HR: 0830h
AN: T31D-0870    [PDF]
TI: The Trench Retreat Effect: Dynamics and Slab Folding
AU: * Enns, A
EM: enns@geophysik.uni-frankfurt.de
AF: Institute of Meteorology and Geophysics, J.W.Goethe-University, Feldbergstr. 47, Frankfurt am Main, 60323 Germany
AU: Schmeling, H
EM: schmeling@geophysik.uni-frankfurt.de
AF: Institute of Meteorology and Geophysics, J.W.Goethe-University, Feldbergstr. 47, Frankfurt am Main, 60323 Germany
AU: Becker, T W
EM: tbecker@igpp.ucsd.edu
AF: GPP, Scripps Institution of Oceanography, University of California, La Jolla, San Diego, CA 92093-0225 United States
AB: Subduction influences plate tectonics by modifying the surface area and velocities of plates, and plates connected to slabs move faster than plates without slabs. Most of the subduction zones on Earth show the trench retreat effect, which influences the subduction process and geologic deformation at the surface. To investigate the trench retreat effect we used the 2D finite differences code FDCON (Schmeling and Marquart, 1993). In order to start subduction, we assumed that initially one edge of the subducting plate dips into the mantle. An overriding plate was not included in the models. The models are isotherm and viscous (Stokes flow) with a visco-plastic subducting lithosphere. The plastic rheology of the plate is described by the Byerlee law, mimicking brittle deformation in the shallow lithosphere. The density and viscosity of the mantle and the lithosphere are advected with the tracer approach. We used periodic and reflective free slip boundary conditions. Numerical experiments were done to analyze the relationship between the trench retreat and various subduction parameters using different viscosity structures: (1) homogeneous mantle viscosity and, (2), stratified viscosity to model the upper and the lower mantle. The viscosity of the plate and the mantle, the thickness and the length of the lithosphere were varied. We found that the flow in the lower part of the model box for the models with periodic and reflective boundary conditions influences the way in which the slabs are folded. For the trench retreat, we observed that it depends predominantly on the viscosity of the mantle, rather than on the viscosity of the slab. The velocity of trench retreat decreases when the slab touches the boundary between the upper and lower mantle.
DE: 3210 Modeling
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8122 Dynamics, gravity and tectonics
DE: 8159 Rheology--crust and lithosphere
DE: 8160 Rheology--general
SC: Tectonophysics [T]
MN: 2003 Fall Meeting