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551.
Yoann Quesnel Christophe Sotin Benoit Langlais Simona Costin Mioara Mandea Matthias Gottschalk Jérome Dyment 《Earth and Planetary Science Letters》2009,277(1-2):184-193
This paper proposes a model of serpentinization of the Southern martian crust that may explain the topographic dichotomy, the absence of an associated free-air gravity anomaly and the presence of strong magnetic anomalies in the Southern Hemisphere. The thermodynamical conditions for serpentinization were likely met in the lithosphere during the Noachian period. This process may have decreased the density in the Southern crust and created the topographic dichotomy. Different reactions of serpentinization that can form magnetite have been considered. Assuming an intense magnetic field (core dynamo), we obtain chemical remanent magnetizations that are in the order of the estimates deduced from martian magnetic anomaly studies. The pertinence and the implications of our model concerning the early thermal evolution of Mars are discussed, with emphasis on the intensity of the paleo-magnetic field. 相似文献
552.
Chedliya Ghemari Christophe Waterlot Anas Ayari Julie Leclercq Francis Douay Karima Nasri-Ammar 《Environmental Earth Sciences》2017,76(17):623
In this study, data on several metals (Cd, Pb, Zn and Cu) in soil and isopod Porcellio laevis taken at 21 sites from the most important industrial areas in Tunisia (Bizerte, Nabeul, Zaghouan, Sfax and Gabes) were presented. Heavy metal concentrations in both soil samples and isopods were determined using atomic absorption spectrometry. Soil contamination was estimated using the contamination factor (CF). On the other hand, the bioaccumulation factor (BAF) was determined to estimate metal accumulation in isopods. The CF values show that the level of contamination varies between sampled soils, which may be due to the source of pollution at each site. The BAF values allow defining the order of accumulation in P. laevis which was classified for the majority of the sampled sites as a macro-concentrator of Cu and Zn and a deconcentrator of Cd with some exceptions. A principal component analysis (PCA) was conducted between soil properties (pH, OM and CaCO3) and metal concentrations in soils. Through PCA, we obtained four groups in which soils were distinguished by their physicochemical properties and their metal concentrations. Moreover, linear multiple regressions with a downward stepwise procedure were conducted to test the relationships between the physicochemical parameters and metal concentrations in both soils and isopods. Thus, positive correlations (0.78 < R 2 < 0.99) were obtained for Pb considering dataset from the groups 1, 2 and for Zn with data of groups 2 and 3. Finally, results showed that P. laevis could be used as a bio-indicator for monitoring and reducing the impact of pollution in terrestrial ecosystems. 相似文献
553.
We propose an analytical method, namely the SORTAN method, to determine the sense of slip on faults as induced by stresses. This method is useful to infer the sense of motion along faults whose surface cannot be directly accessed, such as faults imaged in the subsurface. Because the SORTAN method is based on the Wallace–Bott hypothesis, we assume that the shear stress vector applied to a given fault is parallel to the slip vector on this fault. The assumptions allow for simplification of the method that in turn implies very short calculation times. A concise formalism is adopted. We introduce the stress ratio ' that accounts for (1) the type of stress regime (i.e., strike-slip, reverse or normal) and (2) the degree of anisotropy of the stress state. The formalism of the SORTAN method permits an easy exploration and imaging of the complete collection of slip motions that may theoretically occur on fault planes. The input parameters are the fault plane orientation, the type and anisotropy of the stress regime, and the azimuth of the horizontal stress axes. 相似文献
554.
Christophe Leboulanger Louise Oriol Henri Jupin Chantal Desolas-gros 《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12):2131-2139
The concentration of dissolved glycolate in sea water was measured by high performance liquid chromatography in the eastern tropical Atlantic Ocean during the Eumeli 4 oceanographic cruise in June 1992. Diurnal concentrations of glycolate reached 74 kg 1−1 1−1 in mesotrophic waters and 17 μg 1−1 1 in oligotrophic waters. At midday total dissolved glycolate exceeded 1 g of carbon per m2 of ocean, decreasing strongly during the night (less than 0.1 g of carbon per m2). At the three stations studied, glycolate carbon difference between night and day in the water column was of the same order as the daily primary production estimated by incorporation of 14C02. Disappearance of this compound at night suggested a rapid consumption by heterotrophic organisms. These data suggest that glycolate excretion by phytoplankton may be important, and possibly influenced by ambient nutrient concentrations. Further, with glycolate representing up to 50% of daily productivity, our estimates of the total biological reduction of C02 need to be re-examined. 相似文献
555.
Michel?CaraEmail author Wolfgang?Brüstle Monika?Gisler Philipp?K?stli Christophe?Sira Claire?Weihermüller Jér?me?Lambert 《Journal of Seismology》2005,9(3):317-328
The 2003 Ml = 5.4 Rambervillers earthquake, north-east of France, is the largest seismic event recorded north of the Alps
since the 1992 Ms = 5.3, I0 = VII, Roermond earthquake, Netherlands. With a maximum macroseismic intensity of VI-VII EMS-98, the 2003 event was broadly
felt to a distance of 300 km from the epicentre. It provides a unique opportunity to test and compare the different procedures
used in France, Germany and Switzerland when evaluating macroseismic intensities. The main purpose of this paper is to present
a common transfrontier macroseismic map based on the EMS-98 intensity scale. Maximum horizontal accelerations recorded in
the area are compared to the intensity values, and we propose to use a differential technique to re-estimate the magnitude
of the 1682 Remiremont, I0 = VIII, earthquake, which occurred 40 km south of Rambervillers. 相似文献
556.
Infrared spectra of Jupiter's atmosphere were obtained with the infrared spectrometer (IRS) on the 1.5-m telescope at the Cerro Tololo Inter-American Observatory (CTIO) during the first 2 days of the impacts of the fragments of Comet Shoemaker–Levy 9 (1993e). We monitored 3.51 ± 0.17 μm radiation from the impact areas, undisturbed areas, and auroral regions of Jupiter after the A and E impacts. The strong emission of a portion of the P-branch of the ν3band of CH4was detected on the A impact area 4 hr after the impact. H+3emissions are found to be decreased at the A and E impact sites after 4 hr and 10 hr 50 min of the impacts, respectively, compared with undisturbed areas at the same latitude. The temperatures of the southern H+3aurora were normal within the first several hours following the A and E impacts. 相似文献
557.
D. Herranz J. L. Sanz R. B. Barreiro M. López-Caniego 《Monthly notices of the Royal Astronomical Society》2005,356(3):944-954
In this work we study the performance of linear multifilters for the estimation of the amplitudes of the thermal and kinematic Sunyaev–Zel'dovich (SZ) effects. We show that when both effects are present, estimation of these effects with standard matched multifilters is intrinsically biased. This bias is due to the fact that both signals have basically the same spatial profile. We find a new family of multifilters related to the matched multifilters that cancel this systematic bias, hence we call them unbiased matched multifilters. We test the unbiased matched multifilters and compare them with the standard matched multifilters using simulations that reproduce the future Planck mission observations. We find that in the case of the standard matched multifilters the systematic bias in the estimation of the kinematic Sunyaev–Zel'dovich effect can be very large, even greater than the statistical error bars. Unbiased matched multifilters cancel this kind of bias effectively. In concordance with other works in the literature, our results indicate that the sensitivity and resolution of Planck will not be enough to give reliable estimations of the kinematic Sunyaev–Zel'dovich effects of individual clusters. However, as the estimation with the unbiased matched multifilters is not intrinsically biased, it can be possible to use them to study statistically any peculiar cosmological bulk flows via the kinematic SZ effect. 相似文献
558.
Landslide risk management in Switzerland 总被引:1,自引:2,他引:1
559.
Modelling the behaviour of a large landslide with respect to hydrogeological and geomechanical parameter heterogeneity 总被引:2,自引:1,他引:2
Thanks to a sophisticated transient hydrogeological modelling allowing the determination of the pore pressure fields in La Frasse landslide mass during a crisis, it has been possible to model the mechanical behaviour of the slide and obtain results that prove to be similar to the monitored data, in terms of peak velocity, distribution of velocity with time and space and total displacements. Such results are reached only when appropriate constitutive modelling laws are used, and when geotechnical tests supply all the required parameters. The main results concern the potential effect of a drainage system during a crisis, like the one experienced in 1994. It can include vertical boreholes equipped with pumps or drains drilled from a gallery. The draining system reduces horizontal displacements down to 5% of the values modelled during the crisis. This effect, which appears to extend over a large width, will be even more significant if the boreholes discharge the drained water into the gallery, due to its extension in the presently stabilised landslide mass below the active zone. The modelling tools developed for La Frasse landslide thus provide all the necessary information to optimise the drainage scheme. 相似文献
560.
Carmen Sanchez-Valle Bruno Reynard Christophe Lecuyer Jean-Claude Chervin 《Geochimica et cosmochimica acta》2005,69(17):4301-4313
Equilibrium boron isotopic fractionations between trigonal B(OH)3 and tetragonal B(OH)4− aqueous species have been calculated at high P-T conditions using measured vibrational spectra (Raman and IR) and force-field modeling to compute reduced partition function ratios for B-isotopic exchange following Urey’s theory. The calculated isotopic fractionation factor at 300 K, α3/4 = 1.0176(2), is slightly lower than the formerly calculated value of α3/4 = 1.0193 (Kakihana and Kotaka, 1977), due to differences in the determined vibrational frequencies. The effect of pressure on α3/4 up to 10 GPa and 723 K is shown to be negligible relative to temperature or speciation (pH) effects. Implications for the interpretation of boron fractionation in experimental and natural systems are discussed. We also show that the relationship between seawater-mineral B isotope fractionation and pH can be expressed using two variables, α3/4 on one hand, and the pKa of the boric acid-borate equilibrium on the other hand. This latter value is given by the equilibrium of boron species in water for the carbonate-water exchange, but could be governed by mineral surface properties in the case of clays. This may allow defining intrinsic paleo-pHmeters from B isotope fractionation between carbonate and authigenic minerals. Finally, it is shown that fractionation of boron isotopes can be rationalized in terms of the changes in 1) coordination of B from trigonal to tetrahedral in both fluids and minerals; and 2) the ligand nature around B from OH− in the fluid and some hydrous minerals to non-hydrogenated O in many minerals. Relationships are established that allow predicting the isotopic fractionation factor of B between minerals and fluid. 相似文献