HR: 0800h
AN: T41A-0380    [Abstracts]
TI: Lithosphere-Asthenosphere Boundary from S-receiver functions in Ethiopia
AU: * Gashawbeza, E M
EM: ewenet1@stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, California, stanford, ca 94305,
AU: Klemperer, S L
EM: sklemp@stanford.edu
AF: Department of Geophysics, Stanford University, Stanford, California, stanford, ca 94305,
AU: Nyblade, A A
EM: aan2@psu.edu
AF: Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA, University Park, Pen 16802,
AB: Seismological investigations have been carried out in the past in the Main Ethiopian Rift to study crust and upper mantle structures. More constraints on the thickness of the lithosphere and the nature of the lithosphere- asthenosphere boundary (LAB) are needed to better understand the tectonics of the Main Ethiopian Rift and adjacent plateaux. To tackle this, we use the S-receiver function technique to identify the LAB as already successfully performed by other authors in other areas. We computed S-receiver functions from data recorded by the Ethiopian Broadband Seismic Experiment (Nyblade & Langston, 2002, Eos Trans. AGU, 83, 405–410) in central Ethiopia. We used S phases from 20 earthquakes with magnitudes greater than 5.5 (mb) at epicentral distances between 65°–85° and with good azimuthal distribution in order to detect the presence of the (LAB). Preliminary observation of the data shows a clear coherent negative signal following the Moho phase that can most probably be interpreted as the conversion at the LAB. This phase precedes the S-onset by 8-12 seconds suggesting lithospheric thickness of 80 to 120 km.
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting