HR: 0800h
AN: G21A-0115    [Abstracts]
TI: New constraints on the present-day kinematics of the East African Rift from GPS and earthquake slip vector data
AU: Hartnady, C
EM: chris@umvoto.com
AF: UMVOTO Africa Ltd., P.O. Box 61, Muizenberg, 7950 South Africa
AU: * Calais, E
EM: ecalais@purdue.edu
AF: Purdue University, EAS Dpt., West Lafayette, IN 47097 United States
AU: Ebinger, C
EM: cindy@gl.rhul.ac.uk
AF: Royal Holloway University of London, Dpt. of Geology, Egham, TW20 0EX United Kingdom
AU: Nocquet, J
EM: nocquet@ensg.ign.fr
AF: CNRS, Geosciences Azur, Valbonne, 06560 France
AB: The East African Rift (EAR), a major 5,000 km long and up to 1,000 km wide tectonic structure that marks the extensional boundary between the Nubian and Somalian plate, is interpreted either as a wide zone of uniformly distributed, diffuse deformation, or as a mosaic of microplates. Testing these models and quantifying the present-day kinematics of the EAR has so far resited investigation because of a critical lack of geodetic data within the EAR as well as on the surrounding Nubian and Somalian plates. Here, we present an updated GPS velocity field covering the Nubian and Somalian plates and combine it with earthquake slip vectors along the EAR in a joint inversion. Our objectives are to better constrain the Somalia/Nubia plate motion and to try to resolve block motions within the plate boundary zone. We find a Somalia/Nubia angular velocity similar to the one proposed by Fernandes et al. (EPSL, 222, 2004). We show that Tanzanian craton, nested between the western and eastern branches of the EAR and underlained by an upper mantle plume, can be modeled as an independent block, rotating counterclockwise w.r.t. Nubia. We discuss the implications of this kinematic model on the tectonics of the EAR.
DE: 7223 Seismic hazard assessment and prediction
DE: 8107 Continental neotectonics
DE: 1208 Crustal movements--intraplate (8110)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting