Geothermal System of the Rausu Field, Eastern Hokkaido

Abstract

The Rausu field is the most active geothermal field in the Shiretoko Peninsula, Eastern Hokkaido, Although the discharge area of geothermal fluid does not widely spread in the field, the underground temperature is regarded as the high class in the geothermal fields of Hokkaido.
The Rausu field facing the Nemuro Channel at the central part of the Shiretoko Peninsula, is composed of hornblende porphyry and Miocene members. The former intruded into the latter showing monoclinic structure as a whole, The Miocene members dip toward the Nemuro Channel.
The geothermal system of the Rausu field is considered as follows.
1) Meteoric water penetrates into the Miocene members, and is removed from the ridge of the Shiretoko Peninsula toward the Nemuro Channel.
2) The geothermal fluid, which is heated meteoric water, is reserved and removed to the geomorphic surface through fractures of the hornblende porphyry. The discharge area is bounded by the flexural zone of the Miocene members in the east.
3) In the discharge area, the maximum underground temperature is estimated at more than 200°C.