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891.
Abdelhalim Miftah Driss El Azzab Ahmed Attou Ahmed Manar 《Arabian Journal of Geosciences》2017,10(21):460
Our investigation relates to the interpretation of the magnetic data of Jbel Saghro, by aeromagnetic processing using Geosoft and ArcGis software. The data were obtained from digitizing the preexisting maps. From the magnetic field anomaly maps, different anomalies were identified with differences in intensities, sizes, and shapes and in being isolated or interfered. The directions are in general ENE-WSW, NNW-SSE, W-E, and NW-SE which are in good agreement with the general tectonic structure of the region. In order to correspond the anomalies to their natural sources and their geometrical configuration, it was necessary to calculate the residual polar. This avoids the presence of two lobes for the same source, what makes it possible to delimit the geological sources laterally. Thus, the attribution of each magnetic anomaly to its geological source becomes possible. Indeed, generally magnetic anomaly of strong intensities and big wavelengths is associated to very magnetized structures related to the Precambrian basement, and the negative a.m. is connected to structures of weak magnetization located in general in the cover. The application of the tilt angle filter allowed the localization of the outcrops of the inliers and new geophysical lineaments. On the other hand, the local maxima of the horizontal gradient made it possible to reveal the large structural features concerning the main tectonic events of the area. 相似文献
892.
Profiles of salinity and temperature were measured in the strait of Hormuz (SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion (DD) processes, Turner (TU) angle values are calculated in all the stations in the SH. Different TU angle values correspond to salt fingering (SF), diffusive convection (DC) and stable stratification. The distributions of the two forms of DD were plotted vertically along transects in the eastern, central and western part of the SH, and corresponding DD processes were described. The results show that both SF and DC occurred in most part of the study area. Two different water masses (the Indian Ocean surface water and the Persian Gulf water) were evident at the SH, and SF and DC were evident at the interface of two water masses. Due to evaporation, SF occurred in the surface layer of most Stations throughout the year. In the eastern part of the SH, occurrences of DC were more feasible in wintertime. SF was the main phenomenon at the end of hot season. For central part, SF occurred throughout the year in water column. In the western part, water column was stable in summer and DC happened in most part of water column in winter. 相似文献
893.
Maher Aldahri Saad mogren Kamal Abdelrahman Hani Zahran Sherif El Hady Mahmoud El-Hadidy 《Journal of the Geological Society of India》2017,89(4):435-443
Ten boreholes drilled in Ubhur area up to the depth of bedrock indicted the shallow depth of bedrock where the average depth ranges between 10 and 15 m. The standard penetration test N-values of these boreholes were measured and averaged. Based on N-values to the depth of bedrock, Ubhur area can be classified as site class C and D. Multichannel analysis of surface waves technique has been applied along seventy six profiles using 24-channel geophone array and 4.5Hz vertical geophones with 1m geophone spacing and sledgehammer and/or weight drop as seismic energy sources. Values of shear wave velocity to 30 m are calculated and then averaged (Vs30) where it ranges between 310.08 m/s and 1139.8 m/s. Therefore, Ubhur area can be classified into site class B, C and D based on site classification of the national earthquake hazards reduction program (NEHRP) recommendations. Accordingly, the greatest part of the study area falls in site class C while class B and D covered limited areas in the western and the eastern parts respectively. Depending on the shallow depth of bedrock in the study area, the Vs30 parameter is not applicable in the study area so the average values of Vs for the soil thickness, excluding the bedrock, have been calculated and mapped for site class C and D only. So Vs30 approach is not applicable for areas with shallow depth of bedrock which gives higher classification. 相似文献
894.
Earthquake imprints on a lacustrine deltaic system: The Kürk Delta along the East Anatolian Fault (Turkey)
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Aurélia Hubert‐Ferrari Meriam El‐Ouahabi David Garcia‐Moreno Ulaş Avşar Sevgi Altınok Sabine Schmidt Nathalie Fagel M. Namık Çağatay 《Sedimentology》2017,64(5):1322-1353
Deltas contain sedimentary records that are not only indicative of water‐level changes, but also particularly sensitive to earthquake shaking typically resulting in soft‐sediment‐deformation structures. The Kürk lacustrine delta lies at the south‐western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re‐evaluates water‐level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic‐reflection profiles and side‐scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water‐level changes provides a temporal framework for the depositional record. In addition to the common soft‐sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake‐induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (137Cs and 210Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X‐ray imagery, X‐ray diffraction, loss‐on‐ignition, grain‐size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post‐seismic sediment reworking of earthquake‐triggered landslides. 相似文献
895.
Numerical modeling of groundwater resource management options in the East Oweinat area,SW Egypt 总被引:1,自引:0,他引:1
A.?M.?EbraheemEmail author H.?K.?Garamoon S.?Riad P.?Wycisk A.?M.?Seif El Nasr 《Environmental Geology》2003,44(4):433-447
Southwest Egypt is an arid area with no surface water and limited resources of useable groundwater in the well-known Nubian Sandstone Aquifer System. These groundwater reserves have been heavily exploited since the 1960s, which has led to substantial decline in the potentiometric surface of the aquifer. A calibrated regional numerical model with refined grids on the pumping centers has been used to investigate the hydrodynamic impacts of different groundwater management options on the potentiometry of the aquifers. The results indicate that there is a real danger of either dewatering the shallow aquifer in some areas (e.g., Kharga Oasis), or increasing the water depth to uneconomic lifting depth. They also indicate that, although the planned extraction rates in Dakhla, Farafra, and Bahariya oases are feasible for at least the coming 100 years, the present rate for Kharga Oasis and the planned rate for the East Oweinat area have to be reduced substantially. 相似文献
896.
Ben Elghali S.E. Balme R. Le Saux K. El Hachemi Benbouzid M. Charpentier J.F. Hauville F. 《Oceanic Engineering, IEEE Journal of》2007,32(4):786-797
This paper deals with the development of a Matlab-Simulink model of a marine current turbine system through the modeling of the resource and the rotor. The simulation model has two purposes: performances and dynamic loads evaluation in different operating conditions and control system development for turbine operation based on pitch and speed control. In this case, it is necessary to find a compromise between the simulation model accuracy and the control-loop computational speed. The blade element momentum (BEM) approach is then used for the turbine modeling. As the developed simulation model is intended to be used as a sizing and site evaluation tool for current turbine installations, it has been applied to evaluate the extractable power from the Raz de Sein (Brittany, France). Indeed, tidal current data from the Raz de Sein are used to run the simulation model over various flow regimes and yield the power capture with time. 相似文献
897.
The thermal instability both as stationary convection and overstability of a nonuniformly rotating fluid layer of vertical extent is considered. It is shown that in both types of instability the effect of the variation of the rate of rotation is to introduce a new branch to the marginal instability curves of uniform rotation which departs from them towards a zero of the Rayleigh number as the horizontal wavenumber approaches zero. The relevance to the solar interior is discussed. 相似文献
898.
899.
Resume. Le pluton calco-alcalin de Za?r est composé de trois principaux faciès pétrographiques répartis en deux unités granitiques
imbriquées. Ces faciès, de différents degrés d’hybridation et de différenciation, résultent de mélanges magmatiques entre
des magmas basiques mantelliques de type ?HAB? (basalte hyperalumineux) et un magma anatectique issu de la fusion partielle
de matériaux crustaux (métapélites ou métagrauwackes).
La répartition des faciès granitiques de Za?r peut s’expliquer selon un modèle pétrogénétique de type ?MASH? (melting-assimilation-storage-homogenization)
où des magmas hybrides seraient formés suivant différentes proportions de mélanges magmatiques acide-basique. Ces magmas auraient
subides conditions d’ascension spécifiques et seraient mis en place sous forme de 3 grandes injections successives:
Manuscrit re?u le 12 décembre 2003 Révision acceptée le 9 mai 2005 相似文献
1) | Une injection précoce de magma fortement hybride donne la granodiorite-tonalite du SW, assez faiblement homogénéisée et à grands xénolites et enclaves microgrenues mafiques (EMM) dont les compositions pétrographiques, chimiques et isotopiques initiales sont bien préservées |
2) | Une injection, plus tardive et sur une longue distance, de magma relativement plus différencié, donne le monzogranite-granodiorite du NE, assez bien homogénéisé et riche en petites EMM dont les compositions ont été rééquilibrées avec celles du granite h?te |
3) | Une injection très tardive après un stockage de quelques millions d’années et un important brassage magmatique ayant permis un mélange magmatique complet (mixing) des deux composants acide et basique. Cela donne le leucogranite central, très différencié et parfaitement homogène |
900.
Hanane Labbardi Omar Ettahiri Said Lazar Zakia Massik Said El Antri 《Comptes Rendus Geoscience》2005,337(5):505-514
Our interest is related to the hydrological characteristics of the Moulay Bousselham lagoon. Water samples were taken monthly from July 2001 to June 2002 in 15 stations distributed along the lagoon. The various measured hydrological parameters (temperature, salinity, suspended matter, chlorophyll a) showed significant monthly variations (), whereas spatially among all sampled stations, only the salinity showed significant variations. The variability analysis approached by the analysis of the normalized principal components combined with discriminate analysis showed very small inter-stations variability. Its percentage is 11% and 9% of the total variance during high and low tide, respectively. To cite this article: H. Labbardi et al., C. R. Geoscience 337 (2005). 相似文献