GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.2 GNGTS 2024 Preliminary characterizaton of the area of the Salse del Dragone mud volcano (Northern Italy) through surface-wave seismic prospectng E. Paolucci 1 , M. Zanet 1 , M. Antonellini 2 , A. Armigliato 1 , N. Carfagna 3 , F. Zaniboni 1 , A. Piombo 1 . 1 Department of Physics and Astronomy “A. Righi”, University of Bologna, Bologna, Italy 2 Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy 3 Department of Physical Sciences, Earth and Environment, University of Siena, Siena, Italy Mud volcanoes are geological structures due to the surface expulsion of fuids, such as mud, water and hydrocarbons which originate within a sedimentary sequence. In partcular, the ascent of these materials is favoured by the presence of fuid-rich over-pressured deep sediments characterized by low density and viscosity respect to the surrounding deposits. The emission actvites related to mud volcanoes have signifcant implicatons in terms of energy resource exploraton, seismicity, atmospheric budget of greenhouse gases (Mazzini and Etope, 2017) as well as geohazard assessment (e.g., Gatuso et al., 2021). About 60 subaerial mud volcanoes exist in Italy, mainly located along the outer Apennine belt and Sicily (Martnelli and Judd, 2004). The structure known as “Salse del Dragone” is one of the 18 mud volcanoes located in the Emilia-Romagna region, specifcally situated in the Northern Apennine belt about 20 km far from the city of Bologna. Actually, the area afected by clear emited mud presence is about 1300 m 2 and the emission area (about 200 m 2 ) is characterized by a fatened positve structure with a plateau-like shape less than 0.5 m high (Martnelli and Judd, 2004). Although the emission actvity currently appears to be quite bland, some historical references (Calindri, 1780; Bombicci, 1873) report intense and loud eruptons with huge mud emission: it is precisely this type of lively actvity that gave the site its name (“Dragon Salsa”). Moreover, a large actve mud debris fow originates from the emission area: actually, it is not clear if these deposits were generated directly from mud volcano fows, if are related to a surface fow of the outcropping formaton (“Argille Varicolori”), or are a combinaton of both. In order to identfy the main subsoil features of the area and try to understand the nature of the debris fow deposits, a preliminary seismic survey based on passive and actve surface-waves acquisitons was carried out; in partcular, several single-staton and multple-staton measurements (e.g., Fot et al., 2018) were performed. The frst ones were analyzed using the HVSR (Horizontal to Vertcal Spectral Ratos) technique, while the later were devoted to retrieve the Rayleigh wave phase velocity dispersion curves. The joint use of these two analyses made it possible to characterize the subsoil materials in