HR: 08:30h
AN: S11E-03    [Abstracts]
TI: Upper Mantle and Transition Zone Seismic Velocity Structure Beneath Ethiopia
AU: * Benoit, M H
EM: mbenoit@geosc.psu.edu
AF: Penn State University, Department of Geosciences , University Park, PA 16801 United States
AU: Nyblade, A A
EM: andy@geosc.psu.edu
AF: Penn State University, Department of Geosciences , University Park, PA 16801 United States
AU: VanDecar, J C
EM: vandecar@dtm.ciw.edu
AF: Carnigie Institution of Washington, 5241 Broad Branch Rd., NW, Washinton, DC 20015 United States
AU: Owens, T J
EM: owens@seis.sc.edu
AF: University of South Carolina, Department of Geological Sciences, Columbia, SC 29201 United States
AB: Throughout much of the Cenozoic, Ethiopia has undergone extensive rifting, volcanism and uplift, though the origin of this tectonism remains ambiguous. Previous studies suggest that slow seismic velocities may extend through the upper mantle beneath this region, consistent with a lower mantle origin for the Cenozoic tectonism. To further understand the origin of the tectonism in Ethiopia, we analyze data collected from the 2000-2002 Ethiopia Broadband Seismic Experiment. We invert P and S wave travel time residuals to examine the upper mantle seismic velocity structure, and use receiver function analysis to map topography on the 410 and 660 km discontinuities. Results from our tomography study beneath Ethiopia reveal a broad westward dipping low velocity anomaly in the upper mantle beneath the Afar triangle and the Western Ethiopia Plateau that appears to extend to depths greater than 400 km. The low velocity anomaly found in our tomographic models appears to be similar to the broad, westward dipping low velocity anomaly beneath Africa (African Superplume) seen in some global tomographic models. This correlation suggests that the low velocity anomaly may extend from the lower mantle to the upper mantle. We have stacked receiver functions to examine the 410 and 660 km mantle discontinuities beneath Ethiopia using both 1D and 3D techniques. The 410 km discontinuity is clearly imaged and shows significant topography. In contrast, the 660 km discontinuity does not appear consistently across the study region. The structure of the discontinuities will be correlated with the P and S wave tomography models to assess further the possibility of a through-going mantle thermal anomaly.
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting