GNGTS 2019 - Atti del 38° Convegno Nazionale

482 GNGTS 2019 S essione 2.2 soil liquefaction, are as follows: The unit all1 shows interlayering of silts and sand levels within the first 20 m b.g.l. and a water table depth less than 15 m b.g.l. Moreover, soft sediment deformation structures, due to paleoliquefaction, were observed in the unit at1 (Fig. 3B) (Storti et al. , 2013). Close to the Pettino Fault, earthquake-induced sinkholes are located in the plain (Fig. 3C). Finally, historical description of liquefaction event was described by Uria de Llanos (1703) during the 2 nd February 1703 earthquake. Conclusions. From the geological-geophysical investigation of the Preturo-Sassa area, we can outline several conclusions related to the geological setting of the investigated area with the definition of the sub-surface geological model to be used for the numerical evaluation of the seismic site amplification. Our results focus the attention on geologic constraints aimed at the reconstruction of the subsurface structural complexities, the 3D geometry of sedimentary bodies, their mutual relationships, and the relations with the bedrock interface. Level 1 is an indispensable step in seismic microzonation studies for a first reconstruction of the shallow subsurface geology and the recognition of critical areas needing additional detailed analyses like susceptibility to permanent coseismic deformation. In general, we found an agreement between the results from microtremor data and the structural-stratigraphic setting obtained by independent geological and geophysical constraints. This suggests that the widespread use of ambient seismic noise measurement is a useful tool for seismic microzonation if the geological setting is well-known through geological survey data and borehole stratigraphy. In summary, the great challenge for supplying the most reliable information to seismic hazard practitioners is the good quality of the input data and the use of suitable methodological approaches able to constrain the uncertainties of the subsoil model. References Albarello D., Castellaro S., 2011: Tecniche sismiche passive: indagini a stazione singola . Ingegneria sismica, 38(2) , 32-49. Bard P. Y., Gariel J. C., 1986: The seismic response of two-dimensional sedimentary deposits with large vertical velocity gradients. Bulletin of the Seismological Society of America, 76(2) , 343-366. Fig. 3 - A) heterometric, matrix-supported slope deposits of unit fal in the hangingwall of the Scoppito-Preturo Fault (modified from Nocentini et al. , 2017); B) notable soft sediment deformation structures, due to paleoliquefaction observed in the unit at1 at Pagliare di Sassa; C) the sinkhole Laghetto Giorgio nearby Preturo.