HR: 17:00h
AN: T54B-05    [Abstracts]
TI: Dynamics of plate bending at the trench and slab-plate coupling
AU: * Capitanio, F A
EM: fabio.capitanio@sci.monash.edu.au
AF: School of Mathematical Sciences, Monash University, Building 28, Clayton, VIC 3800, Australia
AU: Morra, G
EM: gabriele.morra@erdw.ethz.ch
AF: Institute of Geophysics, ETH Zurich, Hoenggerberg, Zurich, 8093, Switzerland
AU: Goes, S
EM: s.goes@imperial.ac.uk
AF: Dept. of Earth Science and Engineering, Imperial College London, London, SW1, United Kingdom
AB: The bending strength of subducting lithosphere plays a critical role in the Earth's plate tectonics and mantle convection. It is the subject of a lively debate how much of the potential energy of the downgoing plate is consumed in bending the plate, and how much of the lithospheric strength is lost in the process. This modulates the amount of slab pull transmitted to the surface, thus setting the boundary conditions under which plates move and deform. We model the subduction of a viscoelastic lithosphere, driven solely by the downgoing plate's buoyancy, freely sinking in the passive mantle, represented by drag forces. To investigate the dynamics of bending, we vary the viscosity profile within the plate, from isoviscous, where the strength is distributed, to strongly layered, where the strength in concentrated in a thin core, and map stress, strain and forces along the downgoing plate. We found that stress and strain distributions and thus the force transmitted to the surface depend strongly on the viscosity profile. While isoviscous plates deform throughout and bending is accompanied by significant thinning, layered plates keep their integrity by localizing strain in the weak outer layers, and stress in the strong core, allowing stress propagation through the bend far into the plate. The low dissipation in both rheological models, the stress magnitude largely below the plastic limit, as inferred from rock mechanics, and the continuity of stress through the bend into the plate suggest strongly that layered lithosphere keeps its integrity while bending. The rheological model presented offers a consistent description of the dynamics of convergent margins and an its relevant properties to global plate tectonics modeling.
DE: 8104 Continental margins: convergent
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8138 Lithospheric flexure
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting