Mountains topographic amplification: implications for gravitational phenomena triggering

This paper analyzes the effects of topographic amplification of seismic action in mountain ranges. Theoretically, amplification might be an issue for avalanches, landslides, and rockfall, which seismic events could trigger. The authors conducted a numerical and experimental analysis on a kilometre scale of a Gran Sasso mountain range segment in Italy. A three-dimensional finite element was created using a digital elevation model of the mountain. This model was used to predict the modal parameters of the terrain rockmass, validated against the experimental ones predicted using operational modal analysis, with an improved version of stochastic subspace identification to characterize the mode uncertainties. The modal analysis results were used to calibrate two-dimensional and mono-dimensional equivalent models used for local seismic response analyses. The surface geotechnical model was assumed based on microtremor measurements. The study helps to clarify the true extent of topographic amplification for a case study known in the literature in the context of seismic triggering of avalanches. The results reveal the presence of a combination of macro, meso and microscale amplification effects.