GNGTS 2014 - Atti del 33° Convegno Nazionale

(DBMI11 database, http://emidius.mi.ingv.it/DBMI11/ ). This could suggest that, for this city, the consequences of an earthquake are also dependent from site effects. The Geological-Technical Map and reconstruction of the subsurface model. The original geological survey provided a lithological and litho-technical characterization of the terrains exposed in the Sulmona area. Regarding the classification of the geological units, they have been divided into marine and continental units. The first commonly represent the geological bedrock units, the second include the Quaternary deposits with a minimum thickness of 3 m. In particular, we have distinguished Meso-Cenozoic calcareous bedrock units, extensively outcropping along the basin sides. These rocks showmiddle to very thick strata and are generally strongly fractured giving rise to cataclastic zones along the Mt. Morrone fault zone. The main Quaternary continental units can be grouped in lacustrine deposits, alluvial deposits (terraced and/or alluvial fan), slope deposits, eluvial-colluvial and landslide deposits. In particular, the stratigraphic succession of the Sulmona basin is made up of fine silty-clay and sandy-silt lacustrine sediments with local intercalations of gravel and conglomerate ( Lower to Middle Pleistocene ). Following the strong regional uplift and the consequent regressive erosion, which characterized the chain from the end of the early Pleistocene, the depositional conditions drastically changed leaving space to a gravelly sand, with silty clay intercalations, fluvial sedimentation. Important detrital supplies and alluvial fans have continuously influenced the sedimentation at the base of the slopes and also in the inner portion of the basin, with more or less intensive phases associated to climatic changes and to the tectonic activity during the Quaternary (e.g., Miccadei et al. , 1997 with references therein). For the reconstruction of the geological and lithotechnical setting, field data have been compared and integrated with the available data from boreholes, well, Down-Holes (DH), Cross Holes (CH), SPT, SDMT and geophysical surveys and 42 new noise acquisitions specifically carried out for the MS project. A first analysis of the geological and lithothecnical setting was already carried out within the Region-sponsored Projects “ S.I.S.M.A. ” and “ Microzonazione sismica di secondo livello; indagini e risultati ai fini della progettazione esecutiva della Microzonazione sismica del centro abitato di Sulmona ”. In these projects, developed between the 2006 and 2007, were involved the University “La Sapienza” of Rome (scient. resp. G. Scarascia Mugnozza), the Ingegneria Strutture, Acque e Terreno Department of L’Aquila University (scient. resp. G. Totani), the Regione Abruzzo (with E. D. Iannarelli) and G. Naso for the Italian Department of Civil Protection. Through the boreholes it was possible to constrain, with an appropriate level of confidence, the base of the sandy-gravel deposits attributed to the “Terrazza Alta di Sulmona” (Fig. 1). It is worth noting that the different data coming from DH and CH seismic tests (in addition to the MASWs), generally show Vs values characterized by a clear velocity inversion at 20-30 m depth, and then in correspondence of the transition between the gravelly “Terrazza Alta di Sulmona” unit and the silty-clay lacustrine one. The synthesis of the underground 2D model has been reconstructed through 11 geological- technical cross section, 9 of which performer in a NE-SW direction and two in a NNW-SSE direction. The NE-SW sections are about perpendicular to the main developing axis of the Sulmona basin, to the main river courses and corresponding terrace escarpments, and to the trace of the active and capable normal faults. The NNW-SSE sections show the relationships between the bedrock and the continental deposits and their probable geometry at depth, moving from the southern bound of the basin toward the depocentral area. Clearly, the correlation performed through the stratigraphic data of all the available boreholes has allowed to represent the lithological variations within every single recognized unit from the field survey and to extrapolate them, with good details, until 20-30 m at depth (mean boreholes depth). The exception is represented by some very deep wells, one of which reaching 435 m (Medibev well) (Fig. 1). In general, we can recognize the presence of two macroareas, both in the surfaces and at 262 GNGTS 2014 S essione 2.2