GROUND DEFORMATION STUDIES AND EVACUATION BEHAVIOR DURING ERUPTIONS AT GUATEMALAN VOLCANOES

Volcanic eruptions can be an especially problematic hazard when considering the uncertainty in eruption timing and magnitude coupled with challenges associated with delivering warnings to remote areas and facilitating effective evacuations. The hazards presented by Guatemala’s active volcanoes demand enhanced monitoring capabilities and instrumentation infrastructure. Strengthening the link between the physical and social sciences should lead to more accurate, reliable, and timely hazard information to the people living in proximity to the volcano and facilitate rational decisions and actions that reduce their level of risk. While there is no one single technique that can provide unambiguous diagnostics about the timing, behavior, and outcome of a volcanic eruption, the use of GPS geodesy can provide valuable insight into the internal dynamics of a volcano allowing for enhanced interpretation of unrest signals that can be relayed to crisis management officials. The 2010 eruption of Pacaya lead to evacuations of more than 2500 people and resulted in damage and destruction to hundreds of homes. During this period of unrest, Pacaya was a poorly monitored volcano with little available quantitative geophysical data. However, despite a pronounced increase in activity prior to the eruption, and the heightened threat of injury or death during the eruption, many residents in communities surrounding the volcano chose to stay in their home throughout the eruptive crisis. Part of this research presents measurements from a campaign GPS network at Pacaya volcano, combined with InSAR data that reveals a large downward vertical and outward horizontal deformation signal at several locations around the volcano associated with two eruptive periods. We invert the available geodetic data to model the magma plumbing system and produce analytical models, which suggest that deformation was dominated by inflation of a sub-vertical dike high within the edifice while deflation of one or two deeper, spherical sources embedded below the edifice occurred during part of the observation period. The second part of this research seeks to understand why some chose to stay in harm’s way. Using data obtained from a door-to-door survey we found that evacuation behavior was strongly influenced by one’s exposure to and perception of the hazards as well as their perception of readiness. We also found that future intention to evacuate is strongly influenced by prior evacuation experience, perception of home vulnerability and warning messages. The research presented in this dissertation integrates geophysics and social vulnerability research with the aim to better understand magmatic system dynamics and associated hazards in volcanic regions in an effort to improve warning messages and evacuation behavior