HR: 08:55h
AN: G31D-04    [Abstracts]
TI: GPS Constraints on Continental Deformation in the Eastern Mediterranean and Caucasus Region
AU: * Reilinger, R E
EM: reilinge@erl.mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences, 77 Massachusetts Ave., Cambridge, MA 02142 United States
AU: McClusky, S
AF: Department of Earth, Atmospheric, and Planetary Sciences, 77 Massachusetts Ave., Cambridge, MA 02142 United States
AU: Vernant, P
EM: vernant@mit.edu
AF: Department of Earth, Atmospheric, and Planetary Sciences, 77 Massachusetts Ave., Cambridge, MA 02142 United States
AB: (Presented on behalf of the E. Med/Caucasus GPS Consortium). We use GPS observations during the period 1988 to 2004 to constrain an elastic block model for deformation within the zone of interaction of the Eurasian, African, and Arabian plates. We constrain present-day motions of the African (Nubian), Arabian, and Eurasian plates, regional deformation within the inter-plate zone, and slip rates for major faults. Kinematically, we interpret the deformation field in terms of a block-like response of the continental lithosphere including the westward motion of Anatolia and the N-E motion of the eastern Turkey/Lesser Caucasus region away from the Arabia-Eurasia collision zone. The eastern Turkey and Lesser Caucasus region is undergoing counterclockwise rotation that results in increasing rates of convergence from west to east along the Main Caucasus Thrust. We observe an apparent change in orientation across the Sevan fault in the Lesser Caucasus consistent with right-lateral strike slip (probable source of the 1988, M=6.9 Spitak Earthquake), but relative motions are constrained to be less than 1 to 2 mm/yr, about an order of magnitude less than the motion between the Lesser and Greater Caucasus blocks. We observe deformation within the Greater Caucasus block at about latitude 47.5řE that may be associated with a change in the strike of the Greater Caucasus thrust fault from ESE to approximately N-S where it may transition into a right-lateral fault along the west side of the Caspian Sea. Although poorly constrained, our investigations suggest shallow locking depths (about 5 km) for the Main Caucasus Thrust and the Hellenic subduction zone, and normal locking depths for other faults (15 to 20 km). This may help account for the low level of historic seismic strain release observed in the Caucasus and along the Hellenic Arc. A particularly interesting result of our model is that the East Anatolian Fault (boundary between the Anatolian and Arabian plates) is transtensional. If this result persists with improved GPS control on Arabia plate motion, it would imply that the westward motion of Anatolia is currently being driven completely by buoyancy forces (i.e., not "extrusion"), including foundering of the down-going African plate along the Hellenic trench.
DE: 8107 Continental neotectonics
DE: 8155 Plate motions--general
DE: 1206 Crustal movements--interplate (8155)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting