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1.
A single‐layer model of the near surface throughout the Kingdom of Saudi Arabia is available. While this simple model suffices for most areas and large subsurface structures, it fails in situations where the surface topography is complex, the base of weathering is below the datum, or where the time structural closure is less than the uncertainty in the static correction. In such cases, multiple‐layered models that incorporate velocities derived from analysis of first arrivals picked from seismic shot records have proved to be successful in defining the lateral heterogeneity of the near surface. The additional velocity information obtained from this first‐arrival analysis (direct as well as refracted arrivals) vastly improves the velocity–depth model of the near surface, regardless of the topography. Static corrections computed from these detailed near‐surface velocity models have significantly enhanced subsurface image focusing, thereby reducing the uncertainty in the closure of target structures. Other non‐seismic methods have been used either to confirm qualitatively or to enhance the layer models previously mentioned. Gravity data may be particularly useful in sandy areas to confirm general structure, while geostatistical modelling of vibrator base‐plate attributes has yielded information that enhances the velocity field. In the global context, exploration targets of the oil and gas industry are seeking smaller and lower relief‐time structures. Thus, near‐surface models will need to enhance and integrate these methods, particularly in areas where the assumption of flat‐lying near‐surface layers cannot be met.  相似文献   

2.
Quaternary alluvium, ranging in thickness from a few to 100 meters underlain by Precambrian rocks of metamor-phic and igneous origin, constitutes an important source of ground water in Wadi Al-Yammaniyah, Saudi Arabia. The purpose of this report is to assess the hydraulic properties, quality of water, and estimated change in storage in waterbearing rocks in the area. The results of eight pumping tests carried out in hand-dug, large-diameter wells, indicate that the hydraulic conductivity of the alluvial aquifer ranges from 5.6 × 10−5 to 1.85 × 10−3 cm/second (3.36 × 10−5 to 1.11 × 10−3 m/minute) and that its storativity varies from 8.23 × 10−2 to 1.17 × 10−1. The aquifer is replenished by sporadic but intensive rainfall of short duration. The present withdrawal is only about 10 percent of the annual recharge which is estimated at 52 × 106 m3. It is shown that there is a substantial potential for the future development of potable ground water which would be required for the development of the area.  相似文献   

3.
Abstract

The Khulais plain lies within a typical arid area in western Saudi Arabia. Groundwater occurs within two aquifers in the area: the alluvium of the wadi system, and the sandy layers of the Cretaceous-Tertiary sedimentary succession. Detailed field investigations and laboratory analysis helped in determining the aquifer properties for each of the water-bearing units. Groundwater movement has been thoroughly studied, and distribution maps prepared to explain the variations in transmissivity, permeability, porosity and specific yield. An attempt has been made to estimate volumes of groundwater flow towards the plain. This study presents a first attempt towards determining groundwater availability in the Cretaceous-Tertiary succession of this part of the world.  相似文献   

4.
《Journal of Hydrology》1989,110(3-4):295-314
Aquifers in sedimentary basins provide a regional domain for the spatial variabilities in geologic, hydrologic, geomorphologic and hydrochemical phenomena. Their study should account for this spatial variability within the study area prior to any formal modelling. A cumulative semivariogram scheme is adopted in this paper for the spatial variability, which is then incorporated with the kriging technique to provide maps of regional variation concerning variables such as storativity, transmissivity, piezometric levels, total dissolved solids and groundwater flow velocity. It is shown that the classical semivariogram models are not capable of accounting for the spatial variability of the Wasia aquifer. Comparison between the cumulative and classical semivariograms are given on the basis of hydrogeologic variables observed in the field. It is concluded, in general, that the cumulative semivariogram modelling of the spatial variability is more effective and yields realistic regional variables.  相似文献   

5.
Abstract

Rainfall is the most important input parameter for water resource planning and hydrological studies because flood risk assessment, rainfall harvesting and runoff estimation depend on the rainfall distribution within a region. Due to practical and economic factors, it is not possible to site rainfall stations everywhere, so representative rainfall stations are sited at specific locations. Rainfall distribution is then estimated from such stations. In this study, rainfall distribution in the southwestern region of Saudi Arabia was estimated using kriging, co-kriging and inverse distance weighted (IDW) methods. Historical records of rainfall from 47 stations for the period 1965–2010 and the altitude of these stations were used. The study shows that co-kriging is a better interpolator than the kriging and IDW methods, with a better correlation between actual and estimated monthly average rainfall for the region.  相似文献   

6.
Water samples collected during April 1982–April 1983 from Red Sea coastal waters at Jeddah, Saudi Arabia, were investigated for dissolved organic carbon, dissolved organic nitrogen, dissolved lipid, dissolved organic phosphorus, dissolved monosaccharides, total dissolved sugars and dissolved polysaccharides. All showed extremely high values at two stations. This can be attributed to the direct effect of untreated wastes on these two locations and the limited water exchange between the study area and the open sea.  相似文献   

7.
8.
9.
Ali Subyani  Zekai en 《水文研究》2006,20(20):4373-4380
The rainfall and infiltration elements of the hydrological cycle in arid regions are characterized by temporal and spatial variations that are random and sporadic. Consequently, the chloride concentration in rainfall has a similar behaviour. Despite this, the classical chloride mass balance (CMB) approach only employs arithmetic and weighted averages for recharge estimation. In this paper, the classical CMB method is modified by taking into account some perceived deficiencies in the methodology. The modified CMB method takes into consideration additional statistical parameters, namely variances and the correlation coefficient between variables concerned based on the application of the perturbation method. Strategic aquifer planning in the Kingdom of Saudi Arabia requires a quick method for estimating groundwater recharge in order to determine the temporal management of available water resources. To demonstrate the difference between the classical and the refined CMB methods, both were applied to a representative basin, i.e. Wadi Yalamlam, in the western part of Saudi Arabia. Based on the refined calculations, recharge to groundwater is found to be 11% of the effective annual rainfall. This refined method provides higher recharge rates because it takes into account the actual variability in the variables concerned and can, thus, improve the accuracy of future groundwater recharge estimation studies. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

10.
The objective of the study was to compare the relative accuracy of three methodologies of regional flood frequency analysis in areas of limited flood records. Thirty two drainage basins of different characteristics, located mainly in the southwest region of Saudi Arabia, were selected for the study. In the first methodology, region curves were developed and used together with the mean annual flood, estimated from the characteristics of drainage basin, to estimate flood flows at a location in the basin. The second methodology was to fit probability distribution functions to annual maximum rainfall intensity in a drainage basin. The best fitted probability function was used together with common peak flow models to estimate the annual maximum flood flows in the basin. In the third methodology, duration reduction curves were developed and used together with the average flood flow in a basin to estimate the peak flood flows in the basin. The results obtained from each methodology were compared to the flood records of the selected stations using three statistical measures of goodness-of-fit. The first methodology was found best in a case of having short length of record at a drainage basin. The second methodology produced satisfactory results. Thus, it is recommended in areas where data are not sufficient and/or reliable to utilise the first methodology.  相似文献   

11.
We propose a framework for spatially estimating a proxy for coral reef resilience using remote sensing. Data spanning large areas of coral reef habitat were obtained using the commercial QuickBird satellite, and freely available imagery (NASA, Google Earth). Principles of coral reef ecology, field observation, and remote observations, were combined to devise mapped indices. These capture important and accessible components of coral reef resilience. Indices are divided between factors known to stress corals, and factors incorporating properties of the reef landscape that resist stress or promote coral growth. The first-basis for a remote sensed resilience index (RSRI), an estimate of expected reef resilience, is proposed. Developed for the Red Sea, the framework of our analysis is flexible and with minimal adaptation, could be extended to other reef regions. We aim to stimulate discussion as to use of remote sensing to do more than simply deliver habitat maps of coral reefs.  相似文献   

12.
This study aimed at the micro-level seismic behavior and zoning of the saline sabkha strata in Jubail industrial area in Eastern Saudi Arabia. It encompasses the evaluation of the site-specific seismic response parameters and the liquefaction potential for various possible subsurface conditions under the probable seismic event(s). The approach to achieve the objectives of this study included the following: analysis of geologic, hydrologic, and geotechnical data of the area; performance of field and laboratory dynamic testing; and dynamic modeling and analysis of the subsurface profiles. The results of the simulation have been used to develop liquefaction potential maps and site-specific spectra of the study area, consisting of ten seismic zones under a range of probable peak horizontal ground acceleration (PHA). Results do not show significant probability of liquefaction of the loose soil layers in the study area at the maximum possible design PHA of 0.035 g; however, liquefaction is anticipated at higher PHA values. Site-specific spectral response resulted in values of S s and S 1 spectral accelerations to be different as compared to those suggested by local standards. The resulting seismic micro-zonation maps and the corresponding parameters are very useful for the stability analysis of the existing and planned structures in the Jubail area.  相似文献   

13.
Cyanobacterial mats are found at various locations along the coast of the Eastern Province of Saudi Arabia. Those mats were affected by severe oil pollution following 1991 oil spill. In this study, samples from Abu Ali Island were collected at three selected sampling sites across the intertidal zone (Lower, Middle, and Upper) in order to understand the effect of extreme environmental conditions of high salinity, temperature and desiccation on distribution of cyanobacteria along the oil polluted intertidal zone. Our investigation of composition of cyanobacteria and diatoms was carried out using light microscopy, and Denaturant Gradient Gel Electrophoresis (DGGE) technique. Light microscopy identification revealed dominant cyanobacteria to be affiliated with genera Phormidium, Microcoleus, and Schizothrix, and to a lesser extent with Oscillatoria, Halothece, and various diatom species. The analysis of DGGE of PCR-amplified 16S rRNA fragments showed that the diversity of cyanobacteria decreases as we proceed from the lower to the upper intertidal zone. Accordingly, the tidal regime, salinity, elevated ambient air temperature, and desiccation periods have a great influence on the distribution of cyanobacterial community in the oil polluted intertidal zone of Abu Ali Island.  相似文献   

14.
Estimation of groundwater recharge to an unconfined aquifer is studied using analytical and numerical techniques and results are compared with field observations. There is an acute need for such estimation in water balance studies in arid climates, and the case study in this paper is for such a region. The wetting front movement in the unsaturated zone depends on antecedent soil moisture, the ponded water depth and its duration, and on the position of the water table and the hydraulic properties of the unsaturated zone. A hydraulic connection between the recharge basin and the aquifer is not immediately established because the wetting front is unsaturated. A numerical model is applied to estimate recharge in an arid-zone wadi, and its validity is tested by comparing it with an analytical solution of the equations. The calculated recharge values matched the piezometric levels observed at a well site at the edge of the wadi channel. The total recharge depths found by integration in the time domain provided a good estimate of the transmitted volume of water per unit length of wadi channel. The findings were confirmed by runoff volume measurements at gauging stations located in the basin. © 1997 John Wiley & Sons, Ltd.  相似文献   

15.
Al Wahbah is a large (∼2.2 km diameter, ∼250 m deep) maar crater in the Harrat Kishb volcanic field in western Saudi Arabia. It cuts Proterozoic basement rocks and two Quaternary basanite lava flows, and is rimmed with an eroded tuff ring of debris from the phreatomagmatic explosion that generated the crater. A scoria cone on the northern wall of the crater was dissected by the explosion and exposes a dolerite plug that was intruded immediately prior to crater formation. The dolerite plug yields a 40Ar/39Ar age of 1.147 ± 0.004 Ma. This is the best possible estimate of the time Al Wahbah crater formed. It is a few tens of thousand years younger than the age of the lower and upper basalt flows, 1.261 ± 0.021 Ma and 1.178 ± 0.007 Ma respectively. A dolerite dyke exposed within the basement in the wall of the crater is dated at 1.886 ± 0.008 Ma. This is the most precise age so far determined for the initiation of basaltic volcanism of Harrat Kishb, and confirms that it is significantly younger than the other post-rift volcanic provinces in the region. This study provides constrains the timing of humid climatic conditions in the region and suggests that the Quaternary basaltic volcanism that stretches the length of the western side of the Arabian peninsula may prove to be useful for establishing palaeoclimatic conditions.  相似文献   

16.
During a 52-day eruption in 1256 A.D., 0.5 km3 of alkali-olivine basalt was extruded from a 2.25-km-long fissure at the north end of the Harrat Rahat lava field, Saudi Arabia. The eruption produced 6 scoria cones and a lava flow 23 km long that approached the ancient and holy city of Madinah to within 8 km. Three chemical types of basalt are defined by data point clusters on variation diagrams, i.e. the low-K, high-K, and hybrid types. All three erupted simultaneously. Their distribution is delineated in both scoria cones and lava flow units from detailed mapping and a petrochemical study of 135 samples. Six flow units, defined by distinct flow fronts, represent extrusive pulses. The high-K type erupted during all six pulses, the low-K type during the first three, and the hybrid type during the first two.Three mineral assemblages occur out of equilibrium in all three chemical types.Assemblage 1 contains resorbed olivine and clinopyroxene megacrysts and ultramafic microxenoliths (Fo90 + Cr spinel + Cr endiopside) which fractionated within the spinel zone of the mantle.Assemblage 2 contains resorbed plagioclase megacrysts (An60) with olivine inclusions (Fo78) which fractionated in the crust.Assemblage 3 contains microphenocrysts of plagioclase and olivine in a groundmass of the same minerals with late-crystallizing titansalite and titanomagnetite; assemblage 3 crystallized at the surface and/or in the upper crust. Each assemblage represents a distinct range in PTX environment, suggesting that their coexistence in each chemical type may be a function of magma mixing. Such a process is confirmed by variable ratios of incompatible element pairs in a range of analyses.All three chemical types are products of mixing. Some of the hybrid types may have developed from surface mixing of the low-K and high-K lavas; however, the occurrence of all three types at the vent system suggests that subsurface mixing was the dominant process. We suggest that the Madinah flow was extruded from a heterogeneous magma chamber containing vertically stacked sections equivalent to the six eruptive pulses. This chamber may have developed contemporaneously with magma mixing when a crustal reservoir containing a magma in equilibrium with assemblage 2 was invaded by a more primitive magma containing cognate microxenoliths and megacrysts of assemblage 1.  相似文献   

17.
Harrat Al-Birk volcanics are products of the Red Sea rift in southwest Saudi Arabia that started in the Tertiary and reached its climax at ~ 5 Ma.This volcanic field is almost monotonous and is dominated by basalts that include mafic-ultramafic mantle xenoliths(gabbro,websterite,and garnet-clinopyroxenite).The present work presents the first detailed petrographic and geochemical notes about the basalts.They comprise vesicular basalt,porphyritic basalt,and flow-textured basalt,in addition to red and black scoria.Geochemically,the volcanic rock varieties of the Harrat Al-Birk are low- to medium-Ti,sodic-alkaline olivine basalts with an enriched oceanic island signature but extruded in a within-plate environment.There is evidence of formation by partial melting with a sort of crystal fractionation dominated by clinopyroxene and Fe-Ti oxides.The latter have abundant titanomagnetite and lesser ilmenite.There is a remarkable enrichment of light rare earth elements and depletion in Ba,Th and K,Ta,and Ti.The geochemical data in this work suggest Harrat Al-Birk basalts represent products of watersaturated melt that was silica undersaturated.This melt was brought to the surface through partial melting of asthenospheric upper mantle that produced enriched oceanic island basalts.Such partial melting is the result of subducted continental mantle lithosphere with considerable mantle metasomatism of subducted oceanic lithosphere that might contain hydrous phases in its peridotites.The fractional crystallization process was controlled by significant separation of clinopyroxene followed by amphiboles and Fe-Ti oxides,particularly ilmenite.Accordingly,the Harrat Al-Birk alkali basalts underwent crystal fractionation that is completely absent in the exotic mantle xenoliths(e.g.Nemeth et al.in The Pleistocene Jabal Akwa A1 Yamaniah maar/tuff ring-scoria cone complex as an analogy for future phreatomagmatic to magmatic explosive eruption scenarios in the Jizan Region,SW Saudi Arabia 2014).  相似文献   

