Un système interactif d'aide à la construction d'applications de traitement d'images

Dans le cadre de la mise au point d'applications de traitement d'images, nous proposons un système d'aide fondé sur la modélisation et l'explicitation de la démarche du traiteur d'images. Les traitements à effectuer y sont représentés sous une forme compréhensible et modifiable par l'utilisateur (enchaînements d'opérateurs sous forme de plans), dans un souci de réutilisation de parties entières de traitement. L'organisation de ce système repose sur une modélisation naturelle des connaissances sous forme de Tâches, Méthodes et Outils. La construction et l'exécution des plans de traitement d'images s'effectuent via une interface graphique qui facilite l'expérimentation de diverses techniques sur une image

Empirical model for rapid macroseismic intensities prediction in Guadeloupe and Martinique Modèle empirique pour la prédiction rapide des intensités macrosismiques en Guadeloupe et Martinique

International audienceWe describe a simple model for prediction of macroseismic intensities adapted to Guadeloupe and Martinique (Lesser Antilles), based on a combination of peak ground acceleration (PGA) predictive equation and a forward relation between acceleration and intensity. The PGA predictive equation is built from a 3-parameter functional form constrained by measurements from permanent accelerometer stations, mostly associated with Les Saintes crustal earthquake (21/11/2004, Mw = 6:3) and its many aftershocks. The forward intensity model is checked on a database of recent instrumental events of various origins with magnitudes 1.6 to 7.4, distances from 4 to 300 km, and observed intensities from I to VIII. Global sigma residual equals 0.8 in the MSK scale, suggesting a larger applicability range than the intermediate PGA predictive equation. The model is presently used by the French Lesser Antilles observatories to produce automatic reports for earthquakes potentially felt

Noeud A VOLCANO de RESIF : bilan et perspectives

Knot A VOLCANO is part of the RESIF research infrastructure information system and concentrates seismic data from the three volcanological and seismological observatories of the Institut de Physique du Globe de Paris. These observatories operate short-seismological stations-analogical period, short-digital three-component period, medium-digital band and digital wideband. These data are used for monitoring regional volcanic and land-based activity, as well as tsunami warning. The poster presents the results at the end of 2017 and the prospects for this knot A.The French Seismological and Geodetic Network RESIF is a national research infrastructure dedicated to the observation and understanding of the structure and dynamics of the Internal Earth. RESIF is based on high-tech observation networks, composed of seismological, geodetic and gravimetric instruments deployed in a dense manner throughout France. The data collected make it possible to study with high spatial and temporal resolution the deformation of the ground, surface and deep structures, seismicity on a local and global scale and natural hazards, and more particularly seismic events, on French territory. RESIF is integrated into European (EPOS - European Plate Observing System) and global systems of instruments for imaging the Earth's interior as a whole and studying many natural phenomena.Le nœud A VOLCANO fait partie du système d'information de l'infrastructure de recherche RESIF et concentre les données sismiques des trois observatoires volcanologiques et sismologiques de l'Institut de Physique du Globe de Paris. Ces observatoires opèrent des stations sismologiques courte-période analogique, courte-période numérique trois composantes, moyenne- bande numérique et large-bande numérique. Ces données sont utilisées pour le suivi de l’activité volcanique et tellurique régionale, ainsi que l’alerte aux tsunamis. Le poster présente le bilan fin 2017 et les perspectives pour ce noeud A.Le Réseau sismologique et géodésique français RESIF est une infrastructure de recherche nationale dédiée à l’observation et la compréhension de la structure et de la dynamique Terre interne. RESIF se base sur des réseaux d’observation de haut niveau technologique, composés d’instruments sismologiques, géodésiques et gravimétriques déployés de manière dense sur tout le territoire français. Les données recueillies permettent d’étudier avec une haute résolution spatio-temporelle la déformation du sol, les structures superficielles et profondes, la sismicité à l’échelle locale et globale et les aléas naturels, et plus particulièrement sismiques, sur le territoire français. RESIF s’intègre aux dispositifs européens (EPOS - European Plate Observing System) et mondiaux d’instruments permettant d’imager l’intérieur de la Terre dans sa globalité et d’étudier de nombreux phénomènes naturels

Mapping of the seismic tsunami intensity along the coast of Martinique, Lesser Antilles

International audienceThe tsunami hazard in Martinique due to local, regional and distant seismicity is investigated. Former deterministic scenarios are processed. They were proposed elsewhere based on historical records and the analysis of the morpho-tectonics of the area, i.e., two local subduction scenarios of magnitudes Mw 7.5 and Mw 8.0 representative of the local 1839 earthquake, the regional Mw 7.2-7.5, 1867 Virgin Island event, along with the distant Mw ~8.5, 1755 Lisbon earthquake. The tsunami runup and currents are simulated and analyzed. Then, a recent tsunami intensity index is applied and discussed. The modeling of the regional 1867 scenario shows negligible impact on the coast of Martinique which could explain the lack of direct observations in Martinique. Despite a difference of one unit magnitude between the local Mw 7.5 and the distant Mw ~8.5 earthquakes, it is found that their tsunami signature for Martinique is nearly equivalent. The local Mw 8.0 event thus controls the tsunami hazard in the island. In the case of this tsunami, whose source is at the east, the western side of the island is not impacted because of wave refraction. Eastward, the coral reef barrier also inhibits tsunami impacts in some sites. Interestingly, it is shown that most of the potentially inundated areas are mangroves that are already subject to daily tidal flooding and seasonal cyclonic activity. They represent an efficient protection against tsunamis. Four occupied locations are however exposed to severe inundation (horizontal penetration of hundreds of meters)

