Thermal structure of the Kanto region, Japan

Using a 3‐D numerical thermal model, we investigate the thermal structure of the Kanto region of Japan where two oceanic plates subduct. In a typical subduction setting with one subducting slab, the motion of the slab drives solid‐state mantle flow in the overlying mantle wedge, bringing in hot mantle from the back‐arc toward the forearc. Beneath Kanto, however, the presence of the subducting Philippine Sea plate between the overlying North American plate and the subducting Pacific plate prevents a typical mantle wedge flow pattern, resulting in a cooler condition. Further, frictional heating and the along‐margin variation in the maximum depth of slab‐mantle decoupling along the Pacific slab surface affect the thermal structure significantly. The model provides quantitative estimates of spatial variations in the temperature condition that are consistent with the observed surface heat flow pattern and distributions of interplate seismicity and arc volcanoes in Kanto.