1. Sezione di Catania, Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy
2. Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, PA, USA
3. Laboratoire Magmas et Volcans, CNRS, IRD, OPGC, Université Clermont Auvergne, Clermont-Ferrand, France