GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 A sneak peek under the Prosecco vineyards L. Peruzza, M. A. Romano, M. Guidarelli, L. Moratto, M. Garbin, E. Priolo National Institute of Oceanography and Applied Geophysics - OGS In August 2021, an extremely productive seismic sequence took place in northeastern Italy, in the homeland of the Prosecco wine. Thanks to the local Collalto Seismic Network (rete-collalto.crs.inogs.it) , installed and managed by OGS since 2012 to better monitor the seismicity in the surroundings of an underground gas storage, in a single month we identified and localized 407 microearthquakes. This is about 20 times the average monthly rate of events detected in the last decade; 92% of these earthquakes are clustered near the village of Refrontolo at about 9 km depth. None of the events of the Refrontolo sequence was felt by the population (main earthquake M L 2.5, M W 2.4). The earthquakes, mostly identified by automatic procedures, were post-processed by manual picking of P, S-phases and polarities; they were localized by different techniques, to obtain the best possible imaging of the source (https://www.frontiersin.org/articles/10.3389/feart.2022.1044296/full ). Acknowledging that unsolvable uncertainties affect the locations, a cloud of hypocenters defines a small SE dipping volume, differently oriented with respect to the brittle surface previously depicted by microseisms and assigned to the NNW dipping Montello Thrust . We interpret the sequence ruptured pre-stressed patches near to failure of subvertical, antithetically oriented faults. The unusual productivity rate and precursory foreshock activity support the hypothesis that the Montello system has a relevant aseismic component. We believe that this episode, irrelevant from an energetic point of view, is of greatest interest for deciphering the seismic potential of this area and for strengthening automatic microearthquake detection and location procedures. Contact: Laura Peruzza, lperuzza@ogs.it