Recent tectonic activity of the Budoia-Aviano Thrust: the example of the Late Pleistocene-Holocene Artugna alluvial fan (eastern Southern Alps, NE Italy)

In the framework of the PRIN2020 “Fault segmentation and seismotectonics of active thrust systems: the Northern Apennines and Southern Alps laboratories for new Seismic Hazard Assessments in northern Italy (NASA4SHA)”, we made a multidisciplinary and multiscale seismotectonic study on the Budoia-Aviano Thrust which is an external splay of the larger Polcenigo-Montereale fault system located in the western Carnic Prealps (Friuli, NE Italy). The investigated area is part of the external Pliocene-Quaternary front of the eastern Southern Alps (ESA) where geodetic (GNSS) time series [Devoti et al., 2011; Serpelloni et al., 2016; Areggi et al., 2023] show a crustal shortening rate of about 2-3 mm/yrs. In the Carnic Prealps, the external front of ESA consists in a series of arch-shape WSW-ENE trending, SSE verging presently mostly believed as blind thin-skinned thrusts, affecting the Late Pleistocene-Holocene piedmont Friuli Plain [Galadini et al., 2005; Poli et al., 2021; 2024]. In particular, the PolcenigoMontereale Thrust System (Figure 1), where the Mesozoic Friuli Carbonate Platform overthrust the Neogene Southalpine Molasse, extends from the Caneva to Montereale Valcellina towns and consists of a series of S-verging splays that show evidence of recent tectonic activity: the Aviano-Budoia and the Vigonovo thrusts, respectively [Poli et al., 2015]. According to the currently available catalogue of historical seismicity (the DBMI Catalogue [Locati et al., 2022]) the area was hit by some historical destructive earthquakes, like the 1776 Tramonti (Mw = 5.78, Io = 8-9); the 1794 Alpi Carniche (Mw = 6.04, Imax = 9); the 1812 Sequals (Mw = 5.7; Imax = 7-8); the 1873 Alpago (Mw = 6.3; Imax = 9-10) and the 1936 Cansiglio (Mw = 6.1; Imax = 9) earthquakes. Concerning the instrumental seismicity (from 1977 to Present), we distinguish the area of Claut that was hit by frequent medium-to-low seismic events (max magnitude 4.3, 1996-04-13 earthquake; [Bernardis et al., 1996]). In this contest, Galadini et al. [2005] indicate the Polcenigo-Montereale Thrust System as the seismogenic source of the aforementioned 1873 Alpago earthquake.