Éditeur(s) : Amer Geophysical Union
Résumé : Seismic noise is an indirect source of information on ocean waves. Using a model of noise generation and propagation, seismic stations can be separated into those that are mostly sensitive to local sea states, and those that integrate sources from a large oceanic area. The model also provides a classification of noise-generating sea states into three classes. The analysis of Central California seismic noise data, well correlated with local waves, reveals that class I events dominate in summer, caused by a single wind-sea system, and for which ocean wave spectral levels are proportional to seismic spectral levels to an exponent b similar or equal to 0.9. In winter, noise is dominated by class II generation, for which coastal reflection is important, with a wave spectral density roughly proportional to the seismic spectral density to an exponent b similar or equal to 0.7. Sporadic events of class III probably produce some of the strongest noise events in Central California and need to be properly screened. These events are caused by opposed wave systems that are usually the wind-sea and a swell. This noise classification can be used to improve on the correlation between measured and estimated wave heights(up to r = 0.93 for daily averages). For other locations, where remote oceanic sources are recorded, a significant wave height estimated from the seismic noise compares well with area-averaged satellite data or wave model results(r > 0.85 for daily averages). These analyses pave the way for quantitative uses of seismic records, including the reconstruction of past wave climates, and the calibration of wave hindcasts.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2012-05 , Vol. 117 , N. C05002 , P. 19 pp.

Droits : 2012 AGU
http://archimer.ifremer.fr/doc/00083/19443/17051.pdf
DOI:10.1029/2011JC007449
http://archimer.ifremer.fr/doc/00083/19443/

Éditeur(s) : HAL CCSD European Geosciences Union (EGU)
Résumé : International audience
The transformation of nonlinear long internal waves in a two-layer fluid is studied in the Boussinesq and rigid-lid approximation. Explicit analytic formulation of the evolution equation in terms of the Riemann invariants allows us to obtain analytical results characterizing strongly nonlinear wave steepening, including the spectral evolution. Effects manifesting the action of high nonlinear corrections of the model are highlighted. It is shown, in particular, that the breaking points on the wave profile may shift from the zero-crossing level. The wave steepening happens in a different way if the density jump is placed near the middle of the water bulk: then the wave deformation is almost symmetrical and two phases appear where the wave breaks.
ISSN: 1023-5809

hal-00331099
https://hal.archives-ouvertes.fr/hal-00331099
https://hal.archives-ouvertes.fr/hal-00331099/document
https://hal.archives-ouvertes.fr/hal-00331099/file/npg-14-247-2007.pdf

Éditeur(s) : Gauthier-Villars
Résumé : Analysis of Geosat sea level data over the period November 1986-November 1987 has evidenced long, low-frequency equatorial wave propagations over most of the equatorial Pacific basin (Delcroix et al.,1991). The succession of downwelling Kelvin, upwelling Kelvin, and upwelling Rossby waves has raised a series of questions. Is the observed upwelling Rossby wave due to a reflection process on the eastern boundary, or due to wind forcing near the equator? Why is there no evidence of a reflection of the downwelling Kelvin wave? Is this wave sequence a feature of the 1986-1987 El Nino phenomenon or is it to be found in the mean seasonal cycle? We used a linear model forced by the FSU wind stress to study these questions. The results, during the period November 1986-November 1987, show the successive downwelling/ upwelling Kelvin waves and upwelling Rossby wave as in the Geosat observations. Another test was made, using only the part of the forcing responsible for creating Kelvin waves, in order to evaluate the portion of the signals that was due to the reflection process and the part due to local forcing. It appears that wind forcing favourable to upwelling in the eastern part of the equatorial basin is the main mechanism which both generates the upwelling Rossby wave and inhibits the reflection of the downwelling Kelvin wave. However, the reflection of the upwelling Kelvin wave contributes to the upwelling Rossby wave signal, and makes it visible all the way from the eastern to the western sides of the equatorial Pacific. Results of a climatological run show that the successive downwelling/upwelling Kelvin and Rossby wave propagations are present in the mean seasonal cycle. However, the corresponding model signals, as well as the wind forcing anomalies, show a larger amplitude in 1986-1987.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1992 , Vol. 15 , N. 5 , P. 545-554

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00101/21180/18797.pdf
http://archimer.ifremer.fr/doc/00101/21180/

