Evolution of rock falls in the Northern part of the Peloponnese, Greece

Abstract

Rock falls are a common fast - moving type of slope failures. Earthquake triggered rock falls attracted widespread attention since they represent serious hazard during strong earthquakes, causing severe damages and even fatalities. Strong earthquakes and their associated rock falls give rise to a sudden change in landscape evolution in tectonically active areas. The associated risk can be high both to communities and to critical infrastructures even far away from the active source slopes. Distinguishing between climatic induced and tectonically induced rock falls triggered by past earthquakes is a challenging task based on the development and the fault related discontinuities of a rock slope. We chose two case studies located in the Northern part of the Peloponnese (in Ilia and Corinthia prefecture), the Skolis Mountain and the Acrocorinthos area, in order to establish the rock fall susceptibility for each case study through the implementation of shadow angle β. The proposed methodology is based on the integrated analysis of the recurrence of rock falls, their spatial distribution and their mapping through field survey and aerial photography. Our mapping is integrated through Geographic Information System taking into account also the catalogue of historical and recent recorded seismicity in an attempt to examine triggering mechanisms and causes including the effects of climatic conditions for each case study. After the analysis of the spatial relationships between rock falls and the distribution of seismic epicentres and active faults as seismogenic sources, we conclude that both studied areas have suffered extensive rock fall phenomena induced by shallow seismicity and that the relationship between geomorphologic parameters and rock fall occurrence is strong. The research steps are described, namely, the recognition, identification, mapping and evolution of rock fall phenomena through time. Our results propose a critical threshold value of 24° for shadow angle β as the worst case scenario, suggesting that isolated boulders pose the greater risk on the associated communities.