The role of geophysical and seismological data in evaluating the subsurface structures and tectonic trends of Nile Delta, Egypt

In the present study, the Bouguer, aeromagnetic, and seismological data analysis for Nile Delta including the Greater Cairo region and its surroundings was used to examine and trace the tectonic framework for some deep-seated faults (mostly normal faults with a small strike–slip component) and their orientation, on which most earthquakes have occurred. The new tilt derivative (TDR) geophysical map and Euler deconvolution presented here can be used to trace the structural relationships and their depth investigations across the entire region. Generally, most of the Euler deconvolution results especially from the gravity map were well coincided with the location of contacts derived by TDR particularly NNW to NS, EW, and NE trended structures. The depths to the gravity or magnetic sources, and the locations of the contacts of density contrast were estimated. Results of the Euler deconvolution method suggested that, in the southeastern part of the area, the basement could be observed to be shallow and has become deeper beneath the northern part. Furthermore, the resulting structural map of this study is well correlated with previous geological and seismological data analyses. At least two sets of predominant faults are suspected, faults with a NNW strike (Clysmic trend) which are particularly felt in the southern portion of the Delta, and some of them give it the shape of a “graben like structure.” Another parallel set of faults, having NE–SW strike (Pelusium trend), was also obvious in the southern part between Cairo and Suez cities (at Abu Zabal area). The evaluated trending faults (NNW–SSE or NE–SW) are intersecting with predominant major WNW–ESE to E–W (Tethys trend) striking faults. These intersections may generate more additional seismic pulses and consequently increase the seismic activity for these structures. However, minor NW (Najd Fault System) is obvious in the TDR magnetic map, whereas less attendance NS (East African trend) structural trends are evident in the TDR gravity map. Moreover, it could be said that the southeastern portion of the Nile Delta (especially the eastern portion of Greater Cairo) is affected by highly tectonic fault systems. Finally, a new tectonic map was also evaluated from the resulting structural map, which helps to quantify different structural patterns (faults and/or contacts), and their relations with the regional tectonic trends are discussed.     

Structural and geomorphic features accommodating groundwater of Al-Madinah City, Saudi Arabia

Al-Madinah City is located in the western part of Saudi Arabia on the Arabian Shield. The area underwent several tectonic events that developed its structural and geomorphic features, such as the Infracambrian Najd strike-slip faults, development of the Cenozoic basaltic flows of Northern Harrat Rahat, and Cenozoic N–S and E–W transtensional faults, related to the Red Sea rifting. These successive events formed a deltaic-shaped basin of Al-Madinah. The Al-Madinah basin is part of a 400?×?150-km² Wadi Qanah–Al-Hamd watershed, which exhibits mainly parallel drainage pattern. Sub-basins, within the main basin, exhibit trellised and radial drainage patterns. The trellised drainage pattern reflects control of the Cenozoic faults, whereas the radial drainage pattern reflects volcanic-related system. Rotation of the Arabian Plate after several extensional events that lead to the opening of the Red Sea influenced the drainage flow to be going from east to west. This geological history that include eruption, normal faulting, and erosion prior to and during the Red Sea rifting formed relief inversion geomorphology of Tertiary basalts that cap Precambrian rocks of the Ayr and Jammah Mountains in western Al-Madinah. The groundwater in the central area is part of the northern Harrat Rahat basaltic aquifer in which the groundwater level rises up in the central area due to the blocking of groundwater flow by constructions below the central area and due to reduced groundwater abstraction. Building a dam 60 km northwest of Al-Madinah would preserve more surface water than the Al-Bayda dam, in which all main valleys join in at the suggested location.     

SARAL/AltiKa Wind and Wave Products: Monitoring,Validation and Assimilation

SARAL/AltiKa surface wind speed (WS) and significant wave height (SWH) measurements are monitored and validated against operational European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric and wave model results in addition to available in-situ observations to access their suitability for various applications, especially SWH data assimilation. The quality of SWH is very high while that of WS is very good except for an underestimation of high wind speeds. The impact of assimilating SWH in the ECMWF Integrated Forecast System was assessed using several numerical experiments. The results show positive impact. Operational assimilation of SWH at ECMWF model is part of the forthcoming model change.     

Divisional morphogenesis in the marine ciliate Anteholosticha manca (Kahl, 1932) Berger, 2003 (Ciliophora: Urostylida)

The cortical development and macronuclear evolution of the marine hypotrichous ciliate Anteholosticha manca, collected from the coastal waters near Qingdao, China, were investigated using the protargol impregnation method. The morphogenesis of A. manca is generally typical for the genus, and can be characterized as the following features ： （ 1 ） in the proter, a new oral primordium is formed on the bottom （beneath the pellicle） of the buccal cavity, disorganization of the parental undulating membranes do not contribute to the formation of this primordium ; （2） FVT-cirral anlagen in both dividers develop independently, and very likely only a few midventral cirri join in the formation of these primordia; （ 3 ） both marginal row and dorsal kinety anlagen develop intrakinetally within the parental structure; （4） at the middle stage, macronuclear segments fuse together to form a single mass as observed in most of its related forms.     

