The formation of earth fissures due to groundwater depletion has been reported in many places in North America, Europe, and Asia. Najran Basin is in the southern part of the Kingdom of Saudi Arabia, and agricultural activities and other groundwater uses have caused significant groundwater depletion there. The basin recently experienced a sudden appearance of numerous earth fissures. An interdisciplinary study consisting of an evaluation of land-use changes, and hydrological, hydrogeological, and geophysical investigations was conducted to determine the reason for the formation of the earth fissures. The hydrological analysis strongly revealed that the groundwater level is decreasing with time. Groundwater depletion would lead to the accumulation of subsurface stress, causing soil hydro-consolidation which creates the ideal condition for the formation of earth fissures. Electrical resistivity, data indicated that there are anomalies in the profiles, which are most probably due to the presence of subsurface topography, another key factor for the formation of the earth fissures. 相似文献
A series of Cretaceous plutons is present in the eastern Pontides of northeastern Turkey.The Turnagl intrusion is the least studied and,thus,the least understood plutons in the orogen.This intrusion consists of hornblende-biotite granodiorites emplaced at 78 Ma based on LA-ICP-MS U-Pb zircon dating.It is of sub- alkaline affinity,belongs to the medium- to high-K calc-alkaline series,and displays features typical of Itype granites.The rocks of the intrusion are enriched in large-ion lithophile elements and light rare earthelements with negative Eu anomalies(Eu/Eu*= 0.69-0.82),but are deficient in high-field-strength elements.They have a small range of (87Sr/86Sr)i(0.7060-0.7063),εNdi(-2.6 to -3.1),and δ18O(+8.1 to +9.1) values.Their Pb isotopic ratios are 206Pb/204Pb = 18.63-18.65,207Pb/204Pb = 15.62-15.63,and 208Pb/204Pb = 38.53-38.55.The fractionation of plagioclase,hornblende,and Fe-Ti oxides had key functions in the evolution of the Tumagl intrusion.The crystallization temperatures of the melts ranged from 758 to 885℃ as determined by zircon and apatite saturation thermometry.All these characteristics,combined with the low values of K2O/Na2O and(Na2O + K2O)/(FeOt+MgO + TiO2),as well as the high values of (CaO + FeOt + MgO + TiO2).suggest an origin by dehydration melting from a metabasaltic lowercrustal source. 相似文献
Five seismic refraction and five high-resolution seismic reflection (HRSR) profiles were carried out in northeastern part of Riyadh city to investigate depth of the weathering layer. Results obtained from seismic refraction survey reveal the depths of weathering layer at 12, 25, 17, 12, and 16?m, respectively. On the other hand, HRSR stack sections illustrate the depths of weathering layer at 14, 28, 20, 13, and 18?m, respectively. The weathering layer is composed of alluvial sediments and gravel, which is underlain by a sequence of limestone and dolomite layer. Seismic results from site no. 2 have been found to be in good agreement with lithological information reported from the adjacent water well. The HRSR data generally reveal better signal-to-noise ratio and enhanced resolution compared to the refraction data. Although, the HRSR data failed in achieving high-quality common midpoint (CMP) stacking profile at site no. 3, it provide an improved image of the subsurface features than the refraction data, recognizing it as a potential seismic technique. 相似文献
Numerical models are capable of simulating various groundwater scenarios and relate it towards groundwater management. This
paper focuses on numerical modeling and water balance approaches in the search for a sustainable management plan in Manukan
Island. The impacts of pumping and recharge rates represented by groundwater scenarios were investigated by means of hydraulic
heads, chloride concentrations and water balance components. Overpumping and inconsistency in recharge rate are the stresses
shown in Scenario A. Scenario B involved with reduction pumping rate by 25% has shown an increase in groundwater levels, chloride
concentration and groundwater storage. Scenario C showed the most promising finding compared with Scenarios A and B. Highest
hydraulic heads, lowest chloride concentration (1,552.2 mg/L) and positive groundwater storage (254.3 m3/day) were obtained in Scenario C. Chloride concentration in pumping wells still exceeds World Health Organization International
Standard limit in Scenario C which illustrates an additional water treatment is needed. Nevertheless, in view of a compromise
groundwater management plan in study area, Scenario C is the best plan so far to protect the groundwater resources in the
study area. More understanding of the artificial recharge method (percolation tank) and study site by means of modeling studies
is needed. Additionally, further progress is needed in obtaining the water usage data from each part to determine the best
pumping rate. A sustainable groundwater management plan is crucial to maintain the natural resources and social benefits as
