Intrinsic and scattering Q near 1 Hz across the East African plateau

Alemayehu L. Jemberie, Andrew Arnold Nyblade

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Crustal attenuation across the East African plateau in Tanzania, an area of uplifted and rifted Precambrian crust, has been investigated using seismic data from regional earthquakes recorded by the 1994-1995 Tanzania broadband seismic experiment. We use 1 Hz Lg coda waves from the 17 events, together with the energy flux model of Frankel and Wennerberg (1987), to obtain estimates of intrinsic (QI) and scattering (QS) attenuation for East Africa. QI values across the plateau are fairly uniform, ranging from a low of ~300 to a high of ~600. QI values for the Tanzania craton, in the middle of the plateau, are similar to those for the mobile belts, which form the sides of the plateau. QI of 300 to 600 is somewhat lower than the average crustal Q for Precambrian terrains elsewhere. Heat flow from the Tanzania craton and surrounding mobile belts is not elevated; therefore, we attribute the lower-thanaverage Q values not to elevated crustal temperatures, but instead to rift faults in the crust that are interconnected and filled with fluids. QS ranges from ~1000 in the mobile belts and along the eastern margin of the Tanzania craton to ~2200 in the north central part of the plateau just south of Lake Victoria.We attribute the variability in QS to scattering of Lg by surface topography, in particular, rift basins along the eastern side of the plateau.

Original languageEnglish (US)
Pages (from-to)3516-3524
Number of pages9
JournalBulletin of the Seismological Society of America
Volume99
Issue number6
DOIs
StatePublished - Dec 1 2009

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Tanzania
plateaus
scattering
plateau
Scattering
mobile belt
cratons
craton
Precambrian
crusts
Surface topography
attenuation
Lg-wave
crust
Lakes
Earthquakes
coda
Fluxes
Heat transfer
energy flux

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology
  • Geophysics

Cite this

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abstract = "Crustal attenuation across the East African plateau in Tanzania, an area of uplifted and rifted Precambrian crust, has been investigated using seismic data from regional earthquakes recorded by the 1994-1995 Tanzania broadband seismic experiment. We use 1 Hz Lg coda waves from the 17 events, together with the energy flux model of Frankel and Wennerberg (1987), to obtain estimates of intrinsic (QI) and scattering (QS) attenuation for East Africa. QI values across the plateau are fairly uniform, ranging from a low of ~300 to a high of ~600. QI values for the Tanzania craton, in the middle of the plateau, are similar to those for the mobile belts, which form the sides of the plateau. QI of 300 to 600 is somewhat lower than the average crustal Q for Precambrian terrains elsewhere. Heat flow from the Tanzania craton and surrounding mobile belts is not elevated; therefore, we attribute the lower-thanaverage Q values not to elevated crustal temperatures, but instead to rift faults in the crust that are interconnected and filled with fluids. QS ranges from ~1000 in the mobile belts and along the eastern margin of the Tanzania craton to ~2200 in the north central part of the plateau just south of Lake Victoria.We attribute the variability in QS to scattering of Lg by surface topography, in particular, rift basins along the eastern side of the plateau.",
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Intrinsic and scattering Q near 1 Hz across the East African plateau. / Jemberie, Alemayehu L.; Nyblade, Andrew Arnold.

In: Bulletin of the Seismological Society of America, Vol. 99, No. 6, 01.12.2009, p. 3516-3524.

Research output: Contribution to journalArticle

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