A giant landslide on the southern flank of Tahiti Island, French Polynesia

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Comments on “Epiclastic deposits and “horseshoe-shaped” caldeiras in Tahiti (Society Islands) and Ua Huka (Marquesas Archipelago), French Polynesia” by Clément et al. (2003)

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Physical characteristics and triggering mechanisms of the 2009–2010 landslide crisis at Montagne Pelée volcano, Martinique: implication for erosional processes and debris-flow hazards

International audienceAbstract Flank destabilizations are common processes in the life of a volcano. Apart from giant landslides with recurrence times of tens of thousands of years and whose deposits are identified in the bathymetry around the islands, less voluminous but more frequent erosional landslides contribute significantly to the morphological development of the topography. In this paper, we present a detailed description of a landslide sequence that occurred in 2009 and 2010 on the western flank of Montagne Pelée volcano, originating at the Samperre cliff. This sequence is characterized by two main events, in August 2009 and May 2010, and hundreds of smaller collapses. From seismic data and high resolution topographic data from airborne Lidar, collapses are counted and volumes of the main events are estimated. The May 2010 landslide has removed 2.1 millions of m3 of debris, which were subsequently remobilized during several hazardous lahars. The mean rates of erosion deduced from these volumes indicate that this kind of erosional landslide could represent a long term contribution of the same order of magnitude as giant flank collapses. The characterization of the runout of the landslides and of the Samperre cliff slopes provide important information for risk assessment, in particular for the risk of lahars that threaten the population living on the lower slopes

A review of historical lahars, floods, and landslides in the Precheur river catchment (Montagne Pelee volcano, Martinique island, Lesser Antilles)

International audienceThe Precheur river catchment belongs to the Montagne Pelee volcano massif located in the north of Martinique island, in the Lesser Antilles arc. In June 19-20, 2010 two high-discharge lahars overflowed and partially damaged the Precheur bridge, interrupting the road traffic for several days, and inundating part of the Abymes quarter. These non-eruptive, rain-triggered lahars were the consequence of the mobilization of loose volcanic material accumulated in the river bed by a massive landslide of the Samperre cliff that occurred on May 11, 2010. In order to improve lahar risk assessment for the Precheur river, we review the existing knowledge on lahars and floods for the period 1851-2011. We improved the database mainly on the basis of geophysical (seismic and acoustic) data for the most recent period (1980-present). We show that: (1) the largest event ever observed in Precheur is the eruption-related lahar of May 8, 1902 at 06:00 UTC, (2) high-discharge, non-eruptive lahars able to partially destroy or submerge the bridge occur every 10.3 years in average since 1950, (3) geophysical records show that there are more low magnitude lahars than previously recognized because witness accounts report the larger events and therefore filter out the smaller ones; by contrast geophysical instruments are able to detect both high and low magnitude events, (4) the recent paroxysms of 2009-2010 belong to a landslide-lahar crisis which started in 2004; the onset of the landslide-lahar crisis was unnoticed by the population due to the low magnitude of the events. The results of this compilation stress the importance of the presence of geophysical instrumentation sufficiently close to the river for monitoring small scale landslides and lahars. Indeed, these low magnitude events are likely to be unnoticed by the local population and therefore likely to be absent from the collective memory and local newspapers. However, they can inform about the imminence of more significant events, as observed in 1980 and 2010

Development of Image Processing applications within a cooperative Knowledge-Based Workbench

International audienceSolving an Image Processing problem involves three main categories of experts: experts from the domain of application (biologists, geographers... ), Image Processing experts and designer-programmers. Domain experts are requested to express clearly and exhaustively the purpose of their application. Image Processing experts have to propose somne kind of answer in terms of Image Processing plans adapted to the specifie features of the request and the nature of images. Designer-programmers have to provide a framework for an efficient implementation. We are interested in setting up a Knowledge-Based workbench directed toward the cooperation between these experts and the system. This approach is motivated by the development of real-world applications, while being concerned in generic principles and knowledge acquisition and integration concerns. It hinges on the supervision of a library of Image Processing operators. Solving a specifie application is a planning process which implies selecting the suitable operators, linking them and tuning their parameters. An application is thus represented as an Image Processing plan. After giving the specifications of our system, which belongs to the more general class of Knowledge-Based systems for program supervision, our software architecture favoring cooperation as well as knowledge integration will be presented. This ref1exive architecture is based on the TASK/METHOD/TOOL paradigm and provides conceptual models of applications that are actually computational. Several Image Processing plans dealing with biomedical (cytological / histological) images have already been built within our workbench, which constitutes a first convincing validation of our approach