Application de la méthode des simulations croisées à l’analyse de tendances dans la relation pluie-débit à partir du modèle GR2M : cas du bassin versant du N’zi-Bandama (Côte d’Ivoire)     

Amani Michel Kouassi  Tozan Michel N’guessan Bi  Koffi Fernand Kouamé  Kassi Alexis Kouamé  Jean-Claude Okaingni  Jean Biemi 《Comptes Rendus Geoscience》2012,344(5):288-296

The study area is the N’zi watershed, sub-watershed of the Bandama River (Ivory Coast). The N’zi watershed is located between longitudes 3°49′ and 5°22′ West and latitudes 6°00′ and 9°26′ North and covers an area of 35,500 km². This study aims to identify trends in the rainfall-runoff relationship by using a monthly conceptual model. The methodology has consisted on the one hand in highlighting the existence of interannual climate and hydrological variability by using the method of segmentation of Hubert, and on the other hand, in applying the crossed simulations method by using the GR2M model, over several 7-year sub-periods. The results of the application of the method of segmentation of Hubert have demonstrated the presence of a hydroclimatic variability in the N’zi watershed. The modifications of the climate and physical conditions of the flow resulted in a modification of the hydrological response of the watershed translated by a non-stationarity in the rainfall-runoff relation.  相似文献   

Preliminary report on a dinosaur tracksite from Lower Cretaceous strata in Mount Lebanon     

Raymond Gèze  Isabelle Veltz  Jean-Claude Paicheler  Bruno Granier  Roland Habchi  Dany Azar  Sibelle Maksoud 《Arabian Journal of Geosciences》2016,9(19):730

A dinosaur tracksite was discovered in Batha on the side of the road from Harissa to Ghosta (Keserwan, Lebanon). About ten trackways are exposed at the top of two beds of Lower Cretaceous limestones over an area of approximately 1000 m². These footprints were probably made by at least two dinosaur species, Sauropoda and either Theropoda or Ornithopoda. The site, which is the first record from Lebanon, should be protected to allow further scientific investigations.  相似文献   

Assessing physical vulnerability in large cities exposed to flash floods and debris flows: the case of Arequipa (Peru)     

Jean-Claude Thouret  Susanne Ettinger  Mathieu Guitton  Olivier Santoni  Christina Magill  Kim Martelli  Giulio Zuccaro  Victor Revilla  Juan Antonio Charca  Anita Arguedas 《Natural Hazards》2014,73(3):1771-1815

Understanding the physical vulnerability of buildings and infrastructure to natural hazards is an essential step in risk assessment for large cities. We have interpreted high spatial resolution images, conducted field surveys, and utilized numerical simulations, in order to assess vulnerability across Arequipa, south Peru, close to the active El Misti volcano. The emphasis of this study was on flash floods and volcanic or non-volcanic hyperconcentrated flows, which recur on average every 3.5 years across the city. We utilized a geographic information system to embed vulnerability and hazard maps as a step to calculate risk for buildings and bridges along the Río Chili valley and two tributaries. A survey of ~1,000 buildings from 46 city blocks, different in age, construction materials, and land usage, provided architectural and structural characteristics. A similar survey of twenty bridges across the three valleys was based on structural, hydraulic, and strategic parameters. Interpretation of high spatial resolution (HSR) satellite images, which allows for quick identification of approximately 69 % of the structural building types, effectively supplemented field data collection. Mapping vulnerability has led us to pinpoint strategic areas in case of future destructive floods or flows. Calculated vulnerability is high if we examine structural criteria alone. We further consider physical setting with the most vulnerable city blocks located on the lowermost terraces, perpendicular or oblique to the flow path. Statistical analysis conducted on 3,015 city blocks, considering nine criteria identified from HSR images, indicated that building-type heterogeneity and the shape of the city blocks, along with building and street network density, are the most discriminant parameters for assessing vulnerability.  相似文献   

Experimental study of mechanical and hydraulic properties of bedded rock salt from the Jintan location   总被引：1，自引：0，他引：1  

Wei Xing  Juan Zhao  Uwe Düsterloh  Dieter Brückner  Zhengmeng Hou  Lingzhi Xie  Jianfeng Liu 《Acta Geotechnica》2014,9(1):145-151

A series of triaxial compression tests, triaxial extension tests, and triaxial compression creep tests were conducted to evaluate the strength, deformability, and permeability of rock salt from the Jintan location. Based on a previous analysis, the measured data can be physically modeled very well as shown by the constitutive model Hou/Lux and indicate that China’s representative bedded rock salt from the Jintan location is characterized by good ductility and deformation properties, similar to the European high-purity rock salt. Based on a comparison of compression as well as extension failure strength determined at rock salt from Jintan location, a similarity of compression and extension failure strength could be demonstrated. Permeation flow seems to be an anisotropic process because the permeability measured at samples prior to failure by compression tests differs to those measured at samples prior to failure by extension tests. The anisotropy of damage and destruction of rock salt has a significant influence on permeability. In case of triaxial compression tests, the measured permeability increases two to six orders of magnitude because of consistent direction of injection and cracks. In case of triaxial extension tests, however, the permeability increases less with a maximum of two orders in magnitude. The test results are significant for understanding the load-bearing behavior of rock salt from Jintan location and investigations with reference to the stability and tightness of underground caverns.  相似文献   

Comparative study of geophysical and soil–gas investigations at the Hartoušov (Czech Republic) natural CO2 degassing site     

Claudia Sandig  Uta Sauer  Karin Bräuer  Ulrich Serfling  Claudia Schütze 《Environmental Earth Sciences》2014,72(5):1421-1434

Our study at this natural analog site contributes to the evaluation of methods within a hierarchical monitoring concept suited for the control of CO₂ degassing. It supports the development of an effective monitoring concept for geological CO₂ storage sites—carbon capture and storage as one of the pillars of the European climate change efforts. This study presents results of comprehensive investigations along a 500-m long profile within the Hartou?ov (Czech Republic) natural CO₂ degassing site and gives structural information about the subsurface and interaction processes in relation to parameters measured. Measurements of CO₂ concentrations and investigation of the subsurface using electrical resistivity tomography and self-potential methods provide information about subsurface properties. For their successful application it is necessary to take seasonal variations (e.g., soil moisture, temperature, meteorological conditions) into consideration due to their influence on these parameters. Locations of high CO₂ concentration in shallow depths are related to positive self-potential anomalies, low soil moistures and high resistivity distributions, as well as high δ13C values and increased radon concentrations. CO₂ ascends from deep geological sources via preferential pathways and accumulates in coarser sediments. Repetition of measurements (which includes the effects of seasonal variations) revealed similar trends and allows us to identify a clear, prominent zone of anomalous values. Coarser unconsolidated sedimentary layers are beneficial for the accumulation of CO₂ gas. The distribution of such shallow geological structures needs to be considered as a significant environmental risk potential whenever sudden degassing of large gas volumes occurs.  相似文献   

Undrained Monotonic Response and Instability of Medium-Dense Sandy Soil     

Noureddine Della  Mostefa Belkhatir  Ahmed Arab  Jean Canou  Jean-Claude Dupla 《Marine Georesources & Geotechnology》2013,31(6):487-495

A series of undrained monotonic triaxial compression tests were performed on natural, medium-dense (relative density (RD) = 50%) Chlef sand containing 0.5% of non-plastic fines, under different confining pressures of 50 kPa, 100 kPa, and 200 kPa. This article focuses on distinctive states of the monotonic undrained response of sands, namely the critical state, the phase transformation state, the quasi-steady state, and the state of undrained instability (onset of flow liquefaction). Specimens were prepared using dry funnel pluviation and wet deposition to investigate the effect of the initial sand fabric on these states. The present data suggest that the initial fabric of the sand appears to have a significant effect on the undrained behavior in the early stages of shearing, with its influence vanishing at large strains. Wet deposition specimens demonstrate considerably larger undrained instability state strength than their dry funnel pluviation counterparts, and a unique critical state locus is reached by both dry funnel pluviation and wet deposition.  相似文献   

Synthetic fluid inclusions. XV. TEM investigation of plastic flow associated with reequilibration of fluid inclusions in natural quartz   总被引：1，自引：0，他引：1  

Maxim O. Vityk  Robert J. Bodnar  Jean-Claude Doukhan 《Contributions to Mineralogy and Petrology》2000,139(3):285-297

The nature and abundance of dislocations in quartz surrounding fluid inclusions were studied to obtain a better understanding of processes associated with fluid inclusion reequilibration. Synthetic fluid inclusions containing 10 wt% NaCl aqueous solution were formed in three samples at 700 °C and 5 kbar. One of the samples was quenched along an isochore to serve as a reference sample. The other two samples were quenched along a P-T path that generated internal pressures in excess of the confining pressure. The two samples were held at the final reequilibration P-T conditions of 625 °C and 2 kbar for 30 and 180 days, respectively. Following the experiments, microstructures associated with fluid inclusions were examined with the TEM. Quartz in healed fractures in the reference sample that was quenched isochorically shows a moderate dislocation activity. Quartz adjacent to reequilibrated fluid inclusions in the other two samples, however, showed a marked increase in dislocation activity compared to the un-reequilibrated sample. Deformation of the inclusion walls occurred anisotropically by expansion of mobile dislocations in their slip systems. Dislocation expansion was controlled by glide in the rhombohedral planes {1 0 1 1} that was restricted to narrow zones (≤3 μm) in the immediate vicinity of the fluid inclusion walls outside of the healed fracture plane. These plastic zones were observed after both short term (30 days) and long term (180 days) experiments and are attributed to hydrolytic weakening of quartz around fluid inclusions owing to diffusion of water into the quartz matrix during the experiment. The close spatial association of submicroscopic water bubbles with dislocations, and the rarity of water bubbles in the reference sample, show clearly that in both the 30 and 180 day experiments reequilibration involves water loss from the fluid inclusions. Our results indicate that synthetic fluid inclusions in this study recover (chemically and volumetrically), even at relatively fast experimental loading rates, such that internal stresses never reach the point of brittle failure. The driving force for fluid inclusion deformation involves two related mechanisms: plastic deformation of hydrolytically weakened wet quartz in the healed fracture, and water leakage associated with preexisting and strain-induced dislocations. Received: 5 May 1998 / Accepted: 10 February 2000  相似文献   

Stable Sulfur Isotopic Evidence for Historical Changes of Sulfur Cycling in Estuarine Sediments from Northern Florida     

Volker Brüchert  Lisa M. Pratt 《Aquatic Geochemistry》1999,5(3):249-268

Data on abundance and isotopic composition of porewater and sedimentary sulfur species are reported for relatively uncontaminated and highly contaminated fine-grained anoxic sediments of St. Andrew Bay, Florida. A strong contrast in amount and composition of sedimentary organic matter at the two sites allows a comparative study of the historical effects of increased organic loading on sulfur cycling and sulfur isotopic fractionation. In the contaminated sediments, an increase in organic loading caused increased sedimentary carbon/sulfur ratios and resulted in higher rates of bacterial sulfate reduction, but a lower efficiency of sulfide oxidation. These differences are well reflected in the isotopic composition of dissolved sulfate, sulfide, and sedimentary pyrite. Concentration and isotopic profiles of dissolved sulfate, organic carbon, and total sulfur suggest that the anaerobic decomposition of organic matter is most active in the upper 8cm but proceeds at very slow rates below this depth. The rapid formation of more than 90% of pyrite in the uppermost 2 cm which corresponds to about 3 years of sediment deposition allows the use of pyrite isotopic composition for tracing changing diagenetic conditions. Sediment profiles of the sulfur isotopic composition of pyrite reflect present-day higher rates of bacterial sulfate reduction and lower rates of sulfide oxidation, and record a profound change in the diagenetic cycling of sulfur in the contaminated sediments coincident with urban and industrial development of the St. Andrew Bay area.  相似文献   

Erosion calderas: origins, processes, structural and climatic control   总被引：1，自引：0，他引：1  

Dávid Karátson  Jean-Claude Thouret  Ichio Moriya  Alejandro Lomoschitz 《Bulletin of Volcanology》1999,61(3):174-193

 The origin and development of erosion-modified, erosion-transformed, and erosion-induced depressions in volcanic terrains are reviewed and systematized. A proposed classification, addressing terminology issues, considers structural, geomorphic, and climatic factors that contribute to the topographic modification of summit or flank depressions on volcanoes. Breaching of a closed crater or caldera generated by volcanic or non-volcanic processes results in an outlet valley. Under climates with up to ∼2000–2500 mm annual rainfall, craters, and calderas are commonly drained by a single outlet. The outlet valley can maintain its dominant downcutting position because it quickly enlarges its drainage basin by capturing the area of the primary depression. Multi-drained volcanic depressions can form if special factors, e.g., high-rate geological processes, such as faulting or glaciation, suppress fluvial erosion. Normal (fluvial) erosion-modified volcanic depressions the circular rim of which is derived from the original rim are termed erosion craters or erosion calderas, depending on the pre-existing depression. The resulting landform should be classed as an erosion-induced volcanic depression if the degradation of a cluster of craters produces a single-drained, irregular-shaped basin, or if flank erosion results in a quasi-closed depression. Under humid climates, craters and calderas degrade at a faster rate. Mostly at subtropical and tropical ocean-island and island-arc volcanoes, their erosion results in so-called amphitheater valleys that develop under heavy rainfall (>∼2500 mm/year), rainstorms, and high-elevation differences. Structural and lithological control, and groundwater in ocean islands, may in turn preform and guide development of high-energy valleys through rockfalls, landsliding, mudflows, and mass wasting. Given the intense erosion, amphitheater valleys are able to breach a primary depression from several directions and degrade the summit region at a high rate. Occasionally, amphitheater valleys may create summit depressions without a pre-existing crater or caldera. The resulting, negative landforms, which may drain in several directions and the primary origin of which is commonly unrecognizable, should be included in erosion-transformed volcanic depressions. Received: 4 January 1998 / Accepted: 18 January 1999  相似文献   

Electrical imaging of lateritic weathering mantles over granitic and metamorphic basement of eastern Senegal, West Africa     

Michel Ritz  Jean-Claude Parisot  S. Diouf  A. Beauvais  F. Dione  M. Niang 《Journal of Applied Geophysics》1999,41(4):105

The electrical properties of several tens of metres of lateritic weathering mantle were investigated by using electrical resistivity tomography (ERT) in two basement areas of eastern Senegal. The field survey was conducted along two profiles providing continuous coverage. Colour-modulated pseudosections of apparent resistivity vs. pseudo-depth were plotted for all survey lines, giving an approximate image of the subsurface structure. In the area underlain by granitic basement, the pseudosection suggests a very inhomogeneous weathered layer in which the apparent resistivity changes more rapidly than thickness. In the second area, underlain by schists, the lateral changes in electrical properties are less pronounced than those of the granitic area. Interpretation of 2D Wenner resistivity data yielded considerable detail about the regolith, even without pit information. In both areas, the near-surface topsoil comprising undersaturated lateritic material is highly resistive. The intermediate layer with low resistivities (e.g., 20–100 Ωm) contains clays including small quantities of water. The third, highly resistive layer reflects the granitic basement. Comparison of ERT survey results with pit information shows general agreement and suggests that ERT can be used as a fast and efficient exploration tool to map the thick lateritic weathering mantle in tropical basement areas with hard rock geology.  相似文献