HR: 13:55h
AN: G13C-02    [Abstracts]
TI: Present-day Kinematics of the East African Rift
AU: * Stamps, D S
EM: dsstamps@memphis.edu
AF: Purdue University, Earth and Atmospheric Sciences Department, West Lafayette, IN 47907, United States
AU: Calais, E
EM: ecalais@purdue.edu
AF: Purdue University, Earth and Atmospheric Sciences Department, West Lafayette, IN 47907, United States
AU: Saria, E
EM: sariah@uclas.ac.tz
AF: University College of Lands and Architectural Studies, University of Dar Es Salaam P.O.BOX 35091, Dar Es Salaam, n/a n/a, Tanzania, United Republic of
AU: Mbede, E
EM: embede@uccmail.co.tz
AF: Department of Geology, University of Dar Es Salaam P.O.BOX 35091, Dar Es Salaam, n/a n/a, Tanzania, United Republic of
AU: Ebinger, C
EM: cebinger@earth.rochester.edu
AF: University of Rochester, Department of Earth and Environmental Sciences, Rochester, NY 14627, United States
AU: Delvaux, D
EM: ddelvaux@africamuseum.be
AF: Royal Museum for Central Africa, Leuvensesteenweg 13 3080 Tervuren, Brussels, n/a n/a, Belgium
AU: Kervyn, F
EM: fkervyn@yahoo.com
AF: Royal Museum for Central Africa, Leuvensesteenweg 13 3080 Tervuren, Brussels, n/a n/a, Belgium
AU: Combrinck, L
EM: ludwig @ ludwig.hartrao.ac.za
AF: Hartebeesthoek Radio Astronomy Observatory, HartRAO Space Geodesy Programme PO BOX 443, Krugersdorp, n/a 1740, South Africa
AU: Hartnady, C
EM: chris@umvoto.com
AF: UMVOTO (Pty) Ltd, PO Box 61, Muizenberg, n/a 7950, South Africa
AU: Nocquet, J
EM: nocquet@geoazur.unice.fr
AF: CNRS Geosciences Azur, Headquarters 3, rue Michel-Ange 75794 Paris cedex 16, Paris, n/a n/a, France
AU: Fernandes, R
EM: rmanuel@di.ubi.pt
AF: University of Porto, Reitoria da Universidade do Porto Parca Gomes Teixeira, Porto, n/a 4099-002, Portugal
AB: The East African Rift (EAR), a ~5000 km-long series of seismically active structures that mark the divergent boundary between the Somalia and Nubia plates, is often cited as a modern archetype for rifting and continental breakup. Paradoxically, its current kinematics is the least well-known of all major plate boundaries, owing to its tremendous extent, difficult access, and lack of geodetic data. The existence of two "new" tectonic plates within the EAR (Victoria and Rovuma) between the main Nubian and Somalian plates has recently been proposed through combined analysis of earthquake slip vector and (sparse) space-geodetic data (Calais et al., 2006). A third, dominantly oceanic Lwandle plate was recently postulated by a re-analysis of the post 3.2 Ma spreading rates and transform-fault azimuths along the Southwest Indian Ridge (SWIR; Horner-Johnson et al., 2007). Here we use an updated geodetic solution -- a combination of all continuous GPS stations on the Nubia, Somalia, and Antarctic plates, campaign GPS measurements in Africa, and a global DORIS solution -- together with earthquake slip vectors in the EAR and transform azimuth and spreading rates along the SWIR. We show that the space geodetic data and the 3.2 Ma average oceanic data along the SWIR are consistent with each other at the 95% confidence level. The data support a kinematic model with (1) a present-day Nubia-Somalia Euler pole located to the SE of the southern tip of Africa, (2) the existence of three distinct microplates embedded in the EAR: Victoria, Rovuma, and Lwandle. Additional geodetic data in the EAR are now needed to confirm and further refine this model. References Calais, E., C. Hartnady, C. Ebinger, and J.M. Nocquet, Kinematics of the East African Rift from GPS and earthquake slip vector data, In: Yirgu, G., Ebinger, C.J. & Maguire, P.K.H. (eds) Structure and Evolution of the Rift Systems within the Afar volcanic province, Northeast Africa, Geological Society Special Publications, 259, p.9-22, 2006. Horner-Johnson, B., R.G. Gordon, D.F. Argus, Plate kinematic evidence for the existence of a distinct plate between the Nubian and Somalian plates along the Southwest Indian Ridge, Journal of Geophysical Research, 112, 2007
DE: 1209 Tectonic deformation (6924)
DE: 1243 Space geodetic surveys
DE: 8103 Continental cratons
DE: 8110 Continental tectonics: general (0905)
DE: 8158 Plate motions: present and recent (3040)
SC: Geodesy [G]
MN: 2007 Fall Meeting