- Tsunami, Seismology (Engineering), Seismic Hazard, Seismology, (Arab J Geosci, Springer Publication, and 9 moreNHESS, Geophysical Journal International (GJI), (Geophys. J. Int, Pp. 653–661 ) DOI: 10.1007/s12517 010 0222 2, 1499–1509) DOI: 10.1111/j.1365 246X.2010.045, 1495–1511, Nat. Hazards Earth Syst. Sci, Acta Geophysica, and earthquakes in Pakistanedit
- Ph.d in applied geophysicsedit
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The Gulf of Aqaba is one of the most active places around Egypt, with several earthquake sequences having occurred there through ancient and modern times. In the last century, four earthquake sequences took place in the gulf (1983, 1990,... more
The Gulf of Aqaba is one of the most active places around Egypt, with several earthquake sequences having occurred there through ancient and modern times. In the last century, four earthquake sequences took place in the gulf (1983, 1990, 1993, and 1995). Recently, on 27 June 2015, a sequence of 96 earthquakes with local magnitudes ranging from 0.7 to 5.2 was recorded by the Egyptian National Seismological Network (ENSN). On 16 May 2016, another earthquake sequence started and continued for several consecutive days, with 95 events with local magnitudes ranging from 1.6 to 5.5 being centered south of the 27 June 2015 sequence. In this paper, we analyse the complete waveform and polarity data set of both earthquake sequences to determine their focal mechanisms and to update our knowledge of the stress field in the Gulf of Aqaba. Through the results obtained, we conclude that, the Gulf of Aqaba is affected by a primary structure of a left-lateral strike-slip fault with a minor normal component in most segments. Our study also infers the presence of a secondary structure, which is indicated to be a right-lateral strike-slip with a minor reverse component.
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In this contribution, new relationship between the fundamental site frequency and the thickness of soft sediments is obtained for many sites in Egypt. The Horizontal-to-Vertical Spectral Ratio (BH/V^) technique (known as Nakamura... more
In this contribution, new relationship between the fundamental site frequency and the thickness of soft sediments is obtained for many sites in Egypt. The Horizontal-to-Vertical Spectral Ratio (BH/V^) technique (known as Nakamura technique) can be used as a robust tool to determine the thickness of soft sediments layers overlaying bedrock from observations and measurements of seismic ambient noise data. In Egypt, numerous seismic ambient noise measurements have been conducted in several areas to determine the dynamic properties of soft soil for engineering purposes. At each site in each studied area, the fundamental site frequency was accurately estimated from the main peak in the spectral ratio between the horizontal and vertical component. Consequently, an extensive database of microtremor measurements, well logging data, and shallow seismic refraction data have been configured and assembled for the studied areas. New formula between fundamental site frequency (f 0) and thickness of soft sediments (h) is established. The new formula has been validated and compared with other formulas of earlier scientists, and the results indicate that the calculated depth and geometry of the bedrock surface using new formula are in a good agreement with well logs data and previously published seismic refraction surveys in the investigated sites.
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Egypt is located in the northeastern corner of Africa within a sensitive seismotectonic location. Earthquakes are concentrated along the active tectonic boundaries of African, Eurasian, and Arabian plates. The study area is characterized... more
Egypt is located in the northeastern corner of Africa within a sensitive seismotectonic location. Earthquakes are concentrated along the active tectonic boundaries of African, Eurasian, and Arabian plates. The study area is characterized by northward increasing sediment thickness leading to more damage to structures in the north due to multiple reflections of seismic waves. Unfortunately , man-made constructions in Egypt were not designed to resist earthquake ground motions. So, it is important to evaluate the seismic hazard to reduce social and economic losses and preserve lives. The probabilis-tic seismic hazard assessment is used to evaluate the hazard using alternative seismotectonic models within a logic tree framework. Alternate seismotectonic models, magnitude-frequency relations, and various indigenous attenuation relationships were amended within a logic tree formulation to compute and develop the regional exposure on a set of hazard maps. Hazard contour maps are constructed for peak ground acceleration as well as 0.1-, 0.2-, 0.5-, 1-, and 2-s spectral periods for 100 and 475 years return periods for ground motion on rock. The results illustrate that Egypt is characterized by very low to high seismic activity grading from the west to the eastern part of the country. The uniform hazard spectra are estimated at some important cities distributed allover Egypt. The deaggregation of seismic hazard is estimated at some cities to identify the scenario events that contribute to a selected seismic hazard level. The results of this study can be used in seismic microzonation, risk mitigation, and earthquake engineering purposes.
