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Maher A. El Amawy Ahmed M. Muftah Mohamed Abd El-Wahed Aymn Nassar 《Arabian Journal of Geosciences》2011,4(7-8):1067-1085
Al Jabal Al Akhdar is a NE/SW- to ENE/WSW-trending mobile part in Northern Cyrenaica province and is considered a large sedimentary belt in northeast Libya. Ras Al Hilal-Al Athrun area is situated in the northern part of this belt and is covered by Upper Cretaceous–Tertiary sedimentary successions with small outcrops of Quaternary deposits. Unmappable and very restricted thin layers of Palaeocene rocks are also encountered, but still under debate whether they are formed in situ or represent allochthonous remnants of Palaeocene age. The Upper Cretaceous rocks form low-lying to unmappable exposures and occupy the core of a major WSW-plunging anticline. To the west, south, and southeast, they are flanked by high-relief Eocene, Oligocene, and Lower Miocene rocks. Detailed structural analyses indicated structural inversion during Late Cretaceous–Miocene times in response to a right lateral compressional shear. The structural pattern is themed by the development of an E–W major shear zone that confines inside a system of wrench tectonics proceeded elsewhere by transpression. The deformation within this system revealed three phases of consistent ductile and brittle structures (D1, D2, and D3) conformable with three main tectonic stages during Late Cretaceous, Eocene, and Oligocene–Early Miocene times. Quaternary deposits, however, showed at a local scale some of brittle structures accommodated with such deformation and thus reflect the continuity of wrenching post-the Miocene. D1 deformation is manifested, in Late Cretaceous, via pure wrenching to convergent wrenching and formation of common E- to ENE-plunging folds. These folds are minor, tight, overturned, upright, and recumbent. They are accompanied with WNW–ESE to E–W dextral and N–S sinistral strike-slip faults, reverse to thrust faults and pop-up or flower structures. D2 deformation initiated at the end of Lutetian (Middle Eocene) by wrenching and elsewhere transpression then enhanced by the development of minor ENE–WSW to E–W asymmetric, close, and, rarely, recumbent folds as well as rejuvenation of the Late Cretaceous strike-slip faults and formation of minor NNW–SSE normal faults. At the end of Eocene, D2 led to localization of the movement within E–W major shear zone, formation of the early stage of the WSW-plunging Ras Al Hilal major anticline, preservation of the contemporaneity (at a major scale) between the synthetic WNW–ESE to E–W and ENE–WSW strike-slip faults and antithetic N–S strike-slip faults, and continuity of the NW–SE normal faults. D3 deformation is continued, during the Oligocene-Early Miocene, with the appearance of a spectacular feature of the major anticline and reactivation along the E–W shear zone and the preexisting faults. Estimating stress directions assumed an acted principal horizontal stress from the NNW (N33°W) direction. 相似文献
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A new methodology is developed in assessing environmental impacts of desalination plants discharging brine into the ground.
The main environmental problem of the desalination of seawater is the brine disposal. The brine is commonly discharged into
the sea or injected into a saline aquifer. In the case of injection into the ground, it is necessary to design a disposal
system in a way that respects the environment and is sustainable. Laboratory and computational methods have been utilized
to simulate the unsteady three-dimensional (3D) phenomena of subsurface brine disposal. The computational software used is
SEAWAT, which is a 3D unsteady variable-density flow simulation model. The model is first used to simulate the laboratory
results, and good agreement is achieved. Then, hypothetical problems are designed and simulated of groundwater extraction
and brine disposal by desalination stations. The major purpose of these hypothetical problems is to delineate a methodology
and to create design charts for design and management of production and injection well fields for coastal desalination plants.
Several design charts have been developed with 36 scenarios for two well configurations created by four design parameters:
relative salt concentration (RSC), production and injection rates (Q
d
, Q
r
), well spacing (S), and simulation period (T). 相似文献
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A combined algorithm of improving INS error modeling and sensor measurements for accurate INS/GPS navigation 总被引：1，自引：1，他引：1
Although the integrated system of a differential global positioning system (DGPS) and an inertial navigation system (INS)
had been widely used in many geodetic navigation applications, it has sometimes a major limitation. This limitation is associated
with the frequent occurrence of DGPS outages caused by GPS signal blockages in certain situations (urban areas, high trees,
tunnels, etc.). In the standard mechanization of INS/DGPS navigation, the DGPS is used for positioning while the INS is used
for attitude determination. In case of GPS signal blockages, positioning is provided using the INS instead of the GPS until
satellite signals are obtained again with sufficient accuracy. Since the INS has a very short-time accuracy, the accuracy
of the provided INS navigation parameters during these periods decreases with time. However, the obtained accuracy in these
cases is totally dependent on the INS error model and on the quality of the INS sensor data. Therefore, enhanced navigation
parameters could be obtained during DGPS outages if better inertial error models are implemented and better quality inertial
measurements are used. In this paper, it will be shown that better INS error models are obtained using autoregressive processes
for modeling inertial sensor errors instead of Gauss–Markov processes that are implemented in most of the current inertial
systems and, on the other hand, that the quality of inertial data is improved using wavelet multi-resolution techniques. The
above two methods are discussed and then a combined algorithm of both techniques is applied. The performance of each method
as well as of the combined algorithm is analyzed using land-vehicle INS/DGPS data with induced DGPS outage periods. In addition
to the considerable navigation accuracy improvement obtained from each single method, the results showed that the combined
algorithm is better than both methods by more than 30%. 相似文献
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Populations of two ornamental exotic species, Kalanchoe daigremontiana and Stapelia gigantea, have been recently detected inside a protected area containing arid ecosystems in Venezuela. We indirectly tested their invasive potential by characterizing their reproductive biology and recruitment patterns and comparing our estimates against Baker's Law and reproductive profiles reported for invasive plants. K. daigremontiana is autogamous, produces >16,000 seeds per plant and also reproduces clonally. Despite low seed viability (17.9%) and germination rates (11.9%), seeds were present in the seed bank. Plantlets of asexual origin showed high survival (75–100%) compared to seedlings of sexual origin (10%). S. gigantea is self-incompatible, xenogamous and produces close to 1500 seeds per m2 of plant tissue. Seed viability (77%) and germination rates (62%) were high, but this species is not represented in the seed bank. It has a vegetative growth. A combination of reproductive and recruitment attributes, which match those considered in Baker's Law and others reported for invasive plants, confer K. daigremontiana and S. gigantea the potential to invade Neotropical arid zones; the former mainly through selfing and production of numerous asexual plantlets, and the latter through an association with a locally abundant pollinator and production of wind dispersed seeds. 相似文献
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Evaluation of a surface energy balance method based on optical and thermal satellite imagery to estimate root‐zone soil moisture 
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下载免费PDF全文 Various remote‐sensing methods are available to estimate soil moisture, but few address the fine spatial resolutions (e.g. 30‐m grid cells) and root‐zone depth requirements of agricultural and other similar applications. One approach that has been previously proposed to estimate fine‐resolution soil moisture is to first estimate the evaporative fraction from an energy balance that is inferred from optical and thermal remote‐sensing images [e.g. using the Remote Sensing of Evapotranspiration (ReSET) algorithm] and then estimate soil moisture through an empirical relationship to evaporative fraction. A similar approach has also been proposed to estimate the degree of saturation. The primary objective of this study is to evaluate these methods for estimating soil moisture and degree of saturation, particularly for a semi‐arid grassland with relatively dry conditions. Soil moisture was monitored at 28 field locations in south‐eastern Colorado with herbaceous vegetation during the summer months of 3 years. In situ soil moisture and degree of saturation observations are compared with estimates calculated from Landsat imagery using the ReSET algorithm. The in situ observations suggest that the empirical relationships with evaporative fraction that have been proposed in previous studies typically provide overestimates of soil moisture and degree of saturation in this region. However, calibrated functions produce estimates with an accuracy that may be adequate for various applications. The estimates produced by this approach are more reliable for degree of saturation than for soil moisture, and the method is more successful at identifying temporal variability than spatial variability in degree of saturation for this region. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Nicolai Mirlean Paulo Baisch Marcelo P. Travassos Cristina Nassar 《Geo-Marine Letters》2011,31(1):65-73
Arsenic levels (up to 130 mg kg−1) substantially exceeding the official threshold have recently been documented in beach and nearshore sediments along more
than 50 km of coastline in the Brazilian state of Espírito Santo between 19°50′ and 20°12′S. In an attempt to assess the sources
of this enrichment, we performed a study on arsenic distribution in the main mineral substances and living organisms in the
beach environment. Laboratory tests on arsenic retention by beach carbonate debris have also been carried out. The data suggest
that sedimentary arsenic occurs largely bound to particles of the calcareous red alga Corallina panizzoi, whereby live specimens contained much smaller amounts of this metalloid than was the case for nonliving material (2.4 and
20.3 mg kg−1, respectively). Experimental tests confirmed the ability of C. panizzoi detritus to retain arsenic at pH intervals and ionic strength characteristic of seawater. There are two potential sources
of that metalloid for calcareous debris in sediments: brown macroalgae, which were found to contain high levels of As (up
to 66.3 mg kg−1), and ferruginized sandstones (up to 23.0 mg kg−1). We argue that any contribution of brown algae to beach sediment enrichment by As would be minor, and consider the ferrous
sandstones from coastal sedimentary rocks of the Barreiras Group as the principal large-scale source of arsenic in the marine
environment of Espírito Santo. The experimental data, together with field studies, corroborate the interpretation that arsenic
anomalies in sediments with calcareous debris can form when weathered continental rocks even only slightly enriched in As
are leached by marine waters, and the As is at least partially retained by biogenic calcareous detritus in nearshore sediments.
Considering that rocks of the Barreiras Group are exposed to marine erosion far to the north of Espírito Santo, we estimate
that marine sediments containing calcareous material are “anomalously” enriched in As along approximately 2,000 km of the
Brazilian tropical coastline. 相似文献
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Rahim Barzegar Asghar Asghari Moghaddam Shahrokh Norallahi Azhar Inam Jan Adamowski Mohammad Reza Alizadeh Jessica Bou Nassar 《Ground water》2020,58(3):441-452
The DRASTIC technique is commonly used to assess groundwater vulnerability. The main disadvantage of the DRASTIC method is the difficulty associated with identifying appropriate ratings and weight assignments for each parameter. To mitigate this issue, ratings and weights can be approximated using different methods appropriate to the conditions of the study area. In this study, different linear (i.e., Wilcoxon test and statistical approaches) and nonlinear (Genetic algorithm [GA]) modifications for calibration of the DRASTIC framework using nitrate (NO3) concentrations were compared through the preparation of groundwater vulnerability maps of the Meshqin-Shahr plain, Iran. Twenty-two groundwater samples were collected from wells in the study area, and their respective NO3 concentrations were used to modify the ratings and weights of the DRASTIC parameters. The areas found to have the highest vulnerability were in the eastern, central, and western regions of the plain. Results showed that the modified DRASTIC frameworks performed well, compared to the unmodified DRASTIC. When measured NO3 concentrations were correlated with the vulnerability indices produced by each method, the unmodified DRASTIC method performed most poorly, and the Wilcoxon–GA–DRASTIC method proved optimal. Compared to the unmodified DRASTIC method with an R2 of 0.22, the Wilcoxon–GA–DRASTIC obtained a maximum R2 value of 0.78. Modification of DRASTIC parameter ratings was found to be more efficient than the modification of the weights in establishing an accurately calibrated DRASTIC framework. However, modification of parameter ratings and weights together increased the R2 value to the highest degree. 相似文献
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Karim Nassar Wael Elham Mahmod Hassan Fath Ali Masria Kazuo Nadaoka Abdelazim Negm 《Marine Georesources & Geotechnology》2019,37(1):81-95
This study focuses on the shoreline change detection along the North Sinai coast in Egypt using geographic information system and digital shoreline analysis system (DSAS) during the elapsed period from 1989 to 2016. The measurement of shoreline variation is mainly described for three zones: zone I, El-Tinah plain bay; zone II, El-Bardawil Lake; zone III, El-Arish valley. The rates of shoreline changes in the form of erosion and accretion patterns are automatically quantified by four statistical parameters functioned in DSAS namely endpoint rate, net shoreline movement, linear regression rate (LRR), and least median of squares. LRR results elucidate that the western seaside of El-Tinah plain bay has experienced an extremely dynamic feature with an average erosion rate of ?8.17?m/year. The littoral drifts have been driven by eastward alongshore currents toward the east side of the bay to be accreted with an average rate of +4.28?m/year. Moreover, the shoreline has progressed west of El-Bardawil inlet (1), El-Bardawil inlet (2), and El-Arish harbor. Subsequently, the corresponding average beach growth rates are found to be +2.7, +8.5, and +6.5?m/year, respectively. In contrast, the shoreline on the down-drift side to the east has negatively retreated, and the corresponding beaches have regressed at rates of ?4.5, ?8.65, and ?2.9?m/year, respectively. 相似文献
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One of the main objectives of geodesy is to establish a framework of well distributed points (geodetic control points). The coordinates of these points should be known with sufficient accuracy in order to detect any crustal movement and to be also used in any application of geodynamics. These in turn need a better defined geodetic datum.Unfortunately, in Egypt such datum has not yet been adopted due to the lack in geodetic observations. The adopted ellipsoid is not the best or even a good fit to the geoid in Egypt. Therefore, the geodetic observations have not been completely and rigorously reduced to the reference ellipsoid. The network suffers from a fairly large distortion in scale and orientation. Quite a part of that distortion is due to the lack in reducing such observations. The objective of this paper is to review both the available geodetic data and to propose an approach to achieve a well defined geometric datum. Such approach should use all types of geodetic observations (astro-gravity-Doppler) in a combined study using a least squares collocation technique. 相似文献
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