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Seismological constraints on the South African superplume; could be the oldest distinct structure on earth

Ni, Sidao and Helmberger, Don V. (2003) Seismological constraints on the South African superplume; could be the oldest distinct structure on earth. Earth and Planetary Science Letters, 206 (1-2). pp. 119-131. ISSN 0012-821X. doi:10.1016/S0012-821X(02)01072-5.

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A recent study of the lower mantle structure beneath Africa revealed strong lateral changes in S-velocity extending upward from the core–mantle boundary to about 1500 km. SKS travel times observed on the South African Array display jumps of about 6 s when ray paths cross these nearly vertical boundaries. Back projecting these delays onto the core–mantle boundary allows a clear image of the horizontal extent of this structure starting at mid-Africa (15°S, 5°E) where it strikes roughly northwest to beyond the tip of South Africa (45°S, 55°E) where it bends toward the Indian Ocean. Waveform sections of S, ScS, SKS, and SKKS are modeled along two corridors, one along strike and one at right angles to establish its uniformity. The structure is about 1200 km wide and has about a 3% drop in S-velocity although some small-scale features are apparent in the roof structure and midsection. If this structure is stabilized by a localized viscosity condition or a dense core as suggested by some joint inversions, gravity, and free oscillations, it may be isolated from mantle stirring and therefore very old with unique chemistry.

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Ni, Sidao0000-0003-2988-4850
Additional Information:© 2002 Elsevier Science B.V. Received 5 August 2002; received in revised form 1 November 2002; accepted 7 November 2002. We thank reviewers Louise Kellogg, Dave Yuen, and Don Anderson for their helpful comments, and Evelina Cui for her help with preparation of the manuscript. This work was supported by NSF Grant EAR97-25808. Contribution Number 8917 of the Division of Geological and Planetary Sciences, California Institute of Technology.[RV]
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Subject Keywords:superplumes; low velocity structure; chemical plume; sharp boundary; lower mantle
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Caltech Division of Geological and Planetary Sciences8917
Issue or Number:1-2
Record Number:CaltechAUTHORS:20121211-111133502
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Official Citation:Sidao Ni, Don V. Helmberger, Seismological constraints on the South African superplume; could be the oldest distinct structure on earth, Earth and Planetary Science Letters, Volume 206, Issues 1–2, 30 January 2003, Pages 119-131, ISSN 0012-821X, 10.1016/S0012-821X(02)01072-5. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35909
Deposited By: Ruth Sustaita
Deposited On:11 Dec 2012 19:30
Last Modified:09 Nov 2021 23:18

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