HR: 0800h
AN: DI41A-1265    [Abstracts]
TI: Subducting Slabs, Long Wavelength Geoid, Layering and Viscosity Stratification
AU: * krien, y
EM: krien@geologie.ens.fr
AF: Laboratoire de geologie de l'Ecole Normale Superieure, 24 rue Lhomond, Paris, 75231 France
AU: Fleitout, L
EM: fleitout@geologie.ens.fr
AF: Laboratoire de geologie de l'Ecole Normale Superieure, 24 rue Lhomond, Paris, 75231 France
AB: We have developped a two-dimensional non-newtonian viscoelastic stationnary flow model of a subduction zone, incorporating a fault which makes the interface between the subducting and the overriding plates. A low viscosity wedge is also included. The flow is driven by a body force imposed in the slab, corresponding to the negative buoyancy of the cold sinking part of the lithosphere. Layering at 660km is introduced by imposing surface anomalies proportional to the mass anomalies needed to obtain a perfectly layered circulation. We use a finite element code, called Zebulon, which allows for a wide variety of rheologies. These model shows that the 660-discontinuity may have a significant influence on the long wavelength geoid, as well as stresses and velocities in the subduction area. We show that the layering may give positive geoid anomalies at the surface even without a viscosity jump at the 660, but these anomalies remain small, and a large viscosity increase seems to be necessary even for a perfectly layered convection. We also used this model to test the ability of models with no lithosphere and imposed surface velocities to reproduce the long wavelength geoid, and to show that the horizontal component of stress within the lithosphere is not continuous across a subduction zone.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Study of Earth's Deep Interior [DI]
MN: Fall Meeting 2005