Earthquake-induced landslide hazard mapping

Abstract

Located in a seismic zone with a rugged topography, Lebanon is classified as highly vulnerable to earthquake and landslide hazards. According to Keefer (1984), even small magnitude earthquakes may trigger landslides leading to significant damages. Regional seismic hazard assessment for landslides has been done using methods based on the traditional infinite slope stability analysis following Newmark (1965). This approach provides a quick assessment of co-seismic landslides but has several disadvantages. In particular, the predefined failure surface leads to overestimated values of the critical accelerations of the slopes and underestimates the hazardous areas. Two newly proposed methods are implemented over a representative region of Lebanon with the use of the geographic information systems (GIS). Data including geological maps, high-resolution digital elevation models of the topography, site investigations and geotechnical data for the different geological units, earthquake peak ground acceleration maps, and a preliminary landslide inventory database are collected for the analysis. A co-seismic landslide hazard map for the country is then produced and the results are presented for a representative area. This hazard assessment represents the initial warning system that identifies high-risk sloping zones. Focus is particularly on densely populated urban areas where the landslide hazard greatly affects currently existing structures.