Coherent Seismic Anisotropy Pattern Across Southern Africa Revealed by Shear Wave Splitting Measurements

Fenitra Andriampenomanana, Andrew Nyblade, Raymond Durrheim, Mark van der Meijde, Hanneke Paulssen, Motsamai Kwadiba, Onkgopotse Ntibinyane, Nortin Titus, Mako Sitali

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We report new PKS, SKS, and SKKS splitting measurements for 88 seismic stations in Namibia, Botswana, South Africa, and Mozambique. When combined with measurements from previous studies, the ensemble of measurements shows a fairly uniform NNE to NE (∼41° on average) fast-polarization direction (ϕ) and delay time (δt) (∼0.7 s on average) across the entire southern African subcontinent. It is difficult to attribute the NNE-NE ϕ direction to just one source of anisotropy either within the lithospheric or sublithospheric mantle. We instead propose the observed anisotropy pattern could result from a combination of several sources that together give rise to a pervasive NNE-NE ϕ direction; (a) fossil anisotropy in the lithospheric mantle resulting from the Neoproterozoic collision of the Congo and Kalahari cratons to form the Damara Belt, (b) movement of the African plate over the asthenosphere, and (c) flow in the upper mantle induced by the African Superplume. In addition, a contribution from anisotropy in the lowermost mantle in the vicinity of the African large low shear velocity province cannot be ruled out.

Original languageEnglish (US)
Article numbere2023EA003469
JournalEarth and Space Science
Issue number5
StatePublished - May 2024

All Science Journal Classification (ASJC) codes

  • Environmental Science (miscellaneous)
  • General Earth and Planetary Sciences

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