Mostafa Toni

Aeromagnetic data of the western part of Koraimat-Alzafarana road, Eastern Desert, Egypt is interpreted to detect the subsurface structures that may resulted in presence of subsurface aquifer. To reach to the main target of this study, many procedures are done using some magnetic analysis techniques (e.g., technique of reduction to the magnetic pole, separation technique of regional-residual anomalies and edge detection methods). The results have been encouraging to merit further estimation of the magnetic depth and analyzing the trends of the study area. To increase the credibility, the depth is revised by the P-depth technique. The shallow and deep magnetic components are calculated to be 2046 and 5680 m. To ease the detection of the structure that encasing the study area and lack the rigorous analysis, reduced the magnetic pole map, residual map and 3D Euler deconvolution are integrated to depict the combined lineament map that prevailing tectonic pattern of the study area. Eventually, NE–SW trend is the predominant structural trend affecting on the study area as deducing from magnetic anomalies. Moreover, there are minor structural trends which were taken N–S, NW–SE, W–E, NNW–SSE and NNE–SSW directions. The presence of subsurface structures may assist in the occurrence and recharging of the groundwater aquifers.

The Sinai Peninsula is a subplate located between the African and Arabian plates. It is an important subplate in the world; however, this region is poorly understood because of the shortage of geophysical data. Thus, this study focuses on built a three-dimensional (3D) high-resolution forward model of the crustal thickness with a new tectonic model and structural evaluation of the Sinai Peninsula to understand this area tectonically and determine its lithospheric and crustal thicknesses. Qualitative and quantitative interpretations of Bouguer gravity, reduced-to-the-pole (RTP) aeromagnetic, and earthquake data are explained to achieve the goals of this study. Two-dimensional (2D) interactive sequential modeling of gravity data is performed along with some well-selected profiles with existing crustal layer depth points from previous works in the studied region. Seventeen 2D models are constructed and used to determine the basement, Conrad (lower crust boundary), and Moho (upper mantl...

Parameters related to local site conditions represent an essential information for earthquake hazard evaluation and seismic risk mitigation at any region. In this research, the authors determine the local site characteristics and seismic ground motions around the Nile River, south of Cairo City, Egypt. This area suffered from a moderate earthquake (Mw 5.8) on 12 October 1992 and influenced by a soil liquefaction. Furthermore, the area is covered by soft sediments with large thickness, which may amplify seismic waves and lead to more damage in the event of earthquakes occurrence. Microtremor survey was carried out at six liquefiable sites in the study area by array of seismic stations. The recorded data was analyzed by the Centerless Circular Array (CCA) method to infer the shear wave velocity (Vs). The dispersion curves yielded from this analysis cover frequency range from 2.3 to 13.5 Hz. An inversion process was applied to get the Vs profile. The obtained velocities were averaged at 30 m depth (Vs 30) which in turn have been used for a soil classification and for calculating the bearing capacity of soil. The H/V spectral ratio method was used for an experimental estimation of the site predominant frequency and its corresponding amplitude of seismic waves. Moreover, seismic amplification was calculated using the shear wave velocities. The Peak Ground Acceleration (PGA) and seismic intensity (MMI) were calculated for the October 12, 1992, earthquake. The results reveal Vs 30 values from 170 to 240 m/s. Soil Class D is predominant in the study area. The amplification factor ranges from 2.5 to 4.5, corresponding to predominant frequency from 0.5 to 1.4 Hz. The allowable bearing capacity ranges from 0.7 to 1.0 Kg/cm 2. The PGA at the surface ranges from 0.16 to 0.4 g. The calculated seismic intensity (MMI) ranges from VII to VIII which are the same with those observed during the 12 October 1992 earthquake. The parameters estimated in this research may effectively contribute to the earthquake risk reduction in the study area.

