GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 The Durresi Backthrust (ALCS325; Caputo and Pavlides, 2013) has a fault trace running along the Albanian shoreline for about 30 km, while it continues northwards offshore for nearly 40 km crossing the Durresi peninsula. Accordingly, the total length of this structure is about 70 km (Aliaj et al. 2000; 2004; Baker et al., 1997; Guzman et al., 2011; Louvari et al., 2001; Mu ҫ o et al., 1994). The strike ranges between 140° and 165° (Aliaj et al., 2000; 2004; Guzman et al., 2011). Seismic reflection profiles and geological sections (Aliaj, 2006; Roure et al., 2004; Skrami, 2001; Velaj, 2001) suggest an overall listric geometry with the dip angle varying between 20° and 65° in the deeper and shallower sectors, respectively. The fault represents an antithetic branch of the Durresi Offshore Thrust and consequently its maximum depth is defined by the branch line whose depth varies between 7-8 km and 10-12 km from north to south. Accordingly, the width ranges between 13 and 17 km (north and south, respectively). The Vore Backthrust (ALCS335; Caputo and Pavlides, 2013) is mainly mapped onshore, eastward of the other two sources. The fault trace strikes between 150° and 170° (Aliaj et al., 2000; 2004; Guzman et al., 2011) showing a total length around 45 km (Aliaj et al. 2000; 2004; Baker et al., 1997; Guzman et al., 2011; Louvari et al., 2001; Mu ҫ o et al., 1994). Also this tectonic structure is characterized by a curved shape in section view and this implies a dip angle varying from 65° to 30°, moving from the top to the bottom (Aliaj, 2006; Roure et al., 2004; Skrami, 2001; Velaj, 2001). From our rheological modelling and seismicity review, the maximum depth of this source is fixed at 8-10 km, and consequently the calculated width is 10-12 km. Based on geodetic data processing, some authors (Govorcin et al., 2020; Pezzo et al., 2022) refer to the Vore Backthrust as the causative source of the Mw 6.4 26 November, 2019 Durres mainshock. parameters/CSS ALCS315 ALCS325 ALCS335 strike [deg] 330-345 140-165 150-170 dip [deg] 20-50 20-65 30-65 rake [deg] 80-100 80-100 80-100 total length [km] 70 71 45 total width [km] 40 13-17 10-12 max depth [km] 18 7-8 (N), 10-12 (S) 8-10 max Mw 6.7-7.3 6.7-7.2 6.5-7.0 Table 1. Inferred parameters for the Composite Seismogenic Sources recognized in the studied sector (GreDaSS database; Caputo and Pavlides, 2013) Methods and Results Based on properly calibrated input parameters and devoted MatLab scripts (Maggini and Caputo, 2020a; 2020b; 2021), a 3D rheological model was produced for reconstructing the depth of the BDT (Brittle Ductile Transition) characterizing the broader investigated area. Indeed, the BDT represents a good proxy of the seismic/aseismic transition and fundamentally corresponds to a