Éditeur(s) : HAL CCSD
Résumé : International audience
In this paper we investigate solutions to the semi-linear wave equation in canonical form with non Lipschitz non-linearity and distributions or other generalized functions as data. To give a meaning to the Goursat problem with irregular data, we replace it by a biparametric family of problems. The first parameter turns the problem into a family of Lipschitz problems, the second one regularizes the data. Finally, the problem is solved in an appropriate algebra. We show that the solution is equal to the non-regularized one. In the examples, we take advantage of our results to give a new approach of the blow-up problem.
Differential Equations & Applications

Droits : info:eu-repo/semantics/OpenAccess
hal-00345090
https://hal.archives-ouvertes.fr/hal-00345090
https://hal.archives-ouvertes.fr/hal-00345090v2/document
https://hal.archives-ouvertes.fr/hal-00345090/file/Devoue-Goursat-wellposed-12-08.pdf

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
We develop and implement a new method to take into account the impact of waves into the 3-D circulation model SYMPHONIE (Marsaleix et al., 2008, 2009a), following the simplified equations of Bennis et al. (2011) which use glm2z-RANS theory (Ardhuin et al., 2008b). These adiabatic equations are completed by additional parameterizations of wave breaking, bottom friction and wave-enhanced vertical mixing, making the forcing valid from the surf zone through to the open ocean. The wave forcing is performed by wave generation and propagation models WAVEWATCH III® (Tolman, 2008, 2009; Ardhuin et al., 2010) and SWAN (Booij et al., 1999). The model is tested and compared with other models for a plane beach test case, previously tested by Haas and Warner (2009) and Uchiyama et al. (2010). A comparison is also made with the laboratory measurements of Haller et al. (2002) of a barred beach with channels. Results fit with previous simulations performed by other models and with available observational data. Finally, a realistic case of energetic waves travelling over a coast of the Gulf of Lion (in the northwest of the Mediterranean Sea) for which currents are available at different depths as well as an accurate bathymetric database of the 0-10 m depth range, is then simulated. A grid nesting approach is used to account for the different forcings acting at different spatial scales. The simulation coupling the effects of waves and currents is successful to reproduce the powerful northward littoral drift in the 0-15 m depth zone. More precisely, two distinct cases are identified: when waves have a normal angle of incidence with the coast, they are responsible for complex circulation cells and rip currents in the surf zone, and when they travel obliquely, they generate a northward littoral drift. These features are more complicated than in the test cases, due to the complex bathymetry and the consideration of wind and non-stationary processes. Wave impacts in the inner shelf are less visible since wind and regional circulation seem to be the predominant forcings. Besides, a discrepancy between model and observations is noted at that scale, possibly linked to an underestimation of the wind stress. Lastly, this three-dimensional method allows a good representation of vertical current profiles and permits to calculate the shear stress associated with wave and current. Future work will focus on the combination with a sediment transport model.
ISSN: 1812-0806

hal-00766548
https://hal.archives-ouvertes.fr/hal-00766548
https://hal.archives-ouvertes.fr/hal-00766548/document
https://hal.archives-ouvertes.fr/hal-00766548/file/os-8-657-2012.pdf
DOI : 10.5194/osd-8-2417-2011

Résumé : Cette thèse à pour objet l'étude théorique et numérique de solutions dans les équations aux dérivées partielles non linéaires de la physique, en particulier en dynamique des fluides. La présence de discontinuités dans les solutions de ces équations complique la compréhension mathématique des phénomènes mis enjeu et leur traitement numérique, notamment en vue de simulations informatiques . Nous étudions ces équations par une méthode de régularisation dans un espace fonctionnel approprié. Lorsque des schémas numériques construits par des méthodes différentes conduisent à des résultats identiques, ceci jusque dans leurs moindres détails, il semble alors naturel de s'interroger dans quelle mesure ces suites de solutions numériques constituent une approximation d'une solution des équations étudiées. Nous construisons des suites de solutions approchées à partir d'un schéma numérique original,stable et suffisamment simple pour démontrer que ses suites constituent une méthode asymptotique de Maslov au sens des distributions en dimension trois d'espèce. La technique de régularisation employée consiste à étendre les variables réelles du problème ne des variables complexes, ce qui nous permet de construire des familles de solutions particulières que l'on ramène au cas réel en faisant tendre un petit paramètre vers O. Les solutions physiques recherchées apparaissent alors comme valeurs au bord de fonction holomorphes. Nous illustrons les résultats obtenus par des applications en cosmologie dans les cadres Newtoniens et relativistes pour des systèmes sans pression, puis avec pression et auto-gravitation, ainsi que pour le système des gaz parfaits.
This thesis is devoted to the theoretical and numerical study of singular solutions appearing in nonlinear partial differential complicates the mathematical understanding of the phenomena under concem as well as their numerical treatment, in particular in view of computation. These equations are studied by a regularization method in an appropriate functional space. When completely different numerical methods give the same results up to the smallest details one can reasonably expect that these numerical results suggest the existence of a mathematical solution of theses equations. We construct sequences of approximate solutions from an original numerical scheme, which is stable and simple enough to prove that these sequences constitute a Maslov asymptotic method in three space dimension. The regularization technique in use consits in extending the real variables of the problem into complex ones, which perrnits to construct families of particular equations that we bring back to the real case by letting a small paramater tend to zero. The expected physical solutions appear as boundary values of holomorphie functions . Illustrations are given by applications to cosmology in the Newtorian and re1ativistic settings for pressure1ess fluid dynamics, then in presence of self-gravitation and pressure as weil as for the systemof ideal gases

