GNGTS 2022 - Atti del 40° Convegno Nazionale

80 GNGTS 2022 Sessione 1.1 PRESENT AND MEDIEVAL DESTRUCTIVE EARTHQUAKES IN DURRES (ALBANIA): NEW INSIGHTS FROM INTEGRATED ARCHAEOLOGICAL AND GEOPHYSICAL STUDIES D. Talone 1,2 , S. Antonelli 1 , F. Brozzetti 1,2 , C. Casolino 1 , C. Cirillo 1,2 , E. Metalla 3 , G. Lavecchia 1,2 , R. de Nardis 1,2 1 DiSPuTer, University of Chieti-Pescara “G. d’Annunzio”, Chieti, Italy 2 CRUST - Interuniversity Center for 3D Seismotectonics with Territorial Applications, Italy 3 IAT – Albanian Institute of Archeology, Tiranë, Albania Destructive earthquakes have recently struck the eastern coast of the Adriatic Sea, dramatically focusing attention on the high seismogenic potential of the Dinarides-Albanides thrust and fold belt. This orogenic system is characterized by seismogenic compression at crustal depths with earthquakes that rarely exceed M W 7.0 and with a deformation rate between 2 to 4 mm/yr (Jouanne et al. , 2012, Métois et al. , 2015). The focal mechanisms show a pattern of P-axes perpendicular to the western thrusts. The historical and instrumental catalogs show that the peri-Adriatic belt experienced large and destructive earthquakes. Durres, one of the most important ports of Illyricum in the Mediterranean area, has been hit several times by earthquakes that caused significant human and economic losses. Notwithstanding the historical catalog is considered complete since 1200 AD for earthquakes of M>7.0 (Vittori et al. , 2021 and reference therein). Recent archaeological investigations of the Roman amphitheater, located in the southern part of Durres town, highlight significant evidence of wall collapses in two well defined historical periods dated to the end of the XI and XIII centuries, respectively. The damages reported by the amphitheater, related to the XIII century, were commonly attributed to the well-documented 1270 earthquake (Guidoboni and Comastri, 2005; Vittori et al., 2021), but what about the clear indications of collapses and reconstructions dated back to the XI century? The amphitheater stratigraphy documents the collapses of 1) the walls of some galleries, 2) the vault of Gallery VII onto the stairs and 3) the building with the artisanal function located at the limits of galleries VI and VII. This structure was reconstructed following the orientation of the previous one and increasing their size (Casolino, 2022). Geological and geophysical investigations were carried out in July 2019, just before the 26 November 2019 Durres earthquake, to study eventually local amplification effects characterizing the amphitheater area and surroundings. A specific campaign of seismic noise measurements was performed inside and outside the amphitheater, and in other sites of Durres town. The HVSR results show amplification peaks at low frequencies (0.5 and 1 Hz) that rarely exceeds amplitude 2. It is worth noting that similar characteristics are observed both inside the amphitheater and far from it. Our results agree with the ones obtained by other investigators that carried out their measurements after the 2019 Durres earthquake (Mancini et al., 2021). Therefore, all the available data confirm that local effects inside and in the surroundings of the amphitheater are negligible; consequently, all the observed collapses would be mainly attributed to a significant earthquake not far from the town. The available catalogs locate the 1270 earthquake in Durres, with an estimated epicentral intensity (Io) of IX-X MCS but, they do not report any information about earthquakes occurred along the Albanian coast at the end of the XI century. To deep investigate on the possible occurrence of such an earthquake, we collected data from historical catalogs and specific papers available in the literature (Sulstarova and Kociaj, 1975; Antonopoulos, 1979; Molin and Guidoboni, 1989; Guidoboni and Comastri, 2005; Ambraseys, 2009; Grünthal et al. , 2012; Stucchi et al. , 2013; Rovida et al. , 2021) and we tried to reconstruct the Durres seismic history by integrating these information. We found that the Italian Archive of Historical Earthquake Data (CFTI5med) and the Parametric Catalogue of Italian Earthquakes CPTI15v.4 (Guidoboni et al. , 2018; Guidoboni et al. , 2019; Rovida et al. , 2020; Rovida et al. , 2022) report an earthquake occurred on 10 September