الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Egypt is about 1001449 Km2 , located in the Northern corner of Africa. The present Nile Delta region is about 25000 Km2 and it is one of the largest deltas in the world. It is about 270 Km wide at the shoreline and only 16 km in the south. The seismicity of Nile Delta itself shows no significant activity due to its tectonic stability. The aim of this study is to get microzonation map. To achieve this aim, two methods were applied, Microtremors and Shallow seismic refraction techniques. The first technique applied is to know the site effects in terms of fundamental resonance frequency (fo) which is associated with the ground motion (Ao). Local site effect may cause amplification of seismic waves during earthquakes and plays an important role for site-specific ground motion predictions and seismic hazard assessment. Data from 70 points in Nile Delta region and Helwan seismic station were collected. The value of resonance frequency (fo) and the associated amplification of ground motion (Ao) at every site were calculated. from the results we can conclude that the value of resonance frequency (fo) is nearly the same at all the points ranged from 1.1 to 1.3 in the area controlled by the Nile branches because the IV thickness of sediments is nearly the same in all this area. The values of (Ao) in the Central, Eastern and Northern part of Nile Delta are the same in most points and varied from 4 to 5. In Alexandria Governorate the values varies from points to points and the value of resonance frequency (fo) varied from 0.9 to 1.8. We recommend and advice a very detailed study in this area in near future. The value of (Ao) in the North Western part of Nile Delta and Alexandria is the same in most points and varied from 5 to 7 and this is may be one of the reasons of building collapse in Alexandria governorate. The second part of this study is to determine the dynamic characteristics (elastic parameters) in Nile delta of Egypt. To achieve this aim, we used Seismic refraction technique to calculate the seismic velocities of subsoil (Vp and Vs) in the Nile Delta of Egypt, Twenty-five sites were selected. Shallow seismic refraction survey was carried out to determine the ground model and subsurface structures and to define the geotechnical characteristics for the shallow subsurface layers. Twenty-five sites are used in Damietta Governorate, Alexandria, Kfr El- Sheikh and El Gharbia Governorates respectively. At each site, two seismic profiles were measured V in order to get P and S wave velocities as well as the geological structure below each profile. The length of each profile is varied between 120 to 48 m according to the site condition. Also one SH wave profile was measured. In order to know the nature of subsoil structure below 25 sites at Nile Delta, elastic modulei are deduced. The estimation of elastic modulei (geotechnical parameters) depends on the propagation of seismic waves through rock materials (Vp and Vs – velocities). Kfr El-Sheikh, Damietta and El Gharbia Governorates, are located in Nile Delta. The P- wave velocity of these three Governorates are nearly the same and varied in first layers from 290 to 346 m/s and the second layer is varied from 1388 to 1542 m/s. Also the S- wave velocities is nearly the same in the three Governorates and varied from 177 to 268 m/s and for the second layer the value of S- wave velocity is varied from 793 to 897 m/s. Therefore, the values elastic parameters are almost the same in these three governorates, which are considered as the main parts of Northern and Central Nile Delta. For Alexandria Governorates and Coastal area. The subsoil structure is little –bit different from the subsoil of Nile VI Delta. By comparing the velocity results of the last three locations, ( Kfr El-Sheikh , Damietta and El Gharbia Governorates) with typical rock velocities which illustrate that the vegetal soil P- wave velocity is varied from 300 to 700 m/s while S-wave velocity varied from 100 to 300 m/s . In water saturated shale and clays, it is varied from 1100 to 2500 m/s while S -wave velocity varied from 200 to 800 m/s. This is compatible with most results, which are obtained in all locations of Damietta Governorates. Also, the microzonation map was constructed in Nile Delta area. The map illustrate that the Nile Delta is in low hazard. But Alexandria area is the only area that illustrates higher hazard compared with all the Nile Delta.