Effect of plate thickness on bending radius and energy dissipation at the subduction zone hinge

Despite the thickness of subducting oceanic plates being identified as a control on slab and hinge behavior during subduction, there have been few attempts to quantify its effect with fully dynamic models. This paper presents a series of dynamic laboratory experiments of progressive subduction of a narrow plate into an upper mantle reservoir in which plate thickness is systematically varied from 4 mm (scaling to 20 km), up to 24 mm (120 km). The experiments investigate its effect on bending radius, subduction kinematics and the rate of energy dissipated at the hinge as a percentage of the total potential energy released through subduction. The bending radius of the hinge is found to have a strong linear relationship with plate thickness, where an increase in plate thickness corresponds to an increase in bending radius. Subduction velocity increases with plate thickness due to the increased negative buoyancy of thicker slabs, which is not compensated for by any significant increase in mantle drag on the slab. This increase is almost entirely accommodated by an increase in trench retreat rate, with a fivefold increase over the whole thickness range, while subducting plate velocity remains relatively constant. The energy dissipation ratio (Φ_Be/Φ_Bu) is low across all plate thicknesses, with the plates falling within a range of ∼4-10% during steady state subduction. The models show a moderate trend toward decreasing Φ_Be/Φ_Bu with increasing plate thickness.