The February 2013 paroxysmal activity at the New South-East crater of Mt. Etna observed by infrasound, seismic, radiometric and plume SO2 flux data

Between January 2011 and April 2013, Mt. Etna's eruptive activity has consisted of episodic intra-crater strombolian activity and paroxysms from Bocca Nuova and Voragine, and the New South-East (NSEC) summit craters, respectively. Eruptions from NSEC was characterised by initial increasing strombolian activity and lava flow output, passing to short-lasting lava fountaining. In this study we focus on seismic, infrasound, radiometric, and plume SO2 flux data simultaneously collected by the INGV monitoring networks between January and February 2013. The combination of the different parameters allowed us characterising the NSEC eruptive activity at both daily and monthly time scale. In particular, whilst the seismic, infrasound and radiometric signals illuminated on the energy and features of the six paroxysmal events fed by NSEC, the SO2 flux shed light on the likely mechanisms triggering the eruptive phenomena observed at the surface. In detail, we propose that the paroxysms' sequence represented the climax of a waxing-waning phase of SO2 degassing that had started since August 2012 and eventually ended in June 2013. In this view, the January-February 2013 eruptive activity reflects the phase of release of a volatile-rich batch of magma that had stored in the volcano shallow plumbing system at least four months before.