抄録
Nagata district can be divided into two areas on the basis of geological conditions, particularly, Jyomon coast line which was formed by Jyomon transgression about 6000 years ago.
The first area is the northern part which is characterized by the uplift of Suma Fault which forms mountains and hilly lands. The mountains are composed of Cretaceous granitic rocks. This area has very weak earthquake disasters except for slope failure, even though active fault (Suma Fault) is located on this area. The hilly lands consist of Plio-Pleistocene Osaka Group. This earthquake had caused various damages on this hilly lands. Many wooden buildings which were located on the bankings were collapsed by the 1995 Hyogoken-Nanbu Earthquake. Serious damaged grounds were observed on the margin of the hilly lands.
The second area is alluvial formation which is located in southern part of the Jyomon coast line. This area is composed of clay rich deposits. Concentrative damaged area caused by the 1995 Hyogoken-Nanbu Earthquake is located in this area. About 70% of Wooden buildings were collapsed and elevated-railroads were destroyed by the 1995 Hyogoken-Nanbu Earthquake. The reason for this seriously damaged wooden buildings is soft ground which is mainly composed of clay. Geologic hazards associated with this great earthquake are slightly weak in sand rich alluvial formation area compared with those of the clay rich alluvial formation area.
The 1995 Hyogoken-Nanbu Earthquake had caused various damages. The damage associated with the earthquake had close relation to the geologic conditions and the ground.
