Reestimation of slab dehydration fronts in Kuril-Kamchatka using updated global subduction zone thermal structures

Abstract

Previous subduction thermal models are inconsistent with the values of forearc heat flow (50-140 mW/m2) and global P‒T conditions of exhumed rocks, both suggesting a shallow environment 200-300°C warmer than model predictions. Here, we revaluate these problems in Kuril-Kamchatka using 3D thermomechanical modeling that satisfies the observed subduction history and slab geometry, while our refined 3D slab thermal state is warmer than that predicted by previous 2D models and better matches observational constraints. We show that warmer slabs create hierarchical slab dehydration fronts at various forearc depths, causing fast and slow subduction earthquakes. We conclude that fast-to-slow subduction earthquakes all play a key role in balancing plate coupling energy release on megathrusts trenchward of high P-T volcanism.