No.36 Mount Fuji Scientific Research Institute

(Inagi Newsletter, October 15, 2014 issue)

On August 22, 2014, we visited the Fujisan Science Research Institute in Yamanashi Prefecture as part of a joint training session of the Tokyo Mayors' Association, and listened to a lecture by Director Toshitsugu Fujii.
Mr. Fujii is a leading expert who obtained a Doctor of Science degree from the University of Tokyo, worked at the university's Earthquake Research Institute, served as the director of that institute, and has been the chairman of the Japan Meteorological Agency's Volcanic Eruption Prediction Liaison Committee since 2003.
The theme of the day was "The Formation of Mount Fuji and Its Impact on the Metropolitan Area Due to Eruptions." Mount Fuji was registered as a World Cultural Heritage site last June, and this facility was renamed from "Environmental Science Research Institute" to "Mount Fuji Science Research Institute" in April of this year. While the media and locals are in a celebratory mood, this theme reminded us that this mountain is an active volcano.
Active volcanoes are said to include not only those that are currently exhibiting vigorous fumarolic activity but also those that have erupted in the last 10,000 years. It is puzzling to think that a volcano that has not erupted for 10,000 years is still considered active, but in the case of Chile's Chaiten Volcano, which erupted dramatically after 9,400 years without any prior signs, it is reported that a major eruption occurred 27 hours after the first earthquake was detected, so we must not let our guard down.

Japan is said to have 110 active volcanoes, which accounts for 7% of the world's active volcanoes, making it one of the most earthquake-prone countries in the world. Among them, the volcanoes that could affect the metropolitan area are Mount Hakone, Mount Asama, and Mount Fuji.
The most recent significant impact is from Mount Hakone, where a pyroclastic flow occurred during a major eruption 65,000 years ago, leaving a pumice layer of about 20 centimeters in some areas of Tokyo. The major damage comes from Mount Fuji, where the Hoei eruption 300 years ago resulted in ash fall of about 2 to 10 centimeters in Tokyo. While large volcanic rocks do not reach directly from Mount Fuji, volcanic ash accumulates widely carried by the westerly winds.
It is concerning that, according to current knowledge, predicting a volcanic eruption of Mount Fuji is difficult, but the only solace is the theory that the probability of the next eruption being small is high.
Regarding the registration of Mount Fuji as a World Cultural Heritage site, there are outstanding environmental measures that need to be addressed, and neglecting them could lead to the possibility of cancellation of the registration. Among the pointed-out issues, there was a mention of the urgent need for a crisis management plan that functions in the event of an eruption or fire.
Since the Great East Japan Earthquake, we have been working to eliminate unexpected events, but it seems that defending against a volcanic eruption of Mount Fuji is quite difficult. However, it is necessary to prepare for recovery after a disaster. The Inagi City Regional Disaster Prevention Plan has so far focused on measures primarily against earthquakes and wind and flood damage, but through this training, I felt that volcanic eruptions should also be a research topic in the future.