  Natural disasters such as hurricanes are increasing and causing widespread
devastation. People's decisions and actions regarding whether to evacuate or
not are critical and have a large impact on emergency planning and response.
Our interest lies in computationally modeling complex relationships among
various factors influencing evacuation decisions. We conducted a study on the
evacuation of Hurricane Irma of the 2017 Atlantic hurricane season. The study
was guided by the Protection motivation theory (PMT), a widely-used framework
to understand people's responses to potential threats. Graphical models were
constructed to represent the complex relationships among the factors involved
and the evacuation decision. We evaluated different graphical structures based
on conditional independence tests using Irma data. The final model largely
aligns with PMT. It shows that both risk perception (threat appraisal) and
difficulties in evacuation (coping appraisal) influence evacuation decisions
directly and independently. Certain information received from media was found
to influence risk perception, and through it influence evacuation behaviors
indirectly. In addition, several variables were found to influence both risk
perception and evacuation behaviors directly, including family and friends'
suggestions, neighbors' evacuation behaviors, and evacuation notices from
officials.
