GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.1 127 This observation has relevant implications for seismic hazard assessment in Central Italy, since this area host the NW-SE striking Monte Gorzano Fault, interpreted by several authors as active and able to generate an earthquake with maximum magnitude Mw 6.5-6.7 (Barchi et al. , 2000; Boncio et al. , 2004; Galadini and Galli, 2003). In order to deepen the knowledge of the area and therefore to better understand the timing of the activity of the Monte Gorzano normal Fault, we carried out an integrated structural and stratigraphic field analysis. The displacement-length ratio (see also Boncio et al. , 2004) for the whole Monte Gorzano Fault is significantly larger with respect to commonly described values from normal faults worldwide. From a stratigraphic point of view, the Monte Gorzano fault cuts Mesozoic carbonate succession and Upper Miocene siliciclastic formations (the Laga Formation, Marini et al. , 2015). The Laga basin has a triangular shape and is surrounded by main tectonic elements: the Monti Sibillini thrust from West and East, and the Gran Sasso thrust from South. The activity of the aforementioned thrusts is coeval to the deposition of the Laga Formation. Lateral variation of the stratigraphy is given by passage from channelized deposits in the western and southern part to the lobe deposits to the east and south-east (Marini et al. , 2015). The interpretation of available well data in Campotosto area, and correlation with field-based outcomes helped to select several marker beds, such as turbiditic marker beds, arenaceous-pelitic levels. The thickness was evaluated between two recognized stratigraphic levels: top of Orbulina formation and turbiditic marker beds recognizable both in the field and from the well. From the field mapping, this thickness corresponds to 750 - 780 m within the footwall. Meanwhile the estimation of the thickness of this package in the hanging wall (measured from the well and field mapping) corresponds to ~ 900-1050 m. This portion of the Laga Formation results 150 – 300 m thicker in the hanging-wall than in the footwall. These features and field evidences of buttressing of the hanging-wall succession against the fault (Calamita et al. , 2018), are consistent with the pre-thrusting syn-sedimentary Upper Miocene Fig. 2 - 3D model of the Campotosto linkage fault zone in between the Paganica and Monte Vettore seismogenic faults. The seven south-west dipping seismogenic faults belonging to the relay has been modelled on the base of the available focal mechanisms and the released seismic moment.