HR: 14:00h
AN: U53A-02    [Abstracts]
TI: Three Dimensional Modeling of Lithosphere and Mantle Dynamics Elucidating Lithosphere-Mantle Coupling
AU: * Ghosh, A
EM: aghosh@mantle.geo.sunysb.edu
AF: Stony Brook University, Department of Geosciences, 255 Earth and Space Sciences Building, Stony Brook, NY 11794 United States
AU: Wen, L
EM: wen@mantle.geo.sunysb.edu
AF: Stony Brook University, Department of Geosciences, 255 Earth and Space Sciences Building, Stony Brook, NY 11794 United States
AU: Holt, W
EM: wholt@mantle.geo.sunysb.edu
AF: Stony Brook University, Department of Geosciences, 255 Earth and Space Sciences Building, Stony Brook, NY 11794 United States
AU: Haines, A
EM: ajh50@cam.ac.uk
AF: University of Cambridge, Department of Earth Sciences, Downing Street, Cambridge, CB2 3EQ United Kingdom
AU: Flesch, L
EM: lmflesch@purdue.edu
AF: Dept. of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907 United States
AB: We present a global study of joint modeling of lithosphere dynamics and three dimensional mantle circulation. Our study provides insight into the lithosphere-mantle coupling problem emphasizing the role of lateral viscosity variations in the asthenosphere that affect basal tractions associated with density buoyancy driven mantle convection. Forces driving lithospheric motion can be categorised into: (1) forces due to gravity acting on density variations within the lithosphere and (2) those acting at the base of the lithosphere (basal tractions) generated by density variations deeper than the lithosphere. Density variations within the lithospheric thin sheet give rise to horizontal gradients in gravitational potential energy (GPE) which in turn produce deviatoric stresses. These stresses coupled with the stresses from basal tractions contribute to a total deviatoric stress field that should match stress field indicators, such as the style of strain and directions of principal axes of strain from the Global Strain Rate Map (GSRM), as well as stress directions from the World Stress Map (WSM). We test different mantle density and viscosity models in order to find the best mantle-lithosphere coupling model, which, when added to the GPE solution gives a best fit to the stress field indicators from GSRM and WSM. The vertically averaged deviatoric stress field from GPE differences is constrained by gravity, topography, geoid and crustal thickness data. The mantle circulation models, which provide the basal traction field, are constrained by long wavelength observations of geoid, topography and plate motion, together with seismic tomography and the inferred history of subduction. Our modeling results indicate that the lithosphere-mantle coupling is laterally varying. In some areas, the GPE variations play a dominant role in generating the observed stresses and the lithosphere-mantle coupling is inferred to be weak, while in other areas stresses from basal tractions are required in addition to the stresses from GPE in order to satisfy the observed stresses. We will present observationally-constrained circulation and rheological models that would generate global traction fields capable of explaining the lateral variation of lithosphere-mantle coupling and the high-resolution observations of strain rate and stress at the Earth's surface.
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8107 Continental neotectonics (8002)
DE: 8122 Dynamics: gravity and tectonics
DE: 8150 Plate boundary: general (3040)
SC: Union [U]
MN: Fall Meeting 2005