HR: 0800h
AN: G11A-0761    [Abstracts]
TI: Mechanical modelling of oblique convergence in the Zagros, Iran
AU: * Chery, J
EM: jean@dstu.univ-montp2.fr
AF: Jean Chery, Laboratoire DL, CNRS-UMII, pl. bataillon, Montpellier, 34095 France
AU: Vernant, P
EM: vernant@mit.edu
AF: Philippe Vernant, EAPS Dpt, MIT, Cambridge, MA 54617 United States
AB: Recent GPS surveys indicate that Zagros kinematics corresponds to an oblique convergence between a rigid central iranian plateau and the arabian plate at 6-8 mm/yr at the longitude of the Persian gulf. Convergence is almost frontal in central Zagros and oblique (45ø) in northern Zagros. It has been proposed that internal deformation of northern Zagros occurs in a partitionned mode. In such a view, the main recent fault bordering the iranian plateau accomodates all the tangential motion, while shortening happens by pure thrusting within the fold and thrust belt. We test this tectonic concept using a 3D mechanical finite element model of Zagros which accounts for the horizontal rheological layering of the lithosphere (strong upper crust, weak lower crust, strong or weak uppermost mantle) as well as the possible vertical heterogeneity of the main recent fault. Surprinsingly, a partitionning mode only occurs when the collision is very oblique. As this is not the case in northern Zagros, we find that 25 percent only of the tangential motion can be taken by the main recent fault. As the GPS based tangential motion across Zagros is 5 mm/yr, the present-day geodetic slip rate of this fault should be as low as 1.2 mm/yr. Also, our model predict no strike-slip activity of a vertical fault when convergence is more frontal. This last result appears consistent with the distributed strain occuring in central Zagros. We discuss the implications of our findings with respect to seismic and geological data available in Zagros.
DE: 8102 Continental contractional orogenic belts
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8160 Rheology--general
DE: 5120 Plasticity, diffusion, and creep
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting