Structural field survey of Fiandaca - Pennisi shear zone (Mt. Etna volcano) affected by seismic swarm occurred on 26th December 2018.

This work introduces the results of geological survey along the fracturing field developed during the seismic event occurred 48 hours after the short but intense flank eruption of Etna volcanic complex. The eruptive event was developed from SE crater base of Mt. Etna from 24 till 27 December 2018. The NNWSSE eruptive fracture represents the surface on the surface of the hydrofracture feeding system, which probably affected the entire structural frame of the Etna eastern flank, reactivating FiandacaPennisi shear zone [Monaco et al., 2010]. During the seismic swarm, the maximum magnitude (ML 4.9) was recorded at 3.19 AM, 2 km N away from Viagrande (CT) with a depth of 1.0 km [http://cnt.rm.ingv.it/event/21285011]. The fracturing field was recognized by geological maps [Monaco et al., 2010; Branca et al., 2011] and field survey, collecting the geometrical and kinematics parameters related to the shear segments. The trend deformation field was observed from Acireale area (NNWSSE strike) to Fleri area (WNWESE strike) near Mt. Ilice. The deformation area is about 6 km length and width ranging from few meters to hundreds. During field survey, Fractures measured have been interpreted as Riedel's R or T type fractures in a right lateral shear zone [Riedel, 1929]. The results of this work will allow us to define the areas vulnerable to structural deformation affected by superficial earthquakes, which usually happen on the Etna volcanic complex [De Guidi et al., 2012]. In conclusion this work is aimed to better define risk areas for population and anthropic structures, useful for official istitutions. (Civil Protection, National Institute of Geophisics and Vulcanology (INGV), University Institutes). References Branca S., Coltelli M., Groppelli G., Lentini F., (2011). Geological map of Etna volcano, 1:50,000 scale. Ital J Geosci 130(3):265–291. De Guidi G., Scudero S., Gresta, S., (2012). New insights into the local crust structure of Mt. Etna volcano from seismological and morphotectonic data. J. Volcanol. Geotherm. Res. 223224, 83–92. https://doi.org/10.1016/j.jvolgeores.2012.02.001. Monaco C., De Guidi G., Ferlito C., (2010). The morphotectonic map of Mt. Etna. Ital. J. Geosci. 129, 408–428 Riedel W., 1929. “Zur mechanik geologischer brucherscheinungen.” zentralblatt für mineralogie. Geol. Paläontol. B 1929, 354–368.