抄録
Old historical documents on 1779 AD An’ei eruption of Sakurajima, southwest Japan were collected from distal places as well as those from neighboring area of the volcano. These records revealed that the ash-fall front traveled to the northeast at about 50-100km/h, reached as far as Tohoku district 1200km from Sakurajima, and covered area of ca. 2.33×105km2. Investigation of old documents helped to improve understanding of behavior of the volcano and environmental effects at the time of infrequent and great eruption. The wide distribution of ash-fall in 1779 Sakurajima eruption suggests that there is a high potential that ash discharged by future eruption of Sakurajima may cover down through the mainland of Japan. We should keep in mind both physical and economical effects of ash-fall in assessing the activity and making the scenario of an eruption.
