Role of variable plate kinematics history in the back-arc deformation regime along the western Pacific margin (Japan Sea)

Extension at back-arc basins generally occurs behind arc-trench systems and the mechanisms which act at its origin, as well as the deformation regime developed, are strongly related to the subduction of oceanic lithosphere. Here, we examine the Japan Sea back-arc basin evolution using numerical simulations along the western margin of the Pacific plate, where the subduction processes have been responsible for the deformation style during the last 57 Ma. We carried out 2D high-resolution thermo-mechanical numerical models of subduction dynamics in this area, increasing the simulation complexity integrating into the computations i) the kinematic variability of the Pacific plate over the geological past with respect to a fixed Eurasia, ii) a Low-Viscosity Zone within the asthenosphere, iii) a horizontal eastward mantle flow. Our results show a main kinematic control of the subduction trench position, which advances and retreats in time, providing stages of compression and extension in the Japan Sea back-arc basin. The obtained deformation regime is comparable with the tectonic evolution history occurred along the Eastern Eurasian margin and with analyses on paleo-volcanic front position and paleo-stress reconstructions in the Japan Sea area.