Upper mantle Q and thermal structure beneath Tanzania, East Africa from teleseismic P wave spectra

Anupama Venkataraman, Andrew A. Nyblade, Jeroen Ritsema

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ∼ 175 beneath the cratonic lithosphere, while it is ∼ 80 beneath the rifted lithosphere. By combining the Q P values and a model of P wave velocity perturbations, we estimate that the temperature beneath the rifted lithosphere (100-400 km depth) is 140-280 K higher than ambient mantle temperatures, consistent with the observation that the 410 km discontinuity in this region is depressed by 30-40 km.

Original languageEnglish (US)
Pages (from-to)L15611 1-4
JournalGeophysical Research Letters
Volume31
Issue number15
DOIs
StatePublished - Aug 16 2004

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Tanzania
teleseismic wave
wave spectrum
thermal structure
P waves
lithosphere
P-wave
upper mantle
Earth mantle
mantle
wave attenuation
cratons
estimates
wave velocity
craton
discontinuity
earthquakes
stations
attenuation
temperature

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

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abstract = "We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ∼ 175 beneath the cratonic lithosphere, while it is ∼ 80 beneath the rifted lithosphere. By combining the Q P values and a model of P wave velocity perturbations, we estimate that the temperature beneath the rifted lithosphere (100-400 km depth) is 140-280 K higher than ambient mantle temperatures, consistent with the observation that the 410 km discontinuity in this region is depressed by 30-40 km.",
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Upper mantle Q and thermal structure beneath Tanzania, East Africa from teleseismic P wave spectra. / Venkataraman, Anupama; Nyblade, Andrew A.; Ritsema, Jeroen.

In: Geophysical Research Letters, Vol. 31, No. 15, 16.08.2004, p. L15611 1-4.

Research output: Contribution to journalArticle

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AU - Nyblade, Andrew A.

AU - Ritsema, Jeroen

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AB - We measure P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania network to estimate regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. One-dimensional profiles of QP adequately explain the systematic variation of P wave attenuation in the sublithospheric upper mantle: QP ∼ 175 beneath the cratonic lithosphere, while it is ∼ 80 beneath the rifted lithosphere. By combining the Q P values and a model of P wave velocity perturbations, we estimate that the temperature beneath the rifted lithosphere (100-400 km depth) is 140-280 K higher than ambient mantle temperatures, consistent with the observation that the 410 km discontinuity in this region is depressed by 30-40 km.

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