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Meghraoui M.,EOST IPG Strasbourg | Amponsah P.,GAEC | Ayadi A.,CRAAG | Ayele A.,Addis Ababa Institute of Technology | And 8 more authors.
Episodes | Year: 2016

We present the Seismotectonic Map of Africa based on a geological, geophysical and geodetic database including instrumental seismicity and re-appraisal of large historical events, and harmonization and homogenization of earthquake parameters in the catalogues. Although establishing the seismotectonic framework of the African continent is a difficult task, several previous and ongoing projects provide a wealth of data and outstanding results. The database of large and moderate earthquakes in different geological domains includes the coseismic and Quaternary faulting that reveals the complex nature of the active tectonics in Africa. The map benefits from previous works on local and regional seismotectonic maps that needed to be integrated with the lithospheric and upper mantle structures, seismic anisotropy tomography and gravity anomaly, into a continental framework. The synthesis of earthquake and volcanic studies obtained from the analysis of late Quaternary faulting and geodetic data will serve as a basis for hazard calculations and the reduction of seismic risks. The map will be useful for the seismic hazard assessment and earthquake risk mitigation for significant infrastructures and their socio-economic implications in Africa. The constant population increase and infrastructure growth in the continent that exacerbate earthquake risk justify the necessity of continuously updating this map.

ArRajehi A.,King Abdulaziz City for Science and Technology | McClusky S.,Massachusetts Institute of Technology | Reilinger R.,Massachusetts Institute of Technology | Daoud M.,Syrian National Earthquake Center | And 13 more authors.
Tectonics | Year: 2010

Five years of continuously recording GPS observations in the Kingdom of Saudi Arabia together with new continuous and survey-mode GPS observations broadly distributed across the Arabian Peninsula provide the basis for substantially improved estimates of present-day motion and internal deformation of the Arabian plate. We derive the following relative, geodetic Euler vectors (latitude (̊N), longitude (̊E), rate (̊/Myr, counterclockwise)) for Arabia-Nubia (31.7 ± 0.2, 24.6 ± 0.3, 0.37 ± 0.01), Arabia-Somalia (22.0 ± 0.5, 26.2 ± 0.5, 0.40 ± 0.01), Arabia-India (18.0 ± 3.8, 87.6 ± 3.3, 0.07 ± 0.01), Arabia-Sinai (35.7 ± 0.8, 17.1 ± 5.0, 0.15 ± 0.04), and Arabia-Eurasia (27.5 ± 0.1, 17.6 ± 0.3, 0.404 ± 0.004). We use these Euler vectors to estimate present-day stability of the Arabian plate, the rate and direction of extension across the Red Sea and Gulf of Aden, and slip rates along the southern Dead Sea fault south of the Lebanon restraining bend (4.5-4.7 ± 0.2 mm/yr, left lateral; 0.8-1.1 ± 0.3 mm/yr extension) and the Owens fracture zone (3.2-2.5 ± 0.5 mm/yr, right lateral, increasing from north to south; 1-2 mm/yr extension). On a broad scale, the Arabian plate has no resolvable internal deformation (weighted root mean square of residual motions for Arabia equals 0.6 mm/yr), although there is marginally significant evidence for N-S shortening in the Palmyride Mountains, Syria at ≤1.5 mm/yr.We show that present day Arabia plate motion with respect to Eurasia is consistent within uncertainties (i.e., ±10%) with plate tectonic estimates since the early Miocene when Arabia separated from Nubia. We estimate the time of Red Sea and Gulf of Aden rifting from present-day Arabia motion, plate tectonic evidence for a 70% increase in Arabia-Nubia relative motion at 13 Ma, and the width of the Red Sea and Gulf of Aden and find that rifting initiated roughly simultaneously (±2.2 Myr) along the strike of the Red Sea from the Gulf of Suez to the Afar Triple Junction, as well as along the West Gulf of Aden at 24 ± 2.2 Ma. Based on the present kinematics, we hypothesize that the negative buoyancy of the subducted ocean lithosphere beneath the Makran and the Zagros fold-thrust belt is the principle driver of Arabia-Eurasia convergence and that resisting forces associated with Arabia-Eurasia continental collision have had little impact on plate motion. © 2010 by the American Geophysical Union.

