Effective Messaging for Public Tsunami Warnings: Clarity, Specificity, and Sensemaking

Tsunami events occur infrequently. However, when they do occur, the results can be devastating. Recent tsunamis include the 2004 Boxing Day Tsunami in East Asia, the 2010 Chilean earthquake and tsunami, and the 2013 Tohoku earthquake and tsunami, each of which results in hundreds if not hundreds of thousands of deaths. These events demonstrate the broad reaching impacts of tsunami on both local, hazard-familiar populations as well as those with little historical experience or knowledge of environmental signals and key protective actions that must be taken to save lives.

Effective messages are essential for successful public warnings across all hazards. While significant attention has been given to warnings for weather-related events, lesser scrutiny has been applied to the content and style of messages directed toward the public at risk of tsunami events. This manuscript reports the comprehensive findings from a series of projects that examine public perception and interpretation of tsunami warning products. In this study we present the results from two phases of research: focus groups and online experiments. Focus group research examined message perception (including message interpretation and behavioral intent), and message sensemaking (the strategies used to close interpretation gaps). Message perceptions were affected by unfamiliar concepts, lack of knowledge about the hazard and its impacts, and inability to personally locate oneself in relation to the hazard. Furthermore, message sensemaking was directly affected by heuristics from recently available experiences, media accounts, and knowledge of non-tsunami warnings.

Results of phase one led to the design of a revised public tsunami message, which was then tested through online experiments to assess social-behavioral outcomes and intentions. The revised message consistently outperformed the original message across five different outcome categories (understanding, believing, personalizing, deciding, and milling).

The conclusions of this research demonstrate the value of multi-phased research on warning message design, and the importance of taking into account public hazard knowledge and understanding of relevant protective actions. Furthermore, results indicate that language consistency between hazards is likely to become increasingly important as warning agencies design simplified hazard messaging concepts and strategies for public warnings. Future research should focus on populations with high tsunami hazard familiarity and additional testing of messages with variable message lengths.