Abstract
　The potential of natural disaster prevention using hard countermeasures can be presented in terms of the probability of encounters with natural disaster during one's lifetime. It was found that the average life span can be used to predict most factors related to the soft countermeasures. The Disaster Prevention Appraisal Index (DPAI) which is defined by a multiple logistic function can quantitatively estimate the defensive potential of both soft and hard countermeasures. The DPAI is shown to be highly applicable in the evaluation of countermeasures against huge natural disasters (the number of death is more than l000).

【キーワード】：防災ポテンシャル，巨大災害，防災評価指標，死亡リスク，平均寿命，遭遇確率

*京都大学防災研究所
Disaster Prevention Research Institute, Kyoto University