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In this study we computed recent seismicity and present kinematic regime in the northern and middle zones of Gulf of Suez as inferred from moment tensor settlings and focal mechanism of local earthquakes that happened in this region. On... more
In this study we computed recent seismicity and present kinematic regime in the northern and middle zones of Gulf of Suez as inferred from moment tensor settlings and focal mechanism of local earthquakes that happened in this region. On 18 and 22 of July, 2014 two moderate size earthquakes of local magnitudes 4.2 and 4.1 struck the northern zone of Gulf of Suez near Suez City. These events are instrumentally recorded by Egyptian National Seismic Network (ENSN). The earthquakes have been felt at Suez City and greater Cairo metropolitan zone while no losses were reported. The source mechanism and source parameters of the calculated events were considered by the near-source waveform data listed at very broadband stations of ENSN and supported by the P-wave polarity data of short period stations. The new settling method and software used deem the action of the source time function, which has been ignored in most of the program series of the moment tensor settling analysis with near source seismograms. The obtained results from settling technique indicate that the estimated seismic moments of both earthquakes are 0.6621E + 15 and 0.4447E + 15 Nm conforming to a moment magnitude Mw 3.8 and 3.7 respectively. The fault plan settlings obtained from both settling technique and polarity of first-arrival indicate the dominance of normal faulting. We also evaluated the stress field in north and middle zones of Gulf of Suez using a multiple inverse method. The prime strain axis shows that the deformation is taken up mainly as stretching in the E–W and NE–SW direction.
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We utilized the seismicity and the potential field data to study the tectonic deformation and to delineate the seismically active subsurface tectonic trends of El-Faiyum area. To accomplish these goals, we analyzed and interpreted the... more
We utilized the seismicity and the potential field data to study the tectonic deformation and to delineate the seismically active subsurface tectonic trends of El-Faiyum area. To accomplish these goals, we analyzed and interpreted the seismicity data, the reduced to pole total magnetic intensity, and the Bouguer anomaly maps. We also used the spatial distribution of the recent seismic events and the focal mechanism to outline the local seismic zones that control the seismicity of the study area and to determine the sense of the motion along the subsurface active faults. The focal mechanism of the recent seismic events and the interpreted subsurface tectonic faults from the potential field data reflect strike-slip movements with normal components along the subsurface active faults. The gravity and magnetic maps show a NE-SW regional trend with low gravity and magnetic values. The NE-SW regional trend extends across the whole area and could be related to the Pelusium Megashear fault. A NE-SW trend with high gravity and magnetic exists at the northern part and coincides with the Kattania Uplift and the basaltic flows in Gabal Qatrani area. The gravity and magnetic maps also reveal several local anomalies with different polarities, amplitudes, and extensions, which reflect anticlinal and synclinal structures on the basement surface. The seismotectonic map, generated by linking the basement structure map and the spatial distribution of the recent earthquake foci, reveals the dominant tectonic trends and the subsurface active faults.
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A moderate-sized earthquake of Mw 4.4 occurred in southwestern Saudi Arabia on 23 January 2014. The event is considered as the largest observed earthquake that has occurred in the epicentral area. To examine the seismogenic stress regime... more
A moderate-sized earthquake of Mw 4.4 occurred in southwestern Saudi Arabia on 23 January 2014. The event is considered as the largest observed earthquake that has occurred in the epicentral area. To examine the seismogenic stress regime and resolve the fault plane ambiguity, the hypocenter locations and focal mechanisms were determined using well recorded waveforms of the broadband stations operated by the Saudi Geological Survey. The current analysis included dataset consisting of mainshock and a total number of 113 well-located after-shocks. Focal mechanism solutions of the mainshock and fifteen aftershocks were determined. The focal mechanism solutions were inverted using stress tensor inversion. It indicates that the maximum compressive stress, σ 1 , has a nearly shallow plunge (11.8°) of ESE orientation and minimum compressive stress, σ 3 , has a shallow plunge (0.3°) toward NNE. Our results obtained from precise earthquake locations, focal mechanism solutions and stress tensor inversion reveal dextral strike-slip faulting over the ENE-WSW striking plane. The analysis of Coulomb failure stress emphasized the causative fault of the 2014 Jizan earthquake sequence. The active fault implies a reactivation of a high-angle fault, buried in the Precambrian basement, which is conjugate to the Red Sea spreading axis and NNW-SSE Najd fault system. The present study provided an impetus toward understanding the seismogenic stress regime in a virgin area.
