Overview of some geological hazards in the Saudi Arabia

The Saudi Arabia has harsh environmental conditions which enhance some geomorphologic/geological processes more than in other areas. These processes create different geological hazards. The general physiography of the Saudi Arabia is characterized by the Red Sea coastal plains and the escarpment foothills called Tihama, followed by the Arabian Shield Mountains, the Arabian Shelf plateau and finally the Arabian Gulf coastal plains. These types of geological hazards can be categorized into sand accumulations, earth subsidence and fissures, flash floods, problematic soils, slope stability problems, and karst problems. The current study gives an overview of all these hazards with examples, as well as develops a geo-hazard map for the Saudi Arabia. Our findings indicate that the desert environment needs much concern and care. National and international agencies have to join together with other people to keep the system balanced and to reduce the resulting geological hazards. Also, remedial measures should be proposed to avoid and reduce these natural hazards.     

Land degradation risk assessment in Al-Sawda terraces,Kingdom of Saudi Arabia

Monitoring of soil properties is a significant process and plays an important role about how it can be used sustainably. This study was performed in a local area in Sawda Mountains KSA to map out some soil properties and assess their variability within the area under different land cover. Soil sampling was carried out in four different sites using the grid sampling technique. Ten samples were collected in each location within a 10 by 10 km area; soil was sampled at 0–30-cm depth. The soil samples were air-dried, crushed, and passed through a 2-mm sieve before analyzing it for pH, EC, CaCO₃, organic matter contents, and bulk density. The thematic maps of these characteristics were produced using ArcGIS 10.0 software. Finally, the land degradation was assessed using three factors: soil salinization, compaction, and edibility. The obtained results showed that the high risk of soil compaction, salinization, and erodibility occupied an area 5.6 ha (17.5%), 3.7 ha (11.54%), and 8.1 ha (25.3%), respectively, in the surface soil layer. The land degradation risk in the study area due to salinization was low to high; however, the degree of soil compaction was moderate to very high. The K-factor (soil erodibility) in the area ranged between 0.1 and 0.35 Mg h MJ^?1 mm^?1, and most of the study area was located in moderate to high erodibility classes.     

A geological excursion in the Wadi Fatima area, near Jiddah, Saudi Arabia

Wadi Fatima, east of jiddah on the Red Sea coast of Saudi Arabia, is a microcosm of the geology of the jiddah area. Rocks ranging in age from 800-million-year-old metamorphic rocks to Tertiary lava flows are exposed, and illustrate the geological richness of western Saudi Arabia. The valley is a major south-west-trending fault zone that has been active since Precambrian times. A major Tertiary dyke swarm in the vicinity of Wadi Fatima is related to the opening of the Red Sea as the African-Arabian landmass split apart.     

遥感技术在泸定县地质灾害调查中的应用

泸定县地质灾害频繁发生,严重威胁人民生命财产安全。遥感技术具有时效性好、宏观性强、信息丰富等特点,可以真实地反映地质灾害发生时的具体情况,已经成为地质灾害调查的一种重要技术方法手段。运用SPOT5图像和ETM融合SPOT5-PAN图像,通过一定的图像处理手段,获得地质灾害遥感解译底图,采用机助目视解译方法结合地面调查,可以快速、全面地查明泸定县地质灾害分布、规模和危害,提高地质灾害调查的效率和精度,取得较好的应用效果。     

Earth Fissures in Wadi Najran,Kingdom of Saudi Arabia

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.     

WorldView-2高分辨率卫星数据在西昆仑塔什库尔干地区遥感地质调查中的应用

在西昆仑成矿带塔什库尔干地区,利用WorldView-2高分辨率卫星数据开展了遥感地质综合调查研究,采用最佳指数法选择适于本区遥感解译及信息提取的8-4-3波段组合,利用波段比值、主成分变换等方法增强岩性、构造和矿化信息并进行地质解译;结果表明,波段比值可识别闪长岩、大理岩、片岩等多套岩性并突出岩性之间的界线,主成分变换能增强黑云石英片岩与白色花岗岩体间界线,并能对不同片岩因矿物含量差异而呈现的不同色调、明暗程度有较好的反映。岩矿波谱测试及岩性反演和遥感矿化异常信息提取研究工作表明,大理岩等单矿物岩石波谱反演效果较好,对B1,B4,B8,B6等4个波段进行主成分变换及铁矿化信息的提取结果表明,PC3分量是铁染异常的特征主分量。利用WorldView-2数据在西部裸露地区进行矿产地质遥感综合调查,既有高地面分辨率的光学特征,又具有一定的波谱识别能力,不仅能提取大范围的矿化蚀变信息,还可以识别局部的矿体露头,应用效果较好,值得推广。     

Use of remote sensing, GIS and groundwater monitoring to estimate artificial groundwater recharge in Riyadh, Saudi Arabia

This study aims to estimate artificial recharge of groundwater by using remote sensing technology, geographical information systems, and groundwater surveys. This study is part of the King Fahd project for rainfall and runoff water harvesting, within the premises of Alilb Dam in Diriyah to the west of Riyadh. Digital elevation models were obtained with the help of aerial photography from the year 2007. These models were used to delineate watershed. Average rainfall was calculated using isoheytal method, and the area of each of the storage lakes was measured using SPOT 5 satellite images from 2007. Fluctuations in groundwater levels, evaporation, and infiltration rates were used to determine the water balance for the purpose of estimating of artificial recharge. Artificial recharge rates were found to surpass natural recharge from rainfall. Recharge wells caused a reduction in the effect of evaporation on storage lakes and helped in supplying water to the groundwater reservoir. Moreover, 80% and 86% of the rainwater was found to be available for artificial recharge in Alilb at 2005 and 2007, respectively. The study recommends the establishment of strategic projects for water storage using artificial recharge wells, an increase in the number of monitoring wells around the dams, and the monitoring of hydrochemical changes in groundwater both before and after the artificial recharge. It also recommends the erection of a weather station in the northwest of Wadi Hanifa.     

遥感技术在煤矿开采区详细地质灾害调查中的应用

采煤造成的地质灾害日趋严重,常规手段难以对其定量化调查研究.利用IKONOS卫星影像高分辨率的特点,以白银煤矿区为例,分析该区的地质灾害特点和遥感影像特征,建立了塌陷和地裂缝的遥感解译标志,并运用3S技术手段,对该区地质灾害进行定性和定量化分析,为该地方政府决策和当地的环境治理提供了科学依据.     

Seismic vulnerability assessment in the new urban area of Diriyah Governorate,Riyadh, Saudi Arabia

Nine seismic refraction profiles were conducted and processed to study the near-surface sediments in the new urban area of Diriyah. The 2D geoseismic models illustrate two layers: a surface layer of soft sediments and weathered to hard limestone bedrock. Moreover, microtremor measurements were performed at 38 sites for 40 min using three-component seismographs and processed to assess the peak spectral amplitude and the corresponding fundamental resonance frequency. The seismic vulnerability index at each measurement site was estimated. These results correlate well with the geotechnical borehole data. The north-western zone is highly vulnerable due to the great thickness of the soft sediments.     

Quality assessment of groundwater at south Al Madinah Al Munawarah area, Saudi Arabia

Groundwater is the main source of irrigation within south Al Madinah Al Munawarah region. It is also an important source of drinking water in many areas including Madinah city. The wells installed in the aquifer of the study area (south Madinah city) are not currently regulated by the local authorities although they are a key component of water supply. The aquifers in the study area range from unconfined to semi-confined and confined. The main aim of this study is to assess the groundwater in the region for drinking and agricultural uses. For this purpose, hydrochemical analyses of major, minor and trace constituents and nutrients were performed on 29 groundwater samples from the aquifer located about 20 km south of Madinah. The recharge rate of the aquifer of the study area was estimated to be 6.58 % of the annual precipitation using the chloride mass-balance method. Chloride was positively correlated with major ions, which suggests that agricultural activities have some effect on groundwater chemistry through leaching of readily soluble salts from the soil zone. Groundwater of the study area is characterized by dominance of Na over Ca. Chloride was found to be the most dominant anion and replaced by HCO₃, thus reflecting geochemical evolution in the study area. The groundwater of the study area is not safe for drinking but can be safely used for salt-tolerant crops.     

