A33. Kemp, D. V., and P. Bird (1992) Bending and dynamic support of subducted slabs (abstract), Eos Trans. AGU, 73 (43), Fall Meeting Supplement, 386.
We previously developed a numerical model to simulate subducted plates and their mechanical coupling to the asthenosphere, and have now systematically explored the consequences of varied power-law rheologies and plate thicknesses. This steady-state model integrates forearc tractions, body forces, the plate's finite bending strength, and coupled dynamic support and extends continuously from the open ocean, where the only geometrical constraints are applied, to a depth of 670 km. Thus, observables from any portion of the domain may be used to constrain the dynamics.
A few simple criteria, in fact, provide powerful constraints on the system. As overly stiff plates do not completely unbend, we exclude models that have maximum dips greater than 100° or overturn at depths less than 400 km. We also exclude models with trenches deeper than 12 km or average dips over the depth interval from the arc to 400 km of greater than 70° . The latter excludes unsupported plates.
Only three of over fifty models satisfy these criteria. Although one each is 40, 60, and 80 km thick, a coefficient in the bending-moment/curvature-rate relationship for these models is remarkably similar. This coefficient depends on the plate thickness to the 7/3 power and would vary by a factor of 5 based on plate thickness alone, but is offset by plate rheology differences such that the coefficients match to within 20% for the most reasonable models.
In form, it is notable that these models unbend under their own weight and subduct vertically through the transition zone. At these depths the bending strength fails to transmit support provided from static loads in the forearc region and the dynamic support falls below 30% of its arc value.