, and two reviewers, Michael Thorne and Mingming Li, for their constructive comments and helping to improve the original manuscript. The synthetic modelling in this work was performed using resources provided by the Cambridge Service for Data Driven Discovery (CSD3) operated by the University of Cambridge Research Computing Service (www.csd3.cam.ac.uk), provided by Dell EMC and Intel using Tier-2 funding from the Engineering and Physical Sciences Research Council (capital grant EP/T022159/1), and DiRAC funding from the Science and Technology Facilities Council (www.dirac.ac.uk). The authors would also like to thank Juliane Dannberg, Robert Myhill, and Rene Gassmoeller for providing the geodynamical models of partial melting at the CMB. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 804071 -ZoomDeep).

Funding Information:
This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 804071 -ZoomDeep).

Funding Information:
The synthetic modelling in this work was performed using resources provided by the Cambridge Service for Data Driven Discovery (CSD3) operated by the University of Cambridge Research Computing Service ( www.csd3.cam.ac.uk ), provided by Dell EMC and Intel using Tier-2 funding from the Engineering and Physical Sciences Research Council (capital grant EP/T022159/1), and DiRAC funding from the Science and Technology Facilities Council ( www.dirac.ac.uk ). The authors would also like to thank Juliane Dannberg, Robert Myhill, and Rene Gassmoeller for providing the geodynamical models of partial melting at the CMB.

Funding Information:
The facilities of IRIS Data Services, and specifically the IRIS Data Management Center, were used for access to waveforms, related metadata, and/or derived products used in this study. IRIS Data Services are funded through the Seismological Facilities for the Advancement of Geoscience (SAGE) Award of the National Science Foundation under Cooperative Support Agreement EAR-1851048.

Publisher Copyright:
© 2022 The Author(s)

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