الفهرس 
CHAPTER ONE: IntroductionOnly 14 pages are availabe for public view
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Abstract
Earthquakes are the most important one in between natural hazards in terms of destruction and suffering. A significant feature of earthquake damage is that most of the human and economic losses are not due to the earthquake mechanisms, but are due to failures of buildings and lifelines. Site effect is an important factor influencing greatly earthquake hazards.In the Nile Delta, the site response would be important, due to the presence of a thick sedimentary cover. Dakahlia Governorate has thick stratigraphic succession of Neogene-Quaternary sediments. This may tend to amplify the ground motion during earthquakes. Earthquakes damage may be aggravated by the site effects, when the resonance frequency of buildings coincides with that of the sediments, ground shaking may increase due to high potentiality of increasing the amplitude of the incoming seismic waves and this adding more stress on the man-made structures leading to more damage. As a crucial step for seismic risk mitigation it becomes more important to know the fundamental resonance frequency of the sites to avoid the occurrence of resonance phenomena. Utilization of the ambient noises is an effective tool for assessing the site dynamic characteristics, which include the fundamental frequency (F0) and amplification factor (A0). The H/V ambient noises method (Nakamura’s technique) has become in the last two decades one of the most popular approaches, as being fast and inexpensive for estimating site response in urban areas. This technique was applied in our study area to obtain the site effect parameters including, predominant frequency and amplification factor. It must be noted that, the technique of Nakamura is very effective in obtaining the predominant frequency at the measuring site, but it gives the corresponding H/V amplitude with a lower limit estimates. The present study is conducted at 35 different sites to perform the site response analysis within urban settlements of Dakahlia Governorate, Nile Delta region. This is accomplished by applying the horizontal to vertical spectral ratio ambient noises methodology (Nakamura’s technique). This analysis showed that, the fundamental frequencies of sediments varied slightly between 0.9 and 1.7 Hz, in contrary to the amplification factors, which are highly variable and in the range of 2.2– 6.