well as to protect the ecological balance of Manukan Island. 相似文献
Trace elements and rare earth elements (REEs) of Lias-aged cherts in the Gumushane area were studied in order to understand their origin and depositional environment. Twenty three chert samples from five stratigraphic sections were analysed by inductively coupled plasma-mass spectrometry, X-ray diffraction, and mineralogical investigation. Lias cherts in the study area are microcrystalline, cryptocrystalline quartz, and megaquartz depending on mineralogical content. Trace elements of the cherts were compared with PAAS, Co, Y, and Th had stronger depletions in the five sections, whereas V, Ni, Zr, Nb, and Hf had smaller depletions. The distribution of Zr, Hf, and Ta yields Zr/Hf, Zr/Ta and Hf/Ta ratios (25/645, 37/665, and 0.18/3, respectively) that differ from those of chondrites and average upper continental crust, suggesting that these elements are likely non-detrital but are sourced from seawater. Th/U ratios range from 0.04 to 0.45 and are lower than those of the upper continental crust (average: 3.9). Lias-aged cherts have low total REE abundances and stronger depletions in five sections of the PAAS and chondrite-normalised plots. The cherts are characterised by a positive Eu anomaly (average: 4.9) and LREE-enrichment (LaN/YbN = average: 3.5). In addition, about one-half of the cherts exhibit positive Ce anomaly (range: 0.25–2.58), chondritic Y/Ho values (range: 3.3–60), and low (La/Ce)N values (average: 1.8). REE and trace element abundance in Lias cherts indicate that these elements were likely derived from hydrothermal solutions, terrigenous sources, and seawater. The REE patterns of the cherts show that they were probably deposited close to a continental margin. 相似文献
Gemsa has been chosen as the site for one of a new generation of power stations along the south-western margin of the Gulf of Suez. This site has been affected by a number of destructive earthquakes (Mw> 5), in addition to large number of earthquakes with magnitudes of less than 5. In this study seismic activities in the region were collected and re-evaluated, and the main earthquake prone zones were identified. It is indicated that this site is affected by the southern Gulf of Suez, northern Red Sea and Gulf of Aqaba source zones. The southern Gulf of Suez source zone is the nearest to the proposed site. The stochastic simulation method has been applied to estimate the Peak GroundAcceleration at the site of the proposed Gemsa power plant. It was noticed that the pseudo-spectral acceleration (PSA) reaches 175 cm/sec2 resulting from the southern Gulf of Suez seismic source. In addition, the response spectrum was conducted with a damping value of 5% of the critical damping, and the predominant period reached 0.1sec at the site. These results should be taken into consideration by civil engineers and decision-makers for designing earthquake resistant structures. 相似文献
Given the recent historical disastrous tsunamis and the knowledge that the Arabian Gulf (AG) is tectonically active, this study aimed to evaluate tsunami hazards in Kuwait from both submarine earthquakes and subaerial landslides. Despite the low or unknown tsunami risks that impose potential threats to the coastal area’s infrastructures and population of Kuwait, such an investigation is important to sustain the economy and safety of life. This study focused on tsunamis generated by submarine earthquakes with earthquake magnitudes (Mw) of 8.3–9.0 along the Makran Subduction Zone (MSZ) and subaerial landslides with volumes of 0.75–2.0 km3 from six sources along the Iranian coast inside the AG and one source at the Gulf entrance in Oman. The level of tsunami hazards associated with these tsunamigenic sources was evaluated using numerical modeling. Tsunami model was applied to conduct a numerical tsunami simulation and predict tsunami propagation. For landslide sources, a two-layer model was proposed to solve nonlinear longwave equations within two interfacing layers with appropriate kinematic and dynamic boundary conditions. Threat level maps along the coasts of the AG and Kuwait were developed to illustrate the impacts of potential tsunamis triggered by submarine earthquakes of different scales and subaerial landslides at different sources. GEBCO 30 arc-second grid data and others were used as bathymetry and topography data for numerical modeling. Earthquakes of Mw 8.3 and Mw 8.6 along the MSZ had low and considerable impacts, respectively, at the Gulf entrance, but negligible impacts on Kuwait. An earthquake of Mw 9.0 had a remarkable impact for the entire Gulf region and generated a maximum tsunami amplitude of up to 0.5 m along the Kuwaiti coastline 12 h after the earthquake. In the case of landslides inside the AG, the majority impact occurred locally near the sources. The landslide source opposite to Kuwait Bay generated the maximum tsunami amplitudes reaching 0.3 m inside Kuwait Bay and 1.8 m along the southern coasts of Kuwait.