GNGTS 2013 - Atti del 32° Convegno Nazionale

trend of the tectonic structure and topography, two types of lineaments are distinguished: (1) longitudinal and (2) transverse ones. Longitudinal lineaments are approximately parallel to the regional strike of the tectonic structure and of the topography and, as a rule, include the prominent faults. Transverse lineaments go across the regional trend of the tectonic structure and of the topography. The MZ method differs from the standard morphostructural analysis where the term “lineament” (Hobbs, 1911) is used to define the complex of alignments detectable on topographic maps or on satellite images. According to that definition the lineament is locally defined and the existence of the lineament does not depend on the surrounding areas. In MZ, the primary element is the block – a relatively homogeneous area – while the lineament is a secondary element of the morphostructure. The boundaries of the blocks correspond to the lineaments; this means that the existence and the position of the lineaments are determined not locally, but as a part of a broader hierarchical structure. If a certain alignment does not separate two topographically different areas, that alignment cannot be viewed as a lineament in MZ; therefore, the lineaments are secondary features with respect to the blocks. The preliminary MZ map of the Po plain, shown in Fig. 1, has been compiled using topographical, tectonic and geological maps as well as satellite photos. Geophysical and geological data, available via the portal of the Italian Geological Service on ISPRA website (http://www.isprambiente.gov.it) , as well as the DISS data base of active faults, have been considered. Recent publications on geomorphology, tectonics, seismotectonics and geophysical studies of the Po plain have been taken into consideration as well (Castiglioni, 1999; Livio et al. , 2009; Toscani et al. , 2009; Burrato et al. , 2003; Handy et al. , 2010; Michetti et al. , 2012). The outlined map shows a hierarchical blocks-and-lineaments structure of the region and the locations of the morphostructural nodes that are formed around intersections or junctions of lineaments of different strike. This MZ map has been used for recognizing the nodes capable of earthquakes with M ≥ 5.0, as described in the following. Fig. 1 – The morphostructural zoning map of the Po plain Lines outlining morphostructural lineaments. Bold lines mark first rank lineaments; thick lines show the second rank lineaments; thin lines depict lineaments of third rank. Continuous lines correspond to longitudinal lineaments, while dashed lines indicate transverse lineaments. The Po plain is characterized by a flat topography. Our recent studies of topographically flat basins in the Iberian Peninsula (Gorshkov et al. , 2010) and the wider part of the Rhone Valley, between the Western Alps and Massif Central (Gorshkov and Gaudemer, 2012), have demonstrated the applicability of MZ for studying flat basins, with a relatively flat topography. 88 GNGTS 2013 S essione 2.1