GNGTS 2018 - 37° Convegno Nazionale

204 GNGTS 2018 S essione 1.2 In the present study, we carry out a morphometric investigation of the tectonically-controlled southeastern margin of the Hyblean Plateau by performing fluvial network and relief analyses and marine terraces age modelling. We employ different geomorphic indices (e.g. hypsometric integral, topographic relief, topographic dissection, SLindex, k sn , Vf), combined with long- profile analysis, topographic swath profiles, field-based geomorphological survey and meso- scale structural analysis. As main results, our analysis provides: i) a numerical characterization and age definition of the active landscape response to active half-elliptical crustal deformation; ii) the updating of the geometry and deformation rates of the recent and active tectonic belt that controls the southeastern margin of the Hyblean Plateau; iii) the seismogenic potential of the recognised 20km-long, NNE-trending bounding structure. In particular, our results evidence a deformation rate increase along the investigated tectonic belt since the last 240-200 ka, passing from about 0.6 mm/a to about 1.10 mm/a. In the frame of the geodynamic picture of the region, our results enable to define the tectonic control along the southern margin of an actively NW-ward moving crustal block within the fragmented Hyblean Plateau domain, as also documented by geodetic data (Bonforte et al. , 2015; Chiarabba and Palano, 2017; Vollrath et al. , 2017) and seismological data (Musumeci et al. , 2005). The recognised fault belt (here named Cassibile-Noto Fault, C.N.F. in Fig. 1), together with the Ispica Fault located more to the southwest, would represent a potential seismogenic source that is accommodating at rear the amounts of shortening absorbed along the opposite inverted northwestern margin (i.e. Pedagaggi-Agnone System; Fig. 1) of the Hyblean crustal block. References Bianca M., Monaco C., Tortorici L., and Cernobori L.; 1999: Quaternary normal faulting in southeastern Sicily (Italy): a seismic source for the 1693 large earthquake. Geophys. J. Int. 139, pp. 370-394. Ben Avraham Z., Boccaletti M., Cello G., Grasso M., Lentini F., Torelli L., and Tortorici L.; 1990: Principali domini strutturali della collisione continentale neogenico-quaternaria nel Mediterraneo centrale. Memorie della Società Geologica Italiana 45, pp. 453-462. Boschi E., Ferrari G., Gasperini P., Guidoboni E., and Valensise G.; 1995: Catalogo dei forti terremoti in Italia dal 461 a.C. al 1990. Istituto Nazionale di Geofisica, S.G.A., Roma. Catalano S., De Guidi G., Romagnoli G., Torrisi S., Tortorici G., and Tortorici L.; 2008: The migration of plate boundaries in SE Sicily: Influence on the large-scale kinematic model of the African promontori in southern Italy. Tectonophysics 449; pp. 41-62. Fig. 1 - Kinematic model and seismotectonic picture of the Hyblean Plateau and the western Ionian region. The main fault belts and focal mechanisms of the main medium to low magnitude earthquakes that affected the region (modified from Musumeci et al. , 2005) are reported (S.L.: Scicli Line; S.L.B.: Scordia-Lentini basin; F.B.: Floridia Basin; S.L.: Scicli Line; I.F.: Ispica Fault; C.N.F.: Cassibile-Noto Fault). The shaded dark grey area indicate the eastern Hyblean Plateau kinematic block.