GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 - POSTER GNGTS 2023 Local Earthquake Tomography at the Lipari-Vulcano complex, South Italy: new insights on the active degassing system C. Totaro 1 , M. Aloisi 2 , C. Ferlito 3 , B. Orecchio 1 , D. Presti 1 , S. Scolaro 1 1 Department of Mathematical and Computer Science, Physical Sciences and Earth Sciences, University of Messina, Messina, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania-Osservatorio Etneo, Catania, Italy 3 Department of Biological, Geological and Environmental Sciences, University of Catania, Catania, Italy Seismic tomography represents a very powerful and effective approach to look at depths beneath volcanic systems thus helping to better understand their behaviour. The P-wave and S-wave velocity ratio, in particular, is a key parameter useful to discriminate the presence of gas, fluids and melts. In the present study, we collected ~ 4400 crustal earthquakes that occurred in the last thirty years and we used the LOcal TOmography Software LOTOS (Koulakov, 2009) to estimate the first 3D overall model of Vp, Vs and Vp/Vs for the Lipari–Vulcano complex, Aeolian islands (southern Italy). The investigated area has been characterized both in old and recent times by fumaroles, hydrothermal activity and active degassing. In particular, the Vulcano Island has been interested in the past decades by several episodes of anomalous increases of fumarole temperature and strong degassing, the latter of which started in September 2021. The results of the tomographic investigation indicate the presence of two main anomalies of low Vp and low Vp/Vs (Fig. 1), clearly depicted up to ~ 8 km depths, and related to gas-rich materials beneath the central-northern sector of Vulcano and the western offshore of Lipari, respectively. The anomaly beneath Vulcano is located in close correspondence with La Fossa caldera area and with the sector where fumaroles, hydrothermal activity and active degassing are widely documented (De Ritis et al., 2013; Selva et al., 2020; Di Luccio et al., 2021; https://www.ct.ingv.it/index.php/monitoraggio-e-sorveglianza/prodotti-del-monitoraggio/comunic ati-attivita-vulcanica). Moreover, beneath the western Lipari off-shore a new, previously undetected, volume of strong gas-concentration has been identified. Even if these two anomalies show almost the same intensity, no evidence of degassing activity is available for the latter one because of its location at sea depths where the relevant water column pressure may inhibit the observation of possible degassing processes.