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91.
The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion might result in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard assessment based on geological and hydrological surveys, including small scale hydraulic tests, as well as the risk evaluation that has been performed. The risk management relies first upon a high level monitoring and an emergency plan; various mitigation strategies have been considered. 相似文献
92.
Susan E. Kayser Jean-Louis Bougeret Joseph Fainberg Robert G. Stone 《Solar physics》1987,109(1):107-118
The trajectories of 38 type III storms in the interplanetary medium have been deduced from ISEE-3 radio observations and extrapolated back to the Sun to determine the Carrington coordinates of their footpoints. The analysis assumes radial motion of the solar wind, and the trajectories are projected radially back toward the surface for the last few solar radii. To identify the storm sources, the footpoints were compared to a variety of solar features: to the large-scale neutral line at the base of the current sheet, to active regions, to the small-scale neutral lines and Hα filaments which trace out active regions, and to coronal holes. Most of the footpoints were found to lie near active regions, in agreement with metric storm locations. There is a weak correlation with Hα filaments, no apparent association with the current sheet, and an anticorrelation with coronal holes. There is a small excess of storms in the leading half of magnetic sectors. 相似文献
93.
J. M. Jouanneau O. Weber T. Drago A. Rodrigues A. Oliveira J. M. A. Dias C. Garcia S. Schmidt J. L. Reyss 《Progress in Oceanography》2002,52(2-4)
Thus study is based on 31 box-core samples collected mainly from the mud-patches of the Galician and North-Portuguese shelf. Each of these cores, some decimetres in length, have been described, radiographied and sampled each centimetre for grain-size analysis and measurement of the particulate organic carbon (Corg) content. 210Pb excess profiles have been measured using gamma spectrometry, which, combined with the analysis of the vertical variations of the sedimentary facies, have allowed estimates of sedimentation rates. These rates were found to vary between 0.05 and 0.40 cm yr−1. Considering the latitudinal variation of sedimentation rates around the 100m contour, we note that the maximum rates occurred off the Douro estuary in the southern sector and also near the Galician rias to the north. The organic content (Corg) of sediments varied between 0.4 and 2%. Latitudinally Corg showed a decrease from the South to the North. These results coupled with the sedimentary map (see Dias, Gonzalez, Garcia & Diaz del Rio, 2001) have permitted us to establish the detrital mass budget and an inventory of Corg burial. 相似文献
94.
David Mimoun Mark A. Wieczorek Leon Alkalai W. Bruce Banerdt David Baratoux Jean-Louis Bougeret Sylvain Bouley Baptiste Cecconi Heino Falcke Joachim Flohrer Raphael F. Garcia Robert Grimm Matthias Grott Leonid Gurvits Ralf Jaumann Catherine L. Johnson Martin Knapmeyer Naoki Kobayashi Alexander Konovalenko David Lawrence Mathieu Le Feuvre Philippe Lognonné Clive Neal Jürgen Oberst Nils Olsen Huub R?ttgering Tilman Spohn Susanne Vennerstrom Graham Woan Philippe Zarka 《Experimental Astronomy》2012,33(2-3):529-585
Farside Explorer is a proposed Cosmic Vision medium-size mission to the farside of the Moon consisting of two landers and an instrumented relay satellite. The farside of the Moon is a unique scientific platform in that it is shielded from terrestrial radio-frequency interference, it recorded the primary differentiation and evolution of the Moon, it can be continuously monitored from the Earth–Moon L2 Lagrange point, and there is a complete lack of reflected solar illumination from the Earth. Farside Explorer will exploit these properties and make the first radio-astronomy measurements from the most radio-quiet region of near-Earth space, determine the internal structure and thermal evolution of the Moon, from crust to core, and quantify impact hazards in near-Earth space by the measurement of flashes generated by impact events. The Farside Explorer flight system includes two identical solar-powered landers and a science/telecommunications relay satellite to be placed in a halo orbit about the Earth–Moon L2 Lagrange point. One lander would explore the largest and oldest recognized impact basin in the Solar System— the South Pole–Aitken basin—and the other would investigate the primordial highlands crust. Radio astronomy, geophysical, and geochemical instruments would be deployed on the surface, and the relay satellite would continuously monitor the surface for impact events. 相似文献
95.
Jean-Louis Le Mouël Elena Blanter Mikhail Shnirman Vincent Courtillot 《Journal of Atmospheric and Solar》2009,71(12):1309-1321
Daily temperature and pressure series from 55 European meteorological stations covering the 20th century are analyzed. The overall temperature mean displays a sharp minimum near 1940 and a step-like jump near 1987. We evaluate the evolution of disturbances of these series using mean squared inter-annual variations and “lifetimes”. The decadal to secular evolutions of solar activity and temperature disturbances display similar signatures over the 20th century. Because of heterogeneity of the climate system response to solar forcing, regional and seasonal approaches are key to successful identification of these signatures. Most of the solar response is governed by the winter months, as best seen near the Atlantic Ocean. Intensities of disturbances vary by factors in excess of 2, underlining a role for the Sun as a significant forcing factor of European atmospheric variations. We speculate about the possible origin of these solar signatures. The last figure of the paper exemplifies its main results. 相似文献
96.
Jean-Louis Auriault 《Acta Geophysica》2014,62(5):993-1004
When investigating heterogeneous media such as composite materials or geological structures, it is convenient to replace them by macroscopic equivalent media, which simplifies computations a lot. In the paper, we look for the equivalent macroscopic model for describing seismic wave propagation and transient heat transfers in thermoelastic periodic geological structures made of rock or soil. We follow the route described in Auriault (2012), to investigating thermoelastic composite media. We use the method of multi-scale asymptotic expansions. By estimating the dimensionless numbers in the momentum and energy balances, we show that an equivalent macroscopic model exists for describing seismic waves at very low frequencies only. The model then shows a damping which is due to thermal resonance at the heterogeneity scale. At higher frequencies, such an equivalent macroscopic model does not exist. Macroscopic models for describing transient heat transfers do not exist. 相似文献
97.
Monika?Huraiová Jean-Louis?Paquette Patrik?Kone?ny Abdel-Mouhcine?Gannoun Vratislav?HuraiEmail authorView authors OrcID profile 《Contributions to Mineralogy and Petrology》2017,172(8):59
Anorogenic granite xenoliths occur in alkali basalts coeval with the Pliocene–Pleistocene continental rifting of the Pannonian Basin. Observed granite varieties include peraluminous, calcic to peralkalic, magnesian to ferroan types. Quartz and feldspars are dominant rock-forming minerals, accompanied by minor early ilmenite and late magnetite–ulvöspinel. Zircon and Nb–U–REE minerals (oxycalciopyrochlore, fergusonite, columbite) are locally abundant accessory phases in calc-alkalic types. Absence of OH-bearing Fe, Mg-silicates and presence of single homogeneous feldspars (plagioclase in calcic types, anorthoclase in calc-alkalic types, ferrian Na-sanidine to anorthoclase in alkalic types) indicate water-deficient, hypersolvus crystallization conditions. Variable volumes of interstitial glass, absence of exsolutions, and lacking deuteric hydrothermal alteration and/or metamorphic/metasomatic overprint are diagnostic of rapid quenching from hypersolidus temperatures. U–Pb zircon ages determined in calcic and calc-alkalic granite xenoliths correspond to a time interval between 5.7 and 5.2 Ma. Positive εHf values (14.2 ± 3.9) in zircons from a 5.2-Ma-old calc-alkalic granite xenolith indicate mantle-derived magmas largely unaffected by the assimilation of crustal material. This is in accordance with abundances of diagnostic trace elements (Rb, Y, Nb, Ta), indicating A1-type, OIB-like source magmas. Increased accumulations of Nb–U–REE minerals in these granites indicate higher degree of the magmatic differentiation reflected in Rb-enrichment, contrasting with Ba-enrichment in barren xenoliths. Incipient charnockitization, i.e. orthopyroxene and ilmenite crystallization from interstitial silicate melt, was observed in many granite xenoliths. Thermodynamic modeling using pseudosections showed that the orthopyroxene growth may have been triggered by water exsolution from the melt during ascent of xenoliths in basaltic magma. Euhedral-to-skeletal orthopyroxene growth probably reflects contrasting ascent rates of basaltic magma with xenoliths, intermitted by the stagnation in various crustal levels at a <3 kbar pressure. The Tertiary suite of intra-plate, mantle-derived A1-type granites and syenites is geochemically distinct from pre-Tertiary, post-orogenic A2-type granites of the Carpatho–Pannonian region, which exhibit geochemical features diagnostic of crustal melting along continental margins. 相似文献
98.
Frederic Perrier Jean-Louis Le Mouël Patrick Richon 《Pure and Applied Geophysics》2010,167(3):253-276
Pressure-induced temperature (PIT) variations are systematically observed in the atmosphere of underground cavities. Such PIT variations are due to the compressibility of the air, damped by heat exchange with the rock surface. It is important to characterize such processes for numerous applications, such as the preservation of painted caves or the assessment of the long-term stability of underground laboratories and underground waste repositories. In this paper we thoroughly study the spatiotemporal dependence of the PIT response versus frequency using vertical and horizontal profiles of temperature installed in an abandoned underground quarry located in Vincennes, near Paris. The PIT response varies from about 20 × 10?3°C hPa?1 at a frequency of 2 × 10?4 Hz to 2–3 × 10?3°C hPa?1 at a frequency of one cycle per day. An analytical expression based on a simple heat exchange model accounts for the observed features of the PIT response and allows for correcting the measured time series, having standard deviations of about 10?2°C, to residual variations with a standard deviation of about 2 × 10?3°C. However, a frequency-dependent attenuation of the response, corresponding to a reduction in amplitude with a factor varying from 2 to 3, is observed near the walls. This effect is not included in the simple analytical expression, but it can be accounted for by a one-dimensional differential equation, solved numerically, where temperature variations in the atmosphere are damped by an effective radiative coupling with the rock surface, complemented by a diffusive coupling near the walls. The TIP response is observed to remain stable over several years, but a large transient enhancement of about a factor of two is observed near the roof at one location from July to October 2005. In a cavity located below the Paris Observatory, an additional contribution is identified in the PIT response function versus frequency for frequencies smaller than 2 × 10?5 Hz. This contribution can be described using a modified analytical expression that includes the effect of heat diffusion into the surrounding rock. Using this expression, in this case also, the temperature time series can then be corrected, giving a residual standard deviation smaller than 1.6 × 10?3°C. Transient temporal variations of the PIT response are observed in all sites, with possible nonlinear components in the PIT. Such effects are not properly understood at this stage, and limit the reduction of time series to standard deviations of the order of 2 × 10?3°C, and consequently limit the search for new transient or seasonal temperature signals, for example due to the presence of tiny heat sources in the cavity or to geodynamical effects. 相似文献
99.
Charline Giguet-Covex Fabien Arnaud Jérôme Poulenard Dirk Enters Jean-Louis Reyss Laurent Millet Jérome Lazzaroto Olivier Vidal 《Journal of Paleolimnology》2010,43(1):171-190
Sedimentological, geochemical and particle-size analyses were used to reconstruct the evolution of both trophic state and
hypolimnetic anoxia in Lake Bourget (French Alps) during the last century. Radionuclide dating (210Pb, 137Cs and 241Am) confirmed the annual rhythm of laminations in the upper sediment profile. In Lake Bourget, biochemical varves are triplets
composed of a diatom layer (spring lamina), a bio-precipitated calcite-rich layer (spring/summer lamina), and a layer rich
in organic matter and detrital particles (winter lamina). The onset of eutrophication and the first appearance of an anoxic
facies occurred simultaneously and were dated by laminae counting to AD 1943±1 year. Persistent anoxic conditions began in
AD 1960. Eutrophication is characterised by drastic increases in the flux of biogenic silica (mostly diatoms), lacustrine
organic matter, and larger calcite crystals (15–30 μm). The increase of organic matter also represents a marker of the onset
of anoxic conditions in the hypolimnion. Our results show that eutrophication was the main factor controlling anoxia in the
hypolimnion. This eutrophication was caused mostly by the inflow of untreated sewage effluents, and to a lesser extent, by
input of fertilizer-derived phosphorus during floods of the Rhone River and run-off from the lake catchment. The Rhone River,
however, can also be a source of re-oxygenation via underflows that originate during flood events. Oxygenation of the hypolimnion
is also controlled by low winter temperatures, which enable turnover of the lake. Thus, global warming, associated with a
forecasted reduction in precipitation, might reduce the efficiency of hypolimnetic re-oxygenation in Lake Bourget. 相似文献
100.
Centrifuge modelling of raked piles 总被引:1,自引:1,他引:0
Sandra Escoffier Jean-Louis Chazelas Jacques Garnier 《Bulletin of Earthquake Engineering》2008,6(4):689-704
Inclined piles are prohibited by many codes in seismic areas. Nevertheless the battered effect has not yet been clarified
because very few data are available. The present work is a comparison, at reduced scale in the centrifuge, of the response
of two simplified pile groups: a 1 × 2 vertical piles and 1 × 2 pile group with one inclined pile. Two configurations are
considered: end-bearing and floating pile group, both with pile heads rigidly fixed with a massive cap. First, repeatability
tests under horizontal cyclic loading were performed on both floating pile groups. Secondly, repeated horizontal impact tests
were performed on both end-bearing pile groups. These impact tests, which highlight the influence of inclined piles on the
inertial response of a group, are a first step for the more complex analysis of the performance of such groups under seismic
loads where inertial and kinematic interactions are combined. The first part of this work revealed the influence of sand structure
around the inclined pile tip on the repeatability of the tests performed on floating pile groups. The second part highlighted
differences in the dynamic response between the two end-bearing pile groups through measurements of the pile cap acceleration,
the bending moment profile and the axial load in the piles. 相似文献