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Geological map showing different formations and surface faults of the studied area (after EGSMA (1999)).
Source publication
The area of interest represents the industrial part of Ain El-Sokhna new port, located in the northwestern part of the seismically active Gulf of Suez zone. The main objective of the current study is to estimate the site characteristics of the area of interest in terms of the fundamental frequency and the corresponding peak amplitude using noise me...
Context in source publication
Context 1
... hills (e.g. Ataqa, Kaheleia, Um Zieta Mountains and El- Galala El-Bahariya plateau) and wadis (e.g. Wadi Ghweiba, Wadi El-Badaa and Wadi Hagoul) characterize the study area. Calcareous boulders and gravels cover these wadis. Most of them descend from Ataqa Mountain, Okheider Mountain and El-Galala El-Bahariya plateau (figure 2). According to Sadek (1926), Abdallah and Abdel Hady (1966), Abdallah (1993) and EGSMA (1999), the surface geology from the base to top can be briefly described as follows. (iii) Miocene rocks are composed of white limestone with coral reefs and Oyster fossils, a succession of marl, coarse sand and clay, white coarse sandstone, and a layer of dolomite and conglomerate. They exist below the southern margins of Ataqa Mountain and below the eastern margins of Kaheilia and Um Zieta Mountains, and they occupy the greatest part cropped out in the area and exposed on the sides of Wadi Hommath, Wadi El Naqa, Wadi Okheider, Wadi Ghweiba. Such rocks are separated from the old sediments by many faults (depicted in figure 2). (iv) Recent deposits, which covered the coastal plain and its wadis, represent the Quaternary in the area and the low areas below the surrounding mountains until they reach the shoreline. These deposits include alluvium, wadi deposits, coastal sand and ...
Citations
... The ambient seismic noise (microtremors) data have been used to estimate the site response. It gives a reliable and precise estimate of the fundamental frequency of the near-surface cover (Lermo et al., 1988;Nakamura 1989;Field and Jacob, 1995;Bard, 2000;Parolai et al., 2001Parolai et al., , 2002Mohamed et al., 2008;Mohamed, 2009;El-Husain et al., 2014). ...
In 2001, the earthquake monitoring center (EMC) at Sultan Qaboos University (SQU) started monitoring earthquakes that occur in and around the sultanate of Oman through 10 short-period stations. The number of monitoring stations grew to 20 broadband seismic stations between 2004 and 2011 deployed in different parts of the sultanate. In 2014, EMC-SQU began an extensive project for updating and improving the monitoring network by adding 6 broadband stations and establishing a strong motion network consisting of 67 monitoring stations. This provides a good opportunity to investigate the influences of the seismic source, path, and site effects in the ground motion, particularly in the near-source area. Such data are essential for improving seismic hazard maps and consequently seismic building codes and earthquake-resistant design. A wide site selection survey was carried out for the entire proposed stations taking into account the standard site selection criteria. In order to use the strong motion recordings at their full potential, information on the site response at the recording site is needed. So, site investigation at 25 stations in Muscat region was performed in terms of noise level, resonance frequency (using horizontal-to-vertical spectral ratio (HVSR) method), P-wave velocity (using shallow seismic refraction tomography (SRT) technique), and S-wave velocity (using multichannel analysis of surface waves (MASW) tool), in addition to the available geotechnical boreholes. The results reflect the site classification in the light of NEHRP/IBC standards and consequently the seismic hazard level at the ground surface.
... HVSR has proved to provide a 748 trustworthy Fo evaluation, but it is unsuccessful in estimating the amplification curves accurately (e.g. Theodulidis & Bard 1995;Mohamed et al. 2008). Koller et al. (2004) were implemented here to assure truthful experimental circumstances. ...
A site-specific probabilistic seismic hazard assessment (PSHA) was achieved in the area of special economic zone authority of Duqm, involving hazard evaluation at the bedrock conditions and assurance of potential site influence on seismic ground motion at the bedrock. Appropriate source and ground-motion prediction models were selected and seismic hazards were identified by means of 5% damped Uniform Hazard Spectra (UHS) for three return periods of 475, 975, and 2475 years. A logic-tree algorithm was used to study the influence of the epistemic uncertainties on the source models, earthquake recurrency and maximum magnitude, along with ground-motion prediction equations (GMPEs). The local geology effects were characterized by fundamental resonance frequency (Fo) using the horizontal-to-vertical spectral ratio technique and the soil amplification factors. The effects of soil were assessed using SHAKE91 for soil parameters defined by 55 geotechnical boreholes in conjunction with surveys of 2D multichannel analysis of surface waves (MASW) at 90 sites. Scaling was performed for selected strong-motion applying spectral matching technique to be used at the soil column bottom. Selection of such records is based on scenarios characterized by deaggregation of the PSHA results on the bedrock tops. The Duqm area mostly features low amplifications, below 1.3 for the considered spectrum. Surface ground-motion maps show low hazard values with Peak Ground Accelerations (PGA) vary between about 2 and 5% g for a 475-year return period. Although several sites are assessed to be susceptible to liquefy, liquefaction analyses indicate that surface ground motions for a 475-year return period are insufficient to produce liquefaction.
... Seismic hazard maps in terms of horizontal peak ground acceleration (PGA) and 5% damped spectral acceleration (SA) for 475-and 2475year return periods are presented at the nodes of 0.1°regular grid. At this stage, results could be complemented by comprehensive site characterization studies at important facilities (e.g., Mohamed et al. 2008;El-Hussain et al. 2013). This gives additional flexibility to decision makers and engineers to choose the suitable level of conservatism according to the significance of the project of interest. ...
Earthquake Monitoring Center (EMC) at Sultan Qaboos University (SQU) initiated evaluating the seismic hazard in the Sultanate of Oman in 2009. EMC has produced the first probabilistic and deterministic seismic hazard maps for Oman in 2012 and 2013, respectively. In the current study, the probabilistic seismic hazard assessment (PSHA) is revisited to provide an updated assessment of the seismic actions on the Sultanate. The present study has several advantages over its predecessor: using an updated homogeneous earthquake catalogue, recently developed seismic source model; inclusion of epistemic uncertainties for the source models, recurrence parameters, maximum magnitude, and more recent and applicable ground-motion prediction equations (GMPEs). Epistemic uncertainties were treated using a combination of the best available databases within a properly weighted logic tree framework. Seismic hazard maps in terms of horizontal peak ground acceleration (PGA) and 5% damped spectral accelerations (SA) at the bedrock conditions (VS = 760 m/s) for 475- and 2475-year return periods were generated using the classical Cornell-McGuire approach. Additionally, uniform hazard spectra (UHS) for the important population centers are provided. The results show higher values at the northern parts of the country compared to the hazard values obtained in the previous study.
... The surface geology of the Northwestern Gulf of Suez area as shown in " Fig.2" has been described by many authors such as [8][9][10] [11] [12]. These studies summarized the surface geology of the area as follows: (i)Eocene rocks which are divided into the middle and upper Eocene rocks: (A) the middle Eocene rocks are covering the northern part of the area and are represented by a succession of limestone in Okheider Mountain. ...
... We calculated the bulk's modulus in terms of Young's modulus and Poisson's ratio as follow [6]: K = E/3(1-2ơ) (8). In this work, Bulk's modulus (B) exhibits values from 0.74 GPa to 1.55 GPa in the first layer " Fig.10d" reflecting fairly competent material while, in the second layer, Bulk's modulus (E) ranges from 1.84 GPa to 2.97 GPa " Fig.11d" reflecting good competent material. ...
... Geological map of Northwestern Gulf of Suez area[8]. ...
The objective of the current investigations is to estimate the dynamic geotechnical properties necessary for evaluating the conditions of the subsurface in order to make better decisions for economic and safe designs of the proposed structures at a Steel RollingFactory, Ataqa Industrial Area, Northwestern Gulf of Suez, Egypt. To achieve this purpose, four seismic refraction profiles were conducted to measure the velocity of primary seismic waves (P-waves) and four profiles were conducted using Multichannel Analysis of Surface Waves (MASW) technique in the same locations of refraction profiles to measure the velocity of shear waves (S-waves). SeisImager/2D Software Package was used in the analysis of the measured data. Data processing and interpretation reflect that the subsurface section in the study area consists of two layers, the first layer is a thin surface layer ranges in thickness from 1 to 4 meters with P-wave velocity ranges from 924 m/s to 1247 m/s and S-wave velocity ranges from 530 m/s to 745 m/s. The second layer has a P-wave velocity ranges from 1277 m/s to 1573 m/s and the S-wave velocity ranges from 684 m/s to 853 m/s. Geotechnical parameters were calculated for both layers. Since elastic moduli such as Poisson’s ratio, shear modulus, Young’s modulus, and bulk’s modulus were calculated. Competence scales such as material index, stress ratio, concentration index, and density gradient were calculated also. In addition, the ultimate and allowable bearing capacities.
