埃及东部沙漠Gasco天然气公司工程场地大地构造参数和地震灾害评估

根据埃及Gasco天然气公司工程场地的现场调查资料、地震活动性和地震灾害评估结果,对该场地进行了评估.通过浅源地震波折射勘探,对8个地震剖面上的土壤和岩石的弹性动态常数进行了分析.场地地面模型包括两层,分析表明它们具有从中值到高值的弹性动态常数,说明场地有良好的土壤条件和基岩岩性.同时,我们搜集和分析了研究区周围150 km半径范围内的历史和仪器记录地震,从构造环境、地震活动性、地质构造和主要地震的断层面解等方面进行了研究,认为场地受4个震源区的影响:苏伊士中部海湾、开罗-苏伊士地区、开罗西南和Beni-Suef地区.我们采用地震活动性统计方法并结合专家判定,确定了这些震源区内最大地震的矩震级(MW).另外,依据场地峰值加速度(PGA)和反应谱,用随机方法对场地进行了地震灾害评估.4个震源区中,Beni-Suef地区距离工程场地最近,其PGA最大值为9.34cm/s2,但这个值很小,表明地震不会对工程场地产生破坏性影响.最后,我们还模拟了阻尼为1%、3%和5%时的伪加速度场地反应谱.     

Critical Zone Assessments of an Alluvial Aquifer System Using the Multi-influencing Factor (MIF) and Analytical Hierarchy Process (AHP) Models in Western Iran

Natural Resources Research - Many arid regions in the world suffer from over-exploitation of local groundwater resources leading to the degradation of freshwater aquifer systems, drying of spring...     

Composition, age, and origin of the ~620?Ma Humr Akarim and Humrat Mukbid A-type granites: no evidence for pre-Neoproterozoic basement in the Eastern Desert, Egypt

The Humr Akarim and Humrat Mukbid plutons, in the central Eastern Desert of Egypt, are late Neoproterozoic post-collisional alkaline A-type granites. Humr Akarim and Humrat Mukbid plutonic rocks consist of subsolvus alkali granites and a subordinate roof facies of albite granite, which hosts greisen and Sn–Mo-mineralized quartz veins; textural and field evidence strongly suggest the presence of late magmatic F-rich fluids. The granites are Si-alkali rich, Mg–Ca–Ti poor with high Rb/Sr (20–123), and low K/Rb (27–65). They are enriched in high field strength elements (e.g., Nb, Ta, Zr, Y, U, Th) and heavy rare earth elements (La _n /Yb _n ?=?0.27–0.95) and exhibit significant tetrad effects in REE patterns. These geochemical attributes indicate that granite trace element distribution was controlled by crystal fractionation as well as interaction with fluorine-rich magmatic fluids. U–Pb SHRIMP zircon dating indicates an age of ~630–620?Ma but with abundant evidence that zircons were affected by late corrosive fluids (e.g., discordance, high common Pb). εNd at 620?Ma ranges from +3.4 to +6.8 (mean?=?+5.0) for Humr Akarim granitic rocks and from +4.8 to +7.5 (mean?=?+5.8) for Humrat Mukbid granitic rocks. Some slightly older zircons (~740?Ma, 703?Ma) may have been inherited from older granites in the region. Our U–Pb zircon data and Nd isotope results indicate a juvenile magma source of Neoproterozoic age like that responsible for forming most other ANS crust and refute previous conclusions that pre-Neoproterozoic continental crust was involved in the generation of the studied granites.     

Modelling flash flood propagation in urban areas using a two-dimensional numerical model

This paper reports on the numerical modelling of flash flood propagation in urban areas after an excessive rainfall event or dam/dyke break wave. A two-dimensional (2-D) depth-averaged shallow-water model is used, with a refined grid of quadrilaterals and triangles for representing the urban area topography. The 2-D shallow-water equations are solved using the explicit second-order scheme that is adapted from MUSCL approach. Four applications are described to demonstrate the potential benefits and limits of 2-D modelling: (i) laboratory experimental dam-break wave in the presence of an isolated building; (ii) flash flood over a physical model of the urbanized Toce river valley in Italy; (iii) flash flood in October 1988 at the city of Nîmes (France) and (iv) dam-break flood in October 1982 at the town of Sumacárcel (Spain). Computed flow depths and velocities compare well with recorded data, although for the experimental study on dam-break wave some discrepancies are observed around buildings, where the flow is strongly 3-D in character. The numerical simulations show that the flow depths and flood wave celerity are significantly affected by the presence of buildings in comparison with the original floodplain. Further, this study confirms the importance of topography and roughness coefficient for flood propagation simulation.     

