The impact of subsurface geological structure on the groundwater occurrence using geophysical techniques in wadi El Kallabiyyah and wadi As Sabil,East Esna,Eastern Desert,Egypt

The present study aims to explain some hydrogeological problems that are related to geological setting in two wadis: El Kallabiyyah and As Sabil East Esna. For this purpose, land magnetic, vertical electrical soundings, and two-dimensional electrical resistivity imaging profiles were measured. The lithological succession comprises Upper Cretaceous to Quaternary deposits that rest on a Precambrian basement rock. The results of the interpretation of the land magnetic measurements in wadi El Kallabiyyah represent the depth to the basement rock which ranges from 260 to 660 m and increases towards the northeast trend, but in wadi As Sabil, there is a large basin at the center of the wadi with the recorded depth to the basement reaching 1,300 m due to the effect of two normal faults (F1 and F2). The results of the interpretation of the vertical electrical sounding and two-dimensional imaging confirmed the presence of these faults in wadi As Sabil. The results of the geoelectrical measurements in wadi El Kallabiyyah represented the water-bearing layer at the third unit that consists of sands, gravels, boulders, and clays. The presence of clay will affect the potentiality of a drilled well. For wadi As Sabil, the results of geoelectrical measurements led to the lower part of the second unit which acts as a water-bearing layer that consists of sands, boulders, gravels, and clays. It can be concluded that the best site for drilling wells in wadi El Kallabiyyah is at vertical electrical sounding no.5 with a total depth of not less than 230 m. In wadi As Sabil, the drilled wells must be concentrated at the center and the downstream.     

Uranium-rich opal from the Nopal I uranium deposit, Peña Blanca, Mexico: Evidence for the uptake and retardation of radionuclides

The Nopal I uranium deposit of the Sierra Peña Blanca, Mexico, has been the focus of numerous studies because of its economic importance and its use as a natural analog for nuclear-waste disposal in volcanic tuff. Secondary uranyl minerals such as uranophane, Ca[(UO₂)(SiO₃OH)]₂(H₂O)₅, and weeksite, (K,Na)₂[(UO₂)₂(Si₅O₁₃)](H₂O)₃, occur in the vadose zone of the deposit and are overgrown by silica glaze. These glazes consist mainly of opal A, which contains small particles of uraninite, UO₂, and weeksite. Close to a fault between brecciated volcanic rocks and welded tuff, a greenish silica glaze coats the altered breccia. Yellow silica glazes from the center of the breccia pipe and from the high-grade pile coat uranyl-silicates, predominantly uranophane and weeksite. All silica glazes are strongly zoned with respect to U and Ca, and the distribution of these elements indicates curved features and spherical particles inside the coatings. The concentrations of U and Ca correlate in the different zones and both elements inversely correlate with the concentration of Si. Zones within the silica glazes contain U and Ca in a 1:1 ratio with maximum concentrations of 0.08 and 0.15 at.% for the greenish and yellow glazes, respectively, suggesting trapping of either Ca₁U₁-aqueous species or -particles in the colloidal silica. X-ray photoelectron spectroscopy (XPS), Fourier-transform infra-red spectroscopy (FTIR), and oxygen-isotope ratios measured by secondary-ion mass spectrometry (SIMS) indicate higher U⁶⁺/U⁴⁺ ratios, higher proportions of Si-OH groups and lower δ¹⁸O values for the greenish silica glaze than for the yellow silica glaze. These differences in composition reflect increasing brecciation, porosity, and permeability from the center of the breccia pipe (yellow silica glaze) toward the fault (green silica glaze), where the seepage of meteoric water and Eh are higher.     

Current and turbulence measurements at the FINO1 offshore wind energy site: analysis using 5-beam ADCPs

We report concurrent measurements of ocean currents and turbulence at two sites in the North Sea, one site at upwind of the FINO1 platform and the other 200-m downwind of the Alpha Ventus wind farm. At each site, mean currents, Reynolds stresses, turbulence intensity and production of turbulent kinetic energy are obtained from two bottom-mounted 5-beam Nortek Signature1000s, high-frequency Doppler current profiler, at a water depth of approximately 30 m. Measurements from the two sites are compared to statistically identify the effects of wind farm and waves on ocean current variability and the turbulent structure in the water column. Profiles of Reynolds stresses are found to be sensible to both environmental forcing and the wind farm wake-induced distortions in both boundary layers near the surface and the seabed. Production of turbulent kinetic energy and turbulence intensity exhibit approximately similar, but less pronounced, patterns in the presence of farm wake effects.     

Implementation of viscoelastic mud-induced energy attenuation in the third-generation wave model,SWAN

The interaction of waves with fluid mud can dissipate the wave energy significantly over few wavelengths. In this study, the third-generation wave model, SWAN, was advanced to include attenuation of wave energy due to interaction with a viscoelastic fluid mud layer. The performances of implemented viscoelastic models were verified against an analytical solution and viscous formulations for simple one-dimensional propagation cases. Stationary and non-stationary test cases in the Surinam coast and the Atchafalaya Shelf showed that the inclusion of the mud-wave interaction term in the third-generation wave model enhances the model performance in real applications. A high value of mud viscosity (of the order of 0.1 m²/s) was required in both field cases to remedy model overestimation at high frequency ranges of the wave spectrum. The use of frequency-dependent mud viscosity value improved the performance of model, especially in the frequency range of 0.2–0.35 Hz in the wave spectrum. In addition, the mud-wave interaction might affect the high frequency part of the spectrum, and this part of the wave spectrum is also affected by energy transfer from wind to waves, even for the fetch lengths of the order of 10 km. It is shown that exclusion of the wind input term in such cases might result in different values for parameters of mud layer when inverse modeling procedure was employed. Unlike viscous models for wave-mud interaction, the inverse modeling results to a set of mud parameters with the same performance when the viscoelastic model is used. It provides an opportunity to select realistic mud parameters which are in more agreement with in situ measurements.     

Modeling of Recent Seismicity,Seismic Hazard and Seismotectonic Setting at the New Administrative Capital City Area,Egypt

Geotectonics - The new administrative capital city area in Egypt, planned to be constructed in the area between Cairo and Suez cities, is vulnerable to moderate and strong earthquakes, which are...