GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.2 GNGTS 2024 Dynamic and statc strain sensitvity of velocity variatons at Ischia Island, southern Italy Stefania Tarantno 1 , Piero Poli 2 , Maurizio Vassallo 1 , Nicola D’Agostno 1 1 Isttuto Nazionale di Geofsica e Vulcanologia 2 Department of Goescience, University of Padova, Padova, Italy Ischia Island is the westernmost, actve volcanic complex of the Campanian plain (Southern Italy, Civeta et al., 1991). A long-term depressurizaton (Sepe et al., 2007) in the local hydrothermal system is causing defaton and contracton (Galvani et al., 2021) of the surrounding volcanic edifce. In the 2017 a Mw 3.9 very shallow earthquake occurred in Casamicciola, in the northern part of the island, causing landslides and several collapse. Here we present dv/v measurements over 8 years (2016-2023) for variable coda waves tme lapse using empirical Green's functons reconstructed by autocorrelaton of seismic noise recorded at local velocimeters. We compared velocity variatons tme series with the temporal evoluton of the strain, obtained at the network of GPS statons deployed on the island. We also investgated the coseismic variatons of seismic waves velocity occurred during the 2017 earthquake. We found high values in both dynamic and statc strain sensitvity of velocity variatons with appreciable diferences on the island, refectng the anisotropic patern of the depressurizaton. This also testfy a signifcant non-linearity in the elastc propertes of the local volcanic rocks, as expected for mult-fractured and heterogeneous materials where large amount of microcracks are commonly present. References Civeta, L., Gallo, G., & Orsi, G. (1991). Sr- and Nd-isotope and trace-element constraints on the chemical evoluton of the magmatc system of Ischia (Italy) in the last 55 ka. Journal of Vo l cano l ogy and Geotherma l Resear ch , 46 (3–4) , 213–230 . htps : / /do i . org / 10.1016/0377-0273(91)90084-D Galvani, A., Pezzo, G., Sepe, V., & Ventura, G. (2021). Shrinking of Ischia Island (Italy) from Long- Term Geodetc Data: Implicatons for the Defaton Mechanisms of Resurgent Calderas and Their Relatonships with Seismicity. Remote Sensing , 13 (22), 4648. htps://doi.org/10.3390/ rs13224648