http://www.theses.fr/2011AGUY0478/document

Résumé : La thèse est consacrée à la recherche des catastrophes marines (tsunamis, ondes de tempête) dans les Antilles françaises, en utilisant des modèles analytiques et numériques de mécanique des fluides. L'accent est mis sur le développement de modèles de mouvement de glissements de terrain et des vagues causées par ces glissements. Le modèle le plus simple du glissement de terrain «solide block» est utilisé pour évaluer les caractéristiques des flux pyroclastiques du volcan Soufrière-Hills (Montserrat). Un modèle plus complexe de modélisation de glissement de terrain (modèle de Savage-Hutter) a été étudié analytiquement, donnant ainsi une nouvelle famille de solutions exactes décrivant le mouvement de l'écoulement par gravité non linéaire dans une vallée ou dans un canyon sous-marin. Le modèle comprend des ondes simples (Riemann waves),le cas d'un barrage qui cède (dam-break problem), des solutions auto-similaires dans la M-fonne et « chapeaux paraboliques ». Grâce à la théorie linéaire de l'eau peu profonde nous avons étudié le processus de génération de tsunamis par des glissements de terrain de volume variable, se déplaçant à une vitesse variable dans un bassin de profondeur variable. Dans le cas d'un fond marin particulier (cas sans "réflexion"), les phénomènes de résonnance ont été étudiés dans un bassin à profondeur variable. Nous avons utilisé des méthodes numériques pour la résolution non-linéaire des équations des eaux peu profondes afin d'analyser des catastrophes marines réelles (les ondes de tempête causées par le cyclone Lili en 2002, le tsunami volcanique de 2003 à Montserrat) et probables (un tsunami prés des côtes de la Martinique). Des données sur les catastrophes
The dissertation is devoted to research in the field of marine natural hazards (tsunamis, storm surges) in the French West Indies, using analytical and numerical models of fluid mechanics. Emphasis is placed on the development of models of landslide motion and generated tsunami waves. The simple "solid block" model is used to evaluate the characteristics of pyroclastic flow Soufriere Hills volcano (Montserrat). The "fluid model" of a landslide (so called Savage-Hutter model) is studied analytically; within this model a new family of exact solutions that describe the motion of nonlinear gravity flow in a valley or underwater canyon is found: nonlinear Riemann wave, dan break problem, self-similar solutions (M - wave and parabolic cap). In the framework of the linear shallow water theory the process of generation of tsunami waves by landslides of variable volume moving with variable velocity above the basin of variable depth is studied. For the specific bottom profile ("reflectionless" one) the resonant phenomena is investigated in the basin of variable depth. Numerical methods are used to analyze marine hazards: historical (storm surges, caused by Cyclone LILI in 2002; volcanic tsunami 2003 on Montserrat) and possible events (possible tsunami of the coast of Martinique). Various data on marine natural disasters are obtained during field surveys (volcanic tsunami in 2003, stonn surges caused by Hurricane Dean in 2007). Designed catalogs of tsunamis and storm surges are created based on results of numerical modeling and field studies; some statistical analysis is perfomed

