Multi-method investigation of mass transfer mechanisms in a retrogressive clayey landslide (Harmalière,French Alps)     

Fiolleau  Sylvain  Jongmans  Denis  Bièvre  Gregory  Chambon  Guillaume  Lacroix  Pascal  Helmstetter  Agnès  Wathelet  Marc  Demierre  Michel 《Landslides》2021,18(6):1981-2000

Landslides - The mass transfer mechanisms in landslides are complex to monitor because of their suddenness and spatial coverage. The active clayey Harmalière landslide, located 30 km south of...  相似文献   

Curvature Attribute from Surface-Restoration as Predictor Variable in Kupferschiefer Copper Potentials     

Pablo Mejía-Herrera  Jean-Jacques Royer  Guillaume Caumon  Alain Cheilletz 《Natural Resources Research》2015,24(3):275-290

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Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel,West Africa   总被引：1，自引：0，他引：1  

Maïmouna Ibrahim  Guillaume Favreau  Bridget R. Scanlon  Jean Luc Seidel  Mathieu Le Coz  Jérôme Demarty  Bernard Cappelaere 《Hydrogeology Journal》2014,22(6):1293-1305

Rapid population growth in sub-Saharan West Africa and related cropland expansion were shown in some places to have increased focused recharge through ponds, raising the water table. To estimate changes in diffuse recharge, the water content and matric potential were monitored during 2009 and 2010, and modeling was performed using the Hydrus-1D code for two field sites in southwest Niger: (1) fallow land and (2) rainfed millet cropland. Monitoring results of the upper 10 m showed increased water content and matric potential to greater depth under rainfed cropland (>2.5 m) than under fallow land (≤1.0 m). Model simulations indicate that conversion from fallow land to rainfed cropland (1) increases vadose-zone water storage and (2) should increase drainage flux (～25 mm year^?1) at 10-m depth after a 30–60 year lag. Therefore, observed regional increases in groundwater storage may increasingly result from diffuse recharge, which could compensate, at least in part, groundwater withdrawal due to observed expansion in irrigated surfaces; and hence, contribute to mitigate food crises in the Sahel.  相似文献   

Conditioning of Multiple-Point Statistics Facies Simulations to Tomographic Images   总被引：2，自引：2，他引：0  

Tobias Lochbühler  Guillaume Pirot  Julien Straubhaar  Niklas Linde 《Mathematical Geosciences》2014,46(5):625-645

Geophysical tomography captures the spatial distribution of the underlying geophysical property at a relatively high resolution, but the tomographic images tend to be blurred representations of reality and generally fail to reproduce sharp interfaces. Such models may cause significant bias when taken as a basis for predictive flow and transport modeling and are unsuitable for uncertainty assessment. We present a methodology in which tomograms are used to condition multiple-point statistics (MPS) simulations. A large set of geologically reasonable facies realizations and their corresponding synthetically calculated cross-hole radar tomograms are used as a training image. The training image is scanned with a direct sampling algorithm for patterns in the conditioning tomogram, while accounting for the spatially varying resolution of the tomograms. In a post-processing step, only those conditional simulations that predicted the radar traveltimes within the expected data error levels are accepted. The methodology is demonstrated on a two-facies example featuring channels and an aquifer analog of alluvial sedimentary structures with five facies. For both cases, MPS simulations exhibit the sharp interfaces and the geological patterns found in the training image. Compared to unconditioned MPS simulations, the uncertainty in transport predictions is markedly decreased for simulations conditioned to tomograms. As an improvement to other approaches relying on classical smoothness-constrained geophysical tomography, the proposed method allows for: (1) reproduction of sharp interfaces, (2) incorporation of realistic geological constraints and (3) generation of multiple realizations that enables uncertainty assessment.  相似文献   

Contribution of {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} and 13CTDIC Evaluation to the Identification of CO2 Sources in Volcanic Groundwater Systems: Influence of Hydrometeorological Conditions and Lava Flow Morphologies—Application to the Argnat Basin (Chaîne des Puys, Massif Central, France)     

Guillaume Bertrand  Hélène Celle-Jeanton  Sébastien Loock  Frédéric Huneau  Véronique Lavastre 《Aquatic Geochemistry》2013,19(2):147-171

Mineralization of groundwater in volcanic aquifers is partly acquired through silicates weathering. This alteration depends on the dissolution of atmospheric, biogenic, or mantellic gaseous CO₂ whose contributions may depend on substratum geology, surface features, and lava flow hydrological functionings. Investigations of $ {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} $ and δ¹³C_TDIC (total dissolved inorganic carbon) on various spatiotemporal scales in the unsaturated and saturated zones of volcanic flows of the Argnat basin (French Massif Central) have been carried out to identify the carbon sources in the system. Mantellic sources are related to faults promoting CO₂ uplift from the mantle to the saturated zone. The contribution of this source is counterbalanced by infiltration of water through the unsaturated zone, accompanied by dissolution of soil CO₂ or even atmospheric CO₂ during cold periods. Monitoring and modeling of δ¹³C_TDIC in the unsaturated zone shows that both $ {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} $ and δ¹³C_TDIC are controlled by air temperature which influences soil respiration and soil-atmosphere CO₂ exchanges. The internal geometry of volcanic lava flows controls water patterns from the unsaturated zone to saturated zone and thus may explain δ¹³C heterogeneity in the saturated zone at the basin scale.  相似文献   

Impact basin relaxation at Iapetus     

Guillaume Robuchon  Francis Nimmo  Michelle Kirchoff 《Icarus》2011,214(1):82-90

We investigate impact basin relaxation on Iapetus by combining a 3D thermal evolution model (Robuchon, G., Choblet, G., Tobie, G., Cadek, O., Sotin, C., Grasset, O. [2010]. Icarus 207, 959-971) with a spherical axisymmetric viscoelastic relaxation code (Zhong, S., Paulson, A., Wahr, J. [2003]. Geophys. J. Int. 155, 679-695). Due to the progressive cooling of Iapetus, younger basins relax less than older basins. For an ice reference viscosity of 10¹⁴ Pa s, an 800 km diameter basin relaxes by 30% if it formed in the first 50 Myr but by 10% if it formed at 1.2 Gyr. Bigger basins relax more rapidly than smaller ones, because the inferred thickness of the ice shell exceeds the diameter of all but the largest basins considered. Stereo topography shows that all basins 600 km in diameter or smaller are relaxed by 25% or less. Our model can match the relaxation of all the basins considered, within error, by assuming a single basin formation age (4.36 Ga for our nominal viscosity). This result is consistent with crater counts, which show no detectable age variation between the basins examined.  相似文献   

Photoabsorption in Ganymede’s atmosphere     

Gaël Cessateur  Jean Lilensten  Mathieu Barthélémy  Thierry Dudok de Wit  Cyril Simon Wedlund  Guillaume Gronoff  Hélène Ménager  Matthieu Kretzschmar 《Icarus》2012,218(1):308-319

In the framework of future space missions to Ganymede, a pre-study of this satellite is a necessary step to constrain instrument performances according to the mission objectives. This work aims at characterizing the impact of the solar UV flux on Ganymede’s atmosphere and especially at deriving some key physical parameters that are measurable by an orbiter. Another objective is to test several models for reconstructing the solar flux in the Extreme-UV (EUV) in order to give recommendations for future space missions.Using a Beer–Lambert approach, we compute the primary production of excited and ionized states due to photoabsorption, neglecting the secondary production that is due to photoelectron impacts as well as to precipitated suprathermal electrons. Ions sputtered from the surface are also neglected. Computations are performed at the equator and close to the pole, in the same conditions as during the Galileo flyby. From the excitations, we compute the radiative relaxation leading to the atmospheric emissions. We also propose a simple chemical model to retrieve the stationary electron density. There are two main results: (i) the modelled electron density and the one measured by Galileo are in good agreement. The main atmospheric visible emission is the atomic oxygen red line at 630 nm, both in equatorial and in polar conditions, in spite of the different atmospheric compositions. This emission is measurable from space, especially for limb viewing conditions. The OH emission (continuum between 260 and 410 nm) is also probably measurable from space. (ii) The input EUV solar flux may be directly measured or reconstructed from only two passbands solar observing diodes with no degradation of the modelled response of the Ganymede’s atmosphere. With respect to these results, there are two main conclusions: (i) future missions to Ganymede should include the measurement of the red line as well as the measurement of OH emissions in order to constrain the atmospheric model. (ii) None of the common solar proxies satisfactorily describes the level of variability of the solar EUV irradiance. For future atmospheric planetary space missions, it would be more appropriate to derive the EUV flux from a small radiometer rather than from a full-fledged spectrometer.  相似文献   

Further developments of a transient Poisson-cluster model for rainfall     

Guillaume Evin  Anne-Catherine Favre 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(4):831-847

Stochastic point processes for rainfall are known to be able to preserve the temporal variability of rainfall on several levels of aggregation (e.g. hourly, daily), especially when the cluster approach is used. One major assumption in most of the applications todate is the stationarity of the rainfall properties in time, which must be reconsidered under a climate change hypothesis. Here, we propose new theoretical developments of a Poisson-based model with cluster, namely the Neyman–Scott Rectangular Pulses Model, which treats storm frequency as a nonstationary function. In this paper, storm frequency is modelled as a linear function of time in order to reproduce an increase (or decrease) of the mean annual precipitation. The basic theory is reconsidered and the moments are derived up to the third order. Then, a calibration method based on the generalized method of moments is proposed and discussed. An application to a rainfall time series from Uccle illustrates how this model can reproduce a trend for the average rainfall. This work opens new avenues for future developments on transient stochastic rainfall models and highlights the major challenges linked to this approach.  相似文献   

Soil charcoal stability over the Holocene—Response to comments by Mikael Ohlson     

Guillaume de Lafontaine  Hugo Asselin 《Quaternary Research》2012,78(1):155-156

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Stepwise Tarim Sea Retreat (West China): Eustatic VS. Tectonic Control and Links with Asian Aridification     

Guillaume DUPONT-NIVET  Roderic BOSBOOM  Arjen GROTHE  Henk BRINKHUIS  Giuliana VILLA  Oleg MANDIC  Marius STOICA  HUANG Wentao  YANG Wei  GUO ZhaoJie  Wout KRIJGSMAN 《《地质学报》英文版》2013,87(Z1):210-211

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