Relating rapid plate-motion variations to plate-boundary forces in global coupled models of the mantle/lithosphere system: Effects of topography and friction.

Giampiero Iaffaldano

A detailed understanding of magnitude and distribution of forces causing changes in plate motions over time has become a most important goal in geophysics today. Mantle convection is widely accepted to provide a significant amount of the driving force available to plate tectonics, but the relative magnitudes of other driving and resisting forces still remain unclear. After introducing a recently-developed numerical technique where simulations of global lithosphere dynamics are performed in conjunction with 3D mantle circulation models, I will focus on three convergent-boundary systems: the Nazca/South America margin, the Aleutian trench and the India/Australia deformation area. For the cases at hand, predictions of recent plate-motion changes, as well as of other geophysical observables, compare well with data available through paleomagnetic and geodetic techniques. Numerical results (a) demonstrate that precise budgets of forces acting upon plates can be obtained and (b) support the notion of strong forcing along weak plate boundaries.