Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Seismic anisotropy has been widely studied this last decade, particularly by measuring splitting of vertically propagating core shear waves. The main interest in this technique is to characterize upper mantle flow beneath seismic stations. On the other hand, the major restriction in this method is that a single station gives a single anisotropy measurement. Alternative methods have been developed in order to avoid this restriction. An accurate determination of upper mantle seismic anisotropy beneath a seismic station may allow one, by doing anisotropy correction, to characterize remote or deeper anisotropy. The Geoscope network is ideal for this purpose because it is composed of a large set (about 26) of high-quality, broadband seismometers globally distributed and because some of these stations have run for more than 10 years and most of them for more than 5 years. We selected about 100 events at each site, generally of magnitude (m b) > 6.0, and we performed systematic measurements of the splitting parameters (fast polarization direction φ and delay time δt) on SKS, SKKS, and PKS phases. Splitting on oceanic islands has been difficult to observe owing to the low quality of the signal but also perhaps owing to complex upper mantle structures beneath the stations. Station KIP (Kipapa, Hawaii) in the Pacific is the only oceanic Geoscope station with a clear anisotropy. We determined well-constrained splitting parameters for 10 of the 17 continental stations that may be explained by a single anisotropic layer. The poor correlation between fast polarization directions and the absolute plate motion together with the apparent incoherence between the plate velocities and the observed delay times suggest that a simple drag-induced asthenospheric flow alone fails to explain most of the observations. For some stations located on or near major lithospheric structures (TAM, Tamanrasset, Algeria, for instance), we observe a good correlation between fast polarization directions and regional structures. At station SCZ (Santa Cruz, California), we found clear variations of the splitting parameters as a function of the event backazimuth, compatible with two layers of anisotropy. Three stations (CAN (Canberra), HYB (Hyderabad, India) and SSB (Saint Sauveur Badole, France)) seem to be devoid of detectable anisotropy.
ISSN: 2169-9313

hal-01388830
http://hal.univ-reunion.fr/hal-01388830
http://hal.univ-reunion.fr/hal-01388830/document
http://hal.univ-reunion.fr/hal-01388830/file/Barruol_anisoGeoscope_JGR1999.pdf
DOI : 10.1029/1999JB900033

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
During the GWADASEIS cruise (Lesser Antilles volcanic arc, February-March 2009) a very high resolution (VHR) seismic-reflection survey was performed in order to constrain Late Quaternary to Present faulting. The profiles we obtained evidence frequent "ponding" of reworked sediments in the deepest areas, similar to the deposition of Mediterranean "homogenites". These bodies are acoustically transparent (few ms t.w.t. thick) and are often deposited on the hanging walls of dominantly normal faults, at the base of scarps. Their thickness appears sufficient to compensate (i.e. bury) co-seismic scarps between successive earthquakes, resulting in a flat and horizontal sea floor through time. In a selected area (offshore Montserrat and Nevis islands), piston coring (4 to 7 m long) was dedicated to a sedimentological analysis of the most recent of these particular layers. It corresponds to non-stratified homogenous calcareous silty sand (reworked calcareous plankton and minor volcanoclastics). This layer can be up to 2 m thick, and overlies finegrained hemipelagites. The upper centimeters of the latter represent the normal RedOx water/sediment interface. 210Pb and 137Cs activities lack in the massive sands, while a normal profile of unsupported 210Pb decrease is observed in the hemipelagite below, together with a 137Cs peak correspond- ing to the Atmospheric Nuclear Experiments (1962). The RedOx level was thus capped by a recent instantaneous major sedimentary event considered as post-1970 AD; candidate seismic events to explain this sedimentary deposits are either the 16 March 1985 earthquake or the 8 October 1974 one (Mw=6.3 and Mw=7.4, respectively). This leads to consider that the syntectonic sedimentation in this area is not continuous but results from accumulation of thick homogenites deposited after the earthquakes (as observed in the following weeks after Haiti January 2010 event, McHugh et al., 2011). The existence of such deposits suggests that, in the area of study, vertical throw likely results from cumulated effects of separated earthquakes rather than from aseismic creep. Examination of VHR profiles shows that all major co-seismic offsets are recorded in the fault growth sequence and that co-seismic offsets can be precisely estimated. By using a sedimentation rate deduced from 210Pb decrease curve (0.5 mm yr−1) and taking into account minor reworking events detected in cores, we show that the Redonda system may have been responsible for five >M6 events during the last 34 000 yr. The approach presented in this work differs from fault activity analyses using displaced sets of isochronous surfaces and postulating co-seismic offsets. Combining VHR seismic imagery and coring we can decipher co-seismic vs. slow continuous displacement, and thus actually estimate the amplitude and the time distribution of major co-seismic offsets.
ISSN: 1561-8633

insu-00844581
https://hal-insu.archives-ouvertes.fr/insu-00844581
https://hal-insu.archives-ouvertes.fr/insu-00844581/document
https://hal-insu.archives-ouvertes.fr/insu-00844581/file/nhess-12-1755-2012.pdf
DOI : 10.5194/nhess-12-1755-2012

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
The interpretation of coseismic surface deformation measurements through inversion techniques is of major importance to understand the mechanical behaviour of a seismic fault. Dense geodetic data sets in the vicinity of the ruptured fault provide unique constraints on detailed fault geometry and slip distribution at depth, making them complementary to seismological data. Bam earthquake (Mw 6.6, 2003 December 26) induced surface deformation has been precisely mapped by Envisat ASAR interferometry and by subpixel correlation techniques applied to Spot-5 and ASAR amplitude images. These oblique and horizontal estimations of deformation have been completed with one levelling profile along the main road crossing the rupture from west to east. We process these data (separately and jointly) in a two-step inversion technique, within the elastic half-space theory framework. Our objective is to determine the dislocation model at depth that satisfies simultaneously all the geodetic constraints. Also, we estimate the relative contribution of each geodetic data set to this inversion process.We first use a stochastic direct approach called neighbourhood algorithm in order to estimate the average characteristics of the rupture, and their relative uncertainty. Constraining in this way the geometry of the ruptured fault, we then linearize the inverse problem and compute the slip distribution on the fault using a standard weighted least-square technique, assuming the solution is smooth to some degree. At each step, we discuss the optimal models, their stability as well as the relative influence of each data set on the derived models parameters. Our preferred model reveals a shallow dislocation on a quasi-vertical fault, slightly dipping towards east. The slip vector has a strike-slip component as high as 2 m, while the dip-slip component seems negligible.However, the estimation of the resolution matrices emphasizes the fact that the details of deep fault slip distribution remain out of the scope of this ill-conditioned inverse problem. Yet, our preferred model suggests a main dislocation limited at depth between 1 and 6 km. By contrast, the aftershocks observed in the months following the earthquake are located just beneath the estimated main shock.
ISSN: 0956-540X

hal-00314173
https://hal.archives-ouvertes.fr/hal-00314173
https://hal.archives-ouvertes.fr/hal-00314173/document
https://hal.archives-ouvertes.fr/hal-00314173/file/GJI-2007-169-849-briole.pdf
DOI : 10.1111/j.1365-246X.2007.03358.x

Éditeur(s) : XXXIII International Symposium on New Species for Mediterranean Aquaculture, Alghero, 22-24 Avril 1998
Résumé : Mediterranean aquaculture development is now at a crossroads. The production of seabass and seabream has been increasing at a smart and constant pace for the last ten years. Nevertheless, it is still far behind the Northern European salmonid industry in terms of level of production, reduction of production costs and market internationalisation. Meanwhile, an in depth transformation of market conditions is ongoing in Europe which remains the main target market for Mediterranean aquaculture products. The most important issues are the soaring role of supermarkets in the distribution chain, the development of new processing techniques like pre-packed fresh fish, the growing importance of catering and the evolution of the consumer behaviour. Seafood consumer behaviour results from contradictory attitudes such as scrutiny of products' origin and farming process, research of the best value for money, desire of social image and need for easy to store and ready to cook fish. As in any other seafood industry, product differentiation has become a pre-requisite to fit consumer's demand and reach new consumers thanks to market segmentation. From a theoretical point of view, two kinds of differentiation have to be taken into account: horizontal differentiation basedon the diversity of presentations of the same quality and vertical differentiation based on a hierarchy of quality. Examining precedents in the poultry industry and salmonid industry make it possible to assess the potential role new species may play in product differentiation. In the case of Mediterranean aquaculture, an analysis of the market structure for fresh fish in France, Italy and Greece reveals two different ways of product differentiation: new well known species with a good image for connoisseur markets and standard quality fish provided by species with high growth potential for the mass market. In any case, particular attention has to be given to reputation, long term production costs and capacity to provide a large range of products. [NOT CONTROLLED OCR]

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1998/acte-4008.pdf
http://archimer.ifremer.fr/doc/00000/4008/

Éditeur(s) : HAL CCSD Botanical Society of America
Résumé : Premise of the study : Wood density correlates with mechanical and physiological strategies of trees and is important for estimating global carbon stocks. Nonetheless, the relationship between branch and trunk xylem density has been poorly explored in neotropical trees. Here, we examine this relationship in trees from French Guiana and its variation among different families and sites, to improve the understanding of wood density in neotropical forests. Methods : Trunk and branch xylem densities were measured for 1909 trees in seven sites across French Guiana. A major-axis fit was performed to explore their general allometric relationship and its variation among different families and sites. Key results : Trunk xylem and branch xylem densities were significantly positively correlated, and their relationship explained 47% of the total variance. Trunk xylem was on average 9% denser than branch xylem. Family-level differences and interactions between family and site accounted for more than 40% of the total variance, whereas differences among sites explained little variation. Conclusions : Variation in xylem density within individual trees can be substantial, and the relationship between branch xylem and trunk xylem densities varies considerably among families and sites. As such, whole-tree biomass estimates based on non-destructive branch sampling should correct for both taxonomic and environmental factors. Furthermore, detailed estimates of the vertical distribution of wood density within individual trees are needed to determine the extent to which relying solely upon measures of trunk wood density may cause carbon stocks in tropical forests to be overestimated.
ISSN: 0002-9122

hal-01032401
https://hal.archives-ouvertes.fr/hal-01032401
DOI : 10.3732/ajb.1000034

