Modeling the Probability of Tsunami Fire Ignition Based on Data From the 2011 Tohoku and 2024 Noto Peninsula Earthquakes, With Recommendations to Reduce Emerging Fire Risk in Tsunami Vertical Evacuation Structures

ABSTRACT Recent tsunamigenic earthquakes in Japan have highlighted the emerging fire hazard triggered by tsunami inundation and its impact on tsunami vertical evacuation (TVE) structures. This new type of fire following earthquake, referred to as “tsunami fires,” may be a potential universal hazard that tsunami‐prone countries face; however, it has not been considered in earthquake‐related risk management. As part of initiatives to evolve regional fire‐following‐earthquake risk assessments, this study focuses on modeling the uncertainty of tsunami fire occurrences. An analysis of 92 tsunami fires following the 2011 Tohoku and 2024 Noto Peninsula earthquakes reveals the following. (1) In areas of high tsunami intensity where numerous wooden houses and automobiles are washed away, tsunami fires may mostly start from tsunami debris that is washed away and accumulated by the tsunami or may start while tsunami debris is being transported by the tsunami and then accumulated while burning; conversely, in areas of low tsunami intensity where few wooden houses and automobiles are washed away, tsunami fires may mostly start from electricity‐related sources in tsunami‐inundated buildings and automobiles. (2) The probability of tsunami fire ignition is approximately 2–6 fires on average per 10,000 tsunami‐inundated buildings, depending on the building washout ratio, and varies from approximately 1/3 to 3 times that of the average within one sigma due to unobserved regional differences. Recommendations to prevent losses of life in TVE structures caused by tsunami fires are presented. These findings will help us better understand and prepare for tsunami fires as earthquake‐related cascading hazards.