1. Department of Humanities, University of Catania, Piazza Dante 32, I-95124 Catania, Italy
2. DG-SINA, Sistema Informativo Nazionale Ambientale, ISPRA, Italian National Institute for Environmental Protection and Research, Via V. Brancati 48, I-00144 Roma, Italy
3. Etnean Observatory, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Piazza Roma 2, I-95125 Catania, Italy