GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 Seismic noise surveys in the area of Etna volcano (southern Italy). S. Hailemikael 1 , D. Famiani 1 , G. Milana 1 , G. Tusa 2 , M. Paratore 2 , G. Brunelli 3 , R. Azzaro 2 1 Isttuto Nazionale di Geofsica e Vulcanologia, Rome, Italy. 2 Isttuto Nazionale di Geofsica e Vulcanologia, Catania, Italy. 3 Isttuto Nazionale di Geofsica e Vulcanologia, Milan, Italy. In 2022 the regional Civil Protecton Department started a new project for 3 rd level seismic microzonaton at Etna, coordinated under the umbrella of the Centro per la Microzonazione Sismica e le sue applicazioni (CentroMS). In the wide range of actvites scheduled in the project, one of the targets is the dynamic characterizaton of the subsurface structure through seismic noise measurements. In this framework, a working group of the Isttuto Nazionale di Geofsica e Vulcanologia (INGV) in July 2023 started a campaign of seismic acquisiton in the eastern fank of the volcano, the most exposed in terms of seismic hazard due to a number of highly seismogenic faults crossing a very densely urbanised territory (Azzaro et al., 2012, 2013). In general, the main scientfc issue is to characterise subsurface structures related to very diferent geological and tectonic conditons. In fact, the volcanic environment is highly heterogeneous in terms of lithology for the presence of sof (pyroclastcs) and hard (basalts) units determining strong lateral and vertcal discontnuites. In additon, the tectonic actvity contributes to complicate the geophysical interpretaton, since the bedrock is extremely fractured near the fault zone. This also implies a signifcant role of subsurface fuids circulatons. The frst surveys were carried out at 4 selected sites belonging to the natonal permanent seismic monitoring networks (Nicolosi-ENIC, Sant’Alfo-ESAL; Santa Venerina-EVRN and -SVN). Passive seismic surveys were also carried out at 3 additonal sites to investgate the efect of actve faults on the noise signals (polarizaton, see Di Giulio et al., 2009 and references herein). For each investgated site (Fig. 1), noise data were recorded by nodal seismic sensors in array confguraton adaptng the experimental setup to environmental conditons. Each sensor is composed of a data recorder, which contains a batery, a 24-bit digitzer, 32 Gb solid-state memory, GPS and GLONASS receiver in a sealed case connected with a three-component geophone sensor with 4.5 Hz eigen-frequency.