GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 2.2 407 et al. , 2011). Taking into account the cross section of Fig. 1 we can hypothesize almost two main tectonic events for SSPF during the Quaternary. The first event is constrained between the post- or syn-deposition of Madonna della Strada Synthem (Calabrian) and the pre-deposition of L’Aquila breccia (CMA Synthem) (middle Pleistocene). For the second event, we can say, at the moment, that it is post-dated by the deposition of L’Aquila breccia (CMA) (upper Middle Pleistocene). Investigations on trench excavations for putting in place a smart tunnel network, which are in progress in L’Aquila town, can help to pre-date the activity of the SSPF. Conclusions. An updated GIS database of borehole logs and microtremor recordings coupled with a fine scale geological mapping (Nocentini, 2016; Nocentini et al. , 2016) permitted to refine the subsoil model of L’Aquila town (Fig. 1). It consists of two geologically different areas (the northern and the southern zone) which are sharply bounded by the Synthetic Splay of the Pettino Fault (SSPF). The subsoil model of the northern zone consists of high-Vs units (20-30 thick of L’Aquila breccia onto Meso-Cenozoic limestones), while, the southern zone is composed by 60-100 m thick of high-Vs L’Aquila breccia onto 200-300 m thick of medium-Vs pelite and sand (MDS Synthem). In the northern zone, the Vs values increase with depth, in the southern zone rough decrease of Vs values is recorded passing from L’Aquila breccia to pelite and sand (MDS). The Quaternary cover lays upon Meso-Cenozoic limestones. This updated geological setting leads the seismic site response of L’Aquila town and should be taken into account for a correct seismic site response evaluation. The probable presence of the Pettino Fault and its splay (SSPF) in the L’Aquila town have to be taken into account to update the seismic hazard estimation. Acknowledgements. We would like to thank Giuseppe Di Giulio and Giuliano Milana for the discussions on microtremor technique and Domenico Cosentino on the geology of L’Aquila Basin. References Del Monaco F., Tallini M., De Rose C., Durante F.; 2013: HVNSR survey in historical downtown L’Aquila (central Italy): site resonance properties vs. subsoil model . Engineering Geology, 158 , 34-47. Di Giulio G., Gaudiosi I., Cara F., Milana G., Tallini M.; 2014: Shear-wave velocity profile and seismic input derived from ambient vibration array measurements: the case study of downtown L’Aquila . Geophys. J. Int., 198 , 848- 866. Galli P.A.C., Giaccio B., Messina P., Peronace E., Zuppi G.M.; 2011: Palaeoseismology of the L’Aquila faults (central Italy, 2009, Mw 6.3 earthquake): implications for active fault linkage . Geophys. J. Int., 187 , 1119-1134. Gruppo di Lavoro MS–AQ; 2010: Microzonazione sismica per la ricostruzione dell’area aquilana. Regione Abruzzo – Dipartimento della Protezione Civile , L’Aquila, 3 vol., Cd-rom. Nocentini M.; 2016: Integrated analysis for intermontane basins studies: tectono-stratigraphic and paleoclimatic evolution of the L’Aquila Basin . PhD thesis in Environmental and Resources Geology, University of Roma Tre (XXVII cycle). Nocentini M., Tallini M., Cosentino D., Gliozzi E., Asti R., Durante F., Macerola L.; 2016: Plio-Quaternary geological map of the L’Aquila-Scoppito Basin (central Italy) . Rend. Online Soc. Geol. It., 40(1) , 329. Tallini M., Cavuoto G., Del Monaco F., Di Fiore V., Mancini M., Caielli G., Cavinato G.P., De Franco R., Pelosi N., Rampolla A.; 2012: Seismic surveys integrated with geological data for in-depth investigation of Mt. Pettino active fault area (Western L’Aquila Basin) . Ital. J. Geosci. (Boll. Soc. Geol. It.), 131 , 389-402, doi: 10.3301/ IJG.2012.10. Tallini M., Durante F., Macerola L., Nocentini M.; 2016a: Does a seismic double-resonance affect L’Aquila historical downtown buildings? Rend. Online Soc. Geol. It., 40(1) , 685. Tallini M., Durante F., Macerola L., Nocentini M.; 2016b: Up-to-date L’Aquila town subsoil model for seismic site and hazard evaluation: boreholes and single station microtremor data to investigate the Pettino Fault . Rend. Online Soc. Geol. It., 40(1) , 686.