Integrated Seismic Risk Map of Egypt

Abstract

Egypt is one of the few regions of the world where evidence of historical earthquake activity has been documented during the past 2,800 years ( e.g., Sieberg, 1932; Ismail, 1960; Gergawi and El Khashab, 1968; Karnik, 1969; Ben-Menahem, 1979; Ibrahim and Marzouk, 1979; Maamoun, 1979; Poirier and Taher, 1980; Kebeasy et al., 1981; Makropoulos and Burton, 1981; Maamoun et al., 1984; Savage, 1984; Riad and Meyers, 1985). Instrumental recording of earthquakes started as early as 1899 (Kebeasy, 1990). The unfortunate recent (magnitude 5.9; 12 October 1992) earthquake activity southwest of Cairo (Dahshour) and the earlier earthquake (magnitude 5.5; 14 November 1981) southwest of Aswan brought attention to the need for a better understanding of the seismicity of Egypt, especially in and near densely populated areas and in strategic locations ( e.g., around the Aswan High Dam). To ease the problem of overpopulation of the Nile Delta and the Nile River banks, Egypt recently has embraced ambitious policies to invest in the construction of new cities and industrial and agricultural communities nationwide (Figure 1) (Information and Decision Support Center, 1996). A better understanding of the seismic hazards and risks in Egypt is needed, particularly in this era of investment and construction. Seismic hazard refers to the strength and frequency of shaking from earthquakes, whereas seismic risk refers to the chance of losing human life and/or property because of earthquake ground shaking. Previous seismic hazard assessment studies were restricted to the computation of probabilities of occurrence of ground-shaking in a given time period by using probabilistic seismotectonic methods without incorporating local site effects ( e.g., El-Difrawy et al., 1997). Using a geographic information system (GIS) approach, we generated the first seismic risk map for Egypt by integrating the probabilities of ground shaking and …