HR: 08:15h
AN: S11E-02    [Abstracts]
TI: Evidence for a westward dipping upper mantle thermal anomaly beneath Kenya, East Africa from body wave tomography
AU: Nyblade, A A
EM: andy@geosc.psu.edu
AF: Penn State University, Department of Geosciences, University Park, PA 16802 United States
AU: * Park, Y
EM: ypark@geosc.psu.edu
AF: Penn State University, Department of Geosciences, University Park, PA 16802 United States
AB: Upper mantle structure beneath Kenya, East Africa, is re-examined using body wave tomography. Previous body wave tomography models of the Kenya rift did not include structure deeper than 165 km, leaving open the question of the depth extent and nature of the thermal anomaly beneath this rift. The data for this study come from the 1985 and 1989 KRISP project and the 2001-2002 Kenya Broadband Seismic Experiment. Relative P wave residuals have been obtained using a multi-channel cross correlation method and upper mantle structure has been imaged using the inversion scheme of VanDecar. Preliminary results show that thermally perturbed structure beneath the Kenya rift extends to depths in excess of 300 km, and that the thermal anomaly dips to the west beneath the Tanzania Craton. Our results for Kenya are consistent with a similar study to the south in Tanzania that also shows a deep-seated thermal anomaly that dips to the west under the Tanzania Craton. This finding corroborates previous studies suggesting that the locus of the thermal upwelling beneath East Africa is under the Tanzania Craton and not under the Kenya rift. If a mantle plume is invoked to explain the thermal anomaly, then the plume head must be situated under the Tanzania Craton, with warm plume material flowing around and up the sides of the thermally resistant cratonic lithosphere.
DE: 9305 Africa
DE: 8109 Continental tectonics--extensional (0905)
DE: 7203 Body wave propagation
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting