GNGTS 2013 - Atti del 32° Convegno Nazionale

described by contemporary witnesses, were considered as the superficial expression of the seismogenic fault of the main shock, occurred the 5 February. This ground fracturing well fits with the Cittanova Fault (Fig. 1), a NE-SW trending, 30 km long, west-dipping extensional segment bounding the Aspromonte Mts. from the Gioia Tauro basin (Tortorici et al. , 1995; Jacques et al. , 2001; Galli and Bosi, 2002). Alternatively, this event has been attributed to a blind, east-dipping, low angle fault, located in the Gioia Tauro basin (Basili et al. , 2008 and references therein). Northwards, the Mesima Fault was associated with the 7 February 1783 earthquakes (Jacques et al. , 2001). Southwards, the Scilla Fault, located along the western coast of southern Aspromonte Mts. (Fig. 1), has been associated with the 6 February event (Jacques et al. , 2001). The northern segment of the Santa Eufemia Fault probably ruptured during the 1894 event (Galli and Bosi, 2002); finally the Santa Eufemia Fault and the Armo Fault, more to the south, could have slipped during the 1908 earthquake (Aloisi et al. , 2012). Geomorphological and morphometric analysis. We performed a geomorphological and morphometric study, both quantitative and qualitative, of the Petrace Fiumara and the Catona Fiumara in order to quantify the geomorphological evolution of the studied area and to individuate possible perturbation of the basins that can be due to active tectonics. The term “fiumara” is used to describe a particular typology of river, with limited length and elevated slope, characterized by deep valleys and torrential regime. These water courses typically flow in north-eastern Sicily and Calabria. By using a photo-interpretation analysis (scale 1:10,000) we preliminary localized more accurately the Cittanova Fault, S. Eufemia Fault and Scilla Fault, and mapped the drainage geometry of the Petrace Fiumara and Catona Fiumara and their geomorphological elements. The fluvial network hierarchy has been analysed according to Strahler (1957) ordering. Then, we calculated parameters describing the hierarchical maturity of the drainage and able to highlight anomalies ascribable to active tectonics. Bifurcation index ( R ) highlights possible hierarchical anomalies of the fluvial network providing information on the typology of the Fig. 1 – Seismotectonic map of Southern Calabria and north-eastern Sicily and main historical earthquakes; epicenters (filled circles) from the CPT11 catalogue (Rovida et al. , 2011). Faults associated with the most disastrous earthquakes are also shown: MF = Mesima Fault; CF = Cittanova Fault (Jacques et al. , 2001; Galli and Bosi, 2002); GF = Gioia Fault (Basili et al. , 2008); SF = Scilla Fault (Jacques et al. , 2001; Ferranti et al. , 2007); SEF = Santa Eufemia Fault; AF = Armo Fault (Aloisi et al. , 2012); MSF = east dipping Messina Strait Fault (Pino et al. , 2000; Basili et al. , 2008). Red rectangle is the inset of Fig. 2. 104 GNGTS 2013 S essione 1.1