Studies for subaqueous and submerged landslides and their relation to tsunamis in caldera areas

调查了破火山口地区及其外缘的水下滑坡和水下滑坡，以了解它们的地质结构和地形。第一，在北海道东部的火山口湖库沙罗发现了大量的崩塌滑坡，地形和底质分析及其联合数值模拟表明，滑坡与1923年库沙罗地震的海啸灾害有关的可能性很高。其次，调查了1923年关东大地震引发的外环塌陷沉海实例--内布川滑坡，明确了滑坡的影响范围和鲜有报道的滑坡体形态。第三，在上述研究的基础上，提出了新的声学调查方法。该方法由休闲探鱼仪和侧扫声纳组成，可在狭窄和浅水水域推广使用。

Subaqueous landslides and submerged landslides in caldera areas and their outer rims were investigated to know geologic structures and topographies for them. The important results are following three: First, many sublake landslides in Caldera lake Kussharo, east part of Hokkaido were found, and the high possibility that a landslide related to the tsunami disaster of the 1923 Kussharo earthquake was showed by topographic and bottom material analyses and its combined numerical simulation. Second, an example of collapsed outer rims submerging to the sea, the Nebukawa landslide which induced by the 1923 Kanto great earthquake was investigated, and the affected area of landslide and the shape of landslide body that has been scarcely reported was clarified. Third, the newly acoustic investigating method was developed through these above investigations. This method consists of leisure-use fish finders and side-scan sonar, and it can be introduced in narrow and shallow water.