GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.1 129 HIGH-RESOLUTION SEISMIC PROFILING OF THE CASTELLUCCIO BASIN: NEW CONSTRAINTS ON THE SHALLOW SUBSURFACE OF THE 30 OCTOBER 2016 MW 6.5 NORCIA EARTHQUAKE FAULT (CENTRAL ITALY) F. Villani 1 , S. Maraio 2 , P.P. Bruno 3 , L. Improta 1 , K. Wood 4 , R. Civico 1 , Pa. Baccheschi 1 , V. Sapia 1 , S. Pucci 1 , C.A. Brunori 1 , P.M. De Martini 1 , D. Pantosti 1 , P. Conti 2 , C. Doglioni 1 1 Istituto Nazionale di Geofisica e Vulcanologia, Italy 2 Centro di Geotecnologie, Università di Siena, Italy 3 Università degli Studi di Napoli Federico II, Italy 4 Universitè Montpellier, France In the past twenty years, the central Apennines (Italy) were hit by three important seismic sequences affecting a region >100 km-long parallel to the chain axis, causing heavy damage, economic losses and >600 deaths (Colfiorito, 1997, M w 6.0; L’Aquila, 2009, M w 6.1; Amatrice- Visso-Norcia, 2016, M w 6.1, 5.9 and 6.5). The mainshocks of those sequences were generated by the in-cascade activation of segmented normal fault-systems (Chiaraluce et al. , 2017; Improta et al. , 2019), which at places bound Quaternary extensional basins. The Pian Grande di Castelluccio basin (PGC) is located in the hangingwall of the Mt. Vettore - Mt. Bove normal fault-system (VBFS; Calamita et al. , 1992; Pizzi et al. , 2002), responsible for the 30 October 2016 M w 6.5 Norcia earthquake (Fig. 1). The widespread coseismic surface faulting following this earthquake (Civico et al. , 2018; Villani et al. , 2018b) affected also part of this basin, confirming the occurrence of active fault splays able to rupture up to the surface during large earthquakes (Galadini and Galli, 2003) and linked to the seismogenic fault at depth. Moreover, the basin position matches the locus of the largest long-term displacement of the VBFS, where the width of the coseismic deformation zone attains about 3 km and cumulative coseismic throws locally exceed 2 m (Villani et al. , 2018b). Therefore, unveiling the subsurface structure of the PGC basin provide hints for the long-term behavior of the VBFS. Fig. 1 - The Pian Grande di Castelluccio (geology simplified after Pierantoni et al. , 2013) with the location of the seismic profiles (thick blue lines) and the coseismic surface ruptures following the 30 October 2016 Norcia earthquake (modified after Civico et al. , 2018).