Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The majority of the largest subduction megathrust earthquakes share the common characteristic of rupturing more than one asperity along strike of the margin. Understanding the factors that control coseismic failure of multiple asperities, and thus maximum magnitude, is central for seismic hazard assessment. To investigate the role of asperities size and spacing on maximum magnitude, seismicity rate, and percentage of synchronized ruptures, we use analog models simulating along-strike rupture behavior of megathrust earthquakes. We found negative correlations between the barrier-to-asperity length ratio Db/Da and maximum magnitude and seismicity rate. Db/Da also controls the process of asperities synchronization along the megathrust. A permanent barrier behavior is observed for Db/Da > 0.5. Comparing our experimental results to the Nankai Trough historical seismicity, we propose that the distribution of megathrust frictional heterogeneities likely explains the diversity of earthquakes which occurred there.
ISSN: 0094-8276

hal-01685546
https://hal.archives-ouvertes.fr/hal-01685546
https://hal.archives-ouvertes.fr/hal-01685546/document
https://hal.archives-ouvertes.fr/hal-01685546/file/Corbi_et_al-2017-Geophysical_Research_Letters.pdf
DOI : 10.1002/2017GL074182

Éditeur(s) : HAL CCSD
Résumé : Spatial variability of ground motion may be explained by local soil conditions; it is the so-called "site effects". Site effects are responsible for increasing duration and important amplification of strong ground motion during earthquakes and must be considered as a key parameter in local seismic hazard assessment. French West Indies are prone to strong site effects because of a particular geology, characterized by soft soil deposits and strong alteration of volcanic deposits. In this framework, and considering that French West Indies are considered as a high seismicity level zone in the French building code, part of seismic hazard mitigation policy consists in technical studies to perform identification and mapping of zones characterized by homogeneous seismic response and quantification of associated ground motion. It is the aim of seismic microzonations. In this presentation, we will expose the methodology used on the scale of municipalities for mapping homogeneous seismic areas, based on a study of geological and geotechnical conditions and some geophysical testings. Then, a study of vulnerability of buildings allows to estimate the probability of damage on various sectors for a scenario of risk corresponding to the seismic microzonation.
19ème Conférence Géologique de la Caraïbe
Le Gosier, Guadeloupe, France

hal-00614300
https://hal-brgm.archives-ouvertes.fr/hal-00614300

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We present evidence that GPS velocity estimates of plate motions and fault slip rates agree to within uncertainties with geologic estimates during the most recent phase of the geologic evolution of the E Mediterranean region (post-Late Miocene). On this basis, we use the GPS differential velocities to estimate the timing of initiation of the principal structures in NW Turkey, the N Aegean Sea, and central Greece, including, the Marmara Sea, the Gulfs of Evia (GoE) and Corinth (GoC). and the Kephalonia Transform fault (KTF). We interpret these ages to indicate that the North Anatolian fault propagated across the N Aegean, opening the GoE and GoC and initiating the KTF, during the past 1-4 Ma. We further suggest that Aegean extension that was earlier more distributed across the Aegean Basin became focused on this new fault system allowing the southern Aegean and Peloponnisos to translate SW with little internal deformation, as observed today with GPS. This change in tectonic configuration may account for the clear geologic evidence for crustal thinning throughout the S Aegean in apparent contradiction with low present-day strain rates. We further show that the low present-day strain rate along the southern edge of the Aegean micro-plate requires substantial aseismic slip along the plate interface below Crete, consistent with the low level of historic, subduction-type earthquakes along this segment of the subduction zone.
ISSN: 0040-1951

hal-00512634
https://hal.archives-ouvertes.fr/hal-00512634
DOI : 10.1016/j.tecto.2009.05.027

Éditeur(s) : HAL CCSD
Résumé : International audience
Increasingly, health risk assessment is addressing multiple pathway exposures to multiple contaminants. We reviewed aggregated exposure and cumulative risk approaches for contemporary and ubiquitous semivolatile organic compounds (SVOC). We identified 22 studies aggregating exposure pathways, and 31 cumulating risk. Exposure aggregation is based on the addition of pathway-specific doses, using kinetic modeling where it exists, and classic external dose equations otherwise. In most cases, exposure is dominated by a single route or source of exposure - mainly the oral pathway - via dietary or non-dietary exposure. Preferential routes and sources of exposure are influenced by SVOC physical-chemical properties such as vapor pressure. The cumulative risk approach for contaminants is based on dose addition. Simple sum of hazard quotient (Hazard Index: HI) is the most commonly used cumulative risk assessment approach, while Relative Potency Factor (RPF) appeared to the best suited - although this calls for a level of toxicological information that limits the number of compounds that can be studied simultaneously. Where both were performed, moving from HI to more refined approach produced similar results. In conclusion, both approaches - exposure aggregation and cumulative risk - rely on simple assumptions. Nevertheless, they allow uncertainty to be reduced, in comparison with source-by-source or chemical-by-chemical approaches.
Environmental Research

hal-01579608
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01579608
DOI : 10.1016/j.envres.2017.06.022
PUBMED : 28732321

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
P>Tehran is one of the largest cities in the world (12 million people) facing seismic hazard. Standing at the foothills of Alborz Mountains, the capital of Iran is exposed to potential earthquakes associated with several nearby active faults. Classically mentioned as active features, the Kahrizak, the North Rey and the South Rey scarps cross the town itself and would be the sources of several destructive historical earthquakes. However, the nature of these topographic scarps remains uncertain. To assess whether these features correspond to active faults, we carried out a morphological and stratigraphic study. Our results show that the three scarps define horizontal scarp lines that follow contour lines matching ancient shorelines further East. This point, associated with other morphological characteristics such as the flatness of the upper and the lower surfaces, the long and regular streams that incised the upslope upper surfaces and the fact that the deposits are horizontal and without deformations, suggests in fact that the Kahrizak, the North Rey and the South Rey scarps correspond most likely to ancient shore lines and are not fault scarps.
ISSN: 0954-4879

hal-00496390
https://hal.archives-ouvertes.fr/hal-00496390
DOI : 10.1111/j.1365-3121.2010.00938.x

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
This paper presents a synthesis of a multidisciplinary study carried out along the Nîmes Roman aqueduct, located in the southeast part of France. The study was motivated by archaeologists attempting to explain the partial destructions of only one aerial bridge of the aqueduct (Pont de la Lône). Given its close proximity to the Nîmes seismically active fault, a possible seismic origin for the destructions was invoked. Seismologists and structural engineers thus carried out a variety of field and numerical investigations to test the seismic hypothesis. Supporting field evidence was found first along the aerial bridge section of the aqueduct: broken stalactites, arch warping, cracks and destruction of the bridge just above a breast wall shortly after its construction. Secondly, the underground part of the canal was analysed: irregularity in the thickness of calcite deposits of the canal walls, presence of numerous cracks, horizontal shift of the otherwise linear structure of the canal and presence of calcite twins in the deposits, found only where the canal crosses the Nîmes fault system. Numerical modelling and experimental results show that (1) only the Pont de la Lône would have suffered serious damage under seismic solicitation (assuming an M6 earthquake at 10 km distance). The second aerial bridge, the three levels arches Pont du Gard, an historical monument still standing today, would have suffered less damage, due to its very different fundamental frequency of around 0.4 Hz, far from the amplified seismic near-field spectrum; (2) the numerical models also show that a fall of the canal wall would require a higher magnitude event (M > 6); (3) the presence of calcite twinning requires a differential static stress of 4 MPa or greater, which can only be achieved very close to the fault rupture of a M > 6 earthquake; (4) finally, local surface rupturing of such a fault would also corroborate the hypothesis that the observed offset of the canal may be partly seismically induced. Although other possible origins for each individual evidence may not be excluded, the observed spatiotemporal concentration of architectural/geological anomalies together with the numerical results allow us to support a possible co-seismic origin for these disorders, indirectly attesting to the potential seismic activity (M > 6) of the nearby Nîmes fault. Furthermore, following the conclusions of archaeological studies, the disorders occurred between 250 and 350 year AD, thus providing timing for this possible seismic event, an essential parameter in seismic hazard analysis. These results validate the archaeo-seismological approach as a tool that may help improve the knowledge of major infrequent earthquakes in areas of moderate seismic activity.
ISSN: 0921-030X

hal-00379064
https://hal.archives-ouvertes.fr/hal-00379064
DOI : 10.1007/s11069-008-9276-9

Éditeur(s) : HAL CCSD MDPI
Résumé : International audience
Cyanobacteria are a component of public health hazards in freshwater environments because of their potential as toxin producers. Eutrophication has long been considered the main cause of cyanobacteria outbreak and proliferation, whereas many studies emphasized the effect of abiotic parameters (mainly temperature and light) on cell growth rate or toxin production. In view of the growing concerns of global change consequences on public health parameters, this study attempts to enlighten climate influence on cyanobacteria at regional scale in Brittany (NW France). The results show that homogeneous cyanobacteria groups are associated with climatic domains related to temperature, global radiation and pluviometry, whereas microcystins (MCs) occurrences are only correlated to local cyanobacteria species composition. As the regional climatic gradient amplitude is similar to the projected climate evolution on a 30-year timespan, a comparison between the present NW and SE situations was used to extrapolate the evolution of geographical cyanobacteria distribution in Brittany. Cyanobacteria composition should shift toward species associated with more frequent Microcystins occurrences along a NW/SE axis whereas lakes situated along a SW/NE axis should transition to species (mainly Nostocales) associated with lower MCs detection frequencies.
ISSN: 2072-6651

hal-01122236
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122236
PUBMED : 24476711
DOI : 10.3390/toxins6020509
PUBMEDCENTRAL : PMC3942748

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The island of Taiwan is affected by intense seismic activity, which includes large events as the disastrous 1999 Chi-Chi earthquake. To improve seismic hazard assessment in this area, we estimate the effect of both interseismic loading and major events since 1736 on the state of stress of major active faults. We focus our approach on western Taiwan, which is the most densely populated part of Taiwan. We pay a specific attention to faults geometry and to both interseismic and coseismic slip distributions. Our results suggest that both earthquakes and interseismic loading before 1999 increase the Coulomb stress in the north-western part of the Chelungpu fault, a region which experienced the highest coseismic slip during the Chi-Chi earthquake. More importantly our results reveal a Coulomb stress increase in the southern part of the Changhua thrust fault, below a densely populated area.
ISSN: 0094-8276

hal-00475590
https://hal.archives-ouvertes.fr/hal-00475590
DOI : 10.1029/2009GL042292

Éditeur(s) : HAL CCSD
Résumé : International audience
Space technologies have been used increasingly for assessing the risk of infection by vector-borne diseases, providing tools for delimiting the distribution of vectors. As rodent-borne diseases are a growing concern in Thailand since the emergence of leptospirosis starting in 1998, this study was set up to determine the hazard, related to the potential presence of the main rodent with medical importance, Bandicota indica (Bechstein, 1800), the great bandicoot rat, widely distributed in the country. It was conducted in Nakhon Pathom province (west of Bangkok, Thailand) following a large rodent sampling. Habitats of Bandicota indica were delimited using a Landsat 5 Thematic Mapper image and Multiscope remote sensing software (Fleximage, France). Environmental variables, related to its ecology, were identified by describing the place and surroundings of each capture. An extrapolation to the entire province could generate the potential distribution of Bandicoot rats. This delineation helped at first to improve further sampling ofBandicota indica and adapt the model to other study areas. Furthermore it allowed developing researches on the dynamics of rodents and the risk of transmission of rodent-borne diseases.
Natural History Journal of Chulalongkorn University

ird-00714409
http://hal.ird.fr/ird-00714409
http://hal.ird.fr/ird-00714409/document
IRD : fdi:010045886

Éditeur(s) : HAL CCSD
Résumé :  
The main aspects of wood mechanics are approached through the role played by wood as the building material of the tree. The main concepts used by nature: progressive setting up of tree weight and architecture, multifunctional role of wood and adaptability to hazard and long-term evolution, are clarified together with their consequence on the multilayered, anisotropic nature of wood. The technological choices of the plant world as the cellular structure, the use of composite with oriented fibres and hydro-carbonated polymers, as well as the systematic prestressing of every new layer, bear obvious consequences on the type of mechanical behaviour of wood. The local control of the level of prestressing through minor modifications of the cell-wall biosynthesis allows the tree to adapt to conditions of light exploration that will evolve according to time and risk occurrence. This analysis of wood genesis process permits in return to improve our understanding of the mechanical behaviour of the material in relation with the parameters of the microstructure.
Comptes Rendus de l'Académie des Sciences Série 2

hal-01032151
https://hal.archives-ouvertes.fr/hal-01032151
DOI : 10.1016/S1620-7742(01)01380-0

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
OBJECTIVES: To compare virological effectiveness in patients who continued on a virologically successful first-line boosted protease inhibitor (PI)-containing combination antiretroviral therapy (cART) regimen or who switched to a PI-free cART including efavirenz, nevirapine or abacavir. METHODS: From the French Hospital Database on HIV, we selected 439 patients with undetectable viral load (VL) on a first-line boosted PI-containing cART regimen who switched to a PI-free combination including efavirenz, nevirapine or abacavir. Each of these patients was matched with three patients who continued to take their first-line cART regimen, on the basis of gender, age, CD4 cell count, VL, date of cART initiation and the duration of VL undetectability. Time to virological failure (VF) was analysed with Kaplan-Meier curves and Cox models. RESULTS: The 12 month probabilities of VF were 3.7% and 5.7% in non-switch and switch patients, respectively, and 3.9%, 7.2% and 9.0% in patients switching to efavirenz-, nevirapine- and abacavir-containing cART, respectively. After adjustment, only patients switching to abacavir-containing cART had a higher risk of VF than non-switch patients (adjusted hazard ratio, 1.99; 95% confidence interval, 1.05-3.79). CONCLUSIONS: Switching from a virologically successful first-line boosted PI-containing cART regimen to a non-nucleoside reverse transcriptase inhibitor-containing cART regimen containing either efavirenz or nevirapine is virologically safe, while switching to abacavir-containing cART should be avoided.
ISSN: 0305-7453

hal-00875284
https://hal.archives-ouvertes.fr/hal-00875284
DOI : 10.1093/jac/dkr208
PUBMED : 21636583

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Acknowledging the high exposure of the region to natural and man-made disasters, this article emphasizes the need for the Institutions of Higher Education operating in the Caribbean to improve their level of preparedness and develop efficient mitigation plans. Based on their experience of the Disaster Resistant Universities initiative, the authors suggest a methodology to develop such plans adapted to the Caribbean context. A four-step risk assessment allows the definition and implementation of a hazard mitigation plan for the universities, along with table-top exercises critical for capacity building within the institution.
Reconnaissant le niveau d’exposition élevé de la zone Caraïbe aux catastrophes d’origines naturelle et anthropique, l’article souligne la nécessité pour les établissements d’enseignement supérieur implantés dans la région à la fois d’optimiser leur niveau de préparation face aux catastrophes, et de définir des plans opérationnels de réduction des risques. Sur la base de leur expérience de l’initiative « Universités Résistantes aux Catastrophes », les auteurs suggèrent une méthodologie de planification préventive adaptée au contexte caraïbe. Une évaluation des risques en 4 étapes autorise la mise en place d’un plan de réduction des risques ; le plan ainsi adopté par les universités devra être associé à la mise en œuvre de simulations essentielles au développement des savoir-faire au sein même de l’établissement
Reconociendo la alta exposición de la región a los desastres naturales y artificiales, este artículo da énfasis a la necesidad para las instituciones de educación superior que funcionan en la zona Caribe de mejorar su nivel del estado de preparación, y desarrollar planes eficientes de mitigación. De acuerdo con su experiencia de la iniciativa « Universidades Resistentes a los Desastres », los autores sugieren una metodología para desarrollar tales planes adaptados al contexto Caribeño. Una evaluación de los riesgos en cuatro etapas autoriza la implementación de un plan de reducción de los riesgos para las universidades, junto con las simulaciones esenciales al desarrollo de los conocimientos técnicos dentro del establecimiento.
Caraïbes

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.294
http://journals.openedition.org/etudescaribeennes/294

Éditeur(s) : HAL CCSD
Résumé : International audience
We assessed whether maternal employment during pregnancy - overall and in selected occupational sectors - is associated with birth weight, small for gestational age (SGA), term low birth weight (LBW), length of gestation, and preterm delivery in a population-based birth cohort design. We used data from >200 000 mother-child pairs enrolled in 13 European birth cohorts and compared employed versus non-employed women. Among employees, we defined groups of occupations representing the main sectors of employment for women where potential reproductive hazards are considered to be present. The comparison group comprised all other employed women not included in the occupational sector being assessed. We performed meta-analyses of cohort-specific estimates and explored heterogeneity. Employees had a lower risk of preterm delivery than non-employees [adjusted odds ratio (OR adj) 0.86, 95% confidence interval (95% CI) 0.81-0.91]. Working in most of the occupational sectors studied was not associated with adverse birth outcomes. Being employed as a nurse was associated with lower risk SGA infants (OR adj0.91, 95% CI 0.84-0.99) whereas food industry workers had an increased risk of preterm delivery (OR adj1.50, 95% CI 1.12-2.02). There was little evidence for heterogeneity between cohorts. This study suggests that, overall, employment during pregnancy is associated with a reduction in the risk of preterm birth and that work in certain occupations may affect pregnancy outcomes. This exploratory study provides an important platform on which to base further prospective studies focused on the potential consequences of maternal occupational exposures during pregnancy on child development.
Scandinavian journal of work, environment & health

Droits : info:eu-repo/semantics/OpenAccess
hal-01151621
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01151621
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01151621/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01151621/file/Maternal%20occupation%20during%20pregnancy_supplementary%20material.pdf
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01151621/file/Maternal%20occupation%20during%20pregnancy_accepted.pdf

