Improving Cascadia subduction zone residents’ tsunami preparedness: quasi-experimental evaluation of an evacuation brochure

This study surveyed 227 residents in three US Pacific Coast communities that are vulnerable to a Cascadia subduction zone tsunami. In the Brochure condition, information was presented online, followed by questions about tsunamis. Respondents in the Comparison condition received the same questionnaire by mail but did not view the brochure. Respondents in the Brochure condition had higher levels of perceived information sufficiency than those in the Comparison condition about three of the five tsunami topics. Both conditions had generally realistic expectations about most tsunami warning sources. However, they had unrealistically high expectations of being warned of a local tsunami by social sources, such as route alerting, that could not be implemented before first wave arrival. They also had unrealistically high expectations being warned of a distant tsunami by ground shaking from the source earthquake, whose epicenter would be too far away for them to feel. Moreover, respondents in both conditions expected higher levels of personal property damage and family casualties than is the case for most hazards, but their levels of negative affective response were not especially high. Overall, only 10% of the sample accessed the tsunami brochure even when sent repeated contacts and the brochure demonstrated modest effects for those who did access it. These results suggest that state and local officials should engage in repeated personalized efforts to increase coastal communities’ tsunami emergency preparedness because distribution of tsunami brochures has only a modest effect on preparedness.