Evaluation of a potential supercritical geothermal system in the Kuju region, central Kyushu, Japan

•Candidate supercritical geothermal system identified in the Kuju region.•Potential magmatic heat source identified beneath the Hatchobaru geothermal plant and Kuju volcanoes.•Effects of a deep magmatic intrusion on the shallower geothermal system. We derived the thermal structure of the Kuju region of volcanic activity in central Kyushu, Japan, to assess the potential existence of a supercritical geothermal system. Extrapolation of existing well-logging data suggests the presence of a high-temperature region beneath the area between the Hatchobaru geothermal power plant and Kuju-Iwoyama Volcano, which closely overlaps a low-resistivity body estimated from magnetotelluric data. Based on estimated temperatures exceeding 380 °C at the relatively shallow depth of -3.3 km above sea level, and considering evidence for magmatic fluid transport, this high-temperature region is a potential target for a supercritical geothermal reservoir.