Abstract
In order to determine the fundamental period of soil vibrations in Cairo, 174 microtremors stations, in conjunction with mobile accelerographs, were used. The result was a collection of long-period microtremors and ambient noise arising from cultural disturbances. The Nile Valley shows some fixed peaks at 2.5-3.5 Hz at the center of the basin, while the Nile's surrounding area shows a fundamental peak of 4-5 Hz, leaving a 5-7-Hz resonance peak for the sand-like, gravelly soil from Abbasiya to the airport. A frequency-dependent soil amplification map is drawn, which includes seismic microzonation maps for Cairo. Based on the above, a maximum acceleration map for two important earthquakes affecting Egypt in the last century is produced (Faiyum, 1992, and Aqaba, 1995).