الفهرس 
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Abstract
[Site characterization Utilizing
Seismo-Geotechniques in the Northern Extension of
The15th of May City, Cairo, Egypt]
Conclusion
The geology of study area in northern extension of 15th of May City is considered a part of Mokattam formation in Eocene age which is characterized by a hill that borders the eastern part of Cairo city. The 15th May city generally and northern extension specially divided into many formations are (Wadi deposits, Wadi Garawi formation, Quran formation and observatory formation). Mokattam formation divided into El-Qurn Formation, Gebel Hof Formation and Observatory Formation. Upper Mokattam section that are member of Upper Eocene was divided also into; Wadi Hof series and Wadi Garawi series, which is characterized by yellowish, white limestone Mokattam formation in Middle Eocene Age divided into Lower Mokattam formation and Maddi formation.
Also, this chapter is discus about seismicity of Egypt which describe in the northern Red Sea and the eastern part of Egypt divided into many seismic zones, which may affect Cairo area. These seismic zones is explained as follow: Northern Red Sea; Southern Gulf of Suez; Middle Gulf of Suez; Northern Gulf of Suez; Cairo-Suez District; Beni Suef; Dahshour; Northern Sinai; and Mediterranean coastal dislocation zone.
The most recent damage earthquakes occur in Egypt in last 70 years was the following:
September 12, 1955 Alexandria earthquake (Ms = 6.8), March 31, 1969 Shadwan Earthquake (Mw = 6.9), November 14, 1981 Aswan (Kalabsha) earthquake (Mb = 5.6), October 12, 1992 Cairo (Dahshour) earthquake (Mb = 5.8), November 22, 1995 Gulf of Aqaba earthquake (Mw = 7.3).
Horizontal to vertical spectral ratio (HVSR) also known as Nakamura technique is used to calculate fundamental resonance frequency (fo) of Microtremors, which is associated with the ground motion amplification (Ao). The McSEIS-MT NEO Model 1134 which used in study area is the most suitable instrument to measure and calculate the resonance frequency (fo) and also the Amplification related to this frequency (Ao). The data acquisition of Microtremors data is collected in different 22 sites and processed by using Geopsy software program (http://www.geopsy.org).
The values of recorded ambient vibration (microtremors) from 22 sites in the study area were used in estimation of the site response in terms of predominant frequency (f0) and the corresponding amplification of ground motion (A0). Sites (10, 13, 16 and 20) are flat curve are explain these sites are on the base rocks, Sites (18 and 19) have not clear peak. The Resonance Frequency (f0) between 0.4Hz to 1.0Hz.H/V. The Amplification factor (A0) is between (1.4) and (5.6).
Also Shallow seismic refraction is utilized for Estimation of depth to bedrock, Estimation of depth to water table, Predicting the rip ability of specific rock types (Knowing the velocities of P waves in various layers indicates the types of soil or rock that are present below the ground surface), and Geotechnical investigations.
There are six shallow seismic refraction profile applied in study area by using using24-channels signal enhancement seismograph model GEOMETRICS Strata View. The data was acquired using a refraction profile consisting of 24 geophones spaced at 3 m with total spread length of 72 m. The sensitive vertical geophones (40 Hz) are recorded the direct and refracted waves in these profiles. The method of generate seismic wave is five shots for each profile, at distance of 3 m far from both ends (normal and reverse shooting), at the mid-point (between geophones 12 and 13), between geophones 6 and 7, and between geophones 18 and 19.
Shallow seismic refraction is using to determine the number of layers, thickness of each layer and the (Vp) velocity of Primary seismic wave (P-Wave) for each layer. Also the interpretation techniques are applied to the first arrival times to calculate the seismic velocities of the layers and the depths of individual refracting interfaces. The interfaces are correlated with real physical boundaries in the ground, such as the soil-bedrock interface and other lithological boundaries, to produce a model of the subsurface ground structure. The final interpretation is presented in a format that is easily understood by engineers. All sites have two layers, surface layer and second layer. The thickness of surface layer between 1.5m and 3m, but the second layers have thickness between 8m and 9m. The surface layer exhibits very low P-wave velocity ranging from 500 to 1400 m/s, the second layer reveals P-wave velocity ranging from 1600 to 2100 m/s.
The current study aims to evaulate seismic hazard at the northern extension 15TH of May City using the probabilistic approach. For this purpose, two seismotectonic models are adopted and the ground motion is predicted using realistic ground motion prediction equations.
The main output of the current study was the seismic hazard curve that is calculated for PGA within 50 years design lifetime as well as Uniform Hazard Spectra (UHS). The UHS With probability exceedance of 50%, 10%, and 2% probability of exceedance in 50 years life time are produced with return periods 72, 475, and 2475 years respectively. are 40, 120, 240 cm/s2 for return periods 72, 475 and 2475 years respectivly. The maximum acceleration is corresponding to 0.1s Spectral ratio with values 100, 250 and 520 cm/s2 for return periods 72, 475 and 2475 years respectivly. The maximum acceleration is corresponding to 0.2s Spectral ratio with values 90, 240 and 520 cm/s2 for return periods 72, 475 and 2475 years respectivly. The maximum acceleration is corresponding to 0.3s Spectral ratio with values 70, 190 and 400 cm/s2 for return periods 72, 475 and 2475 years respectivly. The maximum acceleration is corresponding to 0.5s Spectral ratio with values 30, 80 and 190 cm/s2 for return periods 72, 475 and 2475 years respectivly. The maximum acceleration is corresponding to 1s Spectral ratio with values 10, 30 and 60 cm/s2 for return periods 72, 475 and 2475 years respectivly. The maximum acceleration is corresponding to 2s Spectral ratio with values 0.2, 10 and 20 cm/s2 for return periods 72, 475 and 2475 years respectivly.
For the sake of compersion we suammriezed the obtained spectral acceleration in different periods with those obtained from previous studies. The comparison shows that our results are closer to previous ones. The slightly difference in the obtained values of acceleration are mainly related to using the different GMPEs and the dimensions of seismic source zones.