HR: 1340h
AN: S13B-1052    [Abstracts]
TI: Upper mantle structure beneath Ethiopia from a joint inversion of receiver functions and surface wave dispersion
AU: * Dugda, M T
EM: mtd172@psu.edu
AF: Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AU: Nyblade, A A
EM: andy@geosc.psu.edu
AF: Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AU: Julia, J
EM: jordi@duke.edu
AF: Duke University, Division of Earth and Oceanic Sciences, Durham, NC 27708 United States
AU: Ammon, C
EM: cammon@geosc.psu.edu
AF: Pennsylvania State University, Department of Geosciences, University Park, PA 16802 United States
AB: We investigate upper mantle structure beneath the Afar Depression, the Main Ethiopian Rift (MER) and Ethiopian Plateau by jointly inverting receiver functions and Rayleigh wave group velocities. The main aim of this study is to characterize the nature of the thermal anomaly beneath the region and then to use this information to evaluate models for the origin of the hotspot activity. The data for this study come from the Ethiopian Broadband Seismic Experiment in which 27 stations were deployed throughout Ethiopia for two years (2000-2002). Preliminary results suggest contrasting upper mantle structure between the plateau stations and the stations in the MER and Afar Depression. For the plateau stations to the east and west of the MER, the upper mantle has a high velocity lid, with shear wave velocities of around 4.5 km/s that extends to between 70 and 100 km depth. Below the lid is a pronounced low velocity zone with shear wave velocities of about 4.1-4.2 km/s. The lowest velocities are found no deeper than 150 km. In contrast, there is no seismic lid beneath the stations in the MER and Afar Depression. The shear velocities are anomalously low at all mantle depths. These preliminary findings are consistent with a plume model for the hotspot activity.
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting