[S-CG55] Oceanic plate as inputs to subduction zone: from oceanic spreading ridge to subduction trench

[SCG55-06] Thermal structure of the Tohoku subduction zone: effects of plate cooling models

*Manabu Morishige¹ (1.Earthquake Research Institute, the University of Tokyo)

Keywords:Oceanic plate, Subduction zone, Thermal structure, Thermal conductivity

Recent studies have extensively investigated the effects of experimentally constrained thermal conductivity on the thermal structure of oceanic plates. However, little is known about how the updated cooling models affect the thermal structure of subduction zones. In this presentation I investigate the effects of plate cooling models on the thermal structure of the Tohoku subduction zone, with a particular focus on thermal conductivity. Three types of thermal conductivity were tested, including constant (Case 1), temperature-dependent (Case 2), and temperature- and material-dependent (Case 3) types. For each case, the parameters for the plate cooling models were inferred based on the observed variations in surface heat flow and seafloor depth with plate age using Bayes' theorem. It was found that the predicted locations of the blueschist-out boundaries in the oceanic crust and serpentinite-out boundaries in the slab mantle, which are possibly related to intermediate-depth earthquakes, can change by approximately 10 km depending on the assumed thermal conductivity. This may be significant when considering the causes of earthquakes. Therefore, it is desirable to take into account the variations in thermal conductivity when predicting the thermal structure of oceanic plates and subduction zones.