GNGTS 2013 - Atti del 32° Convegno Nazionale

Geological, seismological and geodetic evidence of active thrusting and folding south of Mt. Etna (eastern Sicily) G. De Guidi 1 , G. Barberi 2 , G. Barreca 1 , V. Bruno 2 , F. Cultrera 1 , S. Grassi 1 , S. Imposa 1 , M. Mattia 2 , C. Monaco 1 , L. Scarfì 2 , S. Scudero 1 1 Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Sezione di Scienze della Terra, Università di Catania, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Sezione di Catania, Italy Introduction. Mt. Etna volcano is located in eastern Sicily over the front of the collisional fold and thrust belt, where it is cut by the major Aeolian-Tindari-Malta Escarpment lithospheric boundary (Fig.1, Palano et al. , 2012). Accordingly, in the Mt. Etna area two distinct tectonic domains, characterized by compressive and tensional regimes, coexist (Cocina et al. , 1997; Monaco et al. , 2002). They are separated by a NNW-SSE trending boundary composed of en–echelon normal-dextral faults, roughly extending from the summit craters to the northern suburbs of Catania (Fig. 1a). The eastern sector is characterized by normal-oblique faults, related to WNW-ESE regional extension (Monaco et al. , 1997), and flank sliding phenomena (Azzaro et al. , 2013). Conversely, in the western sector, south of the volcanic edifice, contractional structures mostly occur. They are represented by a W-E trending fold belt that have deformed Pleistocene foredeep deposits in response of NNW-SSE oriented regional compression (Labaume et al. , 1990; Catalano et al. , 2011; Ristuccia et al. , 2013). According to Lavecchia et al. (2007) this area is part a unique regional-scale, deep crustal seismogenic structure (named Sicilian Basal Thrust) whose focal mechanisms are compatible with a nearly average N–S shortening and with some field evidence of active fold-and thrust deformation at the Sicilian chain front. Seismological (Neri et al. , 2005), geodetic data (Mattia et al. , 2012) and stress in situ measurements (Ragg et al. , 1999) confirm the occurrence of a still active compressional regime south of Mt. Etna, accommodated by thrusting and folding. In particular, new interferometric data recorded in the last 20 years, depict a large anticline (named the “Catania anticline”) aseismically uplifting at a rate of ~10 mm/yr in the northern outskirts of Catania (Lundgren et al. , 2004; Bonforte et al. , 2011). In order to verify if this aseismic frontal folding can be related to regional processes, characterized by convergence rates of about 5 mm/yr (Mattia et al. , 2012), in this work we have analyzed deep crustal seismicity, geological field information and morphometric data obtained by 2x2m grid resolution DEM. Moreover, to the aim of verifying if strain accumulation is presently occurring on the growing anticline, we surveyed some benchmarks of a GPS network of the Italian Military Geographical Institute (IGMI) realized in 1994 for cartographic and geodetic purposes. Geological setting. The geodynamic setting of Eastern Sicily (Fig. 1a) is characterized by the Neogene-Quaternary flexure of the African- Pelagian continental paleo-margin beneath the SSE-verging chain, culminating in the south-eastern sectors of the island to form the Hyblean Plateau, the foreland domain (Ben Avraham et al. , 1990). Northwards, the Hyblean slab deepens under the chain, intersecting the Moho at a depth of about 30 km (Lavecchia et al. , 2007 and reference therein) between the northern coast of Sicily and Mt. Etna (Fig. 1b). In such a geodynamic context, the area between the southern edge of the Mt. Etna volcanic edifice and the Catania Plain represents the remnant of a foredeep domain, filled by Pliocene- Pleistocene sediments and volcanics, and by Holocene alluvial-coastal deposits (Longhitano and Colella, 2001). This sedimentary succession is mostly deformed by an asymmetric south- facing anticline, about 10 km long and ~W-E trending (the “Terreforti anticline”, Monaco et al. ,1997; Labaume et al. , 1990) and other minor folds (Catalano et al. , 2011). They have been interpreted as thrust propagation folds at the front of the chain, related to the lately migration of the thrust belt, as a response to the regional NNW-SSE compressive tectonic regime (Palano et al. , 2012). GPS velocity fields (Ferranti et al. , 2008; Mattia et al. , 2012), seismological (Lavecchia et al. , 2007) and interferometric synthetic aperture radar data (Lundgren et al. , 48 GNGTS 2013 S essione 1.1