Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

Abstract

Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.

Pliocene–Quaternary seismogenic faults in the inner Northern Apennines (Valdelsa Basin, southern Tuscany) and their role in controlling the local seismicity

“…Fazzini & Gelmini, 1982;Bemporad et al 1986;Liotta, 1991;Pascucci et al 2007) and their impact in controlling low-magnitude earthquakes has also been highlighted for northern Tuscany (e.g. Molli et al 2021). Many of these 'lineaments' are ascribed to the presence of lithotypes, which react differently to erosion, as could be the case of the 'Piombino-Faenza line'.…”

Dating Low‐Grade Deformation: Role of Lithology and Strain Partitioning on Ar Isotope Records in the Alpi Apuane of Northern Apennines (Italy)

“…During the early stage of D2, crenulation folds with a characteristic subhorizontal axial plane developed on a regional scale, while successive deformation was associated with semibrittle and brittle structures, represented by kink and open folds, as well as low‐angle normal faults (Molli et al., 2018). The final stages of deformation and erosion‐driven unroofing and exhumation are recorded by systems of high‐angle normal to oblique‐normal and transcurrent faults, related with the recent to active deformation regime affecting the area (Molli et al., 2021).…”

Integrating Different Databases to Offer a Geological Perspective of Coastal Management: A Review Case from the Northern Tuscany Littoral Cell (Italy)

“…The activation of the half-graben dates to the upper Miocene. According to [26], the geological boundaries are defined by the Pisan Mounts (north-east), the Livornesi Mounts (south-east), and the Secche della Meloria (south-west); the north-western limit is yet to be unequivocally identified, but a study by [27] indicated the area of Marina di Massa as the possible northern edge. Presently, the depocenter of the basin (up to 2500 m deep) is located in the area of the Arno River mouth.…”

“…The top hundred meters of the coastal plain subsurface consist of a cyclic alternation of continental and nearshore deposits related to glacial-interglacial cycles, which have ultimately been explained as a series of transgressive-regressive sequences [28][29][30]. On the other hand, the Magra Basin is a graben defined by two structures on the western and eastern sides: respectively, the Punta Bianca horst and the Apuan Alps [26]. Its formation dates to the Pliocene and is related to high-angle normal faults, located and still visible in the area of the Punta Bianca headland [26,31,32].…”

“…On the other hand, the Magra Basin is a graben defined by two structures on the western and eastern sides: respectively, the Punta Bianca horst and the Apuan Alps [26]. Its formation dates to the Pliocene and is related to high-angle normal faults, located and still visible in the area of the Punta Bianca headland [26,31,32]. The two extensional basins are characterized by natural subsidence as a result of local tectonics and sediment compaction [24,33].…”