http://www.theses.fr/2011AGUY0435/document

Éditeur(s) : HAL CCSD
Résumé : poster
International audience
Locations for earthquake recorded in the Lesser Antilles subduction zone are processed separately by regional observatories, NEIC and ISC. There is no earthquake location catalog available compiling all available phase arrival data. We propose a new best complete earthquake catalog by merging all available phase arrival data for better constrains on earthquake locations. ISC provides the phase arrival data of 29243 earthquakes (magnitude range from 1.4 to 6.4) recorded by PRSN (Porto Rico), SRC (British West Indies), and from FUNVISIS (Venezuela). We add phases data from IPGP observatories for 68718 earthquakes from magnitudes 0.1 to 7.5 (OVSG, Guadeloupe, recorded 53226 earthquakes since 1981, and OVSM, Martinique, recorded 29931 earthquakes since 1972). IPGP also provides the accelerometer waveform data of the GIS-RAP network. We achieved automatic picking on the GIS-RAP data using the Component Energy Correlation Method. The CECM provides high precision phase detection, a realistic estimation of picking error and realistic weights that can be used with manual pick weights. The CECM add an average of 3 P-waves and 2 S-waves arrivals to 3846 earthquakes recorded by the GIS-RAP network since 2002. The final catalog contains 84979 earthquakes between 1972 and 2013, 24528 of which we compiled additional data. We achieve earthquake location using NonLinLoc, regional P and S waves data and a set of one dimensional velocity models. We produce improved locations for 22974 earthquakes (better residuals, on equal or larger arrival dataset) and improved duration magnitudes for 6258 earthquakes (using duration data and improved locations). A subset of best constrained 15626 hypocenters (with more than 8 phases and an average RMS of 0.48_0.77s) could be used for structural analysis and earthquake local tomography. Relative locations are to be applied in order to image active faulting. We aim to understand coupling in the seismogenic zone as well as triggering mechanisms of intermediate depth seismicity like fluid migration beneath the volcanic arc.
Geophysical Research Abstracts
Vienne, Austria

hal-01059207
https://hal-brgm.archives-ouvertes.fr/hal-01059207

Éditeur(s) : Gauthier-Villars
Résumé : The wind, temperature and current data collected during the joined French-USA FOCAL/SEQUAL programme carried in the equatorial Atlantic band in 1983 and 1984, allowed for the first time a simultaneous study of both the equatorial and coastal (5-degrees-N) upwellings along 4-degrees-W. At the equator, the decreases of both the surface temperature and the depth of the thermocline in boreal summer are correlated with the zonal component of the local windstress in the period band 1-2 months. This corresponds to the time required by the thermocline to lift up at 0-4-degrees-W in the presence of an easterly wind. The local wind cannot however explain the entire vertical variability of the thermal structure at 0-4-degrees-W. The correlation function shows in addition that the temperature there is highly correlated to the wind recorded at St Peter and St Paul Rocks (SPP) in the period band 0-2 months. This time scale is the one required by the Kelvin and Rossby waves to propagate along the equator through equatorial wave guide dynamics. The influence of these waves seems particularly important when considering the upward displacements of the thermocline both in February-March when the winds abruptly relax and in November-December when the wind at 0-4-degrees-W is southwesterly with no secondary negative maximum in the wind record at 1-degrees-N-29-degrees-W (SPP), contrary to the climatological wind field. The computation of the different terms of the heat equation applied to an homogeneous surface layer shows that the cooling is entirely due to vertical advection and eddy diffusion. The cooling would be more effective without the atmospheric heat flux and the horizontal advection of heat transported both by the South Equatorial Current at the surface and the southward current at the bottom of the mixed layer. At the coast, the amplitude and duration of the upwellings are not constant all along the coast: in boreal summer, they are maximum east of the two capes (Palmas and Three Pointes) while in winter the strength of the cooling is maximum in the east of Cape Palmas and then decreases eastward. The meridional slope of the thermocline off the coast concerns a distance which is much larger than the internal Rossby radius of deformation and is coherent with the latitudinal extension and intensity of the Guinea current both in summer and winter. In addition to this geostrophic adjustment, the upward tilt of the thermocline in summer is enhanced by the intensification of the component of the wind parallel to the coast. The application of a simple linear model forced with an eastward wind at that time explains the surface maximum cooling at the coast and the current distribution in both vertical and meridional directions. The two maxima of the zonal component of the Guinea current, in summer (main one) and in winter are in phase with the intensity of the vertical component of the windcurl. The application of the Sverdrup equations shows that the current speeds computed, for both seasons, are of the same order of magnitude as the speeds observed.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1991 , Vol. 14 , N. 3 , P. 223-240

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00101/21252/18865.pdf
http://archimer.ifremer.fr/doc/00101/21252/

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
This study demonstrates that 20-100 GHz range can be used for spatially-accurate focusing of heating inside the skin achieved by varying frequency and exposure beam size, as well as by enforcing air convection. The latter is also used to reduce overheating of skin surface. Heating at different skin depths depending on these parameters is investigated in detail using the hybrid bio-heat equation. In particular, it is shown that decreasing frequency and/or increasing exposure beam size at forced airflow result in elevation of heating of deeper layers of tissue and decrease of skin surface temperature. Changes of water content within 15%, which exceed those due to aging and presence of tumors, only slightly affect heating. Exposure intensity necessary to reach a target temperature significantly increases in different areas of body with elevated blood flow. Dependence on exposure intensity and hyperthermia treatment duration is also investigated and discussed. Results of this study suggest that the lower part of the millimeter-wave range is an attractive alternative for non-invasive thermal treatment of skin cancer with a high spatial resolution. Bioelectromagnetics. 36:464-475, 2015. © 2015 Wiley Periodicals, Inc
ISSN: 0197-8462

hal-01187403
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01187403
DOI : 10.1002/bem.21929
PUBMED : 26179286

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
In this work, we point out and apply some ideas for the numerical simulation by multi- level schemes of several wave equations including dispersive (Korteweg de Vries) and dissipative ones (Kuramoto-Sivashinski). We start from the approach developed for dissipative equations decomposing the solution into large (Y) and small (Z) scales, and we show that it is necessary to have a regularization in time to allow stable numerical treatment of Y and Z which are here generated using hierarchical processes such as Wavelets, Incremental Unknowns or Fourier.
ISSN: 1270-900X

hal-00768332
https://hal.archives-ouvertes.fr/hal-00768332
https://hal.archives-ouvertes.fr/hal-00768332/document
https://hal.archives-ouvertes.fr/hal-00768332/file/esaim_proc_2009_v27.pdf

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
By means of convenient regularization for an ill posed Cauchy problem, we define an associated generalized problem and discuss the conditions for the solvability of it. To illustrate this, starting from the semilinear unidirectional wave equation with data given on a characteristic curve, we show existence and uniqueness of the solution
ISSN: 0973-5348

hal-01529519
https://hal.univ-antilles.fr/hal-01529519
DOI : 10.1051/mmnp/201611207

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Progress in seismic methodology and ambitious large-scale seismic projects are enabling high-resolution imaging of the continental crust. The ability to constrain interpretations of crustal seismic data is based on laboratory measurements on rock samples and calculations of seismic properties. Seismic velocity calculations and their directional dependence are based on the rock microfabric, which consists of mineral aggregate properties including crystallographic preferred orientation (CPO), grain shape and distribution, grain boundary distribution, and misorientation within grains. Single-mineral elastic constants and density are crucial for predicting seismic velocities, preferably at conditions that span the crust. However, high-temperature and high-pressure elastic constant data are not as common as those determined at standard temperature and pressure (STP; atmospheric conditions). Continental crust has a very diverse mineral composition; however, a select number of minerals appear to dominate seismic properties because of their high-volume fraction contribution. Calculations of microfabric-based seismic properties and anisotropy are performed with averaging methods that in their simplest form takes into account the CPO and modal mineral composition, and corresponding single crystal elastic constants. More complex methods can take into account other microstructural characteristics, including the grain shape and distribution of mineral grains and cracks and pores. Dynamic or active wave propagation schemes have recently been developed, which offer a complementary method to existing static averaging methods generally based on the use of the Christoffel equation. A challenge for the geophysics and rock physics communities is the separation of intrinsic factors affecting seismic anisotropy, due to properties of crystals within a rock and apparent sources due to extrinsic factors like cracks, fractures, and alteration. This is of particular importance when trying to deduce crustal composition and the state of deformation from seismic parameters.
ISSN: 8755-1209

Droits : info:eu-repo/semantics/OpenAccess
hal-01685568
https://hal.archives-ouvertes.fr/hal-01685568
https://hal.archives-ouvertes.fr/hal-01685568/document
https://hal.archives-ouvertes.fr/hal-01685568/file/Almqvist_et_al-2017-Reviewssur Geophysics.pdf
DOI : 10.1002/2016RG000552

Éditeur(s) : HAL CCSD
Résumé : The purpose of this work is to specify the deformation offshore East of Taiwan by characterizing major active faults in particular at the level of the Ryukyu forearc. The major problem associated with the study of this region is that earthquakes are located outside the permanent networks. Consequently, this led to some unprecise earthquake locations limiting tectonic and statistical analyses, and therefore the correct estimation of the seismic hazard. This work is included in the project ANR ACTS (Active Tectonics and Seismic Hazard in Taiwan). To achieve this goal, we worked on three different timescales for which a different localization method has been proposed to obtain a clear image of seismic deformation and highlight major faults offhore East of Taiwan. First, at the scale of the century (from the analysis of a seismicity catalogue with homogeneous magnitude), the instrumental historical earthquakes (1897-2007) show that the Ryukyu margin was affected by 6 earthquakes of magnitude greater than 7 with 4 of them for which the responsible fault is unknown. We propose a method of relative location to relocate the historic events from the time difference of P and S arrival times (Ts-Tp) at each station. The location is obtained by searching for "analogue" earthquakes in the recent instrumental catalogue (1991-2008) for which Ts-Tp at each station is close. This method has been applied to the largest (in terms of magnitude) earthquake ever recorded in Taiwan, the earthquake of June 5, 1920 (M7.7 +/- 0.2). A rupture along the interplate of the Ryukyu subduction with a possible nucleation at the downdip limit of a splay-fault is certainly responsible of this earthquake. Then, at the scale of the decade, the improvement of the method of absolute location based on MAXimum of Intersection of EDT (MAXI, EDT: Equal Differential Time) allows to better extract the erroneous arrival times and prevents the "trade-off" between depth and origin time, and between depth and epicentral position when the azimuthal coverage is low (gap Azimuthal > 180degre). Synthetic tests show the effectiveness of MAXI (using P-wave only) to determine the parameters x, y and z even when the azimuthal gap is important. In the latter case, the quality of the results is dependent on the velocity model to represent the 3D structure of the Earth. We propose an approach involving the use of a 3D a priori P-wave velocity model to locate earthquakes which are lateral and remote to the seismic network. An application to the case of Taiwan and Ecuador validates this approach. Finally, at the level of a few months, the marine geophysical campaign RATS (Ryukyu Arc: Tectonics and Seismology) was conducted in two stages. A passive seismology experiment from July to October, 2008 (RATS1) has been conducted over the forearc of the Ryukyus and then active seismic experiment (refraction and reflection) was conducted in May 2009 in a NNE - SSW line through the Ryukyu margin. These two combined experiments allow improving our knowledge about the crustal structure of the margin. At the level of the forearc, the basement of the forearc is characterized by vertical backstop and a very deformed basis certainly associated with a significant out of sequence deformation. In depth, the downgoing plate is certainly affected by a tear that controls the seismicity in the region of transition between the subduction and collision.
