Numerical analysis of the influence of 3D geometry and seismic input on rock-slope failures triggered by moderate to strong earthquakes: An example from the 2016 Central Italy seismic sequence

This study analyzes the Valle Orteccia rock slide, one of the most significant rock slope failures triggered by the 2016 Central Italy seismic sequence. Numerical simulations of the initial stage of the failure were performed in both static and dynamic conditions, using high-resolution geological-structural and geomechanical data derived from UAV (Unmanned Aerial Vehicle) surveys and in-situ investigations. The analysis revealed that the slope reached near-critical conditions during the Mw 5.9 Visso earthquake (26 October 2016) and collapsed in the early stage of the subsequent Mw 6.5 Norcia event (30 October 2016). The failure mechanism was primarily driven by three major discontinuities, in combination with local slope morphology, which enhanced seismic amplification effects in the upper-central part of the slope. This work demonstrates that a 3D modelling approach can be a powerful tool for reconstructing complex slope failure/deformation events controlled by a strongly 3D rock mass structure and directional seismic effects that cannot be adequately considered in simpler analyses. Since the geo-structural setting of Valle Orteccia may be representative of other sectors in the central-northern Apennines and of thrust front areas worldwide, this work may be of general significance for the study of earthquake-induced landslides on a wider scale.