Abstract This article introduces a site investigation study using quick and low-cost passive seismic techniques at Suez city which located in the northeastern part of Egypt. The Spatial Auto Correlation (SPAC) method is applied, as well as the newly developed Centerless Circular Array (CCA) method for estimating the shear wave velocity (Vs) structures of the subsurface layers using microtremor array data. The Horizontal/Vertical Spectral Ratio (HVSR) approach is employed in determination of predominant frequency (f0) of a site and its equivalent peak amplitude of ground motion (A0) using a single station microtremor measurements. In this study, microtremor array measurements have been carried out at five sites distributed in Suez city. In order to cover a wide frequency band, different array sizes are carried out at each observation site. Measurements are made using high performance accelerometers with a sampling rate 100 sample per second. In both SPAC and CCA methods, only the vertical component of microtremor data is considered in the analysis. The analysis includes two main stages, i.e., calculation of surface wave dispersion curves and inversion process to infer the Vs structure of the ground. The obtained dispersion curves cover frequency band (2.0–21.0 Hz) and show a good fitting between the observed and the calculated ones at all measured sites, proving the reliability of the inversion process performed in this work. In HVSR analysis, the E-W, N-S, and vertical components of microtremors are considered, and the ratio between the horizontal and the vertical components spectra is calculated, then the spectral ratio curves are produced. The predominant frequency (f0) and the peak amplitude (A0) of HVSR curve are reported for each site of observation. The inferred Vs profiles are used for calculating the average velocity value of shear wave up to 30 m depth (AVS30) which in turn employed in site classification at the investigated area. The results demonstrate that the parameter AVS30 varies between 248 m/s and 310 m/s in Suez city. The created site classification incorporates only one class (Class D), appearing no significant variation in the characteristics of the superficial and shallow soils in Suez city. The site predominant frequency (f0) ranges between 0.35 Hz and 5.0 Hz with relevant amplification (A0) between 1.6 and 4.2. These outputs represent a crucial site response model for future seismic hazard assessment and risk decrease studies in Suez area which is currently witnesses large investments and rapid land use planning.

Recording microtremor data is increasingly used in determining the site effect on earthquake ground motion especially in regions of moderate to low earthquake activity. In this study we used microtremor data to evaluate the effect of shallow sedimentary layers on earthquake ground motion in Quseir city which is located in the Red Sea coast, Egypt. The increasing in urbanization and land use planning, and the constructions of tourist resorts in Quseir city are the motivation of this work. The microtremor data was recorded by single seismic stations and by array of seismic stations at number of sites at Quseir city. The single stations microtremor data was analyzed based on the horizontal-to-vertical (H/V) spectral ratio technique in order to get the fundamental site frequency (f0) and its associated amplitude of ground motion (A0). The raw data of array was analyzed by using the SPatial AutoCorrelation (SPAC) technique to infer the shear-wave velocity structure beneath Quseir city. The results demonstrate that the value of f0 is ranging between 0.56Hz and 2.5Hz. The retrieved shear-wave velocity profile is characterized by significant interfaces at depths 20m, 50m, and 80m corresponding to velocities 170, 240, and 365 m/s respectively. The resulted f0 values were used in the calculation of bedrock depth at the measured sites. The parameters obtained in this study show a good agreement with the geological setting of Quseir city.

ABSTRACT Abu-Dabbab area is located in the western Red Sea coast at the Eastern Desert of Egypt. This area is characterized by the presence of different geological units and high seismic activity. It is one of the seismic source zones in Egypt. The purpose of this research is the detection of the structural setting and rock units by using the Helicopter Electromagnetic (HEM) technique and its relation to the seismic activity at Abu-Dabbab area. The spatial distribution of earthquakes recorded by the Egyptian National Seismic Network (ENSN) was used to study the seismic activity along the detected structures at the study area. The results of this work show that there is a resistivity variation over the study area. This variation may be due to the difference in the rock composition and its conductivities. In addition, the places of high resistivity values clearly show sites of faults. The sites of approximated values confirm the presence and expansion of the different rock units which are mixed in their electrical properties. The sites of the detected faults are identifying with the seismic activity of the area.

An aeromagnetic reconnaissance study is presented to delineate the subsurface structure and tectonic setting at the Fayoum-Cairo district, which experienced a damaging earthquake on October 12, 1992 of magnitude (M = 5.7). Analysis of aeromagnetic and seismicity data demonstrate three significant tectonic faults with trending to the NE-SW, NW-SE and E-W. The basement is uplifted in the northern and central parts with a depth of 1.3 km, and deepening in the southern part with a depth of 2.5 km. This is a seismically active zone and historically has experienced damaging earthquakes. In 1847, a damaging earthquake with maximum epicentral intensity (Modified Mercalli Intensity (MMI) = VII) was located there. On the eastern side, earthquake sources are well recognized at different locations. These sources created events of moderate size magnitude M < 5. The focal mechanisms of the major events from these sources are generally strike-slip with normal component. The focal mechanism of t...

It is well known that the local geological characteristics in terms of topographic setting and the existence of soft sediments over bedrock may affect earthquake waves and cause seismic amplification. These effects are called “site effects”. Microtremors which provide an efficient practical tool for site effects estimation were recorded at 43 sites in Beni Suef City, Egypt. The recorded seismic signals were analyzed using the Horizontal-to-Vertical Spectral Ratio (HVSR) method. The targeted site parameters are the fundamental frequency ( f0) and the corresponding amplitude of seismic waves ( A0). Selected H/V curves with clear peak frequency have been inverted to infer the S-wave velocity profile of the underlying sediments. Information about subsurface sediments needed for the inversion process was extracted from available boreholes data. Moreover, the estimated values of f0 and A0 have been used for a preliminary calculation of the seismic vulnerability index ( Kg) which represent...