On the development of a seismic source zonation model for seismic hazard assessment in western Saudi Arabia

A new seismic source model has been developed for the western part of the Arabian Peninsula, which has experienced considerable earthquake activity in the historical past and in recent times. The data used for the model include an up-to-date seismic catalog, results of recent studies of Cenozoic faulting in the area, aeromagnetic anomaly and gravity maps, geological maps, and miscellaneous information on volcanic activity. The model includes 18 zones ranging along the Red Sea and the Arabian Peninsula from the Gulf of Aqaba and the Dead Sea in the north to the Gulf of Aden in the south. The seismic source model developed in this study may be considered as one of the basic branches in a logic tree approach for seismic hazard assessment in Saudi Arabia and adjacent territories.     

Detecting temporal shoreline changes and erosion/accretion rates,using remote sensing,and their associated sediment characteristics along the coast of North Sinai,Egypt

The variation during 15 years in the shoreline along the North Sinai coast has been determined by analysing TM and ETM true colour Landsat images from 1986 to 2001. The analyses identified erosion and accretion patterns along the coast. The shoreline has advanced west of El Bardawil inlet1, El Bardawil inlet2, and El Arish Harbour, where the wave-induced littoral transport has been halted by jetty construction and beach growth rates are 20,681, 69,855 and 20,160 m²/year, respectively. On the downdrift side of the constructed jetties to the east, the shoreline is retreating and beaches erode at rates of −71,710, −69,968, and −11,760 m²/year, respectively. Sedimentological analyses of beach sediment samples have indicated selective transport of heavy minerals according to their densities and grain sizes. A general correspondence has been found between variation in grain size, sorting and heavy-mineral content of beach sand and the patterns of shoreline changes.     

Shear wave velocity as function of cone penetration resistance and grain size for Holocene-age uncemented soils: a new perspective

For feasibility studies and preliminary design estimates, field measurements of shear wave velocity, V _s, may not be economically adequate and empirical correlations between V _s and more available penetration measurements such as cone penetration test, CPT, data turn out to be potentially valuable at least for initial evaluation of the small-strain stiffness of soils. These types of correlations between geophysical (Vs) and geotechnical (N-SPT, q _c-CPT) measurements are also of utmost importance where a great precision in the calculation of the deposit response is required such as in liquefaction evaluation or earthquake ground response analyses. In this study, the stress-normalized shear wave velocity V _s1 (in m/s) is defined as statistical functions of the normalized dimensionless resistance, Q _tn-CPT, and the mean effective diameter, D ₅₀ (in mm), using a data set of different uncemented soils of Holocene age accumulated at various sites in North America, Europe, and Asia. The V _s1–Q _tn data exhibit different trends with respect to grain sizes. For soils with mean grain size (D ₅₀) < 0.2 mm, the V _s1/Q _tn ^0.25 ratio undergoes a significant reduction with the increase in D ₅₀ of the soil. This trend is completely reversed with further increase in D ₅₀ (D ₅₀ > 0.2 mm). These results corroborate earlier results that stressed the use of different CPT-based correlations with different soil types, and those emphasized the need to impose particle-size limits on the validity of the majority of available correlations.     

Calcareous nannofossil biostratigraphy of the Paleocene at the Misheiti section,East Central Sinai,Egypt

Integration of calcareous nannofossil data, δ¹³C and δ¹⁸O values, and carbonate contents of the lower Paleocene–upper Paleocene sequence that crops out at the Misheiti section, East Central Sinai, Egypt, were used to denote the Danian/Selandian (D/S) and Selandian/Thanetian (S/T) stage boundaries. The study interval belongs to the Dakhla and Tarawan formations. Four calcareous nannofossil zones (NP4, NP5, NP6, and NP7/8) were recognized. The base of the Selandian Stage is tentatively placed at the lowest occurrences (LOs) of taxa ascribable to the second radiation of fasciculiths (i.e., Lithoptychius janii). This level is marked by a sudden drop of δ¹³C and δ¹⁸O values and carbonate content. No distinctive lithological changes were observed across the D/S boundary at the study section. A hiatus at the NP5/NP6 zonal boundary is indicated by the condensation of zones NP5 and NP6.The base of the Thanetian is placed at the base of Zone NP7/8 at the lithological change observed in correspondence to the boundary between the Dakhla and Tarawan formations. The δ¹³C and δ¹⁸O values abruptly decrease slightly above the base of Zone NP7/8. No consistent variations in the carbonate contents were recorded within Zone NP6 or across the NP6/NP7/8 zonal boundary.     

Natural and anthropogenic influences in the northeastern coast of the Nile delta,Egypt

Landsat enhanced thematic mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret coastal changes in the zone between Kitchener drain and Damietta spit in the northeastern Nile delta, previously recognized as a vulnerable zone to the effects of any sea level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km2 to the agricultural deltaic land. About 48 km2 of backshore flats, marshes, salt pans and Manzala lagoon have been converted to productive fish farms. The main urban centers have expanded; nearly 12.1 km² have been added to their areas, and new urban centers (Damietta harbor and the New Damietta city) with total area reach of ~35.3 km² have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As a consequence of human activities, the size of Manzala lagoon has been reduced to more than 65%. Shoreline changes have been determined from beach profile survey (1990–2000), and comparison of 1955 aerial photographs and ETM satellite image of 2002 reveal alongshore patterns of erosion versus accretion. The short-term rate of shoreline retreat (1990–2000) has increased in the downdrift side of Damietta harbor (≃14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwaters system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures.     

Distribution and Influence of Iron Phases on the Physico—Chemical Properties of Phyllosilicates

Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD,DTA,dissolution analysis(DCB),IR,Moessbauer and X-band Electron Spin Resonance(ESR) spectroscopies.The purity of the samples and the degree of structural order were determined by XRD.The location of Fe in the octahedral sheet is characterized by absorption bands at-875cm^-1 assigned as Al-OH-Fe which is present after chemical dissolution of free iron.The Moessbauer spectra of these clays sow two doublets with isomer shift and quadrupole splitting typical of octahedral coordinated Fe^3 ,in addition to third doubler with hyperfine parameter typical of Fe^2 in the spectra of Abu-Had kaolinite (H)sample.6-lines magnetic hyperfine components which are consistent with those of hematite are confirmed in the spectra of both Isel and Rish kaolinite samples.Goethite was confirmed by both IR and DTA.Multiple nature of ESR of these clays suggested structural Fe in distorted octaedral symmetry and as non-structural Fe.Little dispersion and low swelling indices as well as incomplete activaiton of investigated montmorillonite samples by NaCO3 appear to be due to incomplete disaggregation of montmorillonite particles.This can be explained by the ability of Fe-gel to aggregate the montmorillonite into pseudo-particles and retard the rigid-gel structure.However,extraction of this ferric amorphous compound by dithonite treatment recovers the surface properties of the montmorillonite samples.On the other hand,amounts and site occupation of Fe associated with kaolinite samples show a negative correlation with the parameters used to describe the degree of crystalline perfection,color,brightness and vitrification range of these kaolinite samples.     

Long-term behaviour of three well-known flare stars of the UV Ceti type

Long-term changes in two flare stars, EV Lac and BY Dra, have been detected by Mavridiset al. (1982). These long cyclic periods have been registered in theB-band at their quiescent-state luminosity as well as at their flare activity. Those observational data of the two previously mentioned flare stars as well as another observational data of the flare star, UV Cet, at its flare activity were submitted to our computer programme for periodicity detection excluding cyclic periods which have amplitudes less than tenth magnitude for great significance. Some of our results coincided with the long cyclic periods detected by Mavridiset al. (1982) while the remainder of our results have had no complete coincidence with those registered by Mavridiset al. (1982).