Mt. Etna volcano: what have we learned from 20 years of continuous GNSS observations?

Mt. Etna volcanic activity has been characterized, in the last two decades, by more than 150 paroxysmal events (from moderate to intense and impulsive explosive activity, coupled sometime to voluminous lava flows) as well as by some large eruptive events (e.g., 2001, 2002-03, 2004-05, 2006, 2008) involving the upper sector of the northern and southern flanks of the volcano, along with the summit craters. Taking advantage of an extensive dataset of continuous GNSS stations covering the entire volcano edifice, we propose an unprecedented and detailed picture of different deformative stages. Raw GNSS observations, are processed by using the GAMIT/GLOBK software and achieved results, e.g. station daily time series and network-scale surface deformation fields, are referred to a local reference frame. By inspecting the daily baseline changes for EDAM and EMGL stations we detected a total of 59 different ground deformation phases consisting in 29 inflation phases, 21 deflation phases, 5 magmatic intrusions and 4 periods with no significant deformation. The surface deformation for each detected phase is used to constrain isotropic half-space elastic inversion models, therefore providing significant constraints on subsurface Mt. Etna’s magmatic storages. We integrate our results with recent tomographic models, correlating the inferred sources with V_P and V_P/V_S anomalies, in order to provide exhaustive interpretative model into the general volcano-tectonic context of Mt. Etna and in turn, new insight on hazard assessment.