Le but de ce travail est de préciser la déformation en mer à l'est de Taïwan et de notamment caractériser les failles actives majeures en particulier au niveau de l'avant-arc des Ryukyus. Le problème majeur associé à l'étude de cette région est que les séismes sont localisés en dehors des réseaux permanents et que cela conduit à des localisations peu précises limitant les analyses statistiques, tectoniques et donc l'estimation correcte de l'aléa sismique. Ce travail est inclus dans le projet ANR ACTS (Active Tectonics and Seismic Hazard in Taiwan). Pour atteindre cet objectif, nous travaillons à trois échelles de temps différentes pour lesquelles une méthode de localisation différente a été proposée pour obtenir une image précise de la déformation sismique et mettre en évidence les failles majeures en mer à l'est de Taïwan. D'abord, à l'échelle du siècle (à partir de l'analyse d'un catalogue de sismicité homogène en magnitude), les séismes historiques instrumentaux (1897-2007) montrent que la marge des Ryukyus a été affectée par 6 séismes de magnitude supérieure à 7 dont 4 pour lesquels la faille responsable n'est pas connue. Nous proposons une méthode de localisation relative qui permet de relocaliser les évènements historiques à partir des différences de temps d'arrivées P et S (Ts-Tp) à chaque station. La localisation est obtenue en recherchant les séismes analogues dans le catalogue instrumental récent (1991-2008) pour lesquels Ts-Tp à chaque station est proche. Cette méthode a été appliquée au plus gros séisme (en terme de magnitude) jamais enregistré à Taïwan, le séisme du 5 juin 1920 (M7.7 $pm$ 0.2). Ce séisme a certainement pour origine une rupture sur l'interplaque sismogène de la subduction des Ryukyus avec une possible nucléation à la base d'une faille hors-séquence. Ensuite, à l'échelle de la dizaine d'années, l'amélioration de la méthode de localisation absolue du MAXimum d'Intersection EDT (MAXI, EDT: Equal Differential Time) permet de mieux extraire les temps d'arrivées erronés et empêche les "trade-off" entre profondeur et temps d'origine et, entre profondeur et position épicentrale lorsque la couverture azimutale est faible (gap azimutal > 180°). Des tests synthétiques montrent l'efficacité de MAXI (en utilisant les ondes P uniquement) à déterminer les paramètres x, y et z même lorsque le gap azimutal est important. Dans ce dernier cas, la qualité des résultats reste dépendant du modèle de vitesse à représenter la structure 3D de la Terre. Nous proposons une démarche associant l'utilisation d'un modèle de vitesse des ondes P 3D a priori avec la méthode MAXI pour localiser les séismes qui sont latéraux et éloignés du réseau. Une application au cas de Taïwan et en Équateur valide cette approche. Enfin, à l'échelle de quelques mois, la campagne de géophysique marine RATS (Ryukyu Arc: Tectonics and Seismology) a été menée en deux temps. Une expérience de sismologie passive de juillet à octobre 2008 (RATS1) a été menée au-dessus de l'avant-arc des Ryukyus puis une expérience de sismique active (réfraction et réflexion) a été menée en mai 2009 sur une ligne NNE-SSW à travers la marge des Ryukyus. Ces deux expériences combinées permettent d'améliorer notre connaissance de la structure crustale de la marge. Au niveau de l'avant-arc, le socle de l'avant-arc est caractérisé par une extrémité formant un butoir vertical et une base très déformée certainement associée à une importante déformation hors-séquence. En profondeur, la plaque plongeante est certainement affectée par une déchirure qui contrôle la sismicité dans cette région de transition entre la subduction et la collision.
https://tel.archives-ouvertes.fr/tel-00660737

