GNGTS 2018 - 37° Convegno Nazionale

202 GNGTS 2018 S essione 1.2 reflects the articulated tectonic evolution that affected the eastern Friuli-western Slovenia region. - Dinaric phase: during late Cretaceous-Paleogene a NE-SW compressional regime caused the propagation of NW-SE trending thrusts; - Neoalpine phase: starting from Middle Miocene an about N-S compressional regime is responsible of the formation of S-SE verging, WSW-ENE low angle thrusts and the reactivation of favorably oriented old structures; - starting from Pliocene, the activation of a NNW-SSE compressional regime caused the formation of new NW-SE strike-slip high angle structures that locally displace and/or renew the old structures. According to focal mechanisms of seismic events, two different deformational systems can be distinguished: a western sector where reverse activity on low angle WSW-ENE oriented thrusts prevails, and an eastern sector characterized by strike slip tectonics on high angle NW-SE oriented faults. Both deformational systems are subjected to NNW-SSE compressional regime (Serpelloni et al, 2016) with velocities vectors of 2-3mm/yr (D’Agostino et al. , 2008; Devoti et al. , 2011; Caporali et al. , 2013), responsible of their reverse or transcurrent/transpressive kinematics. Recent and historical earthquakes show that the study area is seismically active, in fact at least three events with M>6 struck the area: Mw 6.63, 1348; Mw 6.32, 1511; Mw 6.45, 1976 (Rovida et al. , 2016). Nevertheless, the seismogenic role of the main tectonic structures is still not completely clear; in this context Quaternary activity has been assumed for the Susans Tricesimo thrust (Zanferrari et al. , 2008; Poli and Zanferrari, 2018), while recent paleoseismological investigations revealed Quaternary dislocations on the Colle Villano thrust (Falcucci et al. , 2018). In this study, we present three crustal geological cross sections of the eastern Friuli plain, that allowed the reconstruction of the tectonic buried setting of the eastern Friuli sector. The geometry of the main stratigraphical horizons (Carnic Unconformity, top Cretaceous-Paleogenic carbonatic platform, bottom and top Cavanella Group, bottom Pliocene marine deposits and Quaternary base) and the main tectonic structures were reconstructed through ENI industrial seismic lines interpretation, together with well logs data. Moreover, the implementation of well logs data allowed us to reconstruct the 3D bottom surface of alluvial Quaternary deposits, detecting the tectonic influence. By merging these new data with morphotectonic observations, the main buried active faults of the area were detected, and possible estimates of their activity rates were performed. Three main fault systems were recognized: • The Palmanova System, composed of many NW-SE and WSW-ENE thrust faults. It represents the most frontal structure of the External Dinarides, reactivated in recent times. In detail, the Pozzuolo-Medea Thrust, the Terenzano Thrust and the Trivignano thrust show evidences of Quaternary activity. • The Trnovo System is composed of the active Udine-Buttrio thrust and the inherited structures of Trnovo and Premariacco thrusts that don’t show evidences of recent activity. • The Borgo Faris-Cividale Fault System composed of dextral strike-slip faults and reverse SW verging associated splay like Colle Villano and Cividale thrusts. Both transcurrent and reverse faults show clear evidences of Quaternary activity. References Caporali A., Neubauer F., Ostini L., Stangl G., Zuliani D.; 2013: Modeling surface GPS velocities in the Southern and Eastern Alps by finite dislocations at crustal dephts . Tectonophysics, 590 , 136-150. DOI http://dx.doi . org/10.1016/j.tecto.2013.01.016 Devoti R., Esposito A., Pietrantonio G., Pisani A.R., Riguzzi F.; 2011: Evidence of large scale deformation patterns from GPS data in the Italian subduction boundary . Earth Planet. Sci. Lett., 311 , 230-241. DOI 10.1016/j. epsl.2011.09.034 D’Agostino N., Avallone A., Cheloni D., D’Anastasio E., Mantenuto S., Selvaggi G.; 2008: Active tectonics of the Adriatic region from GPS and earthquake slip vectors . J. Geophys. Res., 113 . DOI 10.1029/2008JB005860