New Insights on Mt. Etna’s Crust and Relationship with the Regional Tectonic Structure from Joint Active and Passive P-Wave Seismic Tomography
In the Central Mediterranean region, the production of chemically varied volcanic items (e.g., those from Mt. Etna and the Aeolian Islands island chain) testifies to the complexity of the tectonic and geodynamic setting. Regardless of the a great deal of research studies that have actually focused on this area, the relationships among volcanism, tectonics, magma climb, and geodynamic processes stay inadequately understood. We present a tomographic inversion of P-wave speed utilizing active and passive sources. Seismic signals were tape-recorded using both short-lived on-land and ocean bottom seismometers and information from a long-term local seismic network consisting of 267 seismic stations. Active seismic signals were created using air gun shots mounted on the Spanish Oceanographic Vessel ‘Sarmiento de Gamboa’. Passive seismic sources were obtained from 452 local earthquakes recorded over a 4-month duration. In overall, 184,797 active P-phase and 11,802 passive P-phase first arrivals were inverted to provide three different speed models. Our outcomes include the first crustal seismic active tomography for the northern Sicily area, including the Peloritan– southern Calabria area and both the Mt. Etna and Aeolian volcanic environments. The tomographic images offer an in-depth and total local seismotectonic framework and highlight a spatially heterogeneous tectonic routine, which is consistent with and extends the findings of previous models. Among our most substantial results was a tomographic map reaching 14 km depth showing a discontinuity striking roughly NW– SE, extending from the Gulf of Patti to the Ionian Sea, south-east of Capo Taormina, representing the Aeolian– Tindari– Letojanni fault system, a regional contortion belt. For the very first time, we observed a high-velocity anomaly situated in the south-eastern sector of the Mt. Etna area, offshore of the Timpe area, which is suitable with the pipes system of an ancient guard volcano situated offshore of Mt. Etna.

Introduction
The Western– Central Mediterranean is dominated by extensional basins in a back-arc setting, consisting of the Alboran Sea to the west, and the Thyrrenian and Ionian basins in the main area (e.g., Monna et al. 2013; Argnani et al. 2016). The Eastern Mediterranean (Aegean area) has traditionally been thought about an ancient back-arc extensional basin associated with the north-east Hellenic arc subduction zone, which at present is characterized by little or no tectonic activity (e.g., McClusky et al. 2000; Papanikolaou and Royden 2007). In specific, in the southern Tyrrhenian Sea and eastern Sicily, numerous research studies have actually tried to constrain the structure of the crust (e.g., Barberi et al. 2004; Scarfì et al. 2007, 2016).

The function of volcanic activity in the complex local geodynamic setting has actually been noted by numerous studies (e.g., Barberi et al. 1973; Beccaluva et al. 1985; Doglioni et al. 1994, 2001; Mantovani et al. 1996; Branca et al. 2008; Chiarabba et al. 2008). Among the volcanic centres, Nisyros Island is made up of basaltic– andesitic– rhyolitic items representing both early-stage large-scale basaltic flows and Plinian eruptive episodes that formed the contemporary caldera (e.g., Caliro et al. 2005 and recommendations therein). Mt. Vesuvius has produced a variety of magma structures, from basaltic to andesitic, and is defined by Plinian and sub-Plinian episodes followed by a long period of Strombolian and effusive activity (e.g., Saccorotti et al. 2002 and referrals therein).