|
Numerical models of subduction zone dynamics often consider a spatially limited domain of the Earth and need special conditions to initiate subduction. Published models show a large variability in the numerical representation of the area located outside the model domain (i.e. the boundary conditions), the initial mechanical and thermal state implemented and the process used to bypass the subduction initiation phase (eg. localisation of deformation). These choices may influence the dynamic evolution of the slab and upper mantle. We aim to investigate the effects of such numerical implementations on subduction zone dynamics.
We consider a simple 2D setup of an old oceanic lithosphere subducting under a continental crust. The numerical experiments use a two-dimensional finite-element code, which is characterised by a visco-elasto-plastic material behaviour and the ability to achieve large deformations. We investigate the influence of boundary conditions on the vertical sides (reflective or periodic), bottom (outflow or closed) and top (free surface or forced convergence) of the model domain. Subduction is initiated by a surface velocity condition and/or a weak zone that localises deformation. In the latter case, we study the influence of the size, geometry and rheology of the weak zone. The effects of these variations on slab evolution are quantified by slab shape and dip, slab stress field and slab sinking rate through time. Our first results highlight the influence of numerical assumptions on subduction zone evolution.
|
