著者

中田 節也

出版者

特定非営利活動法人日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.61, no.1, pp.199-209, 2016-03-31

---

Deterministic eruption scenarios may mislead taking countermeasures for coming hazards. Preparing the event tree covering all phenomena which may happen in future eruptions even with low probability for the volcano is important not only for forecasting eruptions but also for disaster prevention. Eruption event trees can be prepared in various concepts, for example, eruption type, scale, hazard type, impact direction or area and so on. The probability tree is the event tree equipped with probabilities for the branches. Probability trees by USGS and European scientists include the cumulative trees, trees based on scientists' elicitation and Bayesian trees. Introduction of the eruption event trees into the Japanese volcanologist community began around 2009. Then, event trees were prepared for Izu-Oshima, Miyakejima, Sakurajima, Usu, and Izu-Tobu volcanoes. Reasons for branching and time scales of events were also discussed and shown on the event trees together with probabilities. The event tree for Sinabung volcano, Indonesia, as an example of lava dome-forming eruptions was drawn in 2011, based on the geological study. On-going lava dome/flow eruption at this volcano just followed the most probable scenario. For Sakurajima volcano, a conceptual event tree was drawn for understanding the anomalies controlling the eruption scale.