Éditeur(s) : HAL CCSD
Résumé : Among erosion processes, river incision is classicaly described as a key process controlling erosion of landscapes. Incision efficiency is mainly influenced by climate and erodibility. This latter is not only dependent on the nature of the bedrock, but also on its past deformation, which affects its rheological effective properties, such as fracture density. The main objectives of this thesis are: (1) to better constrain the relationship between effective properties and erodibility, and (2) to quantify the influence of erodibility and erosion on both the temporal and spatial building or decay of the topography. Several numerical tools are developed. A 1D formalism of landscape evolution is introduced, including river incision with stochastic distribution of water discharge and hillslope landsliding. A new remeshing algorithm called Surface Lagrangian Remeshing (SLR) is developed as a complement to remeshing algorithms dealing with internal elements. It allows one to take into account long-term erosion into 2D Lagrangian numerical codes based on triangular finite elements. Then the potentiality of measuring erodibility in-situ using a Schmidt hammer (R) is assessed for the active orogen of Taiwan, the diagenetic Annot sandstones and St Clement fault zone. Results suggest a strong control of R by effective properties. A linear model based on effective medium theory is applied to a fault zone with an unmacthed resolution (750 measures, 25 measures per square meter). The model successfully correlates R to fracture density. These results demonstrate that effective elasticity as well as erodibility are sensitive to the density and type of fractures. Finally I focus on the erosional and rheological conditions that allows reproducing post-orogenic evolution of mountain belts. A model coupling surface erosion and regional isostatic uplift is consistent with observations. The topographic decay and decrease of the ratio of surface elevation over crustal root thickness is at first order controlled by the initial geometry of the mountain belt and erosion efficiency. This new model highlights the control ofclimate and erodibility on the topographic decay and of lithospheric rheology on the perseverance of crustal roots.
Parmi les processus d'érosion, l'incision des rivières est classiquement décrit comme un processus clé contrôlant l'érosion des paysages. L'efficacité de l'incision est principalement influencée par le climat et par l'érodabilité. Ce dernier paramètre ne dépend pas seulement de la nature du substratum rocheux, mais aussi de sa déformation passée qui affecte ses propriétés rhéologiques équivalentes. Les principaux objectifs de cette thèse sont: (1) de mieux contraindre les relations entre propriétés équivalentes et érodabilité, et (2) de quantifier l'influence de l'érosion et de l'érodabilité sur la formation ou la décadence, spatiale et temporelle, de la topographie. Plusieurs outils numériques sont développés. Un formalisme 1D d'évolution des paysages est proposé, prenant en compte simultanément l'incision des rivières avec une distribution stochastique des débits en eau et l'érosion des versants par glissements de terrain. Un nouvel algorithme de remaillage appelé Surface Lagrangian Remeshing (SLR) est développé. Il permet de prendre en compte l'érosion à long terme dans les codes numériques 2D Lagrangiens basés sur des éléments finis triangulaires. Ensuite, la possibilité de mesurer in-situ l'érodabilité avec un marteau de Schmidt (R) est évaluée pour: l'orogène actif de Taiwan, les grès diagénétiques d'Annot et la zone de faille de St Clément. Les résultats suggèrent un fort contrôle de R par les propriétés équivalentes des roches testées. Un modèle linéaire, basé sur la théorie des milieux équivalents, est appliqué à une zone de faille avec une résolution inégalée (750 mesures, 25 mesures par mètre carré). Le modèle permet de corréler avec succès la densité de fracture et R. Ces résultats démontrent empiriquement que l'élasticité équivalente ainsi que l'érodabilité sont sensibles à la densité et à la nature des fractures. Enfin j'étudie les conditions d'érosion et de rhéologie qui permettent de reproduire l'évolution des chaînes de montagnes post-orogéniques. Un modèle couplant érosion en surface et soulèvement isostatique régional est compatible avec les observations. Les taux de décroissance topographique et de diminution du rapport de l'élévation de surface sur l'épaisseur de racine crustale sont contrôlés au premier ordre par la géométrie initiale de la chaîne de montagne et par l'efficacité de l'érosion. Ce nouveau modèle met en évidence le contrôle du climat et de l'érodabilité sur la décroissance topographique et de la rhéologie lithosphérique sur la persévérance des racines crustales.
https://tel.archives-ouvertes.fr/tel-00602341

tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341/document
https://tel.archives-ouvertes.fr/tel-00602341/file/thesephilippesteer.pdf

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
In Taiwan, about one third of the lithospheric plate convergence between Eurasia and the Philippine Sea plate is accommodated on the eastern coast across the narrow Longitudinal Valley (LV). The Longitudinal Valley Fault (LVF) is the main seismically active fault zone in this region. However, the spatial distribution of ground deformation due to interseismic loading on locked fault segments remains widely unknown. To address this problem, we use a "permanent scatterer" (PS) interferometric synthetic aperture radar (InSAR) approach for processing the ERS satellite archives. The PS mean velocity maps allow accurately mapping and quantifying the ground deformation all along the LV. Assuming that, close to the surface, the fault plane along the central LVF creeping segment dips 55 degrees to the east, we derive a slip vector at the surface of similar to 25 mm/yr with a mean rake of 70 degrees. In agreement with our PS observations, shallow seismicity indicates a clear change in the fault mechanical behavior of the creeping segment around Fuli town. Finally, we propose a combination of the PS velocity fields for estimating a 3-D map of ground deformation. In the southern part of the LV, the vertical component reveals an uplift of the Coastal Range with respect to the LV of similar to 10 mm/yr. Moreover, between Taitung and Luyeh, the vertical deformation is essentially accommodated along the Luyeh Strand. Finally, north of Rueisuei, the Coastal Range uniformly subsides at similar to 15 mm/yr relative to the western side of the LV. However, a local uplift pattern is detected around latitude 23 degrees 42'.
ISSN: 0148-0227

hal-00595532
https://hal.archives-ouvertes.fr/hal-00595532
DOI : 10.1029/2010JB007898

