Cycle 1 (2011 Deadline)
Earthquake-generated landslide hazard in Lebanon
PI: Grace Abou-Jaoude, Lebanese American University
U.S. Partner: Joseph Wartman, University of Washington
Project Dates: May 2012 - April 2014
Lebanon is located in a relatively high seismic zone and has a rugged topography, making it vulnerable to hazards from earthquakes and landslides. Records about seismic events in the country go back to 303 AD and contain descriptions about such damages as houses and monuments destroyed and widespread fires, but they offer few if any details about collateral damages from landslide hazards associated with earthquakes. Although Lebanon has not experienced any major earthquake since 1956, the recent discovery of an active thrusting fault close to its coastline has significantly raised its risk of being hit by a high magnitude earthquake. Past studies on seismic hazards in Lebanon have focused on seismic zoning and its impact on structural engineering design. Although many researchers have assessed slope stability hazards in Lebanon based on various static conditions, no effort has been undertaken as yet to assess the impact of a seismic event on triggering landslide hazards in the country.
This project aims to produce a hazard map of Lebanon that clearly shows the critical areas prone to earthquake-induced landslides. This goal will be achieved through three major activities to be conducted over a period of two years. The first task will be mapping the landslide prone zones in the Geographic Information Systems (GIS) framework, followed by a detailed geological field survey. The second task will focus on numerical modeling of slopes, including seismic slope stability analyses in order to evaluate the failure potential of sloping terrains when subjected to different seismic loading events. The third task will be to produce an up-to-date earthquake-induced landslide hazard map, taking into consideration the effects of the active faults in the country, the general terrain parameters, and the seismic slope stability analyses. Ultimately the project should help Lebanese cities to identify areas with high natural hazard potential so they can plan urban growth appropriately, thus preventing damage to critical infrastructure and saving lives in the event natural disasters strike.
Summary of Recent Activities
During the last reporting period, Dr. Abou-Jaoude’s group analyzed the results of the second Newmark model. This model was done on ArcGIS using the 1:50,000 geology maps of Lebanon, the ASTER 30m DEM, and the PSHA data for Lebanon by Huijer et al. (2011). The results of Newmark’s factor of safety against sliding were compared to the very little information about landslides records in Lebanon that could be found in the literature. Despite several attempts, the team was only able to obtain basic information about geology and slope in relation to the landslide records in a tabulated format from the Remote Sensing Unit of the National Council for Scientific Research (CNRS) of Lebanon. Work is now in progress to compare this data to the results of the Newmark analysis. A new full-time research assistant was hired for this quarter and a geologist was hired for two months (proper vetting procedures were completed for both). The geologist provided the team with a complete review about the geology of Lebanon with emphasis on the modes of failure and the strength of each geologic formation. In addition, the geologist and the full-time research assistant completed a two-day field visit to two landslide prone areas in Lebanon. Several rock samples were retrieved from these sites to assess their strength. The research assistant continued the parametric analysis on slope angle, slope height, and failure surface using the Rocscience software that was purchased in order to generate stability charts for use in the next refined analysis. Work on a journal paper is ongoing to publish the results of the Newmark model. Probability of failure will be calculated for all slopes and the initial risk map will be generated for earthquake-induced landslides in Lebanon. Threshold slope angles for the three modes of slope failure will be set and the output of the parametric study will then be used to update the analysis on ArcGIS.