Development of a probabilistic risk assessment method for combined hazards; A Classification and modeling framework for multihazard events

Choi, B.  ; Nishida, Akemi  ; Tsutsumi, Hideaki*; Takada, Tsuyoshi  

The Fukushima Daiichi Nuclear Power Plant accident highlighted the importance of developing safety assessment methods that consider multihazard events involving numerous simultaneously occurring events such as earthquakes (shaking) and tsunamis (submersion). When addressing such multihazard events, traditional methods often focus on assessing the load combinations of general structures in their structural designs and adopt simple selection criteria. However, these methods fall short when evaluating, countering, and screening external events, such as earthquakes, tsunamis, strong winds, and concentrated heavy rainfall, that occur simultaneously or in a chain. To address this, we reviewed existing literature on multihazard assessment methods, focusing particularly on scenarios involving earthquake and tsunami events. Based on concepts and basic theories, we examined various methods for addressing multihazard scenarios and classified their characteristics. Specifically, several multihazard scenarios were surveyed, and the relationships between multiple hazards were organized. In addition, common causes leading to combined events, their mutual influences, and potential cascading effects were analyzed.