GNGTS 2021 - Atti del 39° Convegno Nazionale

85 GNGTS 2021 S essione 1.1 SEISMIC POTENTIAL OF THE SEGMENTED CAMPO FELICE NORMAL FAULTS IN CENTRAL APENNINES, ITALY G. Schirripa Spagnolo 1 , M. Mercuri 1 , A. Billi 2 , E. Carminati 1 and P. Galli 2,3 1 Dipartimento di Scienze della Terra, Sapienza Università di Roma, Rome, Italy 2 Consiglio Nazionale delle Ricerche, IGAG, Rome, Italy 3 Dipartimento della Protezione Civile Nazionale, Rome, Italy Recent seismological studies have highlighted different coseismic rupture scenarios: a) seis- mic sequences, where the mainshock is followed by aftershocks having comparable magnitude (Papadopoulos & Minadakis, 2016); b) quasi-synchronous and cascade slip events over multiple adjacent fault segments during a single seismic event (Xu et al ., 2018). Therefore, in assessing the seismic potential of fault systems, adjacent fault segments should be considered collectively to test the possibility of their coseismic (quasi-)simultaneous activation. Since the seismogenic portions of faults are commonly inaccessible, studying the geometrical and mechanical interac- tion between exhumed fault segments can contribute to the understanding of multisegment and cascade earthquake scenarios. In the central Apennines, during the last 25 years, active faults close to settlements caused hundreds of victims due to Mw ≥ 6.0 earthquakes. Therefore, in these areas, the knowledge of active faults is vital. We focused our study on the Campo Felice fault segments, namely Monte Cefalone and Monte Orsello faults, characterized by geometry and potential mechanical interac- tion that were still unclear (Fig. 1 and 2). These faults have not produced documented records of earthquakes in historical times, but they are aligned with other seismogenic sources of the central Apennines and could represent a future seismic connection between the 1915, Mw 7 Avezzano and 2009, Mw 6.3 L’Aquila earthquakes (Fig. 1). Moreover, paleoseismological evidence of the occurrence of paleo-earthquakes was documented along these faults (Galli et al ., 2008; Benedetti et al ., 2013). Through this study, we aimed at providing significant evidence to draw future seismic scenarios, useful to mitigate the earthquake threat. The capability of multisegment fault activation depends on the degree of mechanical interac- tion (Manighetti et al ., 2007). Thus, the knowledge of fault interaction is essential to decipher possible future rupture scenarios. Results of our field surveys and geological-structural mapping, serial cross-sections, and throw vs. distance diagrams highlighted a soft linkage (Peacock & Sand- erson, 1994) between the Campo Felice faults (Fig. 2). Based on this mechanical interaction and the extensional kinematic indicators measured along these faults (coherent with present-day tectonic setting), we evaluated seismic potential and seismic scenarios for the Campo Felice area, assuming either independent or synchronous activations. To assess the maximum expected potential magnitude for earthquakes generated by the Campo Felice faults, we used empirical relationships linking earthquake rupture size and mag- nitude, assuming that the measured exposed fault lengths correspond to the maximum future coseismic surface rupture lengths (Trippetta et al ., 2019). In particular, we assumed both an inde- pendent motion of the two studied faults, using their single exposed lengths and a synchronous motion of the two faults, using their total exposed length. We used three empirical equations val- id for normal dip-slip faults fromWells and Coppersmith, (1994), Galli et al ., (2008), and Leonard, (2010). These equations, particularly the first and third ones, should be verified and validated locally as the database on which they are founded includes a limited number of events from the studied area and may therefore be poorly applicable. To understand which of these equations are the best for the central Apennines and Campo Felice area, we compared the magnitude deduced from seismic analyses with that predicted from empirical equations for the last seven Mw>5.5 earthquakes (1997-2016) from the central Apennines. These earthquakes are: Colfiorito,