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991.
Feeding multisource Earth observation (EO) data into Earth science models (ESM) remains a daunting challenge. This paper presents a service-oriented approach as an alternative solution. It uses geospatial web services to process the EO data and geoprocessing workflow for automation. Different from existing approaches, it takes advantage of virtual data products (VDP) to release modelers from intensive data processing. It can directly connect ESMs to public EO sources via Cyberinfrastructure. A prototype called CyberConnector is implemented. CyberConnector supports intuitive building of VDP, automatic execution of workflows and effortless retrieval of model-ready input files. We used it to stream multiple datasets to several ESMs including finite-volume coastal ocean model (FVCOM) and cloud-resolving model (CRM). The results show that CyberConnector can truly benefit modelers on time saving and effort minimizing.  相似文献   
992.
Archives across the world contain vast amounts of old or “vintage” seismic reflection data, which are largely inaccessible for geo-scientific research, due to the out-dated media on which they are stored. Despite the age of these data, they often have great potential to be of use in modern day research. It is often the case that seismic reflection data within these archives are only available as a processed stacked section, printed on paper or film. In this study, a method for the conversion (vectorization) of scanned images of stacked reflection seismic data to standard SEG-Y format is presented. The method addresses data displayed with a line denoting the waveform, where areas on one side of the baseline are shaded (i.e. wiggle trace, variable fill). The method provides an improvement on other published methods utilized within currently available academic software. Unlike previous studies, the method used to detect trace baselines and to detect and remove timelines on the seismic image is described in detail. Furthermore, a quantitative analysis of the performance of the method is presented, showing that an average trace-to-trace correlation coefficient of between 0.8 and 0.95 can be achieved for typical plotting styles. Finally, a case study where the method is applied to vectorize over 1700 km of land seismic data from the island of Gotland (Sweden) is presented.  相似文献   
993.
This paper describes analytical protocols adopted for calibrating a portable gamma rays spectrometer using a 2? × 2? NaI(Tl) scintillation detector for performing exploration and environmental surveys. The steps involved the determination of counting times with good accuracy, calibration in energy and concentration, and data conversion to effective dose (Ed) for monitoring the radioactivity levels in the air, for indoor and outdoor environments. The χ2 test was applied to the counting rate data acquired for ten different readings, allowing determine the greater accuracy among them. Some standards yielded values above of the detection limit for calibrating the K, eU, and eTh windows, whereas empirical equations provided satisfactory results. The count rates in these windows were obtained in selected environments related to Geology teaching activities in a Brazilian university. Then, they were converted to Ed, showing the applicability of the adopted procedures for environmental surveys. The radiological monitoring showed two sites exhibiting Ed values above the WHO guideline reference value of 1 mSv/year. The first was in a minerals and rocks museum and the second in a deposit (litoteca) dedicated to the rocks storage. Thus, the members of the public are only occasionally exposed to the natural gamma radiation there. Additionally, the Ed values are much lower than the recommended limit of 20 mSv/year for occupationally exposed individuals.  相似文献   
994.
We propose a multi-fidelity system reduction technique that uses weighted graphs paired with three-dimensional discrete fracture network (DFN) modelling for efficient simulation of subsurface flow and transport in fractured media. DFN models are used to simulate flow and transport in subsurface fractured rock with low-permeability. One method to alleviate the heavy computational overhead associated with these simulations is to reduce the size of the DFN using a graph representation of it to identify the primary flow sub-network and only simulate flow and transport thereon. The first of these methods used unweighted graphs constructed solely on DFN topology and could be used for accurate predictions of first-passage times. However, these techniques perform poorly when predicting later stages of the mass breakthrough. We utilize a weighted-graph representation of the DFN where edge weights are based on hydrological parameters in the DFN that allows us to exploit the kinematic quantities derivable a posteriori from the flow solution obtained on the graph representation of the DFN to perform system reduction and predict the later stages of the breakthrough curve with high fidelity. We also propose and demonstrate the use of an adaptive pruning algorithm with error control that produces a pruned DFN sub-network whose predicted mass breakthrough agrees with the original DFN within a user-specified tolerance. The method allows for the level of accuracy to be a user-controlled parameter.  相似文献   
995.
Although rock glaciers in the Central and Desert Andes of Argentina and Chile have been previously studied in detail, much less attention has been paid to the occurrence of these permafrost forms in Patagonia. Recently, however, the establishment of the Argentinean Glacier Inventory program, which intends to inventory and monitor all ice masses along the Argentinean Andes, has started a large amount of new geocryological research. The project is designed to provide reliable and worldwide comparable results, supported by well established technical procedures and background information. Presented here is the first rock glacier inventory of the Monte San Lorenzo (Cerro Cochrane) region in the southern Patagonian Andes. A total of 130 intact (9.86 km2) and 47 fossil (1.45 km2) landforms were inventoried using two 2.5 m resolution ALOS Panchromatic Remote‐sensing Instruments for Stereo Mapping images. Since the Argentinean federal initiative described above legally protects all rock glaciers in the country as water reserves, and due to the little scientific knowledge concerning rock glaciers in the vast majority of the Patagonian Andes, this inventory provides an important basis for political decision‐making and opens further geocryological research avenues for the Patagonian region in general.  相似文献   
996.
Alluvial fans serve as useful archives that record the history of depositional and erosional processes in mountainous regions and thus can reveal the environmental controls that influenced their development. Economically, they play an important role as groundwater reservoirs as well as host rocks for hydrocarbons in deeply buried systems. The interpretation of these archives and the evaluation of their reservoir architecture, however, are problematic because marked heterogeneity in the distribution of sedimentary facies makes correlation difficult. This problem is compounded because the accumulated sedimentary deposits of modern unconsolidated fan systems tend to be poorly exposed and few such systems have been the focus of investigation using high‐resolution subsurface analytical techniques. To overcome this limitation of standard outcrop–analogue studies, a geophysical survey of an alpine alluvial fan was performed using ground‐penetrating radar to devise a scaled three‐dimensional subsurface model. Radar facies were classified and calibrated to lithofacies within a fan system that provided outcropping walls and these were used to derive a three‐dimensional model of the sedimentary architecture and identify evolutionary fan stages. The Illgraben fan in the Swiss Alps was selected as a case study and a network of ca 60 km sections of ground‐penetrating radar was surveyed. Seven radar facies types could be distinguished, which were grouped into debris‐flow deposits and stream‐flow deposits. Assemblages of these radar facies types show three depositional units, which are separated by continuous, fan‐wide reflectors; they were interpreted as palaeo‐surfaces corresponding to episodes of sediment starvation that affected the entire fan. An overall upward decline in the proportion of debris‐flow deposits from ca 50% to 15% and a corresponding increase in stream‐flow deposits were identified. The uppermost depositional unit is bounded at its base by a significant incision surface up to 700 m wide, which was subsequently filled up mostly by stream‐flow deposits. The pronounced palaeo‐surfaces and depositional trends suggest that allocyclic controls governed the evolution of the Illgraben fan, making this fan a valuable archive from which to reconstruct past sediment fluxes and environmental change in the Alps. The results of the integrated outcrop–geophysical approach encourage similar future studies on fans to retrieve their depositional history as well as their potential reservoir properties.  相似文献   
997.
The effect of changing palaeoclimate and palaeoenvironment on human evolution during the Pleistocene is debated, but hampered by few East African records directly associated with archaeological sites prior to the Last Glacial Maximum. Middle to Late Pleistocene deposits on the shoreline of eastern Lake Victoria preserve abundant vertebrate fossils and Middle Stone Age arte‐facts associated with riverine tufas at the base of the deposits, which are ideal for palaeoenvironmental reconstructions. New data from tufas identified on Rusinga Island and on the mainland near Karungu, Kenya are provided from outcrop, thin sections, mineralogical, stable isotopic and U‐series dating analyses. Tufa is identified in four sites: Nyamita (94·0 ± 3·3 and 111·4 ± 4·2 ka); Kisaaka, Aringo (455 ± 45 ka); and Obware. The age ranges of these tufa deposits demonstrate that spring‐fed rivers were a recurrent, variably preserved feature on the Pleistocene landscape for ca 360 kyr. Poor sorting of clastic facies from all sites indicates flashy, ephemeral discharge, but these facies are commonly associated with barrage tufas, paludal environments with δ13C values of ca 10‰ indicative of C3 plants and fossil Hippopotamus, all of which indicate a perennial water source. Other tufa deposits from Nyamita, Obware and Aringo have a mixed C3/C4 signature consistent with a semi‐arid C4 grassland surrounding these spring‐fed rivers. The δ18O values of tufa from Nyamita are on average ca 1‰ more negative than calcite precipitated from modern rainfall in the region, suggesting greater contribution of depleted monsoonal input, similar to the Last Glacial Maximum. Microdebitage and surface‐collected artefacts indicate that early modern humans were utilizing these spring‐fed rivers. The presence of spring?fed rivers would have afforded animals a reliable water source, sustaining a diverse plant and animal community in an otherwise arid environment.  相似文献   
998.
Journal of Earth System Science - This paper presents result of 30 vertical electrical soundings carried out in Makurdi, Benue state capital, north–central Nigeria to evaluate aquifer...  相似文献   
999.
Slushflows are natural hazards that pose considerable danger to communities across the globe. These events are characterized by the rapid mass movement of water-inundated snow downslope, and they cause economic damage as well as fatalities in many different climates and regions. As the global climate changes and human populations and industries potentially expand to higher latitudes, it will be important to fully understand the slushflow hazard since an anticipated increase in the frequency of rain-on-snow events and an earlier spring thaw would likely increase the probability of slushflows. This article: (1) summarizes the factors that favor the development of slushflows; (2) discusses the hazard management implications of slushflows; (3) examines the policies employed to prevent and mitigate slushflow damage; and (4) sets out the need for modifications in hazard management systems. Conclusions drawn hope to address future research needs in an effort to create policies that better suit the needs of at-risk communities.  相似文献   
1000.
Synthetic CaAlSiO4F, the Al-F analog of titanite, has been investigated using single-crystal synchrotron diffraction experiments at Beamline X06DA (Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland) and Raman spectroscopy. The presented structural model with 40 parameters was refined against 506 unique reflections to a final R o b s of 0.026 (space group A2/a, a = 6.9120(11), b = 8.5010(10), c = 6.435(2) Å, β = 114.670(11)°, and Z = 4) and exhibits less distorted coordination polyhedra than earlier models from powder data. Vibrational spectra were calculated in harmonic approximation at the Γ point from fully relaxed energy optimisations of the crystal structure, using 3D-periodic density functional theory with Gaussian basis sets and the software CRYSTAL06. The lattice parameters of the fully relaxed structure were in good agreement with the experimental values, with the calculated values 0.8 ± 0.4 % too large; the monoclinic angle was calculated 0.4° too large. The agreement of the calculated Raman frequencies with the observed ones was very good, with standard deviation ±3 cm?1 and maximum deviations of ±7 cm?1. Furthermore, a detailed discussion of the atomic displacements associated with each Raman mode is given.  相似文献   
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