Space Sciences

Abstract. An analytical methodology is presented to evalu-ate rock slope stability under seismic conditions by consider-ing the geomechanical and topographic properties of a slope. The objective is to locate potential rockfall source areas and evaluate their susceptibility in terms of probability of failure. For this purpose, the slope face of a study area is discretized into cells having homogenous aspect, slope angle, rock prop-erties and joint set orientations. A pseudostatic limit equilib-rium analysis is performed for each cell, whereby the desta-bilizing effect of an earthquake is represented by a horizontal force. The value of this force is calculated by linear interpo-lation between the peak horizontal ground acceleration PGA at the base and the top of the slope. The ground acceleration at the top of the slope is increased by 50 % to account for to-pographic amplification. The uncertainty associated with the joint dip is taken into account using the Monte Carlo method. The proposed methodology was applied to a study site with moderate seismicity in Sola ̀ de Santa Coloma, located in the Principality of Andorra. The results of the analysis are con-sistent with the spatial distribution of historical rockfalls that have occurred since 1997. Moreover, the results indicate that for the studied area, 1) the most important factor controlling the rockfall susceptibility of the slope is water pressure in joints and 2) earthquake shaking with PGA of ≤0.16 g will cause a significant increase in rockfall activity only if water levels in joints are greater than 50 % of the joint height.