Iris van Zelst , Cedric Thieulot , Timothy J Craig

To a large extent, the thermal structure of a subduction zone determines where seismicity occurs through the transition from brittle to ductile deformation and the depth of dehydration reactions. Thermal models of subduction zones can help understand this seismicity by accurate modelling of the thermal structure of the subduction zone. Here, we assess a common simplification in thermal models of subduction zones, i.e., constant values for the thermal parameters. We use temperature-dependent functions constrained by lab estimates for the thermal conductivity, heat capacity, and density, to systematically test their effect on the resulting thermal structure of the slab. To isolate this effect, we use the well-constrained and thoroughly studied model setup of the subduction community benchmark by Van Keken et al., 2008 in a 2D finite element code. To ensure a self-consistent and realistic initial temperature-profile for the slab, we implement a 1D plate model for cooling of the oceanic lithosphere with an age of 50 Myr in favour of the previously used half-space model in Van Keken et al., 2008.
Our results show that using temperature-dependent thermal parameters in thermal models of subduction zones result in a cooler plate, which leads to a larger estimated seismogenic zone and a larger depth at which dehydration reactions responsible for intermediate-depth seismicity occur. We therefore recommend that thermo(-mechanical) models of subduction take temperature-dependent thermal parameters into account for accurate modelling of the thermal structure of subduction zones.