Regional scale assessment of the seismic performance of natural slopes

This paper analyses the seismic response of natural slopes within a probabilistic framework with reference to the Italian seismicity. Once combined with a proper semi-empirical relationship linking the permanent earthquake-induced displacements of slopes to one or two synthetic ground motion parameters, the probabilistic approach allows to evaluate the permanent displacements for a given return period and a given yield seismic coefficient, the latter accounting synthetically for the seismic resistance of the slope. The results are illustrated in terms of hazard maps showing the distribution of the displacements at a regional scale and are therefore useful to identify slopes in areas that are prone to earthquake instability. In detail, scalar and vector probabilistic approaches based on the ground motion parameter PGA and the couple PGA, PGV, respectively, are employed to produce hazard maps for two Italian regions characterised by severe seismicity. Finally, the results obtained through the fully probabilistic approach are critically analysed and compared with those determined through a simplified decoupled method that combines a standard probabilistic seismic hazard analysis (PSHA) with the displacement semi-empirical relationships. The maps presented in this work represent a reliable and simple tool for preliminary, screening level analyses of natural slopes in terms of seismic-induced displacements.