The geological evolution of the Gangpur Schist Belt,eastern India: Constraints on the formation of the Greater Indian Landmass in the Proterozoic

The Central Indian Tectonic Zone (CITZ) is a Proterozoic suture along which the Northern and Southern Indian Blocks are inferred to have amalgamated forming the Greater Indian Landmass. In this study, we use the metamorphic and geochronological evolution of the Gangpur Schist Belt (GSB) and neighbouring crustal units to constrain crustal accretion processes associated with the amalgamation of the Northern and Southern Indian Blocks. The GSB sandwiched between the Bonai Granite pluton of the Singhbhum craton and granite gneisses of the Chhotanagpur Gneiss Complex (CGC) links the CITZ and the North Singhbhum Mobile Belt. New zircon age data constrain the emplacement of the Bonai Granite at 3,370 ± 10 Ma, while the magmatic protoliths of the Chhotanagpur gneisses were emplaced at c. 1.65 Ga. The sediments in the southern part of the Gangpur basin were derived from the Singhbhum craton, whereas those in the northern part were derived dominantly from the CGC. Sedimentation is estimated to have taken place between c. 1.65 and c. 1.45 Ga. The Upper Bonai/Darjing Group rocks of the basin underwent major metamorphic episodes at c. 1.56 and c. 1.45 Ga, while the Gangpur Group of rocks were metamorphosed at c. 1.45 and c. 0.97 Ga. Based on thermobarometric studies and zircon–monazite geochronology, we infer that the geological history of the GSB is similar to that of the North Singhbhum Mobile Belt with the Upper Bonai/Darjing and the Gangpur Groups being the westward extensions of the southern and northern domains of the North Singhbhum Mobile Belt respectively. We propose a three‐stage model of crustal accretion across the Singhbhum craton—GSB/North Singhbhum Mobile Belt—CGC contact. The magmatic protoliths of the Chhotanagpur Gneisses were emplaced at c. 1.65 Ga in an arc setting. The earliest accretion event at c. 1.56 Ga involved northward subduction and amalgamation of the Upper Bonai Group with the Singhbhum craton followed by accretion of the Gangpur Group with the Singhbhum craton–Upper Bonai Group composite at c. 1.45 Ga. Finally, continent–continent collision at c. 0.96 Ga led to the accretion of the CGC with the Singhbhum craton–Upper Bonai Group–Gangpur Group crustal units, synchronous with emplacement of pegmatitic granites. The geological events recorded in the GSB and other units of the CITZ only partially overlap with those in the Trans North China Orogen and the Capricorn Orogen of Western Australia, indicating that these suture zones are not correlatable.     

Performances of Landfill Liners under Dry and Wet Conditions

This paper addresses the study conducted on the performance of landfill liner interface parameters. Interface shear strength parameters for various combinations of 9 different lining materials were studied and presented in this paper. This comprehensive testing program covers the interfaces between: (1) soil and compacted clay liner (CCL), (2) geomembrane (HDPEs or PVC) and soil, (3) geosynthetic clay liner (GCL)/CCL and soil, (4) geomembrane and geotextile, (5) geotextile and soil, (6) geotextile and GCL/CCL, and (7) geomembrane and GCL/CCL. The experiments were conducted for both at dry or optimum moisture condition and at saturated or wet condition. The interface performance under both conditions were compared to access the material performances. Tabulated summaries of interface test data under dry or optimum moisture condition (OMO) and saturated or wet condition are presented in the paper.     

Geochemical and isotopic evolution of groundwater in the Wadi Watir watershed,Sinai Peninsula,Egypt

