Plate boundary segmentation in the northeastern Caribbean from geodetic measurements and Neogene geological observations

AbstractThe Caribbean–North America plate boundary in the northeastern Caribbean shows a remarkable example of along-strike transition from plate boundary–normal subduction in the Lesser Antilles, oblique subduction with no strain partitioning in Puerto Rico, and oblique subduction/collision with strain partitioning further west in Hispaniola. We show that this segmentation is well marked in the interseismic strain, as measured using space geodetic data, and in the Neogene deformation regime, as derived from geological observations. Hence, interseismic segmentation, which reproduces the geological segmentation persistent over a long time interval, is inherited from the geological history and long-term properties of the plate boundary. This result is relevant to the assessment of seismic hazard at convergent plate boundaries, where geodetic measurements often show interseismic segmentation between fully–and partially–coupled plate interface regions

La politique d'un auteur (une analyse critique des personnages renoiriens)

Dans le premier volume, nous aborderons la création du personnage sur le papier en différenciant si possible les créations originales des transpositions de personnages "littéraires". A partir des influences biographiques, il sera question du phénomène de la création et de ce qu'il doit aux répétitions et aux tournages (inscription du personnage dans son décor architectural et musical), moments de maturation et d'accouchement après la conception sur le papier. Cela nous permettra d'approcher certaines des constantes chez les personnages avant de préciser l'aspect gigogne des films du réalisateur et les cousinages qui s'établissent entre eux. Notre conviction est qu'entrer dans une oeuvre cohérente comme celle de Renoir peut se faire aussi par la description et l'analyse des personnages. Le deuxième volume de cette thèse dresse un catalogue comparatif et une typologie des personnages renoiriens.In the first volume, we will broach the creation of the character on paper while differentiating, if possible, the original creations of "literary" characters' transpositions. From the biographical influences, the creation phenomenon will be dealt with as what is due to the rehearsals and filming (inscription of the character in his architectural and musical setting), moments of maturation and delivery after the conception on paper. It will enable us to approach some of the permanent features of the characters before specifying the nesting aspect of the filmmaker's films and their interacting relationship. Our convition is that entering a coherent work such as Renoir's one can also be done by the description and the analysis of the characters. The second volume of this thesis draws up a comparative catalogue and a typology of the "renoirian" characters.NANCY2-Bibliotheque electronique (543959901) / SudocSudocFranceF

Le GPS en géomorphologie dynamique. Application à la surveillance de mouvements de terrain (Super-Sauze, Alpes du Sud, France) / GPS in geomorphological studies. Application to the survey of landslides (Super-Sauze, South France)

Abstract Recent research has demonstrated the applicability of using Global Positioning System (GPS) techniques to precisely determine the 3-D coordinates of moving points in the field of natural hazards. Indeed, the detailed analysis of the motion of a landslide, in particular for a "near real-time" warning system, requires the combination of accurate (infra-centimetric) positioning in three dimensions and fine temporal resolution (hourly or less). The monitoring of landslides with the GPS is usually performed using repeated campaigns as a complement to conventional geodetic methods. Continuous monitoring of landslides with GPS is usually not performed instrumentally because of the cost of such a system compared to conventional deformation monitoring techniques. In addition, if GPS measurements can reach a millimetre-level accuracy for long observation sessions (typically 24 h), their accuracy decreases with the duration of the sessions because of errors introduced by variations of the satellite constellation and multipath effects at the sites. The purpose of this study is to determine the experimental accuracy of GPS measurements for the continuous monitoring of landslides. In particular, we seek to calibrate the variation of measurement accuracy as a function of the duration of the observation sessions. The study was carried out on the Super-Sauze earthflow (Southern Alps, France) which evolves towards a channelised flow with surface displacements reaching a few tens of centimetres to a few metres per year. The accuracy reaches 2 mm for a 1-hour session. The flow motion is clearly detected by the GPS measurements and has been compared with the results obtained with conventional geodetic methods or with a wire extensome- ter device. The analysis of the relationships between rainfall, groundwater level, and displacements allows us to understand the behaviour of the flow and to determine thresholds in the pore water pressures that accelerate the movement.Résumé De récentes recherches ont démontré la validité du Global Positioning System (GPS) pour déterminer avec précision les coordonnées 3-D de points mobiles dans le domaine des risques naturels. L'analyse détaillée de la cinématique d'un mouvement de terrain, en particulier pour l'installation de systèmes d'alerte en temps réel, exige la combinaison d'un positionnement précis dans les trois dimensions (infra-centimétrique) et une résolution temporelle fine (horaire ou infra-horaire). Pour la surveillance, le GPS n'est utilisé que lors de campagnes de mesures répétées, en combinaison avec des méthodes d'auscultation géodésique conventionnelles. La surveillance par GPS n'a jamais été utilisée en continu sur de longues périodes. Outre le coût de l'équipement, la raison principale est la suivante : si le GPS, en mode différentiel, permet d'atteindre des précisions millimétriques pour des sessions longues de 24h, la précision se dégrade lorsque la durée des sessions diminue, à cause des biais introduits par les multi-trajets et les variations de la constellation satellitaire au cours du temps. Le potentiel du GPS à conjuguer précision spatiale et résolution temporelle a été évalué en étalonnant, en particulier, la variation de la précision en fonction de la durée des sessions de mesure. L'étude a été réalisée sur le glissement-coulée de Super-Sauze (Alpes-de-Haute-Provence, France) dont les vitesses de déplacements atteignent quelques dizaines de centimètres à quelques mètres par an. La précision du positionnement est millimétrique pour des sessions d'une heure. Le mouvement de la coulée est clairement détecté par les mesures GPS et a été comparé aux résultats obtenus avec des méthodes conventionnelles (station totale) ou avec un dispositif extensométrique. L'analyse des relations entre les précipitations, les fluctuations de la nappe et les déplacements nous permet de déterminer des seuils de pressions interstitielles initiant une accélération du mouvement.Malet Jean-Philippe, Maquaire Olivier, Calais Éric. Le GPS en géomorphologie dynamique. Application à la surveillance de mouvements de terrain (Super-Sauze, Alpes du Sud, France) / GPS in geomorphological studies. Application to the survey of landslides (Super-Sauze, South France). In: Géomorphologie : relief, processus, environnement, Avril-juin, vol. 8, n°2. pp. 165-179

New Seismotectonic Zoning Model for Seismic Hazard Assessment of the Lesser Antilles

Seismic hazard levels used as reference for the French Lesser Antilles are derived fromprobabilistic seismic hazard assessment studies performed in 2002. However, scientificknowledge has greatly increased over the past 20 years in this area, warranting an update of the seismic hazard models. As part of a project linking the French Ministry of Ecological Transition and Territory Cohesion, and the Seismicity Transverse Action of RESIF-EPOS (French seismological and geodetic network), we developed a new seismotectonic zoning model of the Lesser Antilles. The Lesser Antilles tectonic system results from the subduction of the North and South American plates beneath the Caribbean plate since the Eocene. The boundary extends along 850 km with a convergence of 18-20 mm/yr oriented ENE-WSW. Significant north-south variations in tectonics, seismic and volcanic activities highlight the lateral variability of the undergoing geodynamic processes. Oceanic fractures and ridges entering into the subduction zone impact the trench, the subduction interface, and upper plate tectonics, adding seismotectonic complexities. Several controversial questions remain, such as the origins of the 1839 (Mw=7.5-8) and 1843 (Mw=8-8.5) earthquakes or the state of interseismic coupling of the subduction interface (potentially very low compared to other subduction systems). In this study, we propose new seismotectonic models and associated seismotectonic zoning for seismic hazard. We treat all components of the Lesser Antilles system: subducted oceanic plate, subduction interface, mantle wedge, upper plate crust and associated volcanisms. Our work is based on a compilation of up-to-date seismicity and fault catalogs as well as research-based active tectonic hypotheses, completed by an analysis of focal mechanisms rupture styles and strain tensor derived from geodetic data. Compared to previously published models, our new seismotectonic zoning model provides better depth resolution, a fully revised zoning around Guadeloupe, new mantle wedge and volcanic zones, and a complete redefinition of the subduction interface and slab. Our results also highlight specific needs for better seismic hazard assessment in this region

Characteristics and possible origins of the seismicity in northwestern France

International audienceThe macroseismic and instrumental observations accumulated by the Bureau Central Sismologique Français and other national agencies over the last 100 years show that the northwestern part of metropolitan France is affected by an apparently diffuse and moderate intraplate seismicity. Far from any plate boundary, well-documented inherited structures, such as the Armorican shear zone network, the Sillon Houiller, and the normal faults related to the Atlantic ocean margin, likely exert significant control on the regional seismicity pattern. However, in the absence of a clearly measurable strain field, processes other than far-field tectonic stress loading such as erosion, gravitational potential energy, and/or hydraulic loadings can co-exist, but their respective influence on the current seismicity is debated and remains to be fully addressed. Reliable detection/location of low-to-moderate magnitude events is one of the most important challenges in the near future to better understand the processes that control this intraplate seismicity. As shown here for a limited region, this issue can be achieved positively, thanks to the new Résif-Epos network, in conjunction with sophisticated algorithms for both earthquakes’ detection and discrimination