Éditeur(s) : HAL CCSD John Libbey Eurotext
Résumé : International audience
Environmental health risk assessment is commonly used in France for risk management purposes. The Methodology section of the "Société française de santé environnement" (French Society for Environmental Health) seeks to improve the utility and implementation of risk assessment in France. An initial operational objective is to make a list of short-, intermediate- and long-term improvements. This inventory is based in part on the experience and expertise of society members in this area and in part on their analysis of "Science and Decisions: Advancing Risk Assessment" (National Research Council 2009). In this paper, the Society recommends modifications in the indications for and use of risk assessments, during each of the four stages of the process: hazard identification and dose-response assessment, exposure assessment, risk characterization, and results interpretation. Some may be implemented now, while others need consensus building or research because of gaps in knowledge. Environmental health risk assessment must be understood as a decision tool for risk management in situations of uncertainly. Thus, appropriate linkage is required between decision making and assessment, and between the methods and the expected results.
L'évaluation des risques sanitaires est fréquemment utilisée en France dans les processus de décision en santé environnementale. La section " Méthodologie d'évaluation des risques sanitaires " de la Société française de santé environnement (SFSE) s'est donnée pour objectif de proposer des éléments de réflexion et des outils méthodologiques en vue d'améliorer l'utilité et les pratiques de l'évaluation des risques sanitaires. Un premier objectif opérationnel est l'inventaire des améliorations possibles à court, moyen et long termes à apporter à la démarche et à son utilisation. Ce travail s'est fondé, d'une part, sur la pratique et l'expertise des membres de la section, et, d'autre part, sur une lecture critique du rapport " Science and Decisions : Advancing Risk Assessment " publié en 2009 par le National Research Council et portant également sur les évolutions de la démarche. Dans cet article, la section restitue les conclusions de cet inventaire critique et propose un certain nombre d'améliorations en termes d'indications et d'utilisations de l'évaluation des risques sanitaires pour chacune des quatre étapes : identification des dangers et relation dose-réponse ; évaluation de l'exposition ; caractérisation des risques ; et interprétation des résultats. Certaines recommandations peuvent être mises en oeuvre immédiatement ; d'autres, en préalable à leur mise en oeuvre, nécessitent un consensus ou encore de la recherche car les connaissances manquent. En conclusion, la section insiste sur le fait que l'évaluation des risques sanitaires doit être comprise comme une aide à la décision en situation d'incertitude ; l'articulation entre le contexte décisionnel et l'évaluation, sa méthodologie et les résultats attendus est donc primordiale.
ISSN: 1635-0421

ineris-00963325
https://hal-ineris.archives-ouvertes.fr/ineris-00963325
DOI : 10.1684/ers.2011.0435
INERIS : EN-2012-016

Éditeur(s) : HAL CCSD
Résumé : International audience
The INTERREG Caribbean IV program recommends the valorization and protection of the region's environmental core, through collaborative and sustainable management of resources. It uses Martinique as the test case. The French territories of Saint-Martin, Saint-Barthélemy, Guadeloupe, and Martinique, and the member states of the Organization of Eastern Caribbean States are part of a geographic continuum that can easily be identified through its similar landscapes, climates, and natural resources and also through the environmental degradation the states have to face, caused by human activity (pollution and deterioration of ecosystems and habitats), natural hazards, and climate change including sea level rise. Therefore the islands of the Lesser Antilles are faced with an important developmental and environmental challenge, which could be easily summarized as a struggle for balance.
Meteorological Technology International

ird-00742661
http://hal.ird.fr/ird-00742661
http://hal.ird.fr/ird-00742661/document
IRD : fdi:010057442

Éditeur(s) : HAL CCSD
Résumé : International audience
Objective: In order to determine how risk factors of death among HIV-infected patients in French Guiana interact with one another and to define high risk population segments, an alternative statistical method to Cox proportional hazards models was used. Patients and methods: Data from HIV+ patients followed in the three main hospitals of French Guiana were used. Data were extracted from the prospective French Hospital Database for HIV (FHDH). To examine the nature of the relationships between time of death since the first consultation and a set of predictor variables (age at enrolment, gender, nationality, CD4 count at enrolment, presence or absence of HAART at enrolment, a declared addiction, and mode of acquisition of the virus) a survival tree analysis was used. Survival rates at 5 years and 10 years and their 95% confidence interval were also calculated. Results: This analysis permitted to reveal a new specific subgroup of HIV+ patients particularly at risk in French Guiana not already mentioned in the literature: the HIV+ female patients with a declared addiction. Conclusions: Prevention and care in this vulnerable segment of the HIV+ population identified by this methodology should be reinforced.
J AIDS Clinic Res

Droits : info:eu-repo/semantics/OpenAccess
inserm-00914956
http://www.hal.inserm.fr/inserm-00914956
http://www.hal.inserm.fr/inserm-00914956/document
http://www.hal.inserm.fr/inserm-00914956/file/2012_Hanf_-_Hierarchysur Determinants_Underlying_Death_among_HIV-Infected_patients_in_French_Guiana.pdf
DOI : 10.4172/2155-6113.1000172

Résumé : Ce travail est l'expression d'une volonté de chercheurs, de la Carabe d'améliorer les connaissances scientifiques méso- et micro-météorologiques appliquées aux milieux insulaires sous influence des alizés et de développer la recherche dans ces domaines.On sait que le phénomène météorologique le plus remarquable impactant les îles de la Caraïbe reste le cyclone tropical. Mais d'autres phénomènes, a des échelles inferieures, telles que les pluies intenses, les houles, la dégradation de la qualité de l'air ont une importance aigüe en termes de risques naturels ou de risques sur la sante. Ces exemples attestent la nécessité d'utiliser des méthodes de descente d'échelle pour exploiter l'information météorologique et/ou climatique de grande échelle et dériver des scenarios locaux et régionaux appliques aux territoires insulaires. Ce défi est important car l'attente d'analyses scientifiques pertinentes dans ces domaines est grande.Les travaux présentés dans ce mémoire ont pour principaux objectifs la simulation numérique puis l'analyse des mécanismes méso- et micro-échelles qui induisent des circulations locales diurnes et nocturnes sur l'archipel de la Guadeloupe à l'aide de codes numériques météorologiques éprouves car largement utilises en recherche et en prévision opérationnelle.Ils constituent donc la première étude de modélisation numérique à haute résolution en basse atmosphère, par descente d'échelle dynamique, pour des intervalles d'espace compris entre 1 km et 111 m sur cet archipel.Le modelé atmosphérique Weather Research and Forecasting ARW V3.4 (WRF ARW), non-hydrostatique, a été utilise pour l'ensemble des simulations pour modéliser la troposphère depuis l'échelle globale à l'échelle de la turbulence.Trois situations météorologiques classiques réelles d'une durée de 48 heures, correspondant à 80 % des situations météorologiques observées dans la zone, alizes soutenus (AS), alizes moyens (AM), alizes faibles (AF) ont été examinées. Ces situations sont caractérisées par les valeurs du nombre de Froude local suivantes : 0,82 (AS), 0,41 (AM) et 0,21 (AF). Six domaines de modélisation ont été sélectionnés pour effectuer les descentes d'échelle dynamiques : D01 (maille de 27 km), D02 (maille de 9 km), D03 (maille de 3 km), D04 (maille de 1 km), D05 (maille de 333 m) et D06 (maille de 111 m) avec soixante-dix niveaux verticaux. Les quatre premiers domaines (D01 à D04) couvrent l'archipel de la Guadeloupe et sont utilisés en mode méso-échelle à l'aide d'un schéma d'ensemble de couche limite planétaire YSU. Les domaines D05 (couvrant l'île de la Basse-Terre et le centre de l'archipel) et D06 (couvrant la zone littorale et rurale du Petit Cul-de-Sac Marin et la zone urbaine de l'agglomération pointoise) sont utilisés en mode Large Eddy Simulation avec une fermeture de la turbulence 1,5 TKE 3D. Le modèle WRF a été forcé toutes les six heures par l'assimilation des champs d'analyses globales du modèle NCEP FNL (1° de résolution). Les simulations effectuées ont permis d'obtenir des champs de variables météorologiques 10-minutes à très hautes résolutions spatiales.Les résultats des simulations méso- et micro-échelles ont été confrontés aux valeurs expérimentales obtenues à l'aide de capteurs places sur des mâts météorologiques (campagne Atmo-Mangrov et réseau de mesure Météo-France). Il s'agissait d'optimiser l'utilisation des couplages de codes numériques tout en conservant la possibilité de les confronter aux observations expérimentales.Les résultats des simulations numériques micro-échelles, des différents cas (AS, AM, AF) sont utilisées pour forcer (c'est-à-dire définir les conditions limites) un modèle lagrangien de dispersion de particules : FLEXPART. Le système couple FLEXPART-WRF a été employé dans le domaine D06 pour étudier la dispersion du panache d'oxydes d'azote émis par la principale usine de production d'électricité de l'île.
The present work expresses the will of Caribbean researchers to improve the meso- and micro-meteorological scientific knowledge of the trade winds influenced island areas, and to develop research in these domains.It is well known that tropical hurricanes remain the most remarkable meteorological phenomena that affect the Caribbean islands. But some other phenomena, of smaller scale, such as intense rainfall events, swells, or air quality degradation, are of extreme importance for natural or health hazards. These examples show the need to use downscaling methods to exploit large scale meteorological or climatic information, and to obtain local and regional scenarios for the island areas. This is an important challenge, as sound scientific studies in these matters are eagerly expected. The aim of the research works exposed in the present dissertation is numerical simulation and analysis of the meso- and microscale mechanisms that induce diurnal and nocturnal local circulations in the Guadeloupe archipelago, using numerical meteorological models that are widely used in research and in operational forecasting.These works represent the first high-resolution (1 km to 111 m) numerical study of the lower atmosphere over the Guadeloupe archipelago. The Weather Research and Forecasting ARW 3.4 (WRF-ARW) model is used to simulate the troposphere from global scale to turbulence scale. Real cases of three typical weather types (80% of cases during a year) are examined during 48 hours : strong trade winds (STW), medium trade winds (MTW) and weak trade winds (WTW). These weather types are characterized by values of the local Froude number : 0.82 (STW), 0.41 (MTW) and 0.21 (WTW). Six domains have been selected for the dynamical downscaling : D01 (grid spacing of 27 km), D02 (grid spacing of 9 km), D03 (grid spacing of 3 km), D04 (grid spacing of 1 km), D05 (grid spacing of 333 m) and D06 (grid spacing of 111 m), including 70 vertical levels. The first four domains (D01 to D04) cover the Guadeloupe archipelago and are used in the meso-scale simulations with the planetary boundary layer scheme YSU (ensemble mean). Domain D05 (covering the Basse-Terre island and the middle of the archipelago) and domain D06 (covering the coastal and rural area of Le Petit Cul-de-Sac Marin and the urban area of Pointe-à-Pitre), are employed in the micro-scale simulation (LES) with the 3D TKE 1.5 order closure scheme. WRF has been 6 hourly reinitialized with the NCEP FNL global analyses (resolution of 1°). These simulations permitted to obtain 10-minutes meteorological variable fields with a very high resolution (111 m).Meso-scale and micro-scale model results have been evaluated with observational data from meteorological stations (field campaign Atmo-Mangrov, French Met Office).Once validated, the micro-scale model outputs have been used for the assimilation of the lagrangian particle dispersion model : FLEXPART. The coupling FLEXPART-WRF has been employed in domain D06, in order to analyze the dispersion of the nitrogen oxide plume emitted by the main power plant of the archipelago.

