GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.2 169 Tab. 1 - Historical and instrumental major seismic events in the Friuli and western Slovenia (Rovida et al. , 2016). Y/M/D I o M w Epicentre area 1348/01/25 9 6.63 Julian Alps 1511/03/26 9 6.32 Friuli-Slovenia 1794/06/07 8-9 5.96 Carnic Alps 1873/06/29 9-10 6.32 Alpago-Cansiglio 1928/03/27 9 6.02 Verzegnis 1936/10/18 9 6.06 Alpago 1976/05/06 9-10 6.45 Friuli 1976/09/15 8-9 5.95 Friuli partially re-used the inherited NW–SE trending thrusts of the Paleogene External Dinarides), and by the active right lateral strike slip systems of the western Slovenia and eastern Friuli. At present GPS data show 2-3 mm/yr. northward movement of Adria relative to Eurasia. This is absorbed by WSW-ENE trending, SSE-verging thrust front of the eastern Southern Alps and by NW-SE trending, right-lateral strike-slip fault systems in western Slovenia (Vrabec e Fodor, 2006). The external sector of the ESA in Veneto and Friuli is still in evolution, as confirm both historical and instrumental seismicity (Rovida et al. , 2016) and the widespread deformations of the Upper Pleistocene-Holocene deposits cropping out in the piedmont plain (Galadini et al. , 2005; Poli et al. , 2009, 2015; Monegato and Poli, 2015). The Friuli and the western Slovenia are two of the most seismically active areas in the western Mediterranean region (Tab. 1). The seismicity in the eastern Southern Alps shows that both the south-verging Southalpine thrusts and the NW–SE trending Dinaric strike-slip faults are active within the same stress field, but fault plane solutions for western Slovenia typically show dextral strike slip kinematics on steep NE-dipping fault planes (Poljak et al. , 2000) while the eastern southern Alps generally show NNW-dipping reverse faults planes, with local strike slip component (Bressan and Bragato, 2009). Fig. 2 - N-S regional geological cross-section across the ESA thrust belt and its foreland in Friuli. The section highlights the relationships between the active S-verging thrusts of the ESA and the Idrija-Ampezzo dextral strike slip system. W-verging Dinaric thrust: capped lines. Modified from Zanferrari et al. (2013). For location see Fig. 1. Legend: MB) Magnetic basement (Cati et al. , 1987); PT) undifferentiated Permo-Triassic succession; TVZ) Upper Carnian mostly terrigenous-evaporitic succession; CP) undifferentiated Upper Triassic - Upper Cretaceous/Paleocene carbonate platforms; JKB) Jurassic-Cretaceous basin successions; FLY) Upper Cretaceous-Lower Eocene turbiditic succession; CAV) Lower-Middle Miocene Cavanella Group; UM) Middle-Upper Miocene Molassa succession; PQ) Pliocene- Quaternary succession. Legend: BU: Buia th.; GK: Gemona-Kobarid th.; IA: Idrija-Ampezzo fault; MA: Magnano th.; MD: Medea th.; MV: Musi – Verzegnis th.; PA: Palmanova thrust; PV: Pioverno fault; PZ: Pozzuolo th.; RA: Resiutta –Ponte Avons fault; ST: Susans-Tricesimo th.; UD: Udine-Buttrio th.