... Of all types of seismic waves, surface waves have the strongest energy with the highest signalto-noise ratio (S/N) making it a powerful tool for near surface site characterization. The most preferred technique in the recent past is MASW studies (Tokimatsu et al., 1992;Ohori et al., 2002;Paroli et al., 2004;.Kanli et al., 2006;Mohamed et al., 2008;Mohamed, 2009;Seshunarayana., 2011, Mohamed et al., 2012;Mohamed et al., 2013;Mohamed et al., 2016;El-Hussain et al., 2014;El-Hussain et al., 2015). In MASW technique , the field work is much easier and the measurement time is strongly reduced. ...
Shear-wave velocity-depth information plays a significant role in assessing earthquake hazard of any region. Further, it is required for most investigations of ground motion response to earthquakes in areas where significant soil cover exists. The thickness and velocity of geologic formations are the vital parameters above the bedrock that affect the frequency band of the ground motion that may be strongly amplified by the local site conditions. In view of this, shear-wave velocity assumes great importance in earthquake hazard assessment studies. The characteristics of shear-wave velocity profile were determined by multichannel analysis of surface waves (MASW) technique in as many as 99 sites over different geological units in parts of Muscat city in order to evaluate probable hazard if any. The variations of shear wave velocity down to depths of 5 m, 10 m, 15 m and 30 m, respectively are presented. However, the average shear wave velocities calculated down to a depth of 30 m (VS30) vary between 345 m/s and 1197 m/s. The high range of shear-wave velocity almost rules out the liquefaction potential due to earthquakes of moderate to high magnitude.
... where H and V denote the spectra of the horizontal (geometrical mean of H NS and H EW directions) and the vertical components, respectively. Many authors confirmed that Nakamura's (1989) technique is convenient to reliably estimate f o (e.g., Bard 1994, 1995;Lachet et al. 1996;Lebrun et al. 2001;Mucciarelli and Gallipoli 2001;Parolai et al. 2004;Mohamed et al. 2008;Mohamed 2009;Mohamed et al. 2013;Surve and Mohan 2010;El-Hussain et al. 2013). ...
It is well known that the effects of near-surface structures on ground shaking represent an important factor in earthquake ground motion amplification; in particular, soft sedimentary cover could strongly amplify the seismic motion. The parameters of the soft layer that controls the amplification most are the fundamental frequency and the shear-wave velocity. The frequency band of the ground motion that is affected by such factors depends on the thickness and the velocity of the sedimentary layers. In order to investigate and characterize the near-surface structures beneath Quriyat coastal city in the Sultanate of Oman, Nakamura’s technique which was characterized by the horizontal-to-vertical spectral ratio (HVSR) of the ambient noise measurements was used to estimate the fundamental frequency of the soft soil at 70 sites. The shear-wave velocity is an important tool in the design of buildings for site-specific conditions and is a much more diagnostic tool for engineering properties. The multichannel analysis of surface waves (MASW) was carried out at 40 sites at Quriyat City in order to evaluate the near-surface shear-wave velocities. The fundamental frequencies were found to be in the range of 2.0 Hz (occupying the coastal soft soil area) and 23.3 Hz (occupying the area close to the hard rock). The average shear-wave velocities down to 30 m depth (Vs30) ranged from 225 m/s (class D according to NEHRP standard for site classification and covering the coastal area) to 1058 m/s (class B covering the area in vicinity of hard rock). The results demonstrate that the HVSR of ambient vibrations were in a good agreement with the values of VS30. Areas of lower VS30 values exhibit lower fundamental frequency and cover areas with considerable soft soil thickness and vice versa.
... Nakamura (1989) found that the amplitude of the HVSR gives a reliable estimation of the fundamental frequency at the site of interest. Various sets of research confirmed that this technique gives a reliable estimation of the fundamental frequency of the soft soil (Ohmachi et al 1991, Lachet and Bard 1994, Lachet et al 1996, Lebrun 1997, Parolai et al 2004, Mohamed et al 2008, Surve and Mohan 2010. Therefore, the goal of the current research is to compare the depths established from the fundamental frequencies estimated using microtremor measurements, with the thickness determined using the shallow seismic refraction and MASW methods. ...
