Magma storage and diking revealed by GPS and InSAR geodesy at Pacaya volcano, Guatemala

GPS measurements from a campaign network at Pacaya volcano, Guatemala, occupied from 2009 to 2015 were combined with InSAR data from 2013 to 2014 to model deformation sources for two eruptive time periods: 2009–2011 and 2013–2014. The GPS data for both of these time periods show downward vertical and outward horizontal deformation greater than 25 cm at several stations surrounding the volcano, while InSAR data shows up to 15-cm line-of-sight displacement. To better understand the dynamics of the magma storage system and sources of deformation, we inverted available geodetic data for these two periods. Our analytical modeling suggests that horizontal deformation was dominated by inflation of a shallow, subvertical dike, high within the volcanic edifice, while deflation of a deeper, spherical source embedded below the NW flank of the volcano occurred during at least part of the observation period. The source parameters for the dike feature are in good agreement with the observed alignment of recent eruptive vents, while parameters for the deeper, spherical source accommodate the downward vertical deformation observed at stations on and around the volcano.