浅間火山活動記録の再調査
スポンサーリンク
概要
- 論文の詳細を見る
Mt. Asama is one of the most active volcanoes in Japan. We have had some reliable historical documents on its volcanic activity since as early as 1108 (around the end of the Heian era). These historical documents had been collected since the end of the Edo era: middle of the 19th century. In particular, from the Meiji era (1867-1912) untill the present, several authors published eruption histories of Mt. Asama based on geophysical and geological observations conducted with modern technology. To elucidate the long-term pattern of volcanic activity, we compared several publications on the eruption history of Mt. Asama. Eventually, we encountered contradictory and/or confused descriptions of many particular volcanic events among these publications, even in modern times. We investigated and corrected these errorneous records with the aid of some reliable research papers, and finally present the eruption history of Asama volcano from a unified viewpoint. The volcanic activity of Mt. Asama can be summarized and described by subdividing the following four periods depending on the quality of descriptive data: Period 1: 685-1879 AD. Two devastating eruptive activities occurred during this period according to historical documents. Period 2: 1880-1933 AD. A volcanological observatory was established at Yuno-Taira on the western mountainside of the volcano, where observations were made during the summer. Mt. Asama started to experience strong activity from the beginning of the 20th century. Period 3: 1934-19.3 AD. A new volcanological observatory was established on the eastern mountainside by Earthquake Research Institute, the University of Tokyo. Full-time observations were conducted with modern volcanological instruments, which resulted in an empirical law for the forecasting of summit explosions in a typical andesite volcano. Mt. Asama erupted almost continuously during this period. Period 4: 1944-1990 AD. During and just after World War II, the observation system was maintained at a minimal level, but never stopped. After the War, research activity reached the highest instensity, which contributed to the development of observation skills and instruments for volcanology. However, in the latter half of the period, the activity of Asama volcano greatly declined to be almost quiescent. For periods 3 and 4, we attempted to introduce the classification of eruptive intensity.