Estimation of Ground Motion at Damaged Area During 1992 Cairo Earthquake Using Empirical Green's Functions

Abstract

An earthquake with moment magnitude 5.8 occurred at 15:09 local time on 12 October 1992 at an epicentral distance of 25 km southwest of Cairo, the capital of Egypt. In this article, we analyze possible causes for failure of structures at the seriously damaged area. This earthquake was the first disastrous one to have occurred near the city of Cairo since 1847. Although it was defined as a moderate magnitude event, it gave a serious mental shock to many Egyptians in addition to injuries, loss of lives, and property damage. There are no records of strong ground motion at the damaged area for this earthquake. The degree of earthquake damage varied widely according to the construction and engineering quality of structures (Japan Disaster Relief Team 1993). Significant damage was found mostly in adobe or old, nonreinforced masonry buildings and nonengineered reinforced concrete buildings. Meanwhile, no damage to high-rise buildings was reported. At a given location, damage to properly designed structures may have been minor while extensive damage could be found in the nonengineered structures. Devastating damage was confined to old masonry structures, but minor damage such as cracks in walls and falling plaster typify the damage incurred by modern buildings in downtown Cairo, except for the collapse of a 14-story reinforced concrete building. Adobe structures in the suburban areas such as El-Faiyum and Al-Ayat, in the region of the earthquake's epicenter, were seriously damaged. Liquefaction was observed at many sites near the epicenter. To study the possible causes of structural failure at the seriously damaged area, we estimated the ground motions by applying Irikura's (1986) approach using small records as empirical Green's functions (EGF) and nine proposed source models at four observation sites (AYT, FYM, MYD, and SQR) configured around the epicenter, in addition to the distant station KEG, which …