Seismically Induced Rockfall Hazard from Ground Motion Scenarios in Italy

Physically-based simulations for slope stability are conceptually different from widely used statistical approaches. Both methods have specific advantages, depending on available data, their type and resolution and, most importantly, the aim of the study. The majority of landslide susceptibility and hazard zonations are implemented with statistical methods, especially on large scales: mostly because the data needed for physical simulations are only available in small areas.Here, we perform a hazard zonation based on the physical model STONE for the simulation of rockfalls, at 10 m resolution consistently all over Italy, and aggregating results at the slope unit level. This work follows a series of susceptibility zonations at national scale with physical models. The novelty, here, is the introduction of a seismic trigger for rockfalls, which allows to add a temporal component and obtain an estimate of seismically induced rockfall hazard. Peak ground acceleration maps with different return times including seismic amplification represented the earthquake trigger. A data-driven map of possible rockfall sources all over Italy allowed a statistical generalization of sources, mapped by experts in sample representative locations. Eventually, application of a simple linear transformation, to map values of peak ground acceleration into activation probability of sources, links "static" rockfall simulations with time-dependent triggering phenomena.Results are maps of rockfall susceptibility with different return times, i.e., rockfall hazard. Maps of hazard values and corresponding uncertainties, aggregated at slope unit level and categorized, are readily available for download. We suggest that the new model for seismic triggering of rockfalls could be applied at the local and regional scale, for calibration with specific earthquake events, insteadof return time scenarios. On the temporal scale, this approach in principle is suited for application in near-real time.