Shear wave velocity structure of the southern African upper mantle with implications for the uplift of southern Africa

Aubreya Adams, Andrew Nyblade

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Broad-band seismic data from the southern African seismic experiment and the AfricaArray network are used to investigate the seismic velocity structure of the upper mantle beneath southern Africa, and in particular beneath the Kaapvaal Craton. A two-plane approximation method that includes a finite frequency sensitivity kernel is employed to measure Rayleigh wave phase velocities, which are inverted to obtain a quasi-3-D shear wave velocity model of the upper mantle. We find phase velocities for the Kaapvaal Craton and surrounding mobile belts that are comparable to those reported by previous studies, and we find little evidence for variation from east to west across the Namaqua-Natal Belt, a region not well imaged in previous studies. A high-velocity upper-mantle lid is found beneath the Kaapvaal Craton and most of southern Africa. For the Kaapvaal Craton, the thickness of the lid (~150-200 km) is consistent with the lid thicknesses reported in many previous studies. The cratonic lid is underlain by a ~100-km thick low-velocity zone with a 3.9 per cent maximum velocity reduction. By comparing the velocity model to those published for other Archean cratons, we find few differences, and therefore conclude that there is little evidence in the shear wave velocity structure of the mantle to indicate that the southern African plateau is supported by an upper-mantle thermal anomaly.

Original languageEnglish (US)
Pages (from-to)808-824
Number of pages17
JournalGeophysical Journal International
Volume186
Issue number2
DOIs
StatePublished - Aug 1 2011

Fingerprint

Shear waves
velocity structure
cratons
S waves
wave velocity
craton
S-wave
upper mantle
Earth mantle
uplift
phase velocity
Phase velocity
mobile belt
low velocity zone
Rayleigh wave
temperature anomaly
Rayleigh waves
Archean
seismic data
low speed

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

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abstract = "Broad-band seismic data from the southern African seismic experiment and the AfricaArray network are used to investigate the seismic velocity structure of the upper mantle beneath southern Africa, and in particular beneath the Kaapvaal Craton. A two-plane approximation method that includes a finite frequency sensitivity kernel is employed to measure Rayleigh wave phase velocities, which are inverted to obtain a quasi-3-D shear wave velocity model of the upper mantle. We find phase velocities for the Kaapvaal Craton and surrounding mobile belts that are comparable to those reported by previous studies, and we find little evidence for variation from east to west across the Namaqua-Natal Belt, a region not well imaged in previous studies. A high-velocity upper-mantle lid is found beneath the Kaapvaal Craton and most of southern Africa. For the Kaapvaal Craton, the thickness of the lid (~150-200 km) is consistent with the lid thicknesses reported in many previous studies. The cratonic lid is underlain by a ~100-km thick low-velocity zone with a 3.9 per cent maximum velocity reduction. By comparing the velocity model to those published for other Archean cratons, we find few differences, and therefore conclude that there is little evidence in the shear wave velocity structure of the mantle to indicate that the southern African plateau is supported by an upper-mantle thermal anomaly.",
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Shear wave velocity structure of the southern African upper mantle with implications for the uplift of southern Africa. / Adams, Aubreya; Nyblade, Andrew.

In: Geophysical Journal International, Vol. 186, No. 2, 01.08.2011, p. 808-824.

Research output: Contribution to journalArticle

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