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : A preliminary version appeared in the 18th ACM-SIAM Symposium on Discrete Algorithms, pp. 746- 755, 2007
International audience
The Voronoi diagram of a finite set of objects is a fundamental geometric structure that subdivides the embedding space into regions, each region consisting of the points that are closer to a given object than to the others. We may define various variants of Voronoi diagrams depending on the class of objects, the distance function and the embedding space. In this paper, we investigate a framework for defining and building Voronoi diagrams for a broad class of distance functions called Bregman divergences. Bregman divergences include not only the traditional (squared) Euclidean distance but also various divergence measures based on entropic functions. Accordingly, Bregman Voronoi diagrams allow one to define information-theoretic Voronoi diagrams in sta- tistical parametric spaces based on the relative entropy of distributions. We define several types of Bregman diagrams, establish correspondences between those diagrams (using the Legendre transformation), and show how to compute them efficiently. We also introduce extensions of these diagrams, e.g. k-order and k-bag Bregman Voronoi diagrams, and introduce Bregman triangulations of a set of points and their connection with Bregman Voronoi diagrams. We show that these triangulations capture many of the properties of the celebrated Delaunay triangulation.
ISSN: 0179-5376

hal-00488441
https://hal.archives-ouvertes.fr/hal-00488441
https://hal.archives-ouvertes.fr/hal-00488441/document
https://hal.archives-ouvertes.fr/hal-00488441/file/BVD-DCG.pdf

Éditeur(s) : Amer Geophysical Union
Résumé : An analysis is presented for the spatial and intensity distributions of North Atlantic extreme atmospheric events crossing the buoyant Amazon-Orinoco freshwater plume. The sea surface cooling amplitude in the wake of an ensemble of storm tracks traveling in that region is estimated from satellite products for the period 1998-2012. For the most intense storms, cooling is systematically reduced by approximate to 50% over the plume area compared to surroundings open-ocean waters. Historical salinity and temperature observations from in situ profiles indicate that salt-driven vertical stratification, enhanced oceanic heat content, and barrier-layer presence within the plume waters are likely key oceanic factors to explain these results. Satellite SMOS surface salinity data combined with in situ observations are further used to detail the oceanic response to category 4 hurricane Igor in 2010. Argo and satellite measurements confirm the haline stratification impact on the cooling inhibition as the hurricane crossed the river plume. Over this region, the SSS mapping capability is further tested and demonstrated to monitor the horizontal distribution of the vertical stratification parameter. SMOS SSS data can thus be used to consistently anticipate the cooling inhibition in the wake of TCs traveling over the Amazon-Orinoco plume region.
Journal Of Geophysical Research-oceans (0148-0027) (Amer Geophysical Union), 2014-12 , Vol. 119 , N. 12 , P. 8271-8295

Droits : 2014. American Geophysical Union. All Rights Reserved.
http://archimer.ifremer.fr/doc/00252/36326/34855.pdf
http://archimer.ifremer.fr/doc/00252/36326/34856.pdf
DOI:10.1002/2014JC010107
http://archimer.ifremer.fr/doc/00252/36326/

Éditeur(s) : ISTPM
Résumé : The Thalassa, a ship of the Institute of Fishing, carried out two trawling campaigns off the coasts of Rio de Oro, Mauritania and Senegal. The first one took place in November and December 1962; it extended from Cape Juby to Tamxat (17°20'N). The second, directed more towards the south, reached the Fosse de Cayar Submarine Canyon, near Cape Verde; it occurred in March and April 1968. These operations represent in total 100 trawl passes between latitudes 15° and 28°N and depths of 10 to 800 metres. These two campaigns' overall data are introduced incidentally. The data recorded here are exclusively about the twenty species of sparidae harvested. They concern the geographic and bathymetric distribution, frequency and numbers, size and sex. There emerge certain comments on the animal life, biology and fishing. In some cases, it seemed worthwhile to emphasise the morphological differences that make it possible to distinguish among them species at times very closely related.
La « Thalassa », navire de l'Institut des Pêches, a effectué deux campagnes de chalutage au large des côtes du Rio de Oro, de la Mauritanie et du Sénégal. La première a eu lieu en novembre et décembre 1962; elle s'est étendue du cap Juby à Tamxat (17°20'N). La seconde, plus orientée vers le sud, a atteint la fosse de Cayar, à proximité du cap Vert; elle s'est déroulée en mars et avril 1968. Ces opérations représentent au total cent traicts de chalut qui se répartissent entre les latitudes 15° et 28°N et les profondeurs de 10 à 800 m. Les données d'ensemble de ces deux campagnes sont présentées par ailleurs. Celles consignées ici concernent exclusivement les vingt espèces de sparidés récoltées. Elles ont trait à la répartition géographique et bathymétrique, la fréquence et l'abondance, la taille et le sexe. Il s'en dégage certaines remarques sur la faunistique, la biologie et la pêche. Dans certains cas il a paru intéressant de souligner les différences morphologiques qui permettent de distinguer, entre elles, des espèces parfois très voisines.(OCR non controlé)
Revue des Travaux de l'Institut des Pêches Maritimes (0035-2276) (ISTPM), 1969-03 , Vol. 33 , N. 1 , P. 97-116

