GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.1 93 Villani F., D’Amico S., Panzera F., Vassallo M., Bozionelos G., Farrugia D., Galea P.; 2018b: Shallow high-resolution geophysical investigation along the western segment of the Victoria Lines Fault (island of Malta). Tectonophysics, 724, 220-233, 10.1016/j.tecto.2018.01.010. Villani F., Sapia V., Baccheschi P., Civico R., Di Giulio G., Vassallo M., Marchetti M., Pantosti D.; 2019: Geometry and structure of a fault-bounded extensional basin by integrating geophysical surveys and seismic anisotropy across the 30 October 2016 Mw 6.5 earthquake fault (central Italy): the Pian Grande di Castelluccio basin. Tectonics, 38, 1, 26-28, doi: 10.1029/2018TC005205. STRUCTURAL ANALYSIS OF THE 2016 EARTHQUAKE RUPTURES GEOMETRIES IN THE NORTHERN SECTOR OF THE SIBILLINI MOUNTAINS M. Menichetti, E. Tirincanti, M. Roccheggiani Dipartimento di Scienze Pure e Applicate, Università di Urbino, 61029, Urbino (PU) A complete and detailed survey of the geometries of coseismic ruptures is central to define the kinematic and the dynamic relationships of active faults and the regional seismic hazard. Earthquakes producing coseismic surface deformation generate offsets in the landforms that are linked to the kinematics and the magnitude of the seismic events. Even though their importance in the seismic hazard assessment and their utility in the developing hazard reduction procedure, the ground ruptures accurate morphologies and their structural geometries remain uncertain. In many cases, the relevant extension of the coseismic ruptures and the morphologically complex landscape made it necessary to do a long-time fieldwork to recognize and survey each strand of the fractures. During the earthquakes sequence occurred in the Sibillini Mountains in Central Italy from August to October 2016, several ground ruptures have been generated over a large area. These ruptures, that reactivated pre-existing normal faults, extend from the Tronto river valley in the south to the Chienti river valley in the north, over a distance of about 40 km. On August 24th, a Mw 6.1 earthquake struck the southernmost area between the town of Amatrice and Arquata del Tronto. Several ground ruptures along different strands of SW dipping extensional faults developed for more than 20 km in the M.Vettore area. The October 26th Mw 6.0 earthquake was centred in the Visso area, approximately 30 km northwest of the previous event. In this case, only few coseismic fractures have been surveying because, on October 30th, a new seismic event of Mw 6.5 occurred in the area near Norcia. This event, occurred between the epicenters of the former earthquakes. It reactivated existing ground fractures and produced further ruptures over a larger area, including the northernmost sector of the Sibillini Mountains (Fig. 1). Despite many authors published preliminary maps of the ruptures for the central part of the epicentral area, especially for the M.Vettore sector, the structural and kinematic features of the northernmost sector have been poorly investigated. A highly detailed map of the coseismic surface ruptures is proposed for the area between M. Bove, Visso and Pieve Torina integrating a classical geo-structural field survey with low altitude aerial photos and remote sensing data interpretation. Images with centimeter resolution obtained via SfM (Structure From Motion) photogrammetry permitted to map in 3D the details of the vertical and horizontal displacements, constraining the spatial geometrical characteristics of the active faults. The spatial pattern of fracture distribution, ruptures offsets, and links between geometries along the fault strands are fundamental in order to extrapolate and constrain the depth of the fault planes from a seismotectonic point of view. The surveyed ruptures seem to be the result of the cumulative effects of several events during the 2016 earthquake sequence. In the M. Bove area at least three subparallel rupture strands run in the NW-SE direction for about 5 km on the whole western slope of M. Bicco and M. Bove Sud (Fig. 1). Other fractures strands, of many tens of meters of