GIS-based study of physical factors related to landslide events in a tectonically active area

In many cases the impact of physical factors in landslide activity is not well defined. Determining the actual landslide zone induced by geologic, tectonic, and geomorphic factors is crucial to reducing damage and losses in tectonically active areas. The scope of the present study is to identify the influence of physical factors on the spatial distribution of landslides in the mountainous region of northern Peloponnese in southern Greece, which is a tectonically active area. For this purpose, lithology, tectonic features, inclination, aspect of slope, and geometry of main discontinuities of the study area, along with the existing landslides were considered. Each physical factor was further divided into sub-categories. Statistical analysis of landslide frequency and density, as well as frequency and density ratios were applied. The analysis was combined with Geographical Information Systems (GIS) techniques to evaluate the collected data and define the relation of factors with landslide activity. The results provide information on physical factors that characterize landslide events in the study area. Plio-Pleistocene fine-grained sediments and flysch, increase landslide frequency and density. Additionally, the frequency and density of landslides increase near tectonic features. The landslide events and magnitude of landslide area increase in distances of 0 to 50 m from any given tectonic element and decrease in distances beyond 50 m from them. Moderate slopes (5 degrees-15 degrees) and relatively steep slopes (15 degrees-30 degrees), especially those facing northwest and northeast, as well as slopes categorized as sideways and vertical, with a dip of 15 degrees-30 degrees, can increase the frequency and density of landslides. Schist-chert formations, fine-grained and coarse-grained Plio-Pleistocene sediments, and flysch are strongly associated with landslide occurrences. The closer the distance to a tectonic feature, the stronger the relationship with landslide activity. A buffer zone of 100 meters around each tectonic feature suggests a high probability of landslide events. Moderate slopes (5 degrees-15 degrees), relatively steep slopes (15 degrees-30 degrees), very steep slopes (> 45 degrees), northwest and northeast facing slopes, as well as slopes categorized as sideways and vertical, with a dip of 15 degrees-30 degrees and dip of > 30 degrees, are robustly related to landslides. The applied methodology can rapidly estimate areas prone to landslides and may be utilized for landslide hazard assessment mapping and land-use planning projects.