Rabeh T.,NRIAG | Rabeh T.,University of Lisbon | Miranda M.,University of Lisbon | Hvozdara M.,Slovak Academy of Sciences
Natural Hazards | Year: 2010

In this work, we attempt to quantify forces that result from the interaction between the induced Sq-variation currents in the Earth's lithosphere and the regional Earth's magnetic field, in order to assess its influence on the tectonic stress field and on seismic activity. The study area is the Sinai Peninsula, a seismically active region where both seismic and magnetic data are available. We show that both short-term and long-term magnetic changes correlate with the seismic activity extending to this area in other previous studies. We also analyze a set of large earthquakes and magnetic data from observatories around the world to deduce a relationship between earthquake magnitude and maximum distance up to which precursory variations of the magnetic field are observed. © Springer Science+Business Media B.V. 2009.

Atya M.A.,NRIAG | Oleg Hachay A.,Russian Academy of Sciences | Oleg Hachay Y.,Ural Federal University | El Said Ragab A.,NRIAG
Near Surface Geoscience 2012 | Year: 2012

The present work provides a technical procedure to estimate the geomechanical and geoelectrical parameters as key information of the dynamic state and stability of the massive structure. It involves the application of Control Source Electromagnetic "CSEM" approach developed by IGF UB RAS to image the ranked deformation levels in the massive structure. The Wide Profile System of Observation had been used to monitor the three component electromagnetic field along predefined measuring lines at Quarter 27 in the City of 15th of May, Helwan, Egypt. Four cycles of observation had been carried out in 2008, 2010, 2011, and 2012. The acquired data set had been subjected to analytical processing procedure to estimate the changes in the geotechnical parameters over time of observation. Interpreting the measured data concluded that the general dynamic state at the area is getting worse over the time, this is reflected in the crack's densities and positions, also on the changes in the lateral distribution of the geoelectric heterogeneity as indicator for water saturation. This is clearly evinced at profiles 2 and 5. Profile 7 represents a deformation case of instability close to destruction level, so that, it is recommended to annually monitor the massive structure beneath it.

Mohamed A.,NRIAG
Near Surface Geoscience 2014 - 20th European Meeting of Environmental and Engineering Geophysics | Year: 2014

Ground vibrations induced by blasting in the cement quarries are one of the fundamental problems in the quarrying industry and may cause severe damage to the nearby utilities and pipelines. This research paper presents the results of ground vibration measurements induced by blasting at the National Cement Company (NCC) southeast of Helwan city, Egypt. The aim of this study is to investigate the influence of the quarry blasts on the oil pipelines of SUMED Company. The seismic refraction for compressional waves and the shear wave velocity obtained from the Multi channel Analysis of Surface Waves (MASW) are used to evaluate the closest site of the two pipelines to the quarry blasts. The results demonstrate that, the closest site of the two pipelines is of class B, according to the International Building Code (IBC) and the safe distance to avoid any environmental effects is 650 m, following the deduced Peak Particle Velocity (PPV) and Scaled Distance (SD) relationship (PPV = 440.64 × SD-1.225) in mm/s and the Air over Pressure (Air Blast) formula (Air Blast = 152.87 × SD-0.071) in dB. In the light of the prediction analysis.

Zahran K.H.,NRIAG | Attya M.,NRIAG
2nd International Conference on Engineering Geophysics | Year: 2013

Kharga Oasis is the southernmost of five oases in the Western Desert of Egypt. The Oasis bears potential Nubian Sandstone Aquifer, which considered being the most bearing underground reservoir at Egypt. Agricultural and population development of this region suggests the importance of the evaluation of its water storage capacity. Satellite spatial and temporal gravity data have opened new perspectives on the Earth sciences and hydrological studies. The two sets of the satellite data have been utilized to study configuration and temporal water recharge capacity of underground basin reservoirs. The study shows set of faulting led to a complicated configuration of the underground sand basin. In addition, Monthly data from GRACE estimate the irregularities of the water income. Finally, the study pointed out the potentiality of using satellite spatial and temporal gravity data to study configuration and temporal water recharge capacity of underground basin reservoirs.

