HR: 16:15h
AN: S52J-02    [PDF]
TI: A Preliminary Analysis of Crustal Structure Variations Along the Ethiopian Rift
AU: * Keller, G R
EM: keller@utep.edu
AF: University of Texas at El Paso, Dept. of Geological Sciences, El Paso, TX 79968 United States
AU: Harder, S H
EM: harder@geo.utep.edu
AF: University of Texas at El Paso, Dept. of Geological Sciences, El Paso, TX 79968 United States
AU: Tadesse, K
EM: ktadesse@utep.edu
AF: University of Texas at El Paso, Dept. of Geological Sciences, El Paso, TX 79968 United States
AU: Maguire, P
EM: pkm@le.ac.uk
AF: University of Leicester, Department of Geology University Road, Leicester, LE1 7RH United Kingdom
AU: O'Reilly, B M
EM: bor@cp.dias.ie
AF: Dublin Inst. of Advanced Studies, 5 Merrion Square, Dublin, 2 Ireland
AU: Mickus, K
EM: klm983f@smsu.edu
AF: Southwest Missouri State Univ., Department of Geology 901 S. National Ave., Springfield, MO 65804 United States
AU: Mariita, N O
EM: mariita@geo.utep.edu
AF: University of Texas at El Paso, Dept. of Geological Sciences, El Paso, TX 79968 United States
AB: The EAGLE (Ethiopia Afar Geoscientific Lithospheric Experiment) is an ambitious effort that involved a 3-phase seismic experiment that was conducted in January of 2003 and was followed by a magnetotelluric project and a variety of supporting efforts that collectively provide a diversity of data for integrated analysis. The third phase of the seismic experiment featured the deployment of 1100 seismic instruments during a controlled source seismic project involving 20 seismic charges being fired into one 450km cross-rift profile (Profile 1), one 450km axial profile (Profile 2), and a dense 2-D array of instruments in a 150km diameter circle around the intersection of these profiles. This intersection is centered on the magmatically active Nazret region in the Main Ethiopian rift valley. Crust and upper mantle velocity models are being derived from these data and will be used to provide estimates of total crustal thinning across and along the rift, to assess the role of basement in the location of major faults and magmatic segments, and to determine whether significant underplating takes place during the syn-rift stage. Our group is working on the Line 2, which follows the axis of the rift from the southern Afar region southward for over 400 km into the main Ethiopian rift. Along this line, recording stations were deployed at an interval of ~ 1km, and sources were placed at an interval of ~50km. The data quality is generally very good although cultural noise was surprisingly high in one region. Our preliminary interpretation shows that the crust is about 25 km thick in southern Afar about 35 km thick in the main Ethiopian rift. The low-velocity layer (Vp $<$ 4.0 km/s) of volcanics and sediments at the surface is surprisingly thick (~5 km) along most of the profile, but the velocity structure appears to be continental otherwise.
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 8109 Continental tectonics--extensional (0905)
SC: Seismology [S]
MN: 2003 Fall Meeting