Liquefaction During the October 12, 1992 Dahshour, Egypt, Earthquake and Its Potential in the Nile Valley and Delta

Reconnaissance studies carried out following the October 12, 1992 Dahshour earthquake, near Cairo, Egypt indicated significant sand-boil activities and liquefaction at several locations on both sides of the Nile River near the earthquake epicenter. The study reported in this paper gives a brief account of liquefaction activities during the Dahshour earthquake and reviews the geological and geotechnical characteristics of the Nile Valley and River Delta and the associated seismicity of this region in order to identify areas and formations that may be prone to liquefaction. Data from some 50 sites within the study area were analyzed for a preliminary assessment of liquefaction potential under seismic conditions similar to those associated with Dahshour earthquake. The analysis was made using two different methods, namely, Seed's method, and the Chinese Code method. Contrary to results reported for strong earthquakes, the agreement between the two methods at prescribed moderate ground shaking was found to be relatively poor, as Seed's method appears to underestimate the liquefaction potential whereas the Chinese Code method tends to be more conservative. The results, however, generally indicate that, under seismic conditions similar to the Dahshour earthquake, liquefaction potential should be considered at sites having saturated sand layers with SPT-N values less than 15 blows/300 mm within the top 15 m. The results also emphasize the need for more accurate seismic zoning in Egypt as well as the incorporation of a considerably larger amount of field data to produce reliable liquefaction risk zoning information.