Conference Presentations by Raafat E Fat-Helbary
Probabilistic seismic hazard analysis in terms of peak ground acceleration (PGA) and spectral acc... more Probabilistic seismic hazard analysis in terms of peak ground acceleration (PGA) and spectral acceleration (SA) values was assessed for the Egyptian territory. Eighty-eight potential seismic sources (for shallow-and intermediate-depth seismicity) in and around Egypt were identified and characterized based on an updated and unified earthquake catalogue spanning the time period from 2200 B.C. until 2013. Earthquake recurrence rates were computed, from both instrumental and historical data, for the defined seismic sources. Six well-known ground-motion attenuation models were selected to predict the ground motion for the different tectonic environments in and around Egypt. Finally, a logic-tree approach was followed, after a sensitivity analysis, to consider the epistemic uncertainty in different inputs (b-value, maximum expected magnitude and ground-motion attenuation model). In the present study, we show the seismic hazard deaggregation results, in terms of distance and magnitude, for the most important cities in Egypt to help understanding the relative contributions of the different seismic sources. Seismic hazard deaggregation for PGA, 0.2, 1.0 and 2.0 s SA, for 10% probability of exceedance in 50 years (return period of 475 years), was computed in detail. The deaggregation graphs were drawn considering bins of 0.5 for magnitude and 25 km for distance. The mean and modal values of magnitude and distance, to identify the distribution of control earthquakes that contribute to exceedance of the considered SA level were also computed. In general, the results at most of the cities, indicate that the distance to the seismic sources which mostly contributes to the seismic hazard is mainly controlled by the nearby seismic sources (especially for PGA). However, the more distant events contribute more to the hazard for larger spectral periods (for 1.0 and 2.0 s SA). For instance, the control earthquake for Cairo has a moment magnitude (MW) values in the range 5.0-5.5 and a focal distance between 0 and 25 km for PGA, 0.2, and 1.0 s SA, whereas for 2.0 s the distance remains the same but the magnitude become 6.0-6.5. However, for Port Said (located along the Mediterranean Sea coast), values of 7.0-7.5 MW and 375-400 km for the control earthquake has been obtained for all spectral periods. A significant result of this type of work is that seismic hazard deaggregation provides useful data on the distance and magnitude of the contributing seismic sources to the hazard in a certain place, which can be applied to generate scenario earthquakes and select acceleration records for seismic design.
Papers by Raafat E Fat-Helbary
Journal of Applied Geophysics
Modeling Earth Systems and Environment, 2024
Shear-wave velocity is a soil mechanical property. It is the main cause of local ground-motion am... more Shear-wave velocity is a soil mechanical property. It is the main cause of local ground-motion amplification, and it is responsible for a large amount of the damage. Therefore, it is crucial to investigate the soil characteristics down to bedrock to investigate the potential site effect. In this study, seven points in Ras Samadai area have been chosen to be investigated using Multichannel Analysis of Surface Waves (MASW) and Shallow Seismic Refraction (SSR) as active seismic methods. Furthermore, the Frequency-Wavenumber (f-k) and Horizontal-to-Vertical Spectral Ratio (HVSR) techniques were used as passive techniques to obtain the subsurface seismic velocity models and evaluate the site effect beneath the investigated points. The shallow and deep 1-D shear wave velocity models have been obtained at the chosen points using the MASW and f-k approaches. Furthermore, the research area is divided into three main layers based on the seismic refraction approach. At certain cross-sections, there are clear variations in the layers thickness resulting from faults effect. The HVSR method displays two different kinds of curves: flat and one peak curves, due to the variation in impedance contrast between the bedrock and the overlying soil. Moreover, the obtained vulnerability index (Kg) indicates that there is low level of hazards could happen in the study area. Finally, the 2-D lithological models are created to delineate the underground fault lines and displays the lateral variations in lithological composition. This information is useful for the seismic hazard analysis in terms of ground response prediction at ground surface and soil column.
World Academy of Science, Engineering and Technology, International Journal of Civil and Environmental Engineering, 2016
World Academy of Science, Engineering and Technology, International Journal of Civil and Environmental Engineering, 2016
World Academy of Science, Engineering and Technology, International Journal of Civil and Environmental Engineering, 2016
Bulletin of the International Institute of Seismology and Earthquake Engineering, 1996
Land use planning has been used only recently as a method to mitigate losses due to earthquake ha... more Land use planning has been used only recently as a method to mitigate losses due to earthquake hazard. The most fundamental approach in land use planning is to simply avoid proposing development on lands that have seismic hazard. This approach is most applicable in raw land situations where land values are not high and coasts. For the northern part of Aswan High Dam Lake, the seismic microzonation map was developed. From the microzoning maps, the investigation area divided into four zones, in Zonel are not recommended for building construction, in Zones 2 and,3 development with special engineering solutions can be appropriate and Zone4 is more appropriate for development The objective of seismic microzonation of this area was to delineate the seismic hazards that could affect this area and to synthesize and present these data in a format that is useful to government agencies, city planners and the construction industry. The recommendation for land use planning policies relative to s...
