HR: 1340h
AN: S53B-0222    [Abstracts]
TI: Thermal structure beneath Tanzania from attenuation measurements using teleseismic P wave spectra
AU: * Ritsema, J
EM: jeroen@ipgp.jussieu.fr
AF: Institute of Physics of the Globe, Department of Seismology, Paris, 75252 France
AU: Venkataraman, A
EM: anupamav@pangea.stanford.edu
AF: Stanford University, Department of Geophysics, 397 Panama Mall, Stanford, CA 94305 United States
AU: Nyblade, A
EM: andy@geosc.psu.edu
AF: Penn State, Department of Geosciences, 447 Deike Bldg., University Park, PA 16802 United States
AB: Using P wave spectral amplitude ratios from deep-focus earthquakes recorded at broadband seismic stations of the Tanzania PASSCAL network, we estimate the regional variation of sublithospheric mantle attenuation beneath the Tanzania craton and the eastern branch of the East African Rift. To constrain the thermal anomaly beneath the eastern rift, we analyze P wave attenuation beneath the Tanzania seismic network and the adjacent rift system in combination with velocity anomalies determined from seismic tomography. We conclude that the observed variation in $t^*$ can be explained by variation in $Q_p$ in the sublithospheric mantle and obtain values of $Q_{p}\sim$175 beneath the cratonic lithosphere and $Q_{p}\sim$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 (100-400km depth) is 140-280K higher than ambient mantle temperatures, consistent with the observation that the 410km discontinuity in this region is depressed by 30-40km.
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 7200 SEISMOLOGY
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting