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101.
In recent years, Iraq has experienced an increase in seismic activity, especially, near the east boundary with Iran. Previous studies present their results in terms of PGA and for return periods of 500 years and less, and other studies not continued to include the whole PSHA process whereas some recent studies continued to include the whole PSHA process using earthquakes data till 2009 including dependent events. This study includes two main stages, the first is collecting the earthquakes records including the recent events till the end of March 2016 and applying data processing to get the net catalog to independent events. The second stage is applying the steps of PSHA method. Matlab programs have been built to execute these two stages and to convert the results of PSHA computations into contours of 5% damping PGA and spectral accelerations at 0.2 and 1.0 s for a return period of 2475 years, and for rock sites. Also, spectral acceleration against period has been presented for main cities. Also, the PGA map, for a return period of 475 years, has been plotted and then prepared together with similar maps of neighbor countries in one map for comparison. In general, this comparison indicates the similarity in behavior but, the values reveal a relative agreement and they are between Turkish and Iranian values. 相似文献
102.
Rachida Bendaoud M’hamed El Janati Mohamed Elaatmani Luisa Carvalho Zaineb Hajjar Said Ilmen Abdallah Algouti Ahmed Algouti Lahcen Khouchaf 《Arabian Journal of Geosciences》2018,11(17):512
Neoproterozoic volcanic series are exposed in the northern edge of the Saghro massif (Eastern Anti-Atlas, Morocco). Four volcanic rock types (basalt, andesite, dacite, and rhyolite) were distinguished in the Boumalne inlier within the so-called Saghro volcanic sequences based on petrographic and geochemical observations. Boumalne volcanic rocks contain high Al2O3, Fe2O3, Ba, Sr, Zr, Rb, and Nb contents, including calc-alkaline affinity in composition. Boumalne volcanic rocks are similar to other lower-Neoproterozoic volcanic rocks such Agouiniy formation in Sirwa inlier and in other parts of Bou-Azzer inlier. Indeed, they indicate an active subduction signature. The geochemical data show a LREE enrichment compared to HREE. The fractional crystallization has played a major role during the evolution of the magma. The less-siliceous dacitic rocks could have been formed after a low degree of partial melting of mafic parental magma source, whereas the rich-siliceous rhyolite may have been derived from dacitic magma source by a higher degree of fractional crystallization. 相似文献
103.
Boudjema Sehl Mohamed Said Guettouche Hocine Ait Mouheb María Teresa Camacho Olmedo 《Arabian Journal of Geosciences》2018,11(7):143
Modeling techniques have the power to predict land use change. Our research had three main aims: firstly, to compare and contrast the predictive performance of individual models versus consensus methods; secondly, to compare the different consensus methods; and finally, to compare their predictive performance for generalized and marginal land uses in the environment in the study area. Seven individual models were used to generate the suitability maps for each type of land use in Zahrez El Gharbi (Algeria), characterized by the suitability values for their occurrence. Seven consensus methods were created by combining the individual models. The predictive performance of the individual models and of the consensus methods was assessed by calculating the area under the curve (AUC). For each type of land use, the predictive quality of the consensus methods was considerably better than that of the individual models. The weighted averages method (WA) proved the most efficient of the seven consensus methods. The types of land use have a significant influence on the predictive quality, in that the AUC values increase in line with increases in the marginality of the particular type of land use. The improvements in predictive quality achieved by consensus methods in general and the weighted averages method (WA) in particular would substantially resolve the different sources of uncertainties resulting from the use of individual models and from the environmental characteristics of the different types of land use. 相似文献
104.
In this paper a typical soil–structure interaction problem is considered, the case of a vertical pile installed in sand and submitted to an axial compression loading. Results from two full scale pile tests are analysed and the tests are reproduced by numerical simulations via finite elements method (FEM). The choice of the mechanical parameters for the soil and the sand–pile interface and the modelling approach are first described. A new numerical strategy is outlined to account for pile installation effects due to jacking and driving via FEM. The proposed approach is based on the application of existing empirical correlations available for the quantification of residual radial and shear stresses along the pile shaft as well as residual pressures around the pile base after the installation. This approach is proposed as an alternative to more complex methods based on the numerical modelling of the pile penetration problem. The role of the constitutive modelling of the interface is also discussed. Finally, comparative analyses of pile loading tests using FEM are provided and the comparisons between numerical and experimental results are presented and discussed. 相似文献
105.
Mohammed Musa Amro Mohammed Said Benzagouta Wimpy Karnanda 《Arabian Journal of Geosciences》2013,6(3):873-880
The main objectives of this paper are to study crude oil migration as a toxic fluid, its rate of penetration, and its consequences for eventual treatment. To achieve these objectives, an experimental model was designed comprising two separated columns, filled with soil and other rock types to simulate a real case scenario. Crude oil penetration depth versus time was recorded by taking soil samples whereas water samples were collected from the wet system to analyze the penetrating liquid. The results show that penetration depth was greater in the wet system during the early stages rather than in the dry system. However, with time, penetration becomes more developed in both systems. Overall penetration in the final stage was found to be significantly higher in the dry system. In addition, it was observed that during crude oil migration in dry system, chromatographic separation of crude oil components has occurred obviously. The obtained results reveal that immediate treatment must be performed in both systems but particularly in the wet system, due to its higher initial penetration rate. 相似文献
106.
Modeling and risk assessment of landslides using fuzzy logic. Application on the slopes of the Algerian Tell (Algeria) 总被引:2,自引:0,他引:2
Mohamed Said Guettouche 《Arabian Journal of Geosciences》2013,6(9):3163-3173
Natural risk regains the notion of exposure to natural disaster or dangers of any natural hazard. Its management consists in the assessment and the anticipation of risks, as well as to the setting up of an alert system. From natural risk, we mentioned one bound to landslides in natural slopes that are difficult to surround and approach. Nevertheless, the assessment of landslides risk is the object of several works of research and many models, based on the multicriteria analysis, have been established. It should be noted that based on multicriteria approach, we evaluated, in a previous work, the landslide risk using the weighted sum model. The results reveal that the use of qualitative parameters influenced the classification of slope. This led us to adopt fuzzy logic approaches for assessment. This work examines the contribution of fuzzy sets theory to modeling and assessment of landslides risk in natural slopes. It brought to use this approach that permits the survey of these imprecision in adopting a Mamdani model. The method has been applied on slopes, situated in four areas of the Algerian Tell, where each is characterized by the different natural conditions. The result, put in evidence, summarizes modeling and risk assessment of landslides in an optimal classification of slopes according to the degree of instability risk. It allows decision makers to put in strategies for possible work of these slopes. 相似文献
107.
So far, the direction and rate of relative motion between the Rivera and the North American plates (RIV-NAM) has been determined by the combination of two Euler poles: Rivera (RIV), with respect to Pacific (PAC), and PAC with respect to North America. Here, we estimate the relative motion of this plate pair (RIV-NAM) assuming that the horizontal projection of the direction of slip of the earthquakes occurring on the RIV-NAM boundaries reflect their relative plate motion. A catalog of earthquakes for which focal mechanisms are reported since 1976 is used in the analysis. Earthquakes were considered in the three segments of the RIV-NAM plate boundary: the subduction zone of the Rivera plate beneath the Jalisco block, the Tres Marias Escarpment and the events associated with the Tamayo Fracture Zone. The best fitting Euler pole is determined using a grid search of 64 potential poles. The slip direction predicted for each grid point is compared to the slip direction of the focal mechanisms of the earthquakes on the plate boundary. The best fitting Euler pole, determined in a root mean square sense (RMS), is located at 21.8°N, 107.6°W. A rate of rotation of 5.3°/year is estimated assuming the seismic earthquake cycle of the 1932 and 1995 great earthquakes represents a lower bound of the rate of plate motion in the subduction zone. The best fitting Euler pole shows that the subduction of the Rivera plate takes place in a direction perpendicular to the trench with a relative velocity of 4.3 cm/year, offshore Manzanillo. The rate of relative motion RIV-NAM decreases from SE to NW. North of approximately 21°N, the subduction of the Rivera plate becomes oblique to the trench and the relative velocity between the two plates decreases to an average of 1.9 cm/year. This slow rate of convergence may explain the rapid decrease of seismicity in the trench and the apparent absence of large earthquakes in this region. In the Tres Marias Escarpment, our best-fitting pole suggests that subduction stops, giving way to high-angle reverse faulting perpendicular to the Tres Marias Escarpment, in agreement with the reverse faulting earthquakes occurring here. To the north of 22.5°N, the slip predicted by the best-fitting pole suggests right-lateral faulting in a direction parallel to the Tamayo Fracture Zone, at a very low velocity (0.5–1.0 cm/year). The best fitting Euler pole determined here lies very close to the RIV-NAM plate boundary in the vicinity of the Tamayo Fracture Zone. This location of our best fitting Euler pole explains the low relative plate velocity, the relatively low level of seismic activity and the presence of a broad zone of deformation that accommodates the RIV-NAM motion. 相似文献
108.
Said S. Al-Ismaily Ali K. Al-Maktoumi Anvar R. Kacimov Said M. Al-Saqri Hamad A. Al-Busaidi Mansour H. Al-Haddabi 《水文科学杂志》2013,58(8):1779-1788
AbstractA pedological study of the reservoir bed of Al-Khoud Dam, Oman, revealed an unusual sedimentation pattern which evolved into an intricate composition of silt blocks surrounded by vertical cracks and horizontal layers filled with a “proppant” sand. The discovered soil morphology reflects the complex topology of water motion (infiltration–seepage–evaporation) through the sand-filled cracks/layers and blocks during both the rare flood events and ensuing periods of ponding, and the long, intervening dry periods. These naturally formed soils demonstrate an ability to preserve a large quantity of water inside the silty blocks at depths of 0.5 to 1.5 m, despite the high temperature and dryness of the topsoil. The hydrological optimality and “smartness” of these soils is attributed to the unique block-crack system. Natural, lush vegetation was found in adjacent zones of the reservoir bed, and acted as a footprint of the shallow “fractured perched aquifer”. Planted “ivy” (Convolvulaceae) in the vertical face of one pedon showed intensive growth without irrigation. Soil moisture content data confirmed the hydrological immobility of water in the blocks if not depleted by transpiration. The novel phenomena reported unveil the possible alteration of soil heterogeneity for optimization of the soil–water system in arid zone soils.
Editor D. Koutsoyiannis; Associate editor F.F. HattermannCitation Al-Ismaily, S.S., Al-Maktoumi, A.K., Kacimov, A.R., Al-Saqri, S.M., Al-Busaidi, H.A., and Al-Haddabi, M.H., 2013. Morphed block-crack preferential sedimentation in a reservoir bed: a smart design and evolution in nature. Hydrological Sciences Journal, 58 (8), 1779–1788. 相似文献
109.
Delineation of groundwater provenance in a coastal aquifer using statistical and isotopic methods,Southeast Tanzania 总被引:4,自引:3,他引:1
Said Suleiman Bakari Per Aagaard Rolf D. Vogt Fridtjov Ruden Ingar Johansen Said Ali Vuai 《Environmental Earth Sciences》2012,66(3):889-902
Rapid population growth and urbanization has placed a high demand on freshwater resources in southeast costal Tanzania. In this paper, we identify the various sources of groundwater and the major factors affecting the groundwater quality by means of multivariate statistical analyses, using chemical tracers and stable isotope signatures. The results from hierarchical cluster analyses show that the groundwater in the study area may be classified into four groups. A factor analysis indicates that groundwater composition is mainly affected by three processes, accounting for 80.6% of the total data variance: seawater intrusion, dilution of groundwater by recharge, and sewage infiltration. The hydrochemical facies of shallow groundwater was mostly of the Na–Ca–Cl type, although other water types were also observed. The deep groundwater samples were slightly to moderately mineralized and they were of the NaHCO3 type. This water type is induced mainly by dissolution of carbonate minerals and modified by ion exchange reactions. The signal from the stable isotope composition of the groundwater samples corresponded well with the major chemical characteristics. In the shallow groundwater, both high-nitrate and high-chloride concentrations were associated with localized stable isotope enrichments which offset the meteoric isotopic signature. This is inferred to be due to the contamination by influx of sewage, as well as intrusion by seawater. The depleted stable isotope values, which coincides with a chemical signature for the deep aquifer indicates that this deep groundwater is derived from infiltration in the recharge zone followed by slow lateral percolation. This study shows that a conceptual hydrogeochemical interpretation of the results from multivariate statistical analysis (using HCA and FA) on water chemistry, including isotopic data, provides a powerful tool for classifying the sources of groundwater and identifying the significant factors governing the groundwater quality. The derived knowledge generated by this study constitutes a conceptual framework for investigating groundwater characteristics. This is a prerequisite for developing a sound management plan, which is a requirement for ensuring a sustainable exploitation of the deep aquifer water resource in the coastal area of Tanzania. 相似文献
110.
The growth and biomass production of six acacia species were studied in the field for 4 years. The species used were Acacia asak, A. negrii, A. seyal, A. karroo, A. ampliceps, and A. stenophylla. The first three species are indigenous while the others are exotic. The results showed both A. ampliceps and A. asak with 100% survival while all A. negrii died. Acacia ampliceps attained the greatest height, diameter, relative growth rate and above-ground biomass while A. asak had the least. Height and diameter growth of acacia species decreased between warm and cold periods of the year. 相似文献