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We estimated moment tensor and centroid depth of eight small/moderate local earthquakes occurred between 2011 and 2013 in the northern Red Sea Triple Junction using a moment tensor inversion of near-source waveform data recorded by very... more
We estimated moment tensor and centroid depth of eight small/moderate local earthquakes occurred between 2011 and 2013 in the northern Red Sea Triple Junction using a moment tensor inversion of near-source waveform data recorded by very broad-band stations of the Egyptian National Seismic Network (ENSN). We also estimated the focal mechanism using the P-wave polarity data set and then compared it with the moment tensor inversion results. The moment tensor solutions are consistent with the focal mechanism obtained from the P-wave polarity data. We also estimated the stress field in the study area using the Multiple Inverse Method (MIM). Our results indicate that the axis of the minimum principal stress is a nearly horizontal NE-SW direction, while the axis of the maximum principal stress is nearly vertical. The direction of the minimum principal stress is consistent with the opening direction of the northern Red Sea zone, where the southern part of Gulf of Suez is currently under an extensional stress field with a NE-SW trending horizontal extension. These results are compatible with the kinematics of the Red Sea-Gulf of Suez rift.
Recording ambient noise at the surface is increasingly used for the assessment of site response and has become a fundamental task for seismic risk reduction in urbanized areas. Methods based on the measurement of seismic noise, which... more
Recording ambient noise at the surface is increasingly used for the assessment of site response and has become a fundamental task for seismic risk reduction in urbanized areas. Methods based on the measurement of seismic noise, which typically are fast, non invasive, and low cost, have become a very attractive option in microzonation studies. In the current work, we use the ambient noise recordings collected by single seismic stations and two‐dimensional arrays to determine the response of the near-surface soil at the two touristic cities of Hurghada and Safaga which are located at the Red Sea coast in Egypt. Based on the horizontal-to-vertical (H/V) spectral ratio Nakamura's technique, recordings of the single stations are analyzed to estimate the fundamental site frequency (f 0). Using the raw noise signals recorded by two arrays, we present a joint inversion scheme for surface wave dispersion curves. In particular, the Rayleigh wave dispersion curves and the H/V curves are combined in a joint inversion procedure. We present inversion procedure based on the computation of high-frequency correlation functions between arrays' stations. The calculation of Rayleigh wave phase velocities is based on the frequency-domain SPatial AutoCorrelation (SPAC) and frequency-wavenumber (f-k) methods. Constitutively, a tomographic inversion of the travel-times estimated for each frequency is performed, allowing the vertically varying 1-D shear wave velocity structure below the array to be retrieved. Following the relationship between resonance frequency (f 0) and thickness of sediments, the thickness of unconsolidated sediments at the investigated sites are determined.
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A hybrid empirical method is proposed to simulate broadband ground-motion that combines the stochastic method for finite faults and the k-2 slip model. The utilized approach, firstly, subdivides the fault plane into a number of subfaults.... more
A hybrid empirical method is proposed to simulate broadband ground-motion that combines the stochastic method for finite faults and the k-2 slip model. The utilized approach, firstly, subdivides the fault plane into a number of subfaults. Secondly, k-2 slip model characterizing higher wave number of slip distribution is used to account for the earthquake source effect. Influences from all subfaults are then empirically attenuated to the observation sites, where they are summed using the stochastic method for finite faults to produce the synthetic acceleration time history. To validate the reliability of the proposed method to predict earthquake ground-motion in Egypt, the 1992 west Cairo earthquake, is chosen as a case study. Source parameters for the 1992 earthquake estimated by five writers are utilized to generate the k-2 slip model to account for the source effect. The bedrock acceleration time histories on Kottamya (KEG) broadband seismic station are predicted and compared with observed records at the same site. Compared synthetic with observed data showing that, despite the neglected site-effects, the complexities of measured waveforms are relatively well reproduced. Accordingly, the proposed approach can be easily applied in any future earthquake engineering and seismic hazard assessment studies.
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In the current work, we constructed new comprehensive standard seismic noise models and 3D temporal-spatial seismic noise level cubes for Morocco in northwest Africa to be used for seismological and engineering purposes. Indeed, the... more
In the current work, we constructed new comprehensive standard seismic noise models and 3D temporal-spatial seismic noise level cubes for Morocco in northwest Africa to be used for seismological and engineering purposes. Indeed, the original global standard seismic noise models published by Peterson (1993) and their following updates by Astiz and Creager (1995), Ekström (2001) and Berger et al. (2003) had no contributing seismic stations deployed in North Africa. Consequently, this preliminary study was conducted to shed light on seismic noise levels specific to northwest Africa. For this purpose, 23 broadband seismic stations recently installed in different structural domains throughout Morocco are used to study the nature and characteristics of seismic noise and to create seismic noise models for Morocco. Continuous data recorded during 2009, 2010 and 2011 were processed and analysed to construct these new noise models and 3D noise levels from all stations. We compared the Peterson new high-noise model (NHNM) and low-noise model (NLNM) with the Moroccan high-noise model (MHNM) and low-noise model (MLNM). These new noise models are comparable to the United States Geological Survey (USGS) models in the short period band; however, in the period range 1.2 s to 1000 s for MLNM and 10 s to 1000 s for MHNM display significant variations. This variation is attributed to differences in the nature of seismic noise sources that dominate Morocco in these period bands. The results of this study have a new perception about permanent seismic noise models for this spectacular region and can be considered a significant contribution because it supplements the Peterson models and can also be used to site future permanent seismic stations in Morocco.
