GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.2 153 Fig. 2 - 3D model of the Sciacca Fault (Fedorik et al., under review). right-lateral to present day left-lateral strike-slip motion. Instrumental seismicity shows that the Sicilian Channel is dominated by strike-slip focal mechanisms with left-lateral component (Calò and Parisi, 2014; Soumaya et al. , 2015). A set of scaled analogue clay models was carried out in order to better constrain the tectonic processes that led to the structural setting displayed by seismic data. Tectonic structures and uplift/ subsidence patterns generated by the models are compatible with the 3-D model obtained from seismic reflection profiles. A good fit between the Sciacca Fault and the analogue models was obtained imposing a right-lateral movement, coherently with the tectonic regime present in the area up to Lower Pliocene. Analyzing the seismic reflection profiles, it is possible to highlight those faults or fault segments showing active tectonic evidence. Some of the faults belonging to the Sciacca Fault deform Quaternary deposits and cut the seafloor. A structural map where recent and ongoing fault activity was detected was reconstructed. However, these kinds of reconstruction are necessarily dependent on the data (seismic reflection profiles) availability, quality and distribution/spacing. To carry out a complete map where active faults (or active fault segments) are not limited to a restricted sector near the seismic reflection profiles, numerical models are needed in order to check and verify where strain is distributed. The digital 3D model of the Sciacca Fault has been used as input data in a Stress Analysis tool (Poly3D) to check the fault system response. According to availableGPS and literature data, regional strain values were applied to themodeled fault system, and the slip potentional on each fault was calculated (Fig. 3). The numerical model outputs are in good agreement with the observations coming from the seismic reflection profiles analysis and allow to constrain better and highlight which faults are most prone to be activated under the present day regional stress. The Sciacca Fault case study is a good example to test and verify how numerical models output fit with observed data and, at the same time, to constrain the seismic reflection profiles interpretation. In a more general view, the case study once again highlights (i) the importance of 3D reconstructions that lead to well constrained geological reconstructions, (ii) the importance of a multidisciplinary approach using the best and most useful information coming from subsoil data, analogue and numerical models and (iii) how seismotectonic studies, in particular, can significantly be improved merging a different kind of data (seismicity, subsoil data, stress analysis, etc.). Fig. 3 - Numerical model. On the main fault a slip tendency analysis was carried out in order to check where maximum slip is expected.