HR: 0800h
AN: T51B-0542    [Abstracts]
TI: 3D geodynamic evolution of the Mexican Subduction Zone
AU: Manea, V
EM: vlad@gps.caltech.edu
AF: Computational Geodynamics Laboratory, Centro de Geociencias - UNAM Campus, Juriquilla, 3001, Mexico
AU: * Gurnis, M
EM: gurnis@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, United States
AB: A crucial feature of the Mexican Subduction Zone (MSZ) is a shallow subhorizontal plate interface in its central part. This particular configuration of the young subducting Cocos plate (~14 Ma) apparently creates distinct geodynamic consequences, such as thin continental lithosphere, relatively shallow intraslab seismicity, and a distal volcanic front. Despite small variations in convergence and plate age along the trench, MSZ shows large variations in slab geometry. To the North, the young (~10 Ma) Rivera plate subducts at ~45 deg similar to the South where the Cocos plate plunges into the mantle at ~45 deg. The cause of such strong along strike variations are investigated with 3D geodynamic models that incorporate a low viscosity wedge (LVW) that can vary in depth and viscosity reduction. Using GPlates, we include realistic paleoreconstructions of the North America, Caribbean, Cocos, Rivera and Pacific plates for the last 40 Ma. We show that in order to avoid complete slab flattening due to trench rollback the slab needs to be viscously weak. The weakness of the subducting slab is consistent with intense and irreversible internal deformation of the slab bending into subduction. Also we show that a flat slab segment in Central Mexico can be created by shallow LVW (~100-150 km), bounded by steep slabs to the North and South where the LVW extends to higher depths (~300 km). Also the models show a time- dependent LVW that evolves into a low viscosity layer above the flat slab, essentially decoupling the slab from the overriding plate. This result is consistent with the lack of in-plane compression in Central Mexico and the presence of periodically (3-7 years) and large slow slip events.
DE: 8157 Plate motions: past (3040)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8162 Rheology: mantle (8033)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting