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101.
In this study, a novel approach of the landslide numerical risk factor(LNRF) bivariate model was used in ensemble with linear multivariate regression(LMR) and boosted regression tree(BRT) models, coupled with radar remote sensing data and geographic information system(GIS), for landslide susceptibility mapping(LSM) in the Gorganroud watershed, Iran. Fifteen topographic, hydrological, geological and environmental conditioning factors and a landslide inventory(70%, or 298 landslides) were used in mapping. Phased array-type L-band synthetic aperture radar data were used to extract topographic parameters. Coefficients of tolerance and variance inflation factor were used to determine the coherence among conditioning factors. Data for the landslide inventory map were obtained from various resources, such as Iranian Landslide Working Party(ILWP), Forestry, Rangeland and Watershed Organisation(FRWO), extensive field surveys, interpretation of aerial photos and satellite images, and radar data. Of the total data, 30% were used to validate LSMs, using area under the curve(AUC), frequency ratio(FR) and seed cell area index(SCAI).Normalised difference vegetation index, land use/land cover and slope degree in BRT model elevation, rainfall and distance from stream were found to be important factors and were given the highest weightage in modelling. Validation results using AUC showed that the ensemble LNRF-BRT and LNRFLMR models(AUC = 0.912(91.2%) and 0.907(90.7%), respectively) had high predictive accuracy than the LNRF model alone(AUC = 0.855(85.5%)). The FR and SCAI analyses showed that all models divided the parameter classes with high precision. Overall, our novel approach of combining multivariate and machine learning methods with bivariate models, radar remote sensing data and GIS proved to be a powerful tool for landslide susceptibility mapping.  相似文献   
102.
Mesozoic oil in Saudi Arabia exists in north/south-oriented anticlines. Such anticlines are usually studied using subsurface data. The present study introduces, for the first time in Saudi Arabia, a surface analog for these anticlines. The study covers two northerly oriented anticlines located in the Jinadriyah area at 15 km to the northeast of the Riyadh city. They are named herein the North and South Jinadriyah anticlines. The outcrops in both anticlines belong to the Lower Cretaceous Yamama Formation which consists of limestone in its lower part and limestone with shale in its upper part. The study included initially detailed interpretation of Google Earth and Landsat TM images to map the structural pattern of the anticlines. Detailed field mapping confirmed the satellite image interpretation and helped describe the geometry of the two anticlines in detail. The 3.5-km-long South Jinadriyah anticline is an open doubly plunging asymmetric anticline. The western flank is dissected by 13 minor reverse faults of north–south orientation. The North Jinadriyah anticline is about 5.5 km long and is relatively more complex than the South Jinadriyah anticline. It consists of northern, central, and southern segments that differ from each others in orientation and style. The anticline is dissected by 18 minor faults of different orientations and sense of displacement. Two perpendicular fracture sets with one being parallel to the anticline axes were recorded in the two anticlines. Both anticlines are interpreted as fault-propagation folds that were formed during the Late Cretaceous first Alpine orogeny. The mid-Late Tertiary second Alpine orogeny and Late Tertiary eastward tilting of the Arabian Plate increased the degree of folding and faulting.  相似文献   
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This paper discusses the practical use of filtering and inversion in VLF-EM data processing and interpretation. The advantages and disadvantages of both mentioned techniques were outlined to avoid the misleading interpretation of such data in some case studies. Much concern is taken to show the interval distance effect upon the correct depth identification of the anomalous body by either inversion or filtering. The methodology of the study is going through proposing an initial model, generating the synthetic VLF-EM data of the model by means of forward modeling, filtering (Karous–Hjelt filter) and inversion (Inv2DVLF software) of the synthetic data and comparing between the results of both methods and the initial model. The study reached to (1) Karous–Hjelt filter provides misleading depths for his limited depth of resolution and cannot provide estimates of deep targets if the profile is too small, whereas inversion provides exact results, particularly in case of shallow anomalous target; (2) crossover between in-phase and out-of-phase data could resulted from a small shallow conductive target or a large deep one; (3) selection of a reasonable environmental resistivity has an important impact on the inversion process; and (4) the numerical reflection resulted during VLF-EM data inversion could lead to an erroneous interpretation.  相似文献   
106.
Cyclones and storm surges in Bangladesh: Some mitigative measures   总被引:2,自引:2,他引:2  
Bangladesh, with its repeated cycle of floods, cyclones, and storm surges, has proved to be one of the most disaster-prone areas of the world. During the years from 1797 to 1991, Bangladesh has been hit by 60 severe cyclones (mostly accompanied by storm surges). This paper gives a brief account of these disasters with particular reference to the wind speed, surge height, loss of life, and damage to crops and properties, etc.In order to protect the coastal areas of Bangladesh from cyclonic storm surges and floods, a major system of embankments was constructed during the 1960s and 1970s, but this is now in need of rehabilitation. The Cyclone Protection Project, which was approved by the World Bank in 1989, would rehabilitate some of the existing embankments, build new embankments, and construct roads. Locally available materials, indigenous technology, and cheap surplus manpower should be used in this project. A variety of fruit trees should be planted along the dikes and roads.To the south-western part of Bangladesh bordering the Bay of Bengal, lies the world's largest single mangrove tract, known as the Sunderban, which covers a total area of 571 500 ha. This mangrove forest is of extreme importance since it provides efficient protection to life and property against cyclones and storm surges. But due to deforestation, the width of the mangrove belt is being rapidly diminished. The author therefore lays emphasis on coastal afforestation.Absolute security against cyclone hazard is probably out of the question, but an effective cyclone warning response can definitely reduce loss of life and damage to property. The author discusses the current conditions for cyclone forecasting and warning in Bangladesh, and then puts forward some proposals for improving the Cyclone Preparedness Programme.  相似文献   
107.
This study provides an evaluation of the subsurface oil contaminant flow in an oil production field at the Wadi Feiran fan, along the Gulf of Suez, Egypt. The 2D electrical resistivity tomography technique has been applied along four profiles surrounding the spill location of oil dump site. Theoretical soil resistivity response versus fluid resistivity for different cation exchange capacity values has been studied. Then, a physical model for the current situation of flowing the oil over the groundwater (sea invaded water) of saturated fluvial sediments has been introduced. It was supposed that the crude oil has higher resistivity values and turned to be conductive far away from the oil spill source under the effect of microbial biodegradation. Such conditions of contaminated distribution and its resistivity values have been considered during the inversion and interpretation of the acquired data sets. The processed 2D resistivity profiles reveal that oil plumes are accumulated in the seawater invasion direction, whereas it has low signatures along the profiles parallel to the shore line.  相似文献   
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The last decade has seen a marked increase in U-Th-Pb petrochronological studies focused on titanite and apatite. This has motivated the need for detailed, phase-specific method development and well-characterised reference materials with a wide variety of ages and chemical compositions. This study presents new U-Th-Pb isotope and major-, minor- and trace-element mass fraction data for ten titanite and five apatite reference materials based on integrated EPMA, LA-ICP-MS and isotope-dilution (ID) multi-collector (MC)-ICP-MS characterisation. Cross-comparison of EPMA and LA-ICP-MS data for the same titanite reference material suite demonstrates that careful selection of EPMA primary reference materials is necessary to minimise inaccuracies. We further identify a significant X-ray interference when measuring low Ce abundances in Ti-bearing phases and outline a method for its correction. New ID-MC-ICP-MS and LA-ICP-MS data suggest tri-concordance (defined as concordant ages for the 238U-206Pb, 235U-207Pb and 232Th-208Pb decay systems) of the MKED-1 titanite reference material and demonstrate the reproducibility of 208Pb/232Th measurements in some secondary titanite reference materials. Integration of 208Pb/232Th results with U-Pb geochronology provides a meaningful tool to help interpret complex U-Th-Pb isotopic age spectra. We provide example applications of 208Pb/232Th LA-ICP-MS measurements toward interpreting Archaean titanite ages from the Acasta Gneiss Complex, Northwest Territories, Canada.  相似文献   
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