GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 The Seismic History of the Anghiari fault (Upper Tiber Valley), first paleoseismological constraints A. Testa 1 , P. Boncio 2 , S. Baize 3 , F. Mirabella 4 , S. Pucci 5 , C. Pauselli 4 , M. Ercoli 4 , M. Riesner 6 , B. Pace 2 , L. Benedetti 6 1 DiSPUTer Department, Università degli Studi G. d’Annunzio Chieti e Pescara, Italy. 2 InGEO Department, Università degli Studi G. d’Annunzio Chieti e Pescara, Italy 3 Institut de Radioprotection et Sûret́ e Nucĺ eaire, Fontenay-aux-Roses, France 4 Dipartimento di Fisica e Geologia, Università di Perugia, Italy 5 Istituto Vazionale di Geofisica e Vulcanologia (INGV), Rome, Italy 6 Aix-Marseille Université, CEREGE CNRS-IRD UMR 34, Aix-en-Provence, France Introduction The Anghiari fault (AF) is a NE-dipping normal fault bounding the western side of the Sansepolcro basin, the northernmost of the extensional basins composing the Upper Tiber Valley (UTV). Extension in the Northern Apennines is accommodated by the Altotiberina low-angle normal fault (ATF), well known in literature thanks to deep seismic surveys and instrumental seismicity (Barchi et al, 1998a, b; Boncio et al, 1998; Brozzetti et al 2009). The ATF is a 70 km-long, NE-dipping low-angle normal fault with an average dip of 30°, reaching the surface along the western side of the UTV (Boncio et al, 2000). AF is supposed to be the youngest synthetic splay of the ATF (e.g., Brozzetti et al., 2009). However, there are no field outcrops of the AF documented in the literature, and chronologic constraints on its activity, and on its capability of producing surface faulting earthquakes are lacking. Thanks to morphological, geophysical and paleoseismological analysis we present for the first-time proofs of repeated surface faulting episodes along the AF, demonstrating its capability of generating surface faulting earthquakes.