Heat flow in the Southwest Japan Arc and its implication for thermal processes under arcs

We present 35 new heat flow measurements for the Kinki district in the eastern part of the southwest Japan are. Heat flow distribution in this region shows zonal structure parallel to the trench. In the across-are heat flow profile there are two high heat flow peaks: one is located at the volcanic front and the other is between the south coast of this are and the trench. The high heat flow at the volcanic front is probably caused by the induced flow in the mantle wedge. The high heat flow off the south coast is located in the zone where slab depth is 10 similar to 20 km, and is immediately to the ocean side of the boundary at which P-wave velocity increases landward in the upper crust. We thus consider the high heat flow is caused by the uplift of accreted materials along the backstop in the accretionary prism, assuming that seismic velocity is an indicator of rigidity of rocks. The upward flow velocity is estimated to be similar to 1 mm/yr using a simple one-dimensional erosion model, which is consistent with that estimated from the present heights of marine terraces.