18.
40Ar/39Ar plateau-ages at 27–28 Ma obtained on feeder dykes and one lava flow of the alkaline massif of Harrat Hadan are in agreement with the assumed age partly deduced from the conventional K/Ar data of the early activity of other alkaline volcanic massifs from Saudi Arabia. This magmatic activity is spatially distributed over a large area, along the western edge of the Arabian plate, and their N-S to NW-SE volcano-tectonic directions are similar to those of the future Red Sea Rift.Preliminary results obtained on tholeiitic lava flows, dykes and plutons gave 17 plateau-ages which, combined with 6 ages deduced from more disturbed age-spectra, display a main histogram peak from 24 to 21 Ma, much narrower than that obtained with conventional K/Ar ages on the same formations. Therefore, a strong tholeiitic activity affected a narrow linear area following the actual eastern Red Sea coast, over nearly 1700 km, during a brief period of time, and without showing any apparent migration. The main volcano-tectonic features of the future Red Sea are strongly outlined during this event. Such brief magmatic episodes related to continental rifts have also been documented by precise 40Ar/39Ar analyses on the British Tertiary Igneous Province, the Deccan traps and the eastern Central Atlantic.  相似文献   

19.
Quantification of water balance components, under arid conditions, is essential to the development of water management policies. This study demonstrates the application of the mass water balance approach for the assessment of water resources in a typical watershed located in the southwestern region of Saudi Arabia. The water balance approach was used, on an event basis, to express the amount of precipitation for 13 storms over a three year period, as a percentage of other hydrological components such as runoff, evaporation, and recharge. The study indicated that 63 per cent of precipitation is lost through evaporation from the water surface during flooding, and from the upper layers of the soil surface immediately after storms. Another 32 per cent is stored in the form of soil moisture in the unsaturated layers below the effective evaporation depth. Only 3 per cent of the precipitation was transformed into surface runoff; however, 75 per cent of this contributes towards groundwater recharge. This study has illustrated that the mass water balance approach can be used, with reasonable accuracy, to quantify the components of the hydrological processes under arid conditions, where a reliable data base is available. This, in turn, will help in the development of appropriate water management policies for arid regions.  相似文献   

20.
A sequence of earthquakes took place in June 2004 approximately 60 km southeast of Tabuk, Saudi Arabia. The first felt event (M W = 3.9) occurred on June 9 and caused minor damage in the epicentral area according to the National Earthquake Information Center and the local reports. Another moderate size event occurred on June 22 (M W = 5.1) and was followed by a few felt aftershocks without any reported damage. This earthquake sequence caused considerable alarm at Tabuk and highlights the fact that damaging earthquakes can occur in this region away from the major plate boundary in the Red Sea. Being the largest well-recorded event in the area for which the digital and broadband records from Saudi Arabia, Egypt, Israel, Jordan, Turkey, Cyprus, and Kuwait are available, it provides an excellent opportunity to study the tectonic process and present day stress field acting on this area. The digital records from these regional networks were used to relocate the largest three events of this sequence. Focal mechanisms were obtained from full waveform inversion and indicate normal faulting mechanisms with two nodal planes oriented NW–SE in parallel to the faults bounding the Tabuk graben and the Red Sea rift axis. These events originated at shallow focal depths of 4–5 km, possibly contributing to the widely felt ground motions. These events offer a unique opportunity to study the active tectonics of the region as well as inform future studies of seismic hazard in northwestern Saudi Arabia, the Gulf of Aqaba, and eastern Egypt.  相似文献   

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