GNGTS 2015 - Atti del 34° Convegno Nazionale

114 GNGTS 2015 S essione 1.2 Pizzi A., Galadini F.; 2009: Pre-existing cross-structures and active fault segmentation in the northern-central Apennines. Tectonophysics, 476 , 304-319. doi: 10.1016/j.tecto.2009.03.018. Rovida A., Camassi R., Gasperini P., Stucchi M. (eds.); 2011: CPTI11, the 2011 version of the Parametric Catalogue of Italian Earthquakes. ������� ������� � Milano, Bologna - http://emidius.mi.ingv.it/CPTI , DOI:10.6092 /INGV.IT -CPTI11. Royden L. H., Patacca E., Scandone P.; 1987: Segmentation and configuration of subducted lithosphere in Italy: An important control on thrust-belt and foredeep- basin evolution - Geology, 15, 714 – 717. Vezzani L., Ghisetti F,; 1998: Carta geologica dell’Abruzzo, 1:100000, SELCA, Via R. Giuliani, Firenze. A geophysical transect across the central sector of the Ferrara Arc: passive seismic investigations – part II A. Mantovani, N. Abu Zeid, S. Bignardi, G. Santarato Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Italy Introduction. The architecture of the Po Plain foredeep filling, from Pleistocene onward, is characterized by a generally “regressive” trend, interrupted by lesser fluctuations, evidenced by the transition from offshore Pliocene deposits to marine-marginal and then to alluvial Quaternary sediments (Ricci Lucchi, 1986; Amorosi and Colalongo, 2005; Amorosi, 2008). The great number of subsurface data collected during hydrocarbon explorations and water research (AGIP Mineraria, 1959; Aquater, 1976, 1978; Aquater-ENEL, 1981; Pieri and Groppi, 1975, 1981; RER&ENI-AGIP, 1998; Boccaletti et al. , 2004, 2011; Ferrara province - RER 2007) allowed to map the main quaternary unconformities: the most recent surface, at regional scale, is the base of the Upper Emiliano-Romagnolo Synthem (AES; Boccaletti et al. , 2004) which is made up of a series of different depositional cycles whose limits are placed in correspondence of the bottom of the “transgressive” marine deposits. The ‘transgressive’ portion of each cycle is characterized by the presence of fine materials ( e.g. floodplain, marsh and coastal plain clays) with subordinated sandy intercalations. Instead, the ‘regressive’ sequence consists of alluvial plain deposits ( e.g. fine sediments of overflowing river) where channel sands are subordinated in the form of isolated lenticular bodies. On the top of each cycle, the channel sands become abundant, thus forming laterally wider bodies (RER & ENI-AGIP, 1998; ISPRA, 2009). The studies conducted by the Regione Emilia-Romagna & ENI-AGIP (1998), Boccaletti et al. ������ ������ ��� ���� (2004, 2011), Abu Zeid et al . (2014) and Ferrara province - RER (2007) revealed that the Quaternary succession is highly deformed and confirmed that the transitions between marine- continental sediments are the result of important tectonic phases followed by periods of strong subsidence. Therefore, the strong variable thickness of the Quaternary sequence from several hundreds to few tens of meters in correspondence of the growing anticlines; i.e. Mirandola, Casaglia, Argenta reflects the influence of the complex evolution of the blind thrusts belonging to the Ferrara Arc. Previous geophysical studies conducted by numerous authors ( e.g. ������ Priolo et al. , 2012; Paolucci et al. , 2015) focused the attention on mapping the fundamental resonance frequencies and the corresponding shear-wave velocity profiles in the area affected by the Emilia 2012 seismic sequence by independently interpret the HVSR curves (in the first case) or using a simplified power law to describe Vs variation with depth in the latter case. This way, they were able to establish a link between the two main resonance peaks to known subsurface geological contacts. However, no information on possible lateral variations could be deduced from such interpretation. With this premise, we carried out a geophysical survey along a profile, ca. 27-km long and oriented SSW-NNE, almost perpendicular to the regional trend of the buried structures belonging