GNGTS 2021 - Atti del 39° Convegno Nazionale

59 GNGTS 2021 S essione 1.1 CAPABLE FAULTS IN THE RIETI BASIN: NEW GEOLOGICAL, GEOPHYSICAL AND PALEOSEISMOLOGICAL EVIDENCE AT THE RIVODUTRI AND CANTALICE SITES A.M. Michetti 1,7 , F. Livio 1 , G. Binda 1 , M.F. Ferrario 1 , R. Gambillara 1 , E. Scaramuzzo 1 , G. Tringali 1 , A. Peiro 2 , V. Sapia 3 , V. Materni 3 , M. Caciagli 3 , S. Urbini 4 , C.A. Brunori 4 , V. Comerci 5 , P. Lorenzoni 6 1 Università dell’Insubria, Como, Italy 2 Dpto. de Ciencias de la Tierra, Universidad de Zaragoza, Zaragoza, Spain 3 INGV, Roma, Italy 4 INGV, Arezzo, Italy 5 Dipartimento per il Servizio Geologico d’Italia, ISPRA, Roma, Italy 6 Professional consultant, Rieti, Italy 7 INGV, Napoli, Italy Introduzione The Ordinance No. 83 of the Italian Government Commissioner Structure for the 2016 Post- seismic Reconstruction establishes for the in-depth studies of some Active and Capable Faults (FAC; Commissione tecnica per la microzonazione sismica, 2015) mapped in the territory of the 2016 epicentral area in order to a) assess their capability and b) identify their detailed geometry at 1:5000 scale. This analysis allows to redefine the fault width and type of instability associated with the presence of FAC (from “Fault Warning Zones” up to the definition of “Fault Avoidance Zones”), with consequent remodeling of the associated regulatory constraints. As part of this task, INGV has signed in October 2020 the Scientific Collaboration Agreement with the University of Insubria for the study of the FAC mapped in the municipal area of Rivodutri and Cantalice, Rieti Basin (Fig. 1a). In the following we present the first results of this ongoing project. Geological setting The Rieti Basin is a wide Pliocene to Quaternary intermountain depression, located on the western side of the Central Apennines. Origin and evolution of this basin, and nearby simi- lar continental basins (such as Fucino, Leonessa, L’ Aquila, Salto; all characterized by strong historical seismicity), are related to the post-collisional crustal extension that has strongly af- fected the area since the early-middle Pliocene. The Rieti Basin evolved through two main phases of extensional tectonics. During late Pliocene to early Pleistocene, the growth of the NNW-trending normal fault along the Mt. Terminillo W slope generated a half-graben structure filled by a thick sequence of fluvial mostly conglomeratic deposits, evolving from alluvial fan to alluvial plain facies (Fosso Canalicchio and Monteleone Sabino syntems). The Velino River drainage was essentially flowing south, toward the Tyrrhenian coastline. Later, the Middle Pleistocene regional uplift of the Central Apennines and renewed normal faulting generated a full graben structure, and a major drainage reorganization. The Velino River was diverted to the west and then north, captured by the Nera River. The Early Pleistocene conglomerates were downfaulted and eroded, and the small volcanic center of Cupaello formed along the eastern master fault of the basin. A sequence of travertine terraces along the Velino River controlled the deposition of new fluvial and lacustrine deposits, rich in volcanic materials. This includes the main threshold of the present-day basin, the Marmore Platform, which grew by over than 80 m in the post-glacial to Holocene times, and continued to expand repeatedly during histori- cal times (Guerrieri et al ., 2006; Archer et al ., 2019).