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

Abstract

[1] 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 (F Be /F 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 F Be /F Bu with increasing plate thickness.Citation: Irvine, D. N., and W. P. Schellart (2012), Effect of plate thickness on bending radius and energy dissipation at the subduction zone hinge,

A review of analogue modelling of geodynamic processes: Approaches, scaling, materials and quantification, with an application to subduction experiments

“…Faugere and Brun, 1984;Cobbold, 1988, 1991;Faccenna et al, 1996Faccenna et al, , 1999Schellart et al, 2002a,b;Regard et al, 2003Regard et al, , 2005Willingshofer and Sokoutis, 2009;Luth et al, 2013a), or the entire lithosphere (e.g. Funiciello et al, 2003Funiciello et al, , 2006Schellart, 2004aSchellart, , 2008Bellahsen et al, 2005;Guillaume et al, 2009Guillaume et al, , 2010Irvine and Schellart, 2012;Duarte et al, 2013;Martinod et al, 2013;Strak and Schellart, 2014;Chen et al, 2015aChen et al, , 2015b. A significant number of analogue models use visco-plastic and non-linear viscous materials, either exclusively or in combination with linear viscous materials.…”

How weak is the subduction zone interface?

“…For this purpose, we assume that the driving force increases with slab age while the resistive viscous mantle drag force, bending force, and the slab internal deformation either increase at a slower rate, remain constant, or decrease. For example, laboratory models that investigated the role of subducting plate thickness indicate that the subducting plate bending dissipation rate increases at a rate that is slower than the rate of slab potential energy release with increasing plate thickness [Irvine and Schellart, 2012], although the bending dissipation rate is only 4-10% of the potential energy release rate in these experiments. In this scenario, to match the observed age-independent subduction velocity in nature (Figure 2a), the subduction zone interfacial shear stresses must increase with age in order to counteract the increasing available driving force.…”

“…Subduction was driven entirely by the negative buoyancy of the downgoing slab (the only source of energy in our system). The main resistive forces are viscous drag from the ambient viscous mantle (up to 90%) plate bending at the subduction zone hinge (up to 20%) and at the bottom of the tank [e.g., Schellart, 2004b;Capitanio et al, 2007;Irvine and Schellart, 2012], and viscous resistance at the subduction zone interface. Slab internal deformation related to plan-view slab curvature is only a minor component (<1%) [Schellart, 2010].…”

Parameters controlling dynamically self‐consistent plate tectonics and single‐sided subduction in global models of mantle convection

“…Further studies on subduction dynamics using regional numerical models highlighted the importance of bending and downgoing plate properties [ Capitanio et al , ]. It was shown that subducting plates minimize their overall dissipation rate by adjusting their bending curvature at the subduction zone [ Capitanio et al , ; Schellart , ; Irvine and Schellart , ]. Even in the presence of a strong core (i.e., cross‐sectional plate interior), plates only weakly resist bending and generally propagate a large amount (i.e., 75–80%) of slab pull from depth to the surface.…”