Hazards hitting human society are disasters, which have both natural and social attributes. Focusing on the social attributes of disasters, this paper analyses the changing trend of social impacts exerted by earthquakes in contemporary and modern Japan. Japanese have drawn lessons from past disasters and improved their disaster reduction system. However, increasing urbanization has resulted in growing diversity and successiveness of disasters. Nuclear safety is not a new problem in Japan. The lack of forward-looking perspective, however, does expand the nuclear crisis. The authors should learn the lessons from Japan and construct a strategic and forward-looking disaster reduction system.