HR: 13:40h
AN: G13C-01    [Abstracts]
TI: Rotational Motion of the Victoria Plate with Respect to Nubia and Somalia Deduced from Space-Geodetic Observations
AU: * Fernandes, R
EM: rmanuel@di.ubi.pt
AF: UBI, CGUL, IDL, R. Marques d'Avila e Bolama, Bloco 6, Covilhã, 6201-001, Portugal
AU: * Fernandes, R
EM: rmanuel@di.ubi.pt
AF: DEOS, Delft University of Technology, Delft, 2629 HS, Netherlands
AU: Kamamia, C M
EM: muyack@rcmrd.org
AF: Regional Centre for Mapping of Resources for Development, P. O. Box 632, Nairobi, 00618, Kenya
AU: Farah, H
EM: farah@rcmrd.org
AF: Regional Centre for Mapping of Resources for Development, P. O. Box 632, Nairobi, 00618, Kenya
AU: Hunja, E W
EM: hunja@kenuniv.ke
AF: Jomo Kenyatta University, Nairobi, Nairobi, 00615, Kenya
AU: Combrink, A
EM: attie@hartrao.ac.za
AF: HartRAO, P.O.Box 443, Krugersdorp, 1740, South Africa
AU: Miranda, J
EM: jmmiranda@fc.ul.pt
AF: FCUL, CGUL, IDL, Campo Grande, Lisboa, 1409, Portugal
AU: Stamps, D
EM: dsstamps@memphis.edu
AF: Purdue University, Earth and Atmospheric Sciences Department, West Lafayette, IN 47907, United States
AB: The East African Rift, a major tectonic structure that extends from the Afar region to the Southwest Indian Ridge mainly forming the plate boundary between Nubia and Somalia, is split into two branches in the Kenyan region, bordering a third tectonic block, called Victoria block. An angular velocity for this block was been recently proposed (Calais et al., 2006). However, it was based on earthquake slip vector mainly since only one GPS-derived motion was available in the limits of the block (Mbarara, Uganda). The lack of accurate GPS observations has prevented to obtain a more robust prediction of the relative motions of this block with respect to the Nubian and Somalian plates. In this work, we present a model of the present-day motions of the Victoria Block derived from the velocity field derived from a collection of GPS stations, both permanent- and campaign-type. The time-span of the observations is sufficiently long to derive reliable solutions for most of the stations in our network. Such model is compared with the most recent solutions based on the integration of sparse GPS data with earthquake slip vector. In order to properly interpret the motion solutions, the derived near-velocity field is constrained using a model of the present-day angular velocities of the stable part of Nubia and Somalia tectonic plates based on the ITRF2005 solution. The angular velocities are estimated using a network containing all available stations on Africa. We show that there is an anti-clockwise rotation of the Victoria block with respect to Nubia and Somalia plates, which in this region have a clearly relative extensional regime. The relative transverse motion of this block with respect to the neighbouring plates is about 2-3 mm/yr, which is approximately half of the differential motion between Nubia and Somalia in the area.
DE: 1209 Tectonic deformation (6924)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 8110 Continental tectonics: general (0905)
SC: Geodesy [G]
MN: 2007 Fall Meeting