Non-collisional orogeny in northeast Japan driven by nearby same-dip double subduction

Abstract

Same-dip double subduction systems influence plate kinematics, geometry and mantle flow within the region bounded by the two subduction zones. However, whether these effects extend to nearby plate margin tectonics remains an open question. Furthermore, the range of geodynamic processes operating in these margins and driving non-collisional orogeny (that is, the formation of Andean-type mountain ranges) is not yet fully understood. Here we explore the potential geodynamic connection between the tectonic evolution of northeast Japan and the development of the Ryukyu/Izu–Bonin–Marianas same-dip double subduction using three-dimensional geodynamic models. We find that this same-dip double subduction drags the Pacific trench westwards, resulting in northward-propagating trench advance and compression affecting the northeastern Japan arc and back-arc. We thus propose that the dynamics of the Ryukyu/Izu–Bonin–Marianas same-dip double subduction over the past ~10–5 Myr drove the enigmatic plate kinematics responsible for non-collisional orogeny and back-arc subduction initiation in northeast Japan since ~6–3.5 Myr ago, which has made this region prone to catastrophic earthquakes. We also suggest that same-dip double subduction explains various ancient episodes of widespread non-collisional orogenesis and represents a mechanism through which subduction zones establish the plate kinematic conditions necessary for non-collisional orogenesis.