Mapping Neogene and Quaternary sedimentary deposits in northeastern Brazil by integrating geophysics,remote sensing and geological field data

Neogene and late Quaternary sedimentary deposits corresponding respectively to the Barreiras Formation and Post-Barreiras Sediments are abundant along the Brazilian coast. Such deposits are valuable for reconstructing sea level fluctuations and recording tectonic reactivation along the passive margin of South America. Despite this relevance, much effort remains to be invested in discriminating these units in their various areas of occurrence. The main objective of this work is to develop and test a new methodology for semi-automated mapping of Neogene and late Quaternary sedimentary deposits in northeastern Brazil integrating geophysical and remote sensing data. The central onshore Paraíba Basin was selected due to the recent availability of a detailed map based on the integration of surface and subsurface geological data. We used airborne gamma-ray spectrometry (i.e., potassium-K and thorium-Th concentration) and morphometric data (i.e., relief–dissection, slope and elevation) extracted from the digital elevation model (DEM) generated by the Shuttle Radar Topography Mission (SRTM). The procedures included: (a) data integration using geographic information systems (GIS); (b) exploratory statistical analyses, including the definition of parameters and thresholds for class discrimination for a set of sample plots; and (c) development and application of a decision-tree classification. Data validation was based on: (i) statistical analysis of geochemical and airborne gamma-ray spectrometry data consisting of K and Th concentrations; and (ii) map validation with the support of a confusion matrix, overall accuracy, as well as quantity disagreement and allocation disagreement for accuracy assessment based on field points. The concentration of K successfully separated the sedimentary units of the basin from Precambrian basement rocks. The relief–dissection morphometric variable allowed the discrimination between the Barreiras Formation and the Post-Barreiras Sediments. In addition, two units of the latter (i.e., PB1 and PB2) previously mapped in the field were promptly separated based on Th concentration. A regression analysis indicated that the relationship between geophysical and geochemical values obtained for the PB1, PB2 and Barreiras Formation is significant (R-squared = 0.91; p-value <0.05). Map validation presented a high overall accuracy of 84%, with a coefficient of quantity disagreement of 12% and a coefficient of allocation disagreement of 8%. These results indicate that the methodology applied in the central onshore Paraíba Basin can be successfully used for mapping the Barreiras Formation and Post-Barreiras Sediments in other areas of the Brazilian coast. The ability to rapidly and precisely map these units using such methodology could reveal their geographic distribution along the northeastern coast of Brazil.     

基于多源遥感数据的云南西双版纳地区地质构造解译

西双版纳地区地处云南横断山系纵谷南段西双版纳热带雨林区,常年高温多雨、植被茂密、地形复杂,出露地质信息少,给区域地质调查工作造成了很大的困难。为有效获取该地区更多的地质信息,配合使用Landsat 8 OLI、SPOT 6、Sentinel-1A雷达遥感数据和高程数据等多源数据,基于建立的解译标志,提取区内地质构造信息,大至宏观上的大地构造背景信息、小至露头尺度构造信息,并详细分析区内各类型线性断裂构造的遥感影像特征与地质意义。提取的构造结果表明,原地质构造与解译构造吻合度较高,同时新解译出大量的线性构造。研究成果为完善该地区的地质构造轮廓与特征认识提供了丰富的遥感基础资料。     

Red Sea faulting and salt diapirism as a potential geotechnical hazard in Jazan,southwest Saudi Arabia: inferences from gravity data

Natural Hazards - The main objective of this study is to detect the subsurface extension of salt diapirs and structural deformations in the city of Jazan and its suburbs using gravity data. Salt...     