Integrated surface geophysical surveys were conducted along a 3 km line in the sabkha area at the Port of Duqm site in the Sultanate of Oman in order to model the thickness of the uppermost sabkha layer and to determine the existence of a paleo-channel in the area. The spatial location of the survey line was laid out by a geodetic land survey for accurate geophysical measurements. Three geophysical surveys, the shallow seismic refraction method, the 2D multichannel analysis of surface waves (MASW) and the horizontal-to-vertical spectral ratio (HVSR) survey, were conducted. Despite uncertainties that are known to be associated with each of the used methods, a good agreement was revealed between the geophysical results and data from three nearby boreholes in terms of thickness and seismic wave velocity variation. The results of the shallow seismic refraction and MASW methods show a section with three main layers; a near-surface layer with P-wave velocity varying from 300 m s−1 to 500 m s−1, S-wave velocity varying from 150 m s−1 to 350 m s−1 and thickness ranging from 2 m at the northwestern end to 10 m at the southeastern end. This low-velocity layer is interpreted as the sabkha formation. The second layer is characterized by P-wave velocity ranging from 1000 m s−1 to 1600 m s−1, S-wave velocities of 450 m s−1 to 600 m s−1 and thickness varying from 4 m to 8 m. The third layer shows P-wave velocity from 2200 m s−1 to 2700 m s−1 and a shear wave from 650 m s−1 to 850 m s−1. This could be considered as a soft rock layer. The fundamental frequencies indicated by the HVSR results at the southeastern part of the line close to the start point, where relatively thick recent alluvium deposits are present, are lower than those at the northwestern part towards the end point, where rocky outcrops of Tertiary limestone appeared. The results reflect the existence of a paleo-channel at the southeastern part of the profile in agreement with the geomorphological data.
... This means that the transfer function of surface layers may be estimated from the tremor on the surface only. In other words, the vertical tremor on the surface retains the characteristics of horizontal tremor of the substrate [4,20,21,27]. ...
Recent researchers have discovered microtremor applications for evaluating the liquefaction potential. Microtremor measurement is a fast, applicable and cost-effective method with extensive applications. In the present research the liquefaction potential has been reviewed by utilization of microtremor measurement results in Babol city. For this purpose microtremor measurements were performed at 60 measurement stations and the data were analyzed by suing Nakmaura’s method. By using the fundamental frequency and amplification factor, the value of vulnerability index (K
g
) was calculated and the liquefaction potential has been evaluated. To control the accuracy of this method, its output has been compared with the results of Seed and Idriss [1] method in 30 excavated boreholes within the study area. Also, the results obtained by the artificial neural network (ANN) were compared with microtremor measurement. Regarding the results of these three methods, it was concluded that the threshold value of liquefaction potential is K
g
= 5. On the basis of the analysis performed in this research it is concluded that microtremors have the capability of assessing the liquefaction potential with desirable accuracy.
... Several experimental studies (e.g., Lermo and Chavez-Garcia 1994;Theodulidis and Bard 1995;Malagnini et al. 1996;Konno and Ohmachi 1998;Zaslavsky et al. 2003;Parolai et al. 2004;Mohamed et al. 2008;Surve and Mohan 2010) found that the H/V technique provides reliable estimation of the fundamental frequency of soft deposits. In order to conduct seismic microzonation of Muscat city in terms of resonance frequency of the soil column, 459 field experiments using single-station microtremor measurements (Nakamura technique) were carried out (Fig. 3). ...
... The site response (transfer function) is evaluated through the geotechnical parameters (layer thicknesses, densities, P-wave velocities, shear wave velocities and damping factor of layers), that are obtained from both the available geotechnical boreholes and the seismic surveys (Mohamed, 2003(Mohamed, , 2009and Mohamed et al., 2008). The P-wave velocity is obtained from the seismic refraction survey and the S-wave velocity is deduced from the Multi-channel Analysis of Surface Waves (MASW) survey. ...
In order to quantify the near-surface seismic properties (P- and S-wave velocities, and the dynamic elastic properties) with respect to the depth at a specific area (6th of October club), we conducted a non-invasive and low cost active seismic survey. The primary wave velocity is determined by conducting a P-wave shallow seismic refraction survey. The dispersive characteristics of Rayleigh type surface waves were utilized for imaging the shallow subsurface layers by estimating the 1D (depth) and 2D (depth and surface location) shear wave velocities. The reliability of the Multi-channel Analysis of Surface Waves (MASW) depends on the accurate determination of phase velocities for horizontally traveling fundamental mode Rayleigh waves. Consequently, the elastic properties are evaluated empirically. The Vs30 (average shear wave velocity down to 30 m depth), which is obtained from the MASW technique, plays a critical role in evaluating the site response of the upper 30 m depth. The distribution of the obtained values of Vs30 through the studied area demonstrates site classes of C and D, according to the NEHRP (National Earthquake Hazard Reduction Program) and IBC (International Building Code) standards.