tel-00660737
https://tel.archives-ouvertes.fr/tel-00660737
https://tel.archives-ouvertes.fr/tel-00660737/document
https://tel.archives-ouvertes.fr/tel-00660737/file/Thesis_small.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We discuss various methods of regularization of singular differential problems. Their common point is that we use the flexibility of the theories of nonlinear generalized functions for adapting the regularization to the singularity of the problem. We particularly underline the relationship between the generalized solutions and those classical or distribution, when they exist, giving a general result for the case of the regularization of data.
Journal of Mathematical Analysis and applications

hal-01529550
https://hal.univ-antilles.fr/hal-01529550
DOI : 10.1016/j.jmaa.2008.11.077

Éditeur(s) : HAL CCSD
Résumé : Climate change is one of the biggest public health threats in the 21th century. An increase in temperatures will lead to an increase in mortality attributable to temperature. In addition, some populations and territories are particularly vulnerable to the impact of increases in heat. It is thus necessary to identify these populations and territories as well as examine future heat-Related health impacts in order to recommend equity-Oriented policies today and in the future. The general objective of this thesis is to document current and future heat-Related vulnerability factors in the context of climate change. In order to address this general objective, the thesis involved four components: a) to conduct a systematic review and a meta-Analysis to assess the heterogeneity in the heat-Mortality associations with respect to individual and contextual population characteristics; b) to identify whether and how the magnitude of mean temperature effects on all-Cause mortality were modified by chronic air pollution exposure, social deprivation, and a combination of these two dimensions; c) to develop a method to quantify the climate change impacts on heat-Related mortality using climate modeling; d) to assess historical and future social disparities in years of life lost caused by ambient temperature in Montreal and Paris, and compare these estimates as well as the impact of climate change on social disparities between the two cities. This thesis highlights which populations are more vulnerable to heat and shows that several differences exist with regard to guidelines from international public health institutions for the identification of vulnerable populations. This thesis also identified chronic air pollution exposure as a new vulnerability factor in heat-Related mortality and that it has a double interaction with social deprivation. Furthermore, in this thesis a novel method to quantify future heat-Related mortality was developed which emphasized the strong evidence of an increase in heat-Related mortality under climate change. This method was then applied to estimate the increase in daily years of life lost social disparities in both Montreal and Paris under climate change which showed that this increase would be greater in Montreal compared to Paris in the future. Thus, this thesis which used a variety of epidemiologic methods has clarified which populations are particularly vulnerable to heat impacts and challenges guidelines for the identification of vulnerable populations from international public health institutions. It has also highlighted the climate change impacts on health inequalities and aims to reorient equity-Focused policies.
Les changements climatiques constituent l’un des enjeux les plus importants en santé publique du XXIème siècle. En effet, une hausse des températures provoquera une hausse de la mortalité attribuable à la chaleur. En outre, certaines populations et territoires sont particulièrement vulnérables aux effets de la chaleur. Il est donc nécessaire de les identifier clairement ainsi que les impacts futurs pour orienter avec équité les politiques publiques aujourd’hui et à l’avenir. L’objectif de cette thèse est de documenter les facteurs de vulnérabilité à la chaleur dans le présent et les éléments permettant leur prise en compte pour l’avenir dans le contexte des changements climatiques. Quatre étapes ont été menées pour répondre à cet objectif : a) Mener une revue systématique et une méta-Analyse des facteurs de vulnérabilité face aux risques de mortalité en lien avec la chaleur ; b) Analyser si l’exposition chronique à la pollution atmosphérique modifie la relation entre la chaleur et la mortalité dans un contexte urbain (Paris) et explorer la double interaction avec la défaveur sociale ; c) Développer une méthode de quantification des impacts liés à la chaleur en lien avec les changements climatiques en intégrant une grande diversité de simulations climatiques ; d) Estimer les inégalités d’années de vies perdues attribuables à la chaleur et leurs projections futures dans deux contextes distincts (Montréal et Paris) et comparer ces inégalités. Cette thèse a permis de mettre en évidence sur la base de la littérature épidémiologique les groupes de population qui sont les plus vulnérables face aux effets de la chaleur et de montrer qu’il y a plusieurs divergences par rapport aux recommandations émises par les institutions de santé publique vis-À-Vis de l’identification de populations vulnérables. Cette thèse a permis également d’identifier l’exposition chronique à la pollution atmosphérique comme nouveau facteur de vulnérabilité à la chaleur et que cette vulnérabilité était encore plus prononcée lorsqu’il s’agissait de populations défavorisées socialement. Puis, une méthode permettant de quantifier l’impact des changements climatiques sur les décès attribuables à la chaleur et ses sources d’incertitudes a été développée, et a permis de mettre en évidence que la probabilité que les changements climatiques conduisent à une augmentation de la mortalité en lien avec la chaleur est très forte. Cette méthode a ensuite été utilisée pour estimer que l’augmentation de la température conduira à une augmentation des inégalités sociales d’années de vie perdues à la fois à Montréal et à Paris, l’effet des changements climatiques sur l’accroissement de ces inégalités étant plus fort à Montréal qu’à Paris. Cette thèse, en se basant sur diverses méthodes épidémiologiques, a permis dans l’ensemble de clarifier quelles populations étaient particulièrement à risque face aux effets de la chaleur et de questionner les recommandations émises par les organismes tels que l’OMS. Elle a également permis de montrer l’effet des changements climatiques sur l’évolution de vulnérabilités face à la chaleur pour inciter dès aujourd’hui la mise en place de politiques publiques équitables et limiter l’impact des changements climatiques sur l’accroissement des inégalités de santé.
https://tel.archives-ouvertes.fr/tel-01456772

Droits : info:eu-repo/semantics/OpenAccess
NNT : 2015PA11T003
tel-01456772
https://tel.archives-ouvertes.fr/tel-01456772
https://tel.archives-ouvertes.fr/tel-01456772/document
https://tel.archives-ouvertes.fr/tel-01456772/file/VA_BENMARHNIA_TARIK_05022015.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We show that a new definition of the asymptotic structure of the (C,E,P)-algebras (which are a refinement of the Colombeau Generalized Algebras) allows to define a natural topology on them. Furthermore, this topology can be mixed with functorial aspects of the construction in order to give extension principles, which give powerful tools to solve singular differential problems in this framework.
ISSN: 0022-247X

hal-01529551
https://hal.univ-antilles.fr/hal-01529551
DOI : 10.1016/j.jmaa.2009.05.046