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1.
On the use of gravity and magnetic anomalies for locating probable areas of metallic mineralization in South Sinai, Egypt 总被引:1,自引:0,他引:1
The present study deals with processing and interpreting the potential gravity and magnetic data in order to locate promising
sites for metallic mineral occurrences in the basement rocks of South Sinai. Two promising sites were anticipated by combining
the geophysical results and the available geological information. Each site was profiled and interpreted to the nearly approximated
subsurface feature model, and the geometrical parameters of the expected subsurface structures may form mineralized bodies
such as depth, thickness, width, dipping, density contrast, and magnetic susceptibility contrast could be delineated. Detailed
ground Very Low Frequency (VLF) and Vertical Magnetic Gradient (VMG) methods were carried out in the site A2, eight VLF and
VMG anomalies were determined, and their depths were calculated. 相似文献
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Natural Hazards - Cut slope surfaces are affected by excavation activities and weathering agents. Disturbances on the surface can penetrate down to a certain depth. Slope stability analyses made on... 相似文献
4.
Artificial groundwater recharge to a semi-arid basin: case study of Mujib aquifer,Jordan 总被引:1,自引:1,他引:0
Mujib watershed is an important groundwater basin which is considered a major source for drinking and irrigation water in
Jordan. Increased dependence on groundwater needs improved aquifer management with respect to understanding deeply recharge
and discharge issues, planning rates withdrawal, and facing water quality problems arising from industrial and agricultural
contamination. The efficient management of this source depends on reliable estimates of the recharge to groundwater and is
needed in order to protect Mujib basin from depletion. Artificial groundwater recharge was investigated in this study as one
of the important options to face water scarcity and to improve groundwater storage in the aquifer. A groundwater model based
on the MODFLOW program, calibrated under both steady- and unsteady-state conditions, was used to investigate different groundwater
management scenarios that aim at protecting the Mujib basin. The scenarios include variations of abstraction levels combined
with different artificial groundwater recharge quantities. The possibilities of artificial groundwater recharge from existing
and proposed dams as well as reclaimed municipal wastewater were investigated. Artificial recharge options considered in this
study are mainly through injecting water directly to the aquifer and through infiltration from reservoir. Three scenarios
were performed to predict the aquifer system response under different artificial recharge options (low, moderate, and high)
which then compared with no action (recharge) scenario. The best scenario that provides a good recovery for the groundwater
table and that can be feasible is founded to be by reducing current abstraction rates by 20% and implementing the moderate
artificial recharge rates of 26 million(M)m3/year. The model constructed in this study helps decision makers and planners in selecting optimum management schemes suitable
for such arid and semi-arid regions. 相似文献
5.
Short-term periodicities of solar activity were studied. To perform the study, a north-south asymmetry time series was constructed by using the northern and the southern hemisphere flare index values for solar cycle 22. The statistical significance of this time series was calculated. It indicates that in most of cases the asymmetry is highly significant during cycle 22. Power spectral analysis of this time series reveals a periodicity around 25.5 days, which was announced before as a fundamental period of solar activity (Bai and Sturrock, 1991). To investigate the time agreement between the two hemispheres, the phase distribution was studied and a phase shift of about 0.5 was found. An activity trend from the north to the south was found. 相似文献
6.
The paper principally focuses on the durability assessment of various stratigraphic levels of Ahlat ignimbrites collected from the eastern region of Turkey. A total of four different ignimbrite types with dissimilar color, texture and particularly welding degree were tested in laboratory. The laboratory tests performed on the ignimbrite specimens indicate that the welding degree as well as the lithic material content mainly controls the strength and capillarity properties of the ignimbrites. In addition, the durability of highly porous ignimbrites strongly depends upon the degree of welding. The effect of several weathering agents on the ignimbrites was evaluated on the basis of decay constant parameter. Accordingly, salt and ice crystallization pressures are a couple of major destructive agents acting within the micropores of the ignimbrites. Conversely, the investigated specimens are relatively durable against cyclic wetting–drying. Statistical evaluations reveal that the pore diameter is the major controlling factor on the deterioration rate of the ignimbrites after specifically recurrent freeze–thaw cycles. Moreover, the dry unit weight of the ignimbrites is more significant than the uniaxial compressive strength considering the deterioration rates during wetting–drying and salt crystallization. A less significant relationship was obtained between pore diameter and salt crystallization decay constant. 相似文献
7.
