GNGTS 2018 - 37° Convegno Nazionale

248 GNGTS 2018 S essione 1.3 The 3D retrieved images integrated with resistivity section and temperature and CO 2 flux measurements , define the following characteristics: 1. A depth dependent P-wave velocity layer down to 14 m, with V p <700m/s typical of poorly-consolidated tephra affected by CO 2 degassing; 2. An intermediate layer, deepening towards the mineralized liquid-saturated area (Fangaia), interpreted as permeable deposits saturated with condensed and meteoric water; 3. A deep, confined high velocity anomaly associated with a CO 2 reservoir (Fig. 3). The deep high velocity anomaly retrieved in the 3D velocity model, associated with a gas accumulation zone, is very well confined in the layer in the 2D profiles interpreted as a channel for the rising up of deep fluid plumes. The retrieved features are expression of a volume located between the Fangaia, which is water-saturated and replenished from meteoric and condensed water, and the main fumaroles that are the superficial relief of deep rising CO 2 . So, the changes in the outgassing rate greatly affects the shallow hydrothermal system, which can be used as a near-surface proxy of fluid migration processes occurring at greater depths. Conclusion. The importance of this work lies in these principal aspects: (1) the Solfatara crater represents one of the main pressure release areas of the entire Campi Flegrei volcanic system, considering the impressive magnitude of the diffuse degassing process. Hence, the interest in the knowledge of this area grows, especially with the aim of assessing the level of potential danger characterizing this crater; (2) the 2D and 3D tomographic survey allows us to achieve an unprecedented spatial detail on the shallow velocity structure of the central part of the Solfatara crater. The high-resolution tomographic images allow us to better understand, in terms of velocity anomalies and fluid type, the complex hydrothermal processes into the shallow part of the volcano; Fig. 3 - Multiparametric interpretation. Modified after De Landro et al. , 2017.