http://www.theses.fr/2014AGUY0735/document

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : 9 pages
International audience
Potentially hazardous asteroids and comets have hit Earth throughout its history, with catastrophic consequences in the case of the Chicxulub impact. Here we reexamine one of the mechanisms that allow an impact to have a global effect—the release of climate-active gases from sedimentary rocks. We use the SOVA hydrocode and model ejected materials for a sufficient time after impact to quantify the volume of gases that reach high enough altitudes (> 25 km) to have global consequences. We vary impact angle, sediment thickness and porosity, water depth, and shock pressure for devolatilization and present the results in a dimensionless form so that the released gases can be estimated for any impact into a sedimentary target. Using new constraints on the Chicxulub impact angle and target composition, we estimate that 325 ± 130 Gt of sulfur and 425 ± 160 Gt CO2 were ejected and produced severe changes to the global climate.
ISSN: 0094-8276

hal-01639659
https://hal.archives-ouvertes.fr/hal-01639659
DOI : 10.1002/2017GL074879

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : L’incendie de forêt reste incontestablement un des facteurs de dégradation les plus dévastateurs dans le bassin méditerranéen, lequel est caractérisé par une végétation très inflammable et des conditions climatiques chaudes et sèches. Le Maroc, pays du pourtour méditerranéen, n’est pas épargné par ce fléau, avec 3000 ha de forêts qui partent annuellement en fumée ; cette situation est aggravée par les difficultés de régénération et de restauration des espaces, marqués par une vulnérabilité naturelle telle que celle de la Mâamora. Pour répondre à cela, la conception d’un plan d’aménagement anti-feux visant à conférer à la forêt de la Mâamora une immunité élevée contre les incendies, nécessite non seulement une connaissance approfondie du milieu, mais aussi une analyse appropriée du phénomène « incendie ». La présente étude qui se penche sur le diagnostic et l’analyse des incendies survenus en Mâamora, a permis de constater que les zones d’interface homme-forêt (routes, douars, etc.) n’ont pas d’influence sur l’occurrence des incendies. Il ressort également que l’activité pastorale, pratiquée d’une certaine façon, pourrait jouer un rôle important dans la diminution des risques d’incendie. En outre l’étude révèle que la charge du combustible représente le facteur prépondérant qui régit à la fois l’éclosion des incendies et leur propagation, cette charge étant étroitement liée à la qualité de la station (sol et pluviométrie).
Forest fires are the main disturbance and the degradation factor most devastating that can affect forested areas, especially in the Mediterranean basin when species are highly flammable and climate conditions are marginal. Morocco as a Mediterranean country is not spared from this phenomenon, thus 3000 ha of forest are burned every year, and this situation is aggravated by the low rate of regeneration and restoration of the unbalanced ecosystems such as the Mâamora. To mitigate this situation, the establishment of an effective management plan for forest fire prevention requires not only an intimate knowledge of environment but also a perfect analysis of fire phenomenon. Therefore in this study, we focused our diagnosis on the analysis of old fires occurred in the past in Mâamora forest. The study highlighted that human-forest interface areas (roads, villages) have no influence on fires occurrence. Besides it was shown that grazing practiced in a well-balanced way, could play a key role in reducing fire hazards. In addition the study reveals that fuel load of is the major factor that governs both fire ignition and fire spread of, this load is closely related to site quality (soil and rainfall)
Maroc