Antar Abdel Wahab Mohamed Fouad Ghoneim Tamer Abu-Alam 《Arabian Journal of Geosciences》2017,10(2):30
The Cenozoic volcanism of western Saudi Arabia extends from southern Yemen to Jordan northward. They cover an area of nearly 180,000 km2. The rocks are dominated by alkali olivine basalts and olivine basalts. Al-Wahbah crater, a part of Harrat Kishb, represents a model occurrence to study the gneisses of these rocks. New mineral chemistry and isotopic data are presented. It aims to follow the isotopic, mineralogical, and thermobarometry variations among these volcanics. Amphiboles of the studied volcanics belong to the monoclinic calcic group. The chemistry of the amphibole crystals shows two ranges of pressure. They are 3.6–5.6 and 0.38–0.78 kbar. The Aliv values of the amphiboles are in the range of 1.202 and 1.407, indicating corresponding temperature condition of 820–920 and 620–720 °C, respectively. The feldspar of the studied samples has the composition of plagioclase, though some grains have sanidine composition. They are formed in temperature range of 975 and 400 °C. The coexisting amphiboles and plagioclases indicate two sets of pressure and temperature. They are 540–575 °C (3.5–4 kbar) and 510–525 °C (~2 kbar), respectively. Rb–Sr isochron of the whole rock yields an age of 0.867 ± 0.160 Ma with initial Sr87/Sr86 of 0.702 ± 0.00086. The low initial ratio of Sr87/Sr86 together with positive values of εNd today implies that the studied volcanics have mantle source. Meanwhile, the present isotopic data suggest extraction of juvenile magma from asthenosphere source. The present study shows that the Al-Wahbah crater rocks belong to Cenozoic basalts and indicate EM-I-like signature. 相似文献
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The quantification of groundwater recharge is an important but challenging task in groundwater flow modeling because recharge varies spatially and temporally. The goal of this study is to present an innovative methodology to estimate groundwater recharge rates and zone structures for regional groundwater flow models. Here, the unknown recharge field is partitioned into a number of zones using Voronoi Tessellation (VT). The identified zone structure with the recharge rates is associated through a simulation‐optimization model that couples MODFLOW‐2000 and the hybrid PSOLVER optimization algorithm. Applicability of this procedure is tested on a previously developed groundwater flow model of the Tahtal? Watershed. Successive zone structure solutions are obtained in an additive manner and penalty functions are used in the procedure to obtain realistic and plausible solutions. One of these functions constrains the optimization by forcing the sum of recharge rates for the grid cells that coincide with the Tahtal? Watershed area to be equal to the areal recharge rate determined in the previous modeling by a separate precipitation‐runoff model. As a result, a six‐zone structure is selected as the best zone structure that represents the areal recharge distribution. Comparison to results of a previous model for the same study area reveals that the proposed procedure significantly improves model performance with respect to calibration statistics. The proposed identification procedure can be thought of as an effective way to determine the recharge zone structure for groundwater flow models, in particular for situations where tangible information about groundwater recharge distribution does not exist. 相似文献
9.
ABSTRACTIn this surface water modelling study, a new spatial evaluation for assessing the impact of urbanization was applied for the semi-arid watersheds intersecting with the Gaza coastal aquifer. The SWAT model was calibrated and validated in a semi-automated approach for streamflow in the main watersheds. The results show that the model could simulate water budget components adequately within the complex semi-arid watersheds. Linear relationships between the change in urban area and the corresponding change in surface runoff or percolation were concluded for the urbanized sub-basins. The urban-surface runoff index (USI) and the urban-percolation index (UPI) were developed to represent a micro-level evaluation of different urban change scenarios in the sub-basins. The global urban-surface runoff index (GUSI) and the global urban-percolation index (GUPI) were derived as macro-level factors reflecting the influence on the overall Gaza coastal aquifer due to urban area expansion.
Editor D. Koutsoyiannis Associate editor E. Rozos 相似文献
10.
GIS-based landslide susceptibility mapping using bivariate statistical analysis in Devrek (Zonguldak-Turkey) 总被引:15,自引:10,他引:5
Devrek town with increasing population is located in a hillslope area where some landslides exist. Therefore, landslide susceptibility
map of the area is required. The purpose of this study was to generate a landslide susceptibility map using a bivariate statistical
index and evaluate and compare the results of the statistical analysis conducted with three different approaches in seed cell
concept resulting in different data sets in Geographical Information Systems (GIS) based landslide susceptibility mapping
applied to the Devrek region. The data sets are created from the seed cells of (a) crowns and flanks, (b) only crowns, and
(c) only flanks of the landslides by using ten different causative parameters of the study area. To increase the data dependency
of the analysis, all parameter maps are classified into equal frequency classes based directly on the percentile divisions
of each corresponding seed cell data set. The resultant maps of the landslide susceptibility analysis indicate that all data
sets produce fairly acceptable results. In each data set analysis, elevation, lithology, slope, aspect, and drainage density
parameters are found to be the most contributing factors in landslide occurrences. The results of the three data sets are
compared using Seed Cell Area Indexes (SCAI). This comparison shows that the crown data set produces the most accurate and
successful landslide susceptibility map of the study area. 相似文献