GNGTS 2019 - Atti del 38° Convegno Nazionale

154 GNGTS 2019 S essione 1.2 2001), obtaining values of 5.24 ± 0.1, 0.89 ± 0.2 and 2.6 ± 0.35, respectively. Furthermore, we inspected the magnitude of completeness variation over time obtaining values in the range 3.0 - 2.6, with lower values in 2007 and 2014 (Amato and Mele, 2008). The earthquake distribution highlights that seismicity across the Sicily Channel is scant, and is mainly concentrated along a broad N-S elongated tectonic lineament, extending from Lampedusa Island to the Graham Bank, which marks the segmentation of the extensional Sicily Channel system into two separate branches (e.g. Calò et al. , 2013; Chiarabba and Palano, 2017 and references therein; Spampinato et al. , 2017). For the area defined by the blue polygon in Fig. 1, we calculated the seismic moment-rate according to the Hyndman and Weichert (1983) formulation, which was obtained by integrating the cumulative truncated Gutenberg-Richter distribution up to the maximum magnitude value that could occur within our study zone. As the largest earthquake striking the investigated area had an estimated magnitude equal to 5.1, following Kijko and Graham (1998) and Kijko and Singh (2011), we assumed a value of 5.6 as possible maximum magnitude. Estimated seismic moment-rate for the investigated region is 3.32·10 16 Nm/yr. Geodetic data. To provide an improved picture of the current crustal deformation pattern over the investigated area, we analyzed all data coming from the continuous GPS stations installed across the Sicily Channel as well as the southern Sicilian onshore, spanning the 2001.0 - 2018.0 time interval. To improve the overall configuration of the network, and tie the regional measurements to an external global reference frame, data coming from more than 20 continuously operating global tracking stations, largely from the IGS and EUREF permanent networks, have been introduced in the processing. Raw GPS observations have been processed by using the GAMIT/GLOBK software packages (Herring et al. , 2018). After estimating Fig. 1 - Simplified structural map of the Sicily Channel area. Historical (squares) and instrumental (colored circles) seismicity occurring in the investigated area since 1578 and 1983, respectively, is also reported. The blue polygon, whose vertices coincide with continuous GPS stations, defines the area for which the seismic/geodetic moment-rates ratio is evaluated.