Snow preparation in landslide scenarios under multi-hazard perspective: experiences from Lake Campotosto (Italy)

Landslides are a natural land-forming process and their interaction with urbanized areas and infrastructures makes them one of the most common geo-hazards. Landslides are controlled by three macro-categories of factors, namely the “predisposing”, “preparatory”, and “triggering” ones. In particular, preparatory factors are time-changing and gradually reduce the slope stability without initiating the movement. Snow melting and accumulation are generally discussed in the literature as triggering factors of landslides, particularly shallow ones, although, the here presented approach focuses on their contribution as preparatory factors. In mountainous areas, snow loading and, especially, snow melting can increase the soil pore water pressure, causing a reduction of available strength. Their influence on soil stability is time-dependent and, in particular, changes cyclically throughout the year. Snow usually begins to fall in the late autumn and accumulates especially in winter, whereas in spring it melts, resulting in water infiltration into the soil and resistance reduction. In seismic areas, where earthquakes can act as triggers for shallow landslides, seismic action might discover different levels of soil weakness throughout the year depending on the season, resulting in distinct landslide scenarios. This research illustrates some multi-hazard scenarios that consider earthquakes as triggering factor of landslides, varying the degree of saturation of soil covers. The case study is the area around Lake Campotosto (Italy), located in one of the Apennines areas with the highest amount of snowfall per year, is in the near fault sector of one of the most important seismogenic source of the Apennines (Mt. Gorzano Fault System) and is characterized by different sizes and mechanisms landslides. The approach applied for generating landslide scenarios is the PARSIFAL (Probabilistic Approach for Rating Seismically Induced slope FAiLures), a probabilistic multi-hazard tool that includes a three steps procedure: 1) susceptibility analysis including differentiated approach for rock and earth failure mechanisms; 2) slope stability analysis; 3) synthetic mapping of generated scenarios, based on grid or slope units. Preliminary research on the stability of soil covers under seismic conditions emphasizes importance of hydraulic conditions during earthquake, which also suggests the relevance of snow loading and, in particular, snow melting in regulating slope stability. Further research is being done utilizing satellite and meteorological data, and geomorphological features, and then elaborating them using statistical and geostatistical tools, up to advanced computing. The goal is to generate time-dependent landslide hazard scenarios by weighting the effects of snow precipitation throughout the year as a preparatory factor and adding a related tool to PARSIFAL. The majority of these concepts are being studied at Sapienza's Department of Earth Sciences in the CN1 (National Centre for HPC, Big Data, and Quantum Computing) – Spoke5 PNRR Linea Tematica 1 (Reconstruction of multi-hazard scenarios from seismic source models to the simulation of seismic-induced instabilities), which aims at generating ground effects scenarios in terms of instabilities induced by nonlinear effects produced by the propagation of seismic waves from the seismogenic source to the surface, also considering geomorphological and geotechnical characteristics of the near subsurface.