GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 - POSTER GNGTS 2023 Major seismic events Albania is affected by diffuse seismicity, both historical (Aliaj et al. 2010, Guidoboni et al. 2019) and instrumental (Ormeni et al. 2022). In the study area 12 events of M > 6 are known since Roman times, of which 7 in the last two centuries. The 1270 earthquake is the first sufficiently documented event. It caused damages and many victims in Dyrrachium (IX-X MCS, Me 6.2, Guidoboni et al. 2019) (Fig. 1). Supposedly, the source fault was very close to the city, since violent vertical movements were reported. A poorly known event, Me 6.2, hit Kruja in 1617. After, several earthquakes with M>6 took place between Durres and Tirana in the XIX century, the strongest in 1870 (M 6.7). Two strong seismic events followed with epicenter near Durres: 1926 (IX MSK, Mw 6.1) and 2019 (VIII-IX EMS, Mw 6.4) (IGEWE, 2019; Ganas et al. 2020; Vittori et al. 2021). Due to the rather deep hypocentre ( ≥ 20 km), no coseismic surface faulting occurred and tectonic uplift/subsidence and westward movement were the only primary effects (Vittori et al. 2021). The field surveys (Lekkas et al. 2019, Vittori et al. 2021) pointed out widespread secondary effects: mostly, ground fissures, liquefaction and lateral spreading. The focal mechanisms confirm the prevalent compressive tectonics (Ormeni et al. 2022 with references). Morphotectonics The landscape from the Kruja thrust front to the coastline is characterized by folding with narrow anticlines and large synclines, resulting in alternating NW-SE-elongated lowlands and ridges, the latter often bordered by active thrust faults on their western side and/or backthrusts on their eastern flank. The parallel organization of tectonic plains and ridges highly affects the hydrographic network (Fig. 2a). The Tirana-Thumana synform, filled by Late Miocene-Pliocene molasses covered by Quaternary fluvial deposits, is a wide NW-SE depression controlled by the combined activity of the external structures of the Kruja thrust front to the east and the facing Vora backthrust.