HR: 17:15h
AN: T54B-06    [Abstracts]
TI: Numerical Modeling of Free Subduction: a Boundary-Element Approach
AU: * Ribe, N M
EM: ribe@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75005, France
AB: Many important aspects of subduction can be understood by studying an idealized model of purely buoyancy-driven ("free") subduction of an isolated thin fluid sheet with constant viscosity in an ambiant fluid with a lower viscosity. The problem can be efficiently solved using the boundary-element method, wherein a Stokes flow in a given region of space is represented in terms of the velocities and tractions at its boundaries. Essential advantages of the method include reduction of the dimensionality of the problem (from 3D to 2D or 2D to 1D); the capacity to implement a true free surface; accurate interface tracking; and the complete absence of wall effects (unless they are desired.) Moreover, the two-fluid configuration implemented by the method closely resembles that of many recent laboratory experiments on subduction. The study I will describe proceeds hierarchically from simple models to more complex ones. The simplest reference case is free subduction of a 2D sheet in an infinite half-space, with surface topography included to ensure the resolution of Stokes's paradox. Next, an impermeable boundary at 660 km depth is included, and then a viscosity jump. Finally, the same sequence is followed for a 3D sheet of finite width, for which toroidal flow around the sides of the slab is important. I will present a number of quantitative scaling laws for key subduction parameters such as the surface plate speed, the rate of trench rollback, and the slab geometry, and compare their predictions with relevant geophysical observations and with laboratory experiments (e.g., those of the group at the University of Rome-III.)
DE: 4255 Numerical modeling (0545, 0560)
DE: 8104 Continental margins: convergent
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8160 Rheology: general (1236, 8032)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting