Imperial College London


Faculty of EngineeringDepartment of Earth Science & Engineering

Senior Teaching Fellow



+44 (0)20 7594




1.39Royal School of MinesSouth Kensington Campus





Publication Type

7 results found

Yu C, Goes S, Day EA, van der Hilst RDet al., 2023, Seismic evidence for global basalt accumulation in the mantle transition zone., Sci Adv, Vol: 9

The mantle's compositional structure reflects the thermochemical evolution of Earth. Yet, even the radial average composition of the mantle remains debated. Here, we analyze a global dataset of shear and compressional waves reflecting off the 410- and 660-km discontinuities that is 10 times larger than any previous studies. Our array analysis retrieves globally averaged amplitude-distance trends in SS and PP precursor reflectivity from which we infer relative wavespeed and density contrasts and associated mantle composition. Our results are best matched by a basalt-enriched mantle transition zone, with higher basalt fractions near 660 (~40%) than 410 (~18-31%). These are consistent with mantle-convection/plate-recycling simulations, which predict that basaltic crust accumulates in the mantle transition zone, with basalt fractions peaking near the 660. Basalt segregation in the mantle transition zone also implies that the overall mantle is more silica enriched than the often-assumed pyrolitic mantle reference composition.

Journal article

Yu C, Day E, de Hoop M, Campillo M, van der Hilst Ret al., 2018, Mapping Mantle Transition Zone Discontinuities Beneath the Central Pacific With Array Processing of SS Precursors, Journal of Geophysical Research, ISSN: 0148-0227

Journal article

Yu C, Day E, De Hoop M, Campillo M, Goes S, Blythe R, Van der Hilst Ret al., 2018, Compositional heterogeneity near the base of the mantle transition zone beneath Hawaii, Nature Communications, Vol: 9, Pages: 1-9, ISSN: 2041-1723

Global seismic discontinuities near 410 and 660 km depth in Earth’s mantle are expressions of solid-state phase transitions. These transitions modulate thermal and material fluxes across the mantle and variations in their depth are often attributed to temperature anomalies. Here we use novel seismic array analysis of SS waves reflecting off the 410 and 660 below the Hawaiian hotspot. We find amplitude–distance trends in reflectivity that imply lateral variations in wavespeed and density contrasts across 660 for which thermodynamic modeling precludes a thermal origin. No such variations are found along the 410. The inferred 660 contrasts can be explained by mantle composition varying from average (pyrolitic) mantle beneath Hawaii to a mixture with more melt-depleted harzburgite southeast of the hotspot. Such compositional segregation was predicted, from petrological and numerical convection studies, to occur near hot deep mantle upwellings like the one often invoked to cause volcanic activity on Hawaii.

Journal article

Lableis M, Waszek L, Day E, 2017, GrowYourIC: a step towards a coherent model of the Earth's inner core seismic structure, Geochemistry, Geophysics, Geosystems, Vol: 18, Pages: 4016-4026, ISSN: 1525-2027

A complex inner core structure has been well-established from seismic studies, showing radial and lateral heterogeneities at various length scales. Yet, no geodynamic model is able to explain all the features observed. One of the main limits for this is the lack of tools to compare seismic observations and numerical models successfully. We use here a new Python tool called GrowYourIC to compare models of inner core structure. We calculate properties of geodynamic models of the inner core along seismic ray paths, for random or user-specified datasets. We test kinematic models which simulate fast lateral translation, super-rotation, and differential growth. We explore first the influence on a real inner core data set, which has a sparse coverage of the inner core boundary. Such a data set is however able to successfully constrain the hemispherical boundaries due to a good sampling of latitudes. Combining translation and rotation could explain some of the features of the boundaries separating the inner core hemispheres. The depth shift of the boundaries, observed by some authors, seems unlikely to be modelled by a fast translation, but could be produced by slow translation associated to super-rotation.

Journal article

Day EA, Deuss A, 2013, Reconciling PP and P'P' precursor observations of a complex 660 km seismic discontinuity, GEOPHYSICAL JOURNAL INTERNATIONAL, Vol: 194, Pages: 834-838, ISSN: 0956-540X

Journal article

Deuss A, Andrews J, Day E, 2013, Seismic Observations of Mantle Discontinuities and Their Mineralogical and Dynamical Interpretation, Physics and Chemistry of the Deep Earth, Editors: Karato, Publisher: Wiley-Blackwell, ISBN: 9780470659144

Book chapter

Geballe ZM, Lasbleis M, Cormier VF, Day EAet al., 2013, Sharp hemisphere boundaries in a translating inner core, GEOPHYSICAL RESEARCH LETTERS, Vol: 40, Pages: 1719-1723, ISSN: 0094-8276

Journal article

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