ABSTRACT

Landslides are common ground effects induced by earthquakes. Most of them correspond to first-time instabilities induced by the seismic event, being the reactivation of pre-existing landslides less frequent in practice. The case of Güevéjar (Granada province, S Spain) represents a rare example of landslide that was reactivated twice by seismic events occurring in far field: the Mw 8.7, 1755, Lisbon earthquake (with estimated epicentral distance of 680 km), and the Mw 6.5, 1884, Andalucía event (estimated epicentral distance of 45 km). The seismic response of the landslide has been studied through both experimental and numerical methods. Experimental data show that Güevéjar landslide is characterized by a low amplification of ground motion. Numerical stress-strain analyses were performed via finite difference approach and under dynamic configuration by considering several types of seismic inputs; the obtained results show that expected mobility of landslide mass is highly dependent on frequency content of input motion, being computed displacements maxima for events having a high content of low frequencies. This is strictly related to the landslide mass dimensions (i.e. ≅50 m thickness and ≅1 km length) as they control the interaction with the seismic waves propagating within the slope in terms of both local seismic amplification (1D effect) and 2D interactions.