Paola Vannucchi, Royal Holloway University of London, Egham, TW20, United Kingdom, Elena Spagnuolo, National Institute of Geophysics and Volcanology, Rome, Italy, Stefano Aretusini, INGV (Istituto Nazionale di Geofisica e Vulcanologia), Roma, Italy, Giulio Di Toro, University of Padova, Padova, Italy and Stefan Bjorklund Nielsen, University of Durham, Department of Earth Sciences, Durham, United Kingdom