The Wadi Watir delta in the Wadi Watir watershed is a tourist area in the arid southeastern part of the Sinai Peninsula, Egypt, where development and growth of the community on the delta are constrained by the amount of groundwater that can be withdrawn sustainably. To effectively manage groundwater resources in the Wadi Watir delta, the origin of groundwater recharge, groundwater age, and changes in groundwater chemistry in the watershed needs to be understood. Mineral identification, rock chemistry, water chemistry, and the isotopes of hydrogen, oxygen, and carbon in groundwater were used to identify the sources, mixing, and ages of groundwater in the watershed and the chemical evolution of groundwater as it flows from the upland areas in the watershed to the developed areas at the Wadi Watir delta. Groundwater in the Wadi Watir watershed is primarily from recent recharge while groundwater salinity is controlled by mixing of chemically different waters and dissolution of minerals and salts in the aquifers. The El Shiekh Attia and Wadi El Ain areas in the upper Wadi Watir watershed have different recharge sources, either from recharge from other areas or from different storm events. The downgradient Main Channel area receives groundwater flow primarily from the El Shiekh Attia area. Groundwater in the Main Channel area is the primary source of groundwater supplying the aquifers of the Wadi Watir delta.     

Geology and geochemistry of Kurkur bentonites,southern Egypt: provenance,depositional environment,and compositional implication of Paleocene–Eocene thermal maximum

A large lower Eocene bentonite deposit at the top of Sinn El-Kaddab plateau, southern Egypt, is investigated. It forms isolated anticlinal hills as mesa and cuesta geomorphic units. The Sinn El-Kaddab plateau (497 m above sea level) with Gebel Abyad in northern Sudan represent the most southern margin of Tethys realm in East Africa. Clay and silt fractions constitute up to 95 % of the bentonite and calcium montmorillonite is the predominant phase (70–87 %). These sediments were deposited during the Paleocene–Eocene Thermal Maximum (PETM) event. Grain-size distribution in conjunction with their geologic setting argues in favor of a low energy deep hemipelagic, restricted basin within the outer shelf zone. They suggest sporadic deposition in a basin characterized by relief oscillation, in response to continuous tectonic uplifting. The sediments of the peripheral parts of the basin are more calcareous and were deposited in an arid climatic condition. Calcium montmorillonite was deposited in subtropical warm climate, with alternating wet and dry seasons. Compositionally, the bentonite shales are basic to intermediate and exhibit a rather limited range of K₂O/Na₂O and SiO₂/Al₂O₃ ratios. They suggest mature polycyclic siliciclastics as the main provenance and within-plate alkali basalts as a main igneous precursor. They are the product of intensive physical weathering process in response to combined effects of both tectonic disturbance and prevailed climatic conditions during the PETM event. Geochemically, they are interpreted in terms of mixing of two end-members: pure clastic terrigenous component (inherited from the source area) and carbonate-rich matrix.     

New insights on the tectonic and paleogeographic evolution of the central Atlasic domain of Tunisia

Geological and geoseismic profiles and well data gathered with field observations from the Atlasic Chain in central Tunisia highlight folded structures, tectonic events, and significant faults. These events controlled basin formation and evolution during successive Mesozoic extensional phases, followed by the tectonic inversion during the Atlasic Orogeny known on a Tethyan scale. The Cretaceous extension is well recorded through deposition, which supplied the normal faults system and influenced sediment distribution and regional subsidence. The major event is the normal slip of the principle inherited fault during the Cretaceous subsidence. The northwestern blocks, which are north of the faults of Mrhila–Trozza–Cherichira and Ballouta and west of the NS axis, correspond to continually subsiding areas of the Upper Cretaceous series. Subsequent faulting reactivated compressional structures such as strike-slips, reverse, and thrust faults during the Tertiary Orogeny which largely affected the Tunisian Atlasic domain. Geological profiles point out the evidence of the Upper Cretaceous emersion of the central Tunisia domain and lateral thickness variation of the series from Jurassic to Quaternary, unconformities, and halokinesis movement.     

An index to assess the propensity of landfall in Australia of a tropical cyclone

Every year, Australian oceans experience the genesis of many tropical cyclones (TCs). About 40 percent of these make landfall. Because of the enormous difference in impacts between landfalling and non-landfalling TCs on coastal communities, the benefits would be enormous if it were possible to capture early the potentiality of landfall of a TC that has undergone genesis. Published literature identifies many factors such as location, warm sea surface temperature above 26 °C, conditional instability and high relative humidity in the middle troposphere and low vertical wind shear for the genesis of cyclones. Some of these factors could hold information about the potentiality of landfall while a TC is forming. An investigation into these factors actually revealed that a landfall potential index can be developed that can capture the potentiality of making a landfall. An attractive feature of this index is that it uses values at the time and location of genesis, providing a long and useful lead time. Furthermore, it is made into a dimensionless number, which makes for easy comprehension and interpretation.