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To obtain the characterized source model for prediction of strong ground motions, the ground motion generation area and rupture geometry of an inland crustal earthquake from near-source ground motion records has been estimated. An... more
To obtain the characterized source model for prediction of strong ground motions, the ground motion generation area and rupture geometry of an inland crustal earthquake from near-source ground motion records has been estimated. An earthquake, with a magnitude of 4.3 ML and a focal depth of 18 km occurred on September 3, 2015 at 30.45N, 28.44E in the Western Desert of Egypt about 60 km south of El-Dabaa city. This earthquake is the first instrumentally recorded earthquake occurring in this area in several decades. The waveform data of this event has been used for source characterization and ground motion modeling. The present work describes the results of a preliminary study conducted to obtain fault plane solutions of this earthquake from waveform inversion and P-wave polarity. For this purpose, the source parameters related to the strong ground motion were estimated by waveform data and first arrivals recorded by the Egyptian National Seismic Network (ENSN) are used to arrive at focal mechanism solutions. Fault plane solutions for the main shock indicate strike-slip motion. One nodal plate strikes about 330°, is nearly vertical, and indicates right lateral slip. The other nodal plane strikes about 240°, dips very steeply NW, and indicates left lateral slip. Also the peak ground acceleration (PGA) at the El-Dabaa site has been simulated by taking into account an accurate estimation of the source characterization, the path attenuation model, and site amplification. The results have been validated using an actual recording of PGA at one ENSN station that recorded strong ground motion.
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Research Interests:
In this study, an integrated multi-channel analysis of Surface Waves (MASW) technique is applied to explore the geotechnical parameters of subsurface layers at the Zafarana wind farm. Moreover, a seismic hazard procedure based on the... more
In this study, an integrated multi-channel analysis of
Surface Waves (MASW) technique is applied to explore the
geotechnical parameters of subsurface layers at the Zafarana
wind farm. Moreover, a seismic hazard procedure based on the
extended deterministic technique is used to estimate the seismic
hazard load for the investigated area. The study area includes
many active fault systems along the Gulf of Suez that cause
many moderate and large earthquakes. Overall, the seismic activity
of the area has recently become better understood following
the use of new waveform inversion method and software to
develop accurate focal mechanism solutions for recent recorded
earthquakes around the studied area. These earthquakes resulted
in major stress-drops in the Eastern desert and the Gulf of Suez
area. These findings have helped to reshape the understanding of
the seismotectonic environment of the Gulf of Suez area, which
is a perplexing tectonic domain. Based on the collected new
information and data, this study uses an extended deterministic
approach to re-examine the seismic hazard for the Gulf of Suez
region, particularly the wind turbine towers at Zafarana Wind
Farm and its vicinity. Alternate seismic source and magnitudefrequency
relationships were combined with various indigenous
Surface Waves (MASW) technique is applied to explore the
geotechnical parameters of subsurface layers at the Zafarana
wind farm. Moreover, a seismic hazard procedure based on the
extended deterministic technique is used to estimate the seismic
hazard load for the investigated area. The study area includes
many active fault systems along the Gulf of Suez that cause
many moderate and large earthquakes. Overall, the seismic activity
of the area has recently become better understood following
the use of new waveform inversion method and software to
develop accurate focal mechanism solutions for recent recorded
earthquakes around the studied area. These earthquakes resulted
in major stress-drops in the Eastern desert and the Gulf of Suez
area. These findings have helped to reshape the understanding of
the seismotectonic environment of the Gulf of Suez area, which
is a perplexing tectonic domain. Based on the collected new
information and data, this study uses an extended deterministic
approach to re-examine the seismic hazard for the Gulf of Suez
region, particularly the wind turbine towers at Zafarana Wind
Farm and its vicinity. Alternate seismic source and magnitudefrequency
relationships were combined with various indigenous
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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... more
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.