Orbits of colliding galaxies

A simple, semi-analytic method is developed for obtaining the orbits of galaxies undergoing fast collisions in which the galaxies are represented by Plummer models. The results are found to agree fairly well with those of N-body simulations.A simple formula for obtaining the angle of deflection is deduced. The maximum angle of deflection is 180° forV _p/V _esc(p)=1.00, about 36° forV _p/V _esc(p)=1.50, and about 18° forV _p/V _esc(p)=2.00, whereV _p is the velocity at closest approachp, andV _esc(p) is the parabolic velocity of escape atp. The angle of deflection of a pair of colliding elliptical galaxies without halos is about twice that for a pair of galaxies with halos for the same relative velocity at infinite separation.     

Slow-Mode Oscillations and Damping of Hot Solar Coronal Loops

The effect of temperature inhomogeneity on the periods, their ratios (fundamental versus first overtone), and the damping times of the standing slow modes in gravitationally stratified solar coronal loops are studied. The effects of optically thin radiation, compressive viscosity, and thermal conduction are considered. The linearized one-dimensional magnetohydrodynamic (MHD) equations (under low-?? condition) were reduced to a fourth-order ordinary differential equation for the perturbed velocity. The numerical results indicate that the periods of nonisothermal loops (i.e., temperature increases from the loop base to apex) are smaller compared to those of isothermal loops. In the presence of radiation, viscosity, and thermal conduction, an increase in the temperature gradient is followed by a monotonic decrease in the periods (compared with the isothermal case), while the period ratio turns out to be a sensitive function of the temperature gradient and the loop lengths. We verify that radiative dissipation is not a main cooling mechanism in both isothermal and nonisothermal hot coronal loops and has a small effect on the periods. Thermal conduction and compressive viscosity are primary mechanisms in the damping of slow modes of the hot coronal loops. The periods and damping times in the presence of compressive viscosity and/or thermal conduction dissipation are consistent with the observed data in specific cases. By tuning the dissipation parameters, the periods and the damping times could be made consistent with the observations in more general cases.     

The effect of density stratification on the resonant absorption of MHD waves in coronal loops

The standing quasi-modes of the ideal magnetohydrodynamics (MHD) in a zero-β cylindrical magnetic flux tube that undergoes a longitudinal density stratification and radial density structuring are considered. The radial structuring is assumed to be a linearly varying density profile. Using the relevant connection formulae of the resonant absorption, the dispersion relation for the fast MHD body waves is derived and solved numerically to obtain both the frequencies and damping rates of the fundamental and first-overtone,   k = 1, 2  , modes of both the kink  ( m = 1)  and fluting  ( m = 2)  waves, where k and m are the longitudinal and azimuthal mode numbers, respectively.     

Ocellar lamprophyre dyke bearing mineralization,Wadi Nugrus,Eastern Desert,Egypt: Geology,mineralogy and geochemical implications

The ocellar lamprophyre dyke (ENE-WSW) is recorded at Wadi Nugrus, Eastern Desert, Egypt. It cuts porphyritic biotite granites and varies in thickness from 0.5 to 1.5 m and up to 3 km in length. The lamprophyre dyke has been altered, and it is characterized by porphyritic and panidiomorphic textures with plagioclase, olivine, and augite constituting the porphyritic phase in a fine groundmass of the same composition. Rutile, titanite, apatite, fluorite, graphite, calcite, allanite, autunite and Fe-Ti oxides are accessory minerals. Kaolinite, chlorite and epidote are secondary minerals. Carbonitization and hematitization are common. Rounded to sub-rounded porphyritic and zoned ocelli with radiate or brush-like shapes are generally common and represent physical traps for mineralization. The ocellar features are interpreted to represent the late stage of magmatic segregation or magmatic crystallization involving two immiscible magmatic liquids.     

Rock joint modeling using a visco-plastic multilaminate model at constant normal load condition

Rock joints play an important role in the behavior of rock masses under normal and shear loading conditions. Numerical simulation of the behavior of jointed rock masses is not an easy task due to complexities involved in the problem such as joint roughness, joint shear strength, hardening and softening phenomenon and mesh dependency. In this study for modeling purposes, a visco-plastic multilaminate model considering hardening and softening effects has been employed. For providing the necessary data for numerical simulation, a series of laboratory experiments have been carried out on regular tooth-shape asperities made by gypsum, under constant normal load conditions. Shear stress–shear displacement and normal displacement–shear displacement of artificial joint specimens are simulated using the proposed numerical model at constant normal load condition (CNL). The results indicate the capability of the model for simulating rock joints behavior in both strength and deformation field. Although the numerical model has been developed for simulating the behavior of artificial joints, the concept of the method can also be used for natural rock joints.     

Decision support for conceptual performance‐based design

Performance assessment implies that the structural, non‐structural, and content systems are given and that decision variables, DVs, (e.g. expected annual loss, mean annual frequency of collapse) are computed and compared to specified performance targets. Performance‐based design (PBD) is different by virtue of the fact that the building and its components and systems first have to be created. Good designs are based on concepts that incorporate performance targets up front in the conceptual design process, so that subsequent performance assessment becomes more of a verification process of an efficient design rather than a design improvement process that may require radical changes of the initial design concept. In short, the design approach could consist of (a) specifying performance targets (e.g. tolerable probability of collapse, acceptable dollar losses) and associated seismic hazards, and (b) deriving engineering parameters for system selection, or perhaps better, using the relatively simple design decision support tools discussed in this paper. Copyright © 2005 John Wiley & Sons, Ltd.