BIF from Umm Nar, Eastern Desert, Egypt is competitive for test of the geophysical gravity techniques in mineral exploration, including subsurface locating, mapping, and assessing high-density contrasts between host and mineralized rocks, and cost-effective methodological approach. The gravity measurements showed high anomalies of BIF and low anomalies of the metasedimentary country rock. Several results are in preparation. Recommendations for using other geophysical tools are taken into consideration for confirmation our results.

Salem A.S.K.,University of Leeds | Fairhead J.D.,GETECH | Aboud E.,NRIAG
72nd European Association of Geoscientists and Engineers Conference and Exhibition 2010: A New Spring for Geoscience. Incorporating SPE EUROPEC 2010 | Year: 2010

The Extended Tilt-depth method builds on the existing Tilt-depth method to remove one of its constraints - that of relying on the source model being a vertical contact. To achieve this, there is a need to go to the tilt of the local wavenumber, a second order derivative which is independent of structural index. The Extended Tilt-depth method is thus a new interpretation tool for the initial evaluation of high resolution aeromagnetic survey data. The method is tested using a theoretical model and a field example from the North Western Desert of Egypt. In the former, the method estimated the correct depth for the model. For the field data, The Extended Tilt-depth method successfully identifies a number of important tectonic elements known from geologic mapping and known areas of sedimentary basins. Further testing and application of this new method, using known models and field examples, is needed to fully appreciate its strengths and weaknesses. © 2010, European Association of Geoscientists and Engineers.

Pinto C.C.,National Laboratory of Energy and Geology | Carvalho J.P.,National Laboratory of Energy and Geology | Costa M.,National Laboratory of Energy and Geology | Rabeh T.,NRIAG | And 5 more authors.
72nd European Association of Geoscientists and Engineers Conference and Exhibition 2010: A New Spring for Geoscience. Incorporating SPE EUROPEC 2010 | Year: 2010

The Lisbon and Lower Tagus Valley area have suffered the effect of historical earthquakes that caused important damages and loss of lives. Some of these earthquake sources are local but they are still poorly known due to the difficulty in finding geological outcrops, together with low-slip rates and erosion/sedimentation processes that erase surface ruptures. Identification of seismogenic sources capable of producing large earthquakes from low magnitude instrumental seismicity has also proved unreliable in other areas of the world. Therefore, for a proper assessment of seismogenic sources for seismic hazard purposes we have used recently reprocessed and reinterpreted seismic reflection, potential-field data and overlaid relocated epicentres. Here we present a revised structural interpretation of the area based on seismic data and a basement map produced by magnetic modelling, 2D Euler deconvolution and trend analysis. This basement map, which greatly enlarges the seismic coverage of the study area, has shown new insights into deep-seated structures of the Lower Tagus Valley area and their relationship with seismicity. The information from fault parameters collected in this work will also help to locate the sources of historical events such as the 1909 Benavente earthquake using finite-element strong-motion simulation and comparison with observed seismic intensities. © 2010, European Association of Geoscientists and Engineers.

Mohammed H.M.,NRIAG | Ahmed M.K.M.,Cairo University | Owis A.H.,Cairo University
Advances in the Astronautical Sciences | Year: 2012

In this work we investigate the orbit-attitude perturbations of a rigid spacecraft due to the effects of several forces and torques. The spacecraft is assumed to be of a cylindrical shape and equipped with a charged screen with charge density ε. Clearly the main force affecting the motion of the spacecraft is the gravitational force of the Earth with uniform spherical mass. The effect of oblate Earth up to J2 is considered as perturbation on both the orbit and attitude of the spacecraft, where the attitude of the spacecraft is acted upon by what is called gravity gradient torque. Another source of perturbation on the attitude of the spacecraft comes from the motion of the charged spacecraft in the geomagnetic field. This motion generates a force known as the Lorentz force which is the source of the Lorentz force torque influencing the rotational motion of the spacecraft. In this work we give an analytical treatment of the orbital-rotational dynamics of the spacecraft. We first use the definitions of Delaunay and Andoyer variables in order to formulate the Hamiltonian of the orbit-attitude motion under the effects of forces and torques of interest. Since the Lorentz force is a non-conservative force, a potential like function is introduced and added to the Hamiltonian. We solve the canonical equations of the Hamiltonian system by successive transformations using a technique proposed by Lie and modified by Deprit and Kamel to solve the problem. In this technique we make two successive transformations to eliminate.

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