Geophysical survey for geological hazards assessment of Wadi Thuwal area, KSA: a case history

Magnetic and seismic methods have been used in this study as complementary methods to each other to construct a geologic hazard map for Wadi Thuwal area. Magnetic interpretation for deep-seated geologic structures has involved reduction to pole algorithm and downward continuation techniques. It showed that there are three major fault trends: NE-SW and NNE-SSW, NW-SE, and N-S. Furthermore, shear zone has been found close to Harrat Thuwal, which was confirmed by the seismic method. Seismic method revealed three lithologic layers where the depth of the bedrock was found to be ranging between 9?m at the southeastern part of the study area and 24?m at its northern part. It showed also five major fault trends: NW-SE, ENE-WSW, NE-SW, and nearly E-W. Supported by the surface geology, magnetic and seismic results showed that the Wadi Thuwal area can be divided into three zones on the basis of geologic hazards, depending on the presence of geologic features such as faults. It is recommended that before any development plan in Wadi Thuwal area, the delineated hazard zonation should be taken into account.     

蚀变矿物的遥感信息提取研究——以北山方山口为例

北山地区植被稀疏、地势平坦,而且基岩出露好,是遥感地质研究的理想区域。文章利用ASTER数据,采用主成分分析法对北山方山口地区的铁染与羟基蚀变矿物信息进行了提取研究。结果表明,提取结果中蚀变矿物的属性特征能够较好地与实际地质属性相符,且通过野外实地验证蚀变矿物信息发现了矿化点,即利用ASTER数据进行蚀变矿物信息提取可为北山地区矿产资源勘查提供有效的矿化指示遥感信息。     

国道214线西藏段地质灾害遥感调查与评价

同道214线西藏段位于西藏东南部，地形地貌复杂，构造发育，是地质灾害的多发地区。利用以往资料、ETM遥感影像解译及野外调查，在公路沿线圈定出崩塌76处、滑坡26处、泥石流沟101条，并对这些地质灾害的发育状况和危害特征进行了评价。     

山区地质灾害应急调查的内涵及方法分析评述

地质灾害应急调查是针对突发性地质灾害或险情进行的紧急调查,需在一至数日的调查期间及时提供实时信息,并尽快提交应急调查报告,为地质灾害应急救援和处置提供科学依据和技术支撑。根据应急调查技术条件,划分为单点和群发地质灾害应急调查两大类。文章论述了山区地质灾害应急调查主要工作流程,即：基础资料准备、现场协调会议、制订工作方案及协调安排、卫星及无人机遥感调查、野外应急调查、资料综合研究及报告编写,以及各个环节的主要工作方法。地质灾害应急调查主要采用野外现场调查访问、地质测绘与卫星定位以及高分辨率卫星遥感、无人机航拍等便捷有效的工作方法。文中定义了地质灾害应急调查,详细分析评述了山区地质灾害应急调查的基本规则、调查方法和技术要求。     

长春双阳油田遥感综合解译

根据长春双阳油田试验区的影像特征以及放射性能谱检测、地球化学分析结果,综合解译油田的主要构造和油气分布特征.     

Development of storm hyetographs for flood forecasting in the Kingdom of Saudi Arabia

This paper presents the derivation of the design storm hyetograph patterns for the Kingdom of Saudi Arabia based on real rainfall events from meteorological stations distributed throughout the Kingdom. Two thousand twenty-seven rainfall storms for a 20–28-year period were collected and analyzed covering 13 regions of the Kingdom. Four distinct dimensionless rainfall hyetograph patterns have been obtained over the Kingdom, while two patterns have been obtained for each individual region because of the lack of data for long-duration storms in individual regions. The resulting dimensionless rainfall patterns for each region can be used to develop storm hyetographs for any design duration, total rainfall depth and return period. It has been shown that the developed storm hyetographs have different features from other storm patterns that are commonly used in arid zones. The study recommends using these curves for the design of hydraulic structures in Kingdom of Saudi Arabia and regions alike.