A Mw 6.3 earthquake scenario in the city of Nice (southeast France): ground motion simulations     

Jérome Salichon  Carine Kohrs-Sansorny  Etienne Bertrand  Françoise Courboulex 《Journal of Seismology》2010,14(3):523-541

The southern Alps–Ligurian basin junction is one of the most seismically active zone of the western Europe. A constant microseismicity and moderate size events (3.5 < M < 5) are regularly recorded. The last reported historical event took place in February 1887 and reached an estimated magnitude between 6 and 6.5, causing human losses and extensive damages (intensity X, Medvedev–Sponheuer–Karnik). Such an event, occurring nowadays, could have critical consequences given the high density of population living on the French and Italian Riviera. We study the case of an offshore Mw 6.3 earthquake located at the place where two moderate size events (Mw 4.5) occurred recently and where a morphotectonic feature has been detected by a bathymetric survey. We used a stochastic empirical Green’s functions (EGFs) summation method to produce a population of realistic accelerograms on rock and soil sites in the city of Nice. The ground motion simulations are calibrated on a rock site with a set of ground motion prediction equations (GMPEs) in order to estimate a reasonable stress-drop ratio between the February 25th, 2001, Mw 4.5, event taken as an EGF and the target earthquake. Our results show that the combination of the GMPEs and EGF techniques is an interesting tool for site-specific strong ground motion estimation.  相似文献   

Time Transfer Experiments Using GLONASS P-code Measurements from RINEX Files     

Fabian Roosbeek  Pascale Defraigne  Carine Bruyninx 《GPS Solutions》2001,5(2):51-62

We have used GLONASS P-code measurements from different geodetic GPS/GLONASS receivers involved in the IGEX campaign to perform frequency/time transfer between remote clocks. GLONASS time transfer is commonly based on the clock differences between GLONASS system time and the local clock computed by a time transfer receiver. We choose to analyze the raw P-code data available in the RINEX files. This also allows working with the data from geodetic receivers involved in the IGEX campaign. As a first point, we show that the handling of the external frequency in some of the IGEX receivers is not suited for time transfer applications. We also point out that the GLONASS broadcast ephemerides give rise to a considerable number of outliers in the time transfer, compared to the precise IGEX ephemerides. Due to receiver clock resets at day boundaries, which is a characteristic of the R100 receivers from 3S-Navigation, continuous data sets exceeding one day are not available. Invthis context, it is therefore impossible to perform RINEX-based precise frequency transfer with GLONASS P-codes on a time scale longer than one day. Because the frequencies used by GLONASS satellites are different, the time transfer results must be corrected for the different receiver hardware delays. After this correction, the final precision of our time transfer results corresponds to a root-mean-square (rms) of 1.8 nanoseconds (ns) (maximum difference of 11.8 ns) compared to a rms of about 4.4 ns (maximum difference of 31.9 ns) for time transfer based on GPS C/A code observations. ? 2001 John Wiley & Sons, Inc.  相似文献   

Investigation of phase relations in the (Na,K)AlGeO4 system     

J. Barbier  M. E. Fleet 《Physics and Chemistry of Minerals》1988,16(3):276-285

The phase relations in the (Na,K)AlGeO₄ system have been investigated at atmospheric pressure over the temperature range 700–1100° C by X-ray powder diffraction and electron diffraction/microscopy. Four distinct structure-types occur in this system including the beryllonite, nepheline, kalsilite and KAlGeO₄ types in order of increasing KAlGeO₄ content. In contrast to the (Na,K)Al-SiO₄ system, the nepheline structure is only stable over a narrow composition range around 25 percent K at temperatures above approximately 800° C and transforms reconstructively into the beryllonite structure at lower temperatures. The formation of domain microstructures in some K-rich phases has been directly observed by high-resolution electron microscopy and can be associated with the presence of diffuse scattering in their diffraction patterns. The structural trend observed across the (Na,K)AlGeO₄ series as a function of composition can be rationalized to a large extent in terms of the dependence of the framework topology of these tridymite-derivative structures on the size of the alkali atoms.  相似文献   

Mg4Ga8Ge2O20: A new synthetic analog of the mineral sapphirine     

Jacques Barbier 《Physics and Chemistry of Minerals》1990,17(3):246-252

A new sapphirine-analog, Mg₄Ga₈Ge₂O₂₀, has been identified and characterized in the system MgO-Ga₂O₃-GeO₂ in samples quenched from 1400° C, 1 atm. It crystallizes with a triclinic unit-cell and is isostructural with the mineral sapphirine-1Tc, Mg₄Al₈Si₂O₂₀. It is stable over a broad range of stoichiometry associated with the exchange reaction 2 Ga³⁺ = Mg²⁺ }+Ge⁴⁺. TEM examination shows the common occurrence of polysynthetic twinning and suggests the existence of a high-temperature triclinic→monoclinic transition. The observation of sapphirine/spinel intergrowths is consistent with the structural relationships described previously.  相似文献   

L'évaluation quantitative des anomalies géochimiques en sols résiduels: une aide pour le choix des prospects     

Jean Barbier 《Journal of Geochemical Exploration》1989,32(1-3)

Geochemical soil prospecting is carried out before the drilling stage and is therefore a factor in a decision involving quite considerable expense. Hence the need for accurate assessment of the value of anomalies. Two techniques are proposed here.Surface-content curves of anomalies very clearly reveal characteristics such as the sampling grid, background, top and distribution of values. To make decision-making easier, different curves can be drawn on the same diagram for comparison.A calculation of the amount of metal contained in the anomalous zone expressed in tonnes, as proposed by Solovov, is a very interesting idea. Four examples confirm that for a stable metal (Pb) under surface conditions, the figure obtained is of the same order of magnitude as that for the mineralisation at depth. In other words, geochemical sampling of residual soil could be used to calculate the tonnage per metre of depth, in this case at the level z = 0 in relation to the surface.

Résumé

La prospection géochimique en sol s'effectue avant le stade des forages, c'est donc un élément de décision pour des dépenses non négligeables. Une évaluation correct de l'intérêt des anomalies est donc nécessaire; deux techniques sont proposées.Le tracé de courbes teneurs-surfaces anomales permet une très bonne illustration de caractères tels que maille d'échantillonnage, background, top, répartition des teneurs. Les courbes reportées sur un même graphique peuvent être facilement comparées entre elles, ce qui rend plus aisées les décisions.Un calcul en tonnes du métal contenu dans l'anomalie, comme l'a proposé P.A. Solovov, est d'un grand intérêt. On vérifie sur quatre exemples que pour un métal stable dans les conditions superficielles (Pb), l'ordre de grandeur du chiffre obtenu est bien le même que celui de la minéralisation en profondeur. En d'autres termes, l'échantillonnage géochimique en sol résiduel permettrait le calcul du tonnage au mètre d'approfondissement, en l'occurrence au niveau z = 0 par rapport au sol.L'évaluation quantitative des anomalies géochimiques en sols résiduels, peut done constituer un outil important d'aide à la décision pour choisir les meilleurs prospects.  相似文献   

Influence du Bani sur la variabilité saisonnière et interannuelle de la crue du fleuve Niger dans le delta intérieur au Mali     

Aïda Zaré  Gil Mahé  Jean-Emmanuel Paturel  Bruno Barbier 《水文科学杂志》2017,62(16):2737-2752

Le delta intérieur du fleuve Niger est une zone humide sahélienne dont l’inondation dépend de la pluviométrie des bassins supérieurs du fleuve Niger et de son principal affluent, le Bani. La crise climatique qui a débuté en 1970 a très peu influencé les dates de passage des maximums de crue sur le Niger amont et son principal défluent, le Diaka. L’influence par contre est très forte sur le Bani, à la confluence avec le Niger à Mopti et sur le delta aval avec des dates de passages des maximums plus précoces qu’auparavant. Cela est dû à la faiblesse des superficies inondées au cours des années sèches. Pendant les années humides, l’importance des débordements latéraux ralentit la propagation de la crue avec pour conséquence des dates de passages plus tardives des maximums. Par ailleurs pendant les années humides antérieures à 1970 l’importance des débordements latéraux conférait au delta amont un caractère d’autorégulation par écrêtage des crues au niveau de certaines station.  相似文献   

The present and future role of coastal wetland vegetation in protecting shorelines: answering recent challenges to the paradigm   总被引：2，自引：0，他引：2  

Keryn B. Gedan  Matthew L. Kirwan  Eric Wolanski  Edward B. Barbier  Brian R. Silliman 《Climatic change》2011,106(1):7-29

For more than a century, coastal wetlands have been recognized for their ability to stabilize shorelines and protect coastal communities. However, this paradigm has recently been called into question by small-scale experimental evidence. Here, we conduct a literature review and a small meta-analysis of wave attenuation data, and we find overwhelming evidence in support of established theory. Our review suggests that mangrove and salt marsh vegetation afford context-dependent protection from erosion, storm surge, and potentially small tsunami waves. In biophysical models, field tests, and natural experiments, the presence of wetlands reduces wave heights, property damage, and human deaths. Meta-analysis of wave attenuation by vegetated and unvegetated wetland sites highlights the critical role of vegetation in attenuating waves. Although we find coastal wetland vegetation to be an effective shoreline buffer, wetlands cannot protect shorelines in all locations or scenarios; indeed large-scale regional erosion, river meandering, and large tsunami waves and storm surges can overwhelm the attenuation effect of vegetation. However, due to a nonlinear relationship between wave attenuation and wetland size, even small wetlands afford substantial protection from waves. Combining man-made structures with wetlands in ways that mimic nature is likely to increase coastal protection. Oyster domes, for example, can be used in combination with natural wetlands to protect shorelines and restore critical fishery habitat. Finally, coastal wetland vegetation modifies shorelines in ways (e.g. peat accretion) that increase shoreline integrity over long timescales and thus provides a lasting coastal adaptation measure that can protect shorelines against accelerated sea level rise and more frequent storm inundation. We conclude that the shoreline protection paradigm still stands, but that gaps remain in our knowledge about the mechanistic and context-dependent aspects of shoreline protection.  相似文献   

Optical extinction due to aerosols in the upper haze of Venus: Four years of SOIR/VEX observations from 2006 to 2010     

Valérie Wilquet  Rachel Drummond  Arnaud Mahieux  Séverine Robert  Ann Carine Vandaele  Jean-Loup Bertaux 《Icarus》2012,217(2):875-881

The variability of the aerosol loading in the mesosphere of Venus is investigated from a large data set obtained with SOIR, a channel of the SPICAV instrument suite onboard Venus Express. Vertical profiles of the extinction due to light absorption by aerosols are retrieved from a spectral window around 3.0 μm recorded in many solar occultations (～200) from September 2006 to September 2010. For this period, the continuum of light absorption is analyzed in terms of spatial and temporal variations of the upper haze of Venus. It is shown that there is a high short-term (a few Earth days) and a long-term (～80 Earth days) variability of the extinction profiles within the data set. Latitudinal dependency of the aerosol loading is presented for the entire period considered and for shorter periods of time as well.  相似文献   

First observation of 628 CO₂ isotopologue band at 3.3 μm in the atmosphere of Venus by solar occultation from Venus Express     

Jean-Loup Bertaux  Ann Carine Vandaele  F. Montmessin  R. Dahoo  E. Villard  O. Korablev 《Icarus》2008,195(1):28-33

The new ESA Venus Express orbiter is the first mission applying the probing technique of solar and stellar occultation to the atmosphere of Venus, with the SPICAV/SOIR instrument. SOIR is a new type of spectrometer used for solar occultations in the range 2.2-4.3 μm. Thanks to a high spectral resolving power R∼15,000-20,000 (unprecedented in planetary space exploration), a new gaseous absorption band was soon detected in the atmospheric transmission spectra around 2982 cm⁻¹, showing a structure resembling an unresolved Q branch and a number of isolated lines with a regular wave number pattern. This absorption could not be matched to any species contained in HITRAN or GEISA databases, but was found very similar to an absorption pattern observed by a US team in the spectrum of solar light reflected by the ground of Mars [Villanueva, G.L., Mumma, M.J., Novak, R.E., Hewagama, T., 2008. Icarus 195 (1), 34-44]. This team then suggested to us that the absorption was due to an uncatalogued transition of the ¹⁶O¹²C¹⁸O molecule. The possible existence of this band was soon confirmed from theoretical considerations by Perevalov and Tashkun. Some SOIR observations of the atmospheric transmission are presented around 2982 cm⁻¹, and rough calculations of line strengths of the Q branch are produced, based on the isotopic ratio measured earlier in the lower atmosphere of Venus. This discovery emphasizes the role of isotopologues of CO₂ (as well as H₂O and HDO) as important greenhouse gases in the atmosphere of Venus.  相似文献   

Altitude et géochimie des eaux de source,Nord-Ouest du Massif central,France     

Jean Barbier 《Comptes Rendus Geoscience》2005,337(8):763-768

In the northwestern Massif Central (France), groundwater chloride concentrations are inversely correlated with elevation, when nitrate-poor. This can be explained by an evolution of the ratio evapotranspiration/rainfall, or of the rainwater composition. Such a relationship may be used for the detection of denitrification phenomena in groundwaters, or nitrate assimilation in surface waters, or for the computation of evapotranspiration, using the chloride mass balance method. However, the main objective will be the selection of groundwaters free of any chloride-bearing contamination, in order to define the natural groundwater quality background. To cite this article: J. Barbier, C. R. Geoscience 337 (2005).  相似文献