Comprehensive Basic Observational Research on the 2000 Eruption of Mt. Usu and Its Application for Mitigating Related Volcanic Disasters

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On the occasion of 2000 eruption of Mt. Usu, Hokkaido, Japan, prompt scientific advises based on the real-time research data and accumulated knowledge over decades encouraged officials and people in the area for conducting successful evacuation in time. Ca. 15,000 people evacuated and resulted economical and social impacts were very serious at first and central government opened local emergency center in Date City.Members under this scientific program worked hard mostly based at temporary prefab observatory with collaborators over wide academic fields, discussing daily schedule and field gains, and submitting the basic knowledge daily to Mt. Usu Subcommittee of Coordinating Committee for Prediction of Volcanic Eruptions in Japan and Local Emergency Center. Basic knowledge integrated by our group was systematically communicated for the authority for the decision of evacuation cancellation and any difficult operations in risk-prone area. Direct explanation and recommendation to evacuees … More were another type of our academic tasks.Main part of the results came from precise hypocenter determination, other observational results especially from the networks of air wave and GPS, various geodetic, geoelectrical, geomagnetic, geothermal, geochemical, geomorphorogical, geological studies in the field. Modeling the course of volcanic activity and subsurface magma intrusion process, advises for possible mudflows and their mitigation scheme were another concerned subjects by the group.Termination of magmatic activity was clearly detected by the evidences of subsidence of the uplifted area and coincidental seismicity drop to background level. This mechanism was the same as that occurred 1977-1982 activity of Mt. Usu. Caution still need to the phenomena occurring at a few craters and surrounding limited area for the long-lasting geothermal phenomena.Two countries, New Zealand and French sent investigation team to Mt. Usu and scientific results by our group were acknowledged by their reports as a common sense of volcano country. Less