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.10978
http://journals.openedition.org/etudescaribeennes/10978

Éditeur(s) : HAL CCSD
Résumé : The territory of Armenia was located in the collision zone between Arabia and Eurasia, and is the seat of active intercontinental deformations, which was attested by the many historical earthquakes that have occurred in this region. All these destructive earthquakes show a strong regional seismic activity, and therefore it is important to evaluate the seismic hazard associated with active structures that generates this seismicity.This study presents the results of the analysis of the active tectonics within the northwestern and southeastern extensions of the Pambak-Sevan-Syunik fault (PSSF), a major right-lateral strike-slip fault cutting through Armenia (NW - SE). Quantifying the deformations in terms of geometry, kinematics, slip rates and earthquake activity, using cosmogenic 3He, OSL/IRSL and radiocarbon dating techniques, reveal different behaviors between the two regions.Within the northwestern extension, in the region of Amassia, the PSSF bends to the west and splits into two main WNW-ESE trending reverse faults defining a compressional pop-up structure. We estimate an uplift rate and a shortening rate of 0.5 ± 0.1 mm/y and 1.4 ± 0.6 mm/y, respectively. This suggests that most of the ~2 mm/y right lateral movement of the PSSF seems to be absorbed within the Amasia pop-structure.Within the southeastern extension, in the region of Tsghuk volcano, the PSSF shows signs of dying out at the southernmost tip of the Syunik graben. A very slow NS trending normal faulting associated with a slight right-lateral movement characterizes the tectonic activity in the region of Tsghuk volcano. We estimate vertical slip rates, EW stretching rate, and right-lateral slip rate of ~0.2 mm/y, ~0.1 mm/y and ~0.05 mm/y, respectively. These results lead to the conclusion that the right lateral movement observed further north along the PSSF is mainly transferred within other active faults further west within the Karabagh (Hagari fault or other structures further northwestwards).
L’Arménie se situe dans la zone de collision entre Arabie et Eurasie et est le siège d’une déformation intracontinental active comme l’atteste les nombreux tremblements de terre historiques qui s’y sont produits. Tous ces séismes, destructeurs, attestent d’une forte activité sismique régionale, et il est par conséquent important d'évaluer l’aléa sismique associé aux structures actives qui génère cette sismicité.Le travail présenté ici, expose les résultats de l’analyse de la tectonique active au niveau des terminaisons nord-ouest et sud-est de la faille de Pambak-Sevan-Syunik (PSSF), une des failles décrochant majeure qui traverse l'Arménie du NW au SE. La quantification des déformations en termes de géométrie, cinématique, vitesse de glissement et paléosismicité, en utilisant les méthodes de datation 3He cosmogénique, OSL/IRSL et radiocarbone, révèlent des comportements différents entre les deux régions.Au niveau de la terminaison nord-ouest, dans la région d’Amassia, la faille PSSF s’incurve vers l'ouest et se subdivise en deux branches de direction WNW-ESE, et de cinématique inverse, définissant une structure en pop-up. Nous estimons une vitesse de soulèvement de 0.5 ± 0.1 mm/an et une vitesse de raccourcissement NNE-SSW de 1.4 ± 0.6 mm/an. Ces résultats suggère que l’essentiel des ~2 mm/an de mouvement dextre estimés le long de la faille de PSSF sont absorbés au niveau du pop-up d’Amassia.Au niveau de la terminaison sud-est, dans la région du volcan Tsghuk, la faille PSSF semble disparaitre. Le peu d’activité tectonique est caractérisée par des failles normales sub-méridiennes associées à une légère composante décrochant dextre. Nous déterminons une vitesse de glissement vertical de ~0,2 mm/an, une vitesse d’extension ~EW de ~0,1 mm/an associée à une composante dextre de ~0,05 mm/an. Ces résultats suggèrent que le mouvement dextre observé le long de la faille de PSSF plus au nord, a été transféré sur d'autres failles plus à l'ouest dans le Karabakh (faille Hagari ou autres structures situés encore plus au NW).
https://tel.archives-ouvertes.fr/tel-01621440

NNT : 2016MONTT152
tel-01621440
https://tel.archives-ouvertes.fr/tel-01621440
https://tel.archives-ouvertes.fr/tel-01621440v2/document
https://tel.archives-ouvertes.fr/tel-01621440/file/2016_MKRTCHYAN_archivage.pdf