Estimation of the Permanent Seismic Displacements of the Costa Verde Cliffs, Lima, Peru

The city of Lima is located in one of the most seismically active regions on Earth. According to seismic history, in the year 1746 off the coast of Lima an earthquake occurred whose seismic intensity was X on the Modified Mercalli scale, a movement of this size could generate instability to the cliffs of the Costa Verde and produce large displacements in the slopes. For this reason, the estimation of slope displacements in the event of a similar earthquake was carried out. The Costa Verde Cliffs are an important part of the city of Lima, so ensuring their physical stability is of interest to many professionals and state and private institutions. These cliffs have a height that varies from 50 m to 60 m and a slope greater than 60° of inclination and are generally formed by the Lima Conglomerate in almost all its longitudinal extension. The strength of this material has been determined by in situ direct shear and large-scale laboratory direct shear tests, giving average values of friction angle of 40° and cohesion of 55 kPa. An extensive collection of information on the physical and mechanical parameters of the conglomerate was undertaken to reevaluated the stability of slopes in areas that were considered at low, medium and high risk in previous studies, to verify if they can still be considered as stable under pseudostatic conditions and the estimated permanent seismic displacements can be consistent for the Lima Conglomerate.