1. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Via Creti 12, 40128 Bologna, Italy
2. Department of Physics and Astronomy, Alma Mater Studiorum University of Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
3. Department of Civil, Environmental and Architectural Engineering—ICEA, University of Padova, 35131 Padova, Italy