Earth Sciences Remote Sensing Lab
Earth Sciences Remote Sensing Lab |
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We applied a geographic information system approach to generate an integrated seismic risk map for Egypt. We generated and integrated the information contained in (1) a seismic hazard map compiled from peak horizontal ground acceleration and from earthquake epicenters, (2) a fault hazard map outlining surface (from geologic maps) and subsurface (from gravity field data) fault zones susceptible to failure by rupture and proximal to earthquake epicenters, (3) an amplification map showing the distribution of thick alluvium deposits that amplify ground shaking, (4) a liquefaction map showing areas susceptible (shallow groundwater, seismically active) to soil (sand/silt) liquefaction, and (5) a population density map that shows areas subject to increased risk of loss in human life and property. Frequent and large events in the sparsely populated southern Sinai Peninsula, the coastal plain of the Gulf of Aqaba, and the coastal plain of the Red Sea and the Gulf of Suez (between latitudes 26°45'N and 28°15'N) pose little seismic risk. Loss of human life and property is more likely to occur in areas of moderate seismicity (210 gal<PGA <255 gal) that are densely populated and are susceptible to local site effects (e.g., soil amplification, soil liquefaction, failure by rupture). These areas include a major (»350 km long and »130 km wide) northeast-southwest trending zone that incorporates Port Said, Ismailia, Suez, Cairo, and the Fayum areas). Understanding the origin of seismicity in and around Aswan is critical because of the presence of strategic constructions (Aswan and High Dams) within this area. Over half of the new planned developments along the Mediterranean, in the Western Desert, and along the River Nile banks in upper Egypt lie in areas of very low seismic risk. Numerous developments will be built in the areas of moderate to low PGA that comprise a large concentration of zones of weakness (e.g., coastal plain of the Gulf of Suez) or in areas susceptible to soil amplification (River Nile banks, south Cairo) or soil liquefaction (e.g., new developments east of Cairo). A better understanding of the local site effects is needed to construct the planned new urban developments in ways that pose minimal risk to human life and property.
Distribution of epicenters of earthquakes that occurred in and around Egypt during the period prom 1900 to 1996. Also shown are historical earthquake epicenters. Reference: El Araby, H., and Sultan, M., 2000, Integrated seismic risk map of Egypt, Seismological Research Letters, v. 71, p. 52-65.
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