檜原湖湖底の岩屑なだれ堆積物地形  [in Japanese] Volcanic Debris Avalanche Deposits in Lake Hibara  [in Japanese]

The 1888 eruption of Bandai volcano, Fukushima Pref. Northeast Japan is famous for its large debris avalanche that killed 461 people. After the eruption, the avalanche deposit dammed up the old river and made many lakes such as Lake Hibara, Lake Akimoto etc. To investigate the area of the avalanche deposit and structure of the deposit, side scan sonar survey was carryed out at Lake Hibara. Bathymetry and side scan sonar clearly showed the lake bottom fabric. The avalanche deposit with many hummocky mounds reached 11 km from the volcanic edifice, which collapsed in 1888, and covered former existed river which shows smooth bottom surface. The avalanche deposit was, also, divided into two parts from the density and the size of the mounds.