Journal of African Earth Sciences, 2019
Abstract Due to the increasing in the population density, the restriction of the agricultural are... more Abstract Due to the increasing in the population density, the restriction of the agricultural areas and the scarcity of building's lands and their highly costs in Egypt, especially in Sohag province which led the officials and decision-markers to search for alternatives in the desert places to solve this problems. Therefore, New Akhmim area was proposed as a new site for constructing a new city. The main aim of this research is to delineate the engineering characteristic of the soil, identify of the bedrock depth and determine the subsurface structures and lithology of the investigated site. Great effort should be done to determine the depth to competent layer (bedrock) within the proposed site and correlate the results with the available boreholes. Complementary geophysical tool was implemented for the engineering designs in order to ensure stability of building construction and evade the shocking effects of building collapse later. Thus, electrical resistivity tomography (ERT) was undertaken on the present site for monitoring these subsurface engineering issues. The field geometry was made up of eight profiles using Wenner configuration. The data of the 2D resistivity tomography along these profiles with smallest electrode separation of 5 m were interpreted using Res2dinv software. The subsurface is characterized by three different resistivity zones, which were interpreted as gravel intercalated with coarse sands at the top, sand beneath it and shale beneath the sand layer. The ERT results were in consistent with the results of ten engineering boreholes drilling in the study area. The presence of shale was correlated to the cause of chronic differential settlements of some engineering structures like slickensides due to drying and wetting within the area. No serious structural features were detected as faults, karstification phenomena or caving. So the area is valid for construction proposes.
NRIAG Journal of Astronomy and Geophysics, 2019
Journal of African Earth Sciences, 2019
Russian Geology and Geophysics, 2019
Journal of African Earth Sciences, 2019
Geophysical Journal International, 2014
Acta Geodaetica et Geophysica Hungarica, 2006
In this study probabilistic methods have been applied for the estimation of ground motion severit... more In this study probabilistic methods have been applied for the estimation of ground motion severity at selected sites in 8 principal cities in Upper Egypt. A new comprehensive updated earthquake catalog is compiled from a variety of sources. It includes all earthquakes that occurred in Upper Egypt and adjacent regions in the period from 1900 to 2001. Seismic hazard estimates are derived from regional seismogenic zones that are based on interpretations and assumptions relating potential seismic activity to the seismotectonics of the region. The expected values of the horizontal component of PGA with 90 percent probability of not being exceeded in 50, 100 and 200 years of exposure period are calculated. Among the selected sites the highest potential ground motion is found at Aswan and Hurghada, while the lowest is at Luxor. A further seismic hazard curves for the selected sites are designed. The highest potential ground acceleration level is also found at Aswan and Hurghada, which are located relatively near to the Kalabsha area and Shadwan area respectively, where the seismic activity in both areas are considered relatively high, while the lowest is at Luxor and Assuit. Since these areas are proposed for development, application of these methods results in an honest representation of probabilities of earthquake ground shaking or other earthquake hazard can be used to make informed decisions on mitigating earthquake risks in the presence of uncertainty.
Acta Geodaetica et Geophysica Hungarica, 2006
ABSTRACT The study area lies in south Egypt on the west bank of the River Nile about 12 km north ... more ABSTRACT The study area lies in south Egypt on the west bank of the River Nile about 12 km north to the Aswan City. The aim of the present study is a trial to investigate subsurface structure conditions, to determine the dynamic characteristics of the subsurface rocks and to study the effect of the near earthquake activities on the proposed location of Aswan New City. In this study nineteen seismic refraction P- and S-waves profiles were conducted. The output results include velocities of P- and S-wave and the thickness of each layer. The bulk density of soil layers was calculated from determined P-wave values. The measured shear wave velocity and bulk density for each layer were used to compute the maximum shear modulus. These parameters for each layer are used as input data to compute the responses of horizontally layered soil profiles subjected to bedrock input motion from strong earthquake using EERA program. The obtained response values of soil layers are represented by the surface acceleration, from which response spectra with damping ratio of 5% are obtained, surface Fourier amplitude spectra, amplification ratio between rock outcrop and free surface, and the shear stresses and strains characteristics at the sublayer No. 2 in all selected profiles sites. The output of this study is very important for solving the problems, which associated with the construction of various civil engineering purposes and for earthquake resistance structure design.
Bulletin of the Seismological Society of America, 2016
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Conference Presentations by Raafat E Fat-Helbary
Papers by Raafat E Fat-Helbary