GNGTS 2019 - Atti del 38° Convegno Nazionale

30 GNGTS 2019 S essione 1.1 Grünthal G. (Ed.); 1998: European Macroseismic Scale 1998 (EMS-98) . European Seismological Commission, sub commission on Engineering Seismology, Working Group Macroseismic Scales. Conseil de l’Europe, Cahiers du Centre Européen de Géodynamique et de Séismologie 15. Luxembourg, pp. 99, http://www.ecgs.lu/cahiers- bleus/. Haas J. E. and Ayre R.S.; 1969: The western Sicily earthquake of 1968 . Committee on Earthquake Engineering Research, National Academy of Sciences, Washington, D. C., 77 pp. Hanks T.C., Kanamori H.; 1979: A moment magnitude scale . J. Geoph. Res., 84 (B5), 2348–50. Rovida A., Locati M., Camassi R., Lolli B. and Gasperini P. (Eds); 2016: CPTI15, the 2015 version of the Parametric Catalogue of Italian Earthquakes . INGV, doi :http://doi.org/10.6092/INGV.IT-CPTI15. EARTHQUAKE RUPTURE ON THE FIANDACA FAULT, DEC. 26, 2018, MW 4.9: FAULT FABRIC ANALYSIS, INTENSITY VS. SURFACE FAULTING, AND HISTORICAL SEISMICITY AT MT. ETNA VOLCANO, ITALY D. Bella 1 , G. Tringali 1 , R. Pettinato 1 , F. Livio 2 , M.F. Ferrario 2 , A.M. Michetti 2 , S. Porfido 3,4 , A.M. Blumetti 5 , P. Di Manna 5 , E. Vittori 5 , L. Guerrieri 5 , G. Groppelli 6 1 Registered Geologist, Acireale, Italy 2 Università dell’Insubria, Como, Italy 3 CNR-ISA, Avellino, Italy 4 INGV-Osservatorio vesuviano, Napoli, Italy. 5 ISPRA, Roma, Italy 6 CNR – IGAG, Milano, Italy Introduction. On December 26, 2018, a Mw 4.9 earthquake hits the eastern flank of Mount Etna volcano (Sicily). The epicenter is located between the Fleri and Pennisi villages, and focal depth is estimated at 0.3 km (http://cnt.rm.ingv.it/event/21285011 ). This earthquake is part of a seismic sequence begun on December 23, 2018 and a concurrent phase of volcanic eruption, eventually resulting in lava flows and a dyke intrusion (De Novellis et al. , 2019). The earthquake is the result of the activation of the Fiandaca Fault; it is accompanied by widespread surface faulting and secondary environmental effects (Emergeo Working Group, 2019; Figs. 1 - 3), and have a maximum intensity of VIII EMS (Quest WG, 2019). Partial or complete ruptures of the Fiandaca Fault are well-documented in the last 150 years (Fig. 1). The last event that activated the entire structure, as happened in 2018, occurred in 1894 and generated extensive surface faulting and secondary effects (Riccò, 1894; Baratta, 1894; Imbò, 1935). Despite the abundant documentation of previous events, the Fleri earthquake represents the first opportunity to document coseismic effects of a strong, shallow seismic event at Mt. Etna through modern field techniques, sustained by accurate remote-sensed data, including unprecedented InSar measurements. Methods. We started mapping ground ruptures in the morning of December 26, 2018, few hours after the earthquake. We collected original structural data on ground break length and orientation, amount of displacement and slip vectors. We compared field data with InSAR imaging, showing coseismic surface rupture and afterslip on some known capable faults on Mt. Etna eastern and southern slopes. We then compared field measurements with other surface (slope, aspect, elevation) and subsurface (slope and aspect of the basement, thickness of volcanic deposits) data, to evaluate the factors ruling surface faulting occurrence and fabric. We plotted data along the rupture