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Sean L. Bruinsma Christoph Förste Sandrine Mulet Marie-Hélène Rio Oleg Abrikosov Jean-Charles Marty 《Marine Geodesy》2016,39(3-4):238-255
The impact of GOCE Satellite Gravity Gradiometer data on gravity field models was tested. All models were constructed with the same Laser Geodynamics Satellite (LAGEOS) and Gravity Recovery and Climate Experiment (GRACE) data, which were combined with one or two of the diagonal gravity gradient components for the entire GOCE mission (November 2009 to October 2013). The Stokes coefficients were estimated by solving large normal equation (NE) systems (i.e., the direct numerical approach). The models were evaluated through comparisons with the European Space Agency's (ESA) gravity field model DIR-R5, by GPS/Leveling, GOCE orbit determination, and geostrophic current evaluations. Among the single gradient models, only the model constructed with the vertical ZZ gradients gave good results that were in agreement with the formal errors. The model based only on XX gradients is the least accurate. The orbit results for all models are very close and confirm this finding. All models constructed with two diagonal gradient components are more accurate than the ZZ-only model due to doubling the amount of data and having two complementary observation directions. This translates also to a slower increase of model errors with spatial resolution. The different evaluation methods cannot unambiguously identify the most accurate two-component model. They do not always agree, emphasizing the importance of evaluating models using many different methods. The XZ gravity gradient gives a small positive contribution to model accuracy. 相似文献
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Yannick Thomas Bruno Marsset Stéphane Didailler Jean-Pierre Regnault Sandie Le Conte Dominique Le Roux Patrick Farcy Maurice Magueur Pascal Viollette Jacques Herveou Jean-Charles Guedes Bernard Jegot Gilles Gascon Christian Prud&#x;homme Hervé Nouze Estelle Thereau Isabelle Contrucci Jean-Paul Foucher 《Comptes Rendus Geoscience》2004,336(6):579-585
This note presents the first results of the development of 3D high-resolution marine seismic method designed for scientific application. A particular attention was paid to the realisation of an operational system to be in agreement with the expected goals in term of acquisition and processing. To cite this article: Y. Thomas et al., C. R. Geoscience 336 (2004). 相似文献
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Giancarlo Bortolami Jean-Charles Fontes Costanzo Panichi 《Earth and Planetary Science Letters》1973,19(2):154-167
L'enfoncement de la plaine de Venise, quel'on peut estimeràprès de 1 cm/an sous le site historique, est liéàla surexploitation des nappes artésiennes profondes. L'investigation hydrogéologique est rendue délicate par la nature de l'aquifère composéde plusieurs centaines de mètres de dépo?ts quaternaires continentaux et marins. Au sein de ce complexe les nappes se superposent en un système multicouche artésien. L'étude du régime de ces nappes aétéentrepris par les moyens géochimiques et isotopiques (oxygène 18, deuterium, tritium, carbone 13 et carbone 14).Les teneurs en isotopes stables montrent l'existence de deux familles d'eaxu profondes attribuablesàune recharge “froide” (δ18O= ?10 et ?12‰). Ces eaux sont nettements différentes de celles des nappes phréatiques (δ18O ? ?8‰). Les apports profonds peuvente?tre respectivement liés aux bassins des rivières préalpines Brenta et Piave (δ18O ? ?10‰) d'une part et au paléocours de l'Adige, fleuve alpin d'autre part. Les eaux alpines ont un gisement limitéàl'aplomb de la lagune etàla partie sud-ouest de la plaine. Les eaux de type préalpin occupent le reste de la plaine, c'est-à-dire plus grande partie.La détermination des vitesses d'écoulement pose le problème de la validitédes temps estimésàl'aide des teneurs en14C.Les teneurs en13Célevées des eaux alpines montrent clairement que les activités en14C de celles-ci ne sont pas significatives par suite d'unéchange avec l'aquifère ou d'une surcharge en carbone ancien dissous.Pour les eaux qui viennent du domaine préalpin, on observe dans les zones de recharge de fortes teneurs en3H: 85à120 UT alliéesàdes activités relativement faibles en14C (60à70%). Les teneurs en13C indiquent que le carbone dissous n'a pas subi d'échange avec l'aquifère. La discussion de l'ensemble des données suggère que la circulation est rapide dans la zone de recharge oùl'alimentation en eaux d'altitude se faitàpartir d'infiltrations en provenance du réseau hydrographique ou (et) du système karstique des préalpes. Dans les parties basses de la plaine les vitesses sont faibles et décroissent, vers l'Est ou en profondeur, de 3 m/anà1 m/an. Il est possible qu'une rupture dans l'intensitédes vitesses d'écoulement interviennent dans la partie occidentale de la plaine sous l'effet d'une discontinuitésédimentologique majeure (limite occidentale des dépo?ts marins). 相似文献
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Sylvain Loyer Félix Perosanz Flavien Mercier Hugues Capdeville Jean-Charles Marty 《Journal of Geodesy》2012,86(11):991-1003
CNES (Centre National d’Etudes Spatiales) and CLS (Collecte Localisation Satellites) became an International GNSS Service (IGS) Analysis Center (AC) the 20th of May 2010. Since 2009, we are using the integer ambiguity fixing at the zero-difference level strategy in our software package (GINS/Dynamo) as an alternative to classical differential approaches. This method played a key role among all the improvements in the GPS processing we made during this period. This paper provides to the users the theoretical background, the strategies and the models used to compute the products (GPS orbits and clocks, weekly station coordinate estimates and Earth orientation parameters) that are submitted weekly to the IGS. The practical realization of the two-step, ambiguity-fixing scheme (wide-lane and narrow-lane) is described in detail. The ambiguity fixing improved our orbit overlaps from 6 to 3?cm WRMS in the tangential and normal directions. Since 2008, our products have been also regularly compared to the IGS final solutions by the IGS Analysis Center Coordinator. The joint effects of ambiguity fixing and dynamical model changes (satellite solar radiation pressure and albedo force) improved the consistency with IGS orbits from 35 to 18?mm 3D-WRMS. Our innovative strategy also gives additional powerful properties to the GPS satellite phase clock solutions. Single receiver (zero-difference) ambiguity resolution becomes possible. An overview of the applications is given. 相似文献
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A paleoclimatic reconstruction for the past 35,000 years for northern Oman is based on an unusual approach using travertines and fracture calcites associated with hyperalkaline springs. High-pH groundwaters (pH up to 11.9) discharge from the mantle sequence of the Oman Ophiolite as the product of modern, low-temperature serpentinization. Under arid climatic conditions, hyperalkaline discharge occurs at the surface. Uptake of atmospheric CO2 precipitates characteristic laminated travertines, accompanied by strong kinetic depletion of 13C and 18O. Pluvial climates supporting a shallow bicarbonate-groundwater flow system and vegetation are recorded by fracture calcites with equilibrium stable isotope contents and calcite-replaced roots and stems. All such carbonates have modern initial 14C contents, allowing radiocarbon dating and paleoclimatic reconstruction for the late Pleistocene and Holocene. Our reconstruction shows a dominantly wet late Pleistocene up to 19,000 yr B.P., when a phase of climatic deterioration began, leading to a period of hyperaridity which dominated from ca. 16,300 to 13,000 yr B.P. The early Holocene pluvial occurred from 12,500 to ca. 6500 yr B.P. and was followed by renewed climatic deterioration and the current phase of hyperaridity. Comparison of this paleoclimatic reconstruction with that for lacustrine deposits from the A'Rub al Khali of central Saudi Arabia and the summer insolation-driven monsoon record of east Africa and the Arabian Sea is remarkably good. 相似文献
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Ethnic groups’ response to the 26 December 2004 earthquake and tsunami in Aceh, Indonesia 总被引：4，自引：4，他引：0
Jean-Christophe Gaillard Elsa Clavé Océane Vibert Azhari Dedi Jean-Charles Denain Yusuf Efendi Delphine Grancher Catherine C. Liamzon Desy Rosnita Sari Ryo Setiawan 《Natural Hazards》2008,47(1):17-38
The 26 December 2004 earthquake and tsunami unfairly hit the different ethnic groups of Aceh, Indonesia. About 170,000 Acehnese
and Minangkabau people died in the Northern tip of Sumatra while only 44 Simeulue people passed away in the neighbouring Simeulue
island located near the earthquake epicentre. Such a difference in the death toll does not lie in the nature of the hazard
but in different human behaviours and ethnic contexts. The present study draws on a contextual framework of analysis where
people’s behaviour in the face of natural hazards is deeply influenced by the cultural, social, economic and political context.
Questionnaire-based surveys among affected communities, key informant interviews and literature reviews show that the people
of Simeulue detected the tsunami very early and then escaped to the mountains. On the other hand, Acehnese and Minangkabau
people, respectively in the cities of Banda Aceh and Meulaboh, did not anticipate the phenomenon and were thus caught by the
waves. The different behaviours of the victims have been commanded by the existence or the absence of a disaster subculture
among affected communities as well as by their capacity to protect themselves in facing the tsunami. People’s behaviours and
the capacity to protect oneself can be further tracked down to a deep tangle of intricate factors which include the armed
conflict that has been affecting the province since the 1970s, the historical and cultural heritage and the national political
economy system. This paper finally argues that the uneven impact of the 26 December 2004 earthquake and tsunami in Aceh lies
in the different daily life conditions of the ethnic groups struck by the disaster. 相似文献