الفهرس 
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Abstract
Seismic waves generated from local earthquakes are used to carry out a detailed seismic waves study for the Earth’s crust and the upper mantle in the northern Red Sea, Gulf of Suez and southwest Cairo (Dashour seismogenic zone). Significant interest is gone to the one and three dimensional velocity modeling and the attenuation as well. The tomographic results of the velocity and Poisson’s ratio in the study area are analyzed and described. The combined interpretation of the tomographic images, the precise hypocenter locations and all available geophysical information provide valuable results about the evolution of the crust and the upper mantle and its relation to the earthquake nucleation in the northern Red Sea and the southern Gulf of Suez in addition to the important roll of the fluid mechanism and the subsurface magmatic activity. The strong heterogeneity in the tomographic images is considered as additional evidences for the evolution of the Conrad Deep as oceanization cell in the northern Red Sea. With further extension these cells grow, amalgamate to form a continuous spreading center. The observed low velocity and the high Poisson’s ratio in the crust in the southern Gulf of Suez would possibly reflect significant geophysical and geochemical observations as well as terrestrial heat flow. The historical and recent earthquake swarms having high b-values close to or slightly above 1.0 in addition to long continuing seismic activity and the rifting in the southern Gulf of Suez. These many evidences advocate that the earthquakes nucleation in the southern Gulf of Suez is not purely tectonics, but may be related also to mechanical failure affected by probable subsurface magmatic activity and abundant fluid components. In Dahshour area the relocated earthquakes are generally associated with boundaries of high and low Poisson’s ratio anomalies reflecting strong variation in VP/VS. As the area associate with the NW-SE Qatrani fault and the E-W Gabal El Sheeb group faults. These structures are mostly related to compressive stresses (NW-SE) and (E-W) created by rejuvenation on preexisting right lateral strike slip faults.