GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 line in Figure 1a) was observed. Jacques et al. (2001) interpreted this as the coseismic reactvaton of the west dipping CF during the 5 February mainshock. Concerning the seismic source models of 5 February, 7 February, and 1 March events, some authors proposed the CF and SRF west-dipping normal faults as responsible sources (Jacques et al., 2001) (Figure 1a, DSS; Debated Seismic Source). This hypothesis was supported by feld geologic and morphotectonic data and observaton by the distributon of the high-damage sites as exploited by the mesoseismal areas of the 1783 sequence (Barata, 1901) and revisited macroseismic data (Andrenacci et al., 2023), the observed coseismic fracturing (de Dolomieu, 1784), and also by paleoseismological studies. Conversely, other authors inferred ruptures along the Gioia Tauro and the Mesima east-dipping blind low angle (~30°) normal faults for the same events (Loreto et al., 2013 and reference therein) (see also Figure 1a, ISS: Individual Seismic Source). Structural data The CF and SRF border the western sectors of the Aspromonte and Serre mountains, respectvely. These NNE-SSW-oriented, west-dipping, and 40-km-long faults (Figures 1A, C) develop cumulatve scarps of up to 450 m in height. In order to investgate the surface expression and the kinematc of the faults, a geological–structural survey was carried out. Unfortunately, due to the poorly conservatve rock types cropping out in the investgated area, the kinematc indicators are difcult to observe (partcularly in the SRF area). Structural data were collected in a few selected outcrops along the CF near Oppido Marmertna Village. Here we reported only the structural staton 2 (Fig. 1d, e) (for further informaton please refer to Giufrida et al., 2023). The outcrop is located southwest of Oppido Mamertna, along the Spilinga River where the fault meets the Aspromonte gneisses in the footwall and the Middle–Upper Pleistocene deposits in the hanging-wall. Pleistocene deposits are faulted and tlted toward the west (layer attude 310/35). Minor faults are parallel to the master fault and show steep eastward dips (see also Jacques et al., 2001). The master fault (F1 in stereoplot in Fig. 1e and red line in Fig. 1d) is NE-SW-oriented and shows a set of slickenlines consistent with normal-oblique sinistral kinematcs. Seismological data: 3D fault modelling from earthquakes distributon To investgate the recent kinematcs of the faults afectng the studied area, we analysed the available focal solutons from ISC ( htp://www.isc.ac.uk/iscbullet n/search/fmechanisms/) and ISIDe ( htp://iside.rm.ingv.it/tdmt) databases (see Figure 1c). Moreover, earthquakes that have been instrumentally recorded since the early 1980s were used to infer the geometry of the studied faults at depth. We selected the seismic events occurred in the Calabrian Arc from the INGV databases (htps://is ttuto.ingv.it/it/risorse-e-servizi/archivi-e-banche-da t.html) in order to enhance the picture derived from the seismic dataset (refer to Giufrida et al., 2023 for further informaton). The fnal locatons (approximately 8,500 seismic events with magnitudes ranging from 1 to 5.7) resulted with an average uncertainty of 0.20 ± 0. 15 km in both horizontal and vertcal coordinates and an average root-mean-square travel-tme residual of 0.02 s.