Grasp of a latent risk of ship evacuation during a tsunami using AIS data analysis

A massive earthquake occurred in the Tohoku and Kanto regions of Japan on the 11th of March 2011. In response, a tsunami alert, a tsunami warning and an advisory were issued for the entire Pacific coast region. This research investigates the evacuation behavior of ships by AIS data in Sendai port after the tsunami warning was issued. The unusual behavior observed was attributed to the emergency evacuation of ships. We recognize the actual situation of ship refuge in the target port after the Tsunami alert. The result verified that most ships in port started to evacuate approximately 20 minutes after the major tsunami warning and completed offshore evacuation 50 minutes after this warning. Moreover, the drifting or stranding state of ships resulting from the tsunami was recognized from each ship´s behaviour. This contributed in understanding the actual status of the ship refuge action, and the final goal of our research is creation of the optimal safe refuge manual for each harbour.