GNGTS 2013 - Atti del 32° Convegno Nazionale

Southern Alps and the Periadriatic lineament. It is included in a convergent margin zone between the Adria microplate and the Eurasian plate (see e.g. Castellarin et al. , 2006; Burrato et al. , 2008) and it is one of the most seismic active zones of Italy. The area is sited at the tip of Adria plate. The progressive north-eastward pushing of African plate, respect to the Eurasian plate, generates an anticlockwise rotation of Adria microplate, which causes the present complex tectonic deformation (Mantovani et al. , 1996). Several tectonic phases in the region inherited and reactivated the main pre-existing faults and fragmented the crust into different tectonic domains corresponding to different seismotectonic zones (Bressan et al. , 2003). The eastern part of the region, in western Slovenia, is characterized by a strike-slip regime on Dinaric faults. The Friuli Italian region is characterized by thrust tectonic, mainly EW oriented and south verging in the centre and NE-SW-oriented and SE- verging thrust in the western part (Bressan et al. , 2003). Fig. 1 shows both the historical and instrumental seismicity in the area. Brown squares correspond to earthquakes in CPTI04 catalogue (Gruppo di lavoro CPTI, 2004) from 1100 with intensity ≥IX. The other symbols correspond to instrumentally recorded seismicity. In particular, stars correspond to the events with magnitude ≥5 In the area. See figure caption for more details. Red symbols are the earthquakes used in this work. They are the 156 earthquakes with duration magnitude ≥ 3 recorded in the area from 1994 to 2011. In particular, a cluster of seismicity can be easily detected in the northeastern part in correspondence with the two Kobarid 1998 and 2004 seismic sequences. Smaller clusters of lower magnitude seismicity were recorded also after Sernio 2002 mainshock and during and in Claut region (for seismic sequences in the area see Gentili and Bressan, 2008). The instrumentally recorded seismicity roughly follows the historical earthquakes distribution. Fig. 1 – Seismicity in the area. Brown squares: historical seismicity (earthquakes with intensity ≥IX are shown with squares dimensions proportional to earthquake intensity). Red symbols: seismicity with magnitude >3 from 1994 to 2011. Stars: earthquakes with magnitude > 5. Yellow stars: 1976 swarm. Green star: 1977 Trasaghis earthquake. Blue star: 1979 Lusevera earthquake. Red stars: Kobarid and Sernio earthquakes. Dashed lines: Sections shown in Fig. 3. 71 GNGTS 2013 S essione 1.1