An unsually large ULVZ at the base of the mantle near Hawaii

Cottaar, Sanne and Romanowicz, Barbara (2012) An unsually large ULVZ at the base of the mantle near Hawaii. Earth and Planetary Science Letters, 355–56. pp. 213-222. ISSN 0012-821X DOI 10.1016/j.epsl.2012.09.005

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Abstract

Previous studies have documented the presence of ultra-low-velocity-zones (ULVZs) at the base of the mantle, through observations of body wave complexities. Geometrically their heights are in the range of \~ 5 – 30 km , while little is known about their lateral extent beyond about 102 km, due to limitations in sampling. Here we show remarkable features in the waveforms of S/Sdiff phases of western Pacific events observed at stations in North America that indicate the presence of a very large ultra-low-velocity-zone (ULVZ) at the base of the mantle, centered \~ 11 ° to the southwest of Hawaii, within and near the northern border of the Pacific LLSVP. Waveform complexities include strongly delayed ( > 30 s ) postcursors. Measurements of travel times, beamforming analysis of out-of-plane energy, and full waveform comparisons with 3D numerical simulations, constrain the location, lateral extent, height and velocity reduction of the ULVZ with some level of trade-off. The simplified 3D model consists of a cylindrical ULVZ with a large aspect ratio of \~ 20 km in height and \~ 910 km in diameter at the CMB. The shear wave velocity reduction is \~ 20 % . This is to our knowledge the largest ULVZ mapped to date and the first time the lateral extent of a ULVZ has been constrained with some precision. Its location suggests that it may be the root of a long-lived, stable plume responsible for the Hawaiian volcanic chain, the hotspot track with the largest buoyancy

Item Type: Article
Additional Information: Corrigendum: http://www.sciencedirect.com/science/article/pii/S0012821X14000284
Uncontrolled Keywords: NILAREP
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 355–56
Page Range: pp. 213-222
Identification Number: 10.1016/j.epsl.2012.09.005
Depositing User: Sarah Humbert
Date Deposited: 25 Aug 2014 16:06
Last Modified: 25 Aug 2014 21:43
URI: http://eprints.esc.cam.ac.uk/id/eprint/3099

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