Droits : Ifremer
http://archimer.ifremer.fr/doc/1969/publication-3156.pdf
http://archimer.ifremer.fr/doc/00000/3156/

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : New-Caledonia island consists of an ultramafic nappe thrusted over a continental and arc-derived basement as the result of the closure of a back-arc basin during the upper Eocene. The morphology of New-Caledonia is mostly characterized by its elongated shape and rectilinear coastline. Indeed, the western and eastern edges of the island are delineated by N140 trending normal faults that are well imaged on seismic lines. Major tectonic lineaments onland, including the scarps corresponding to the main boundary of the ultramafic nappe, also trend N140 suggesting a morphotectonic control by faults having similar kinematics (longitudinal flexure-fault of previous authors). We provide detailed observations from some of these scarps demonstrating indeed that these are not erosional features in origin. We explore the possibility that such surfaces do represent major tectonic limits that accommodated extension and significant tectonic thinning of both the peridotite nappe and its basement. Remnants of a complex extensional fault zone, 200 m wide, are still preserved along the western scarp of the Mont Dore mountain, close to Noumea city. The deformed zone is composed of an early shallow dipping detachment fault, some decimeters thick, offset by a group of late high angle normal faults and is bounded by cataclastic breccias that progressively pass into the fractured host peridotite. The late high angle fault zones have been the site of important syn-tectonic fluid circulation and are underlined by cm-thick silica infills bearing vertical striae. Typical morphology of the main scarps with break of slope is related to the combination of high angle normal faults and low angle detachment. Similar shallow dipping detachment surfaces have been observed along the east coast of southern New-Caledonia as well as within the ultramafic nappe itself and its basement. This study confirms that N140 oriented, large fault zones, with pure-normal to transtensional component of displacement, controlled the morphotectonic evolution of New-Caledonia at the regional scale, after the obduction of ophiolite nappe at the end of the Eocene. Such a fact has to be taken into account when attempting to reconstruct the post-obduction evolution of the island and more particularly when considering the development and distribution of the Ni-rich lateritic surfaces.
EISSN: 1777-5817

hal-00411855
https://hal.archives-ouvertes.fr/hal-00411855
DOI : 10.2113/gssgfbull.179.3.315

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : We report the northernmost and deepest known occurrence of deep-water pycnodontine oysters based on two surveys along the French Atlantic continental margin to the La Chapelle continental slope (2006) and the Guilvinec Canyon (2008) The combined use of multibeam bathymetry seismic profiling CTD casts and a remotely operated vehicle (ROV) made it possible to describe the physical habitat and to assess the oceanographic control for the recently described species Neopycnodonte zibrowii These oysters have been observed in vivo in depths from 540 to 846 m colonizing overhanging banks or escarpments protruding from steep canyon flanks Especially in the Bay of Biscay such physical habitats may only be observed within canyons where they are created by both long-term turbiditic and contouritic processes Frequent observations of sand ripples on the seabed indicate the presence of a steady but enhanced bottom current of about 40 cm/s The occurrence of oysters also coincides with the Interface between the Eastern North Atlantic Water and the Mediterranean Outflow Water A combination of this water mass mixing internal tide generation and a strong primary surface productivity may generate an enhanced nutrient flux which is funnelled through the canyon When the ideal environmental conditions are met up to 100 individuals per m(2) may be observed These deep-water oysters require a vertical habitat which is often incompatible with the requirements of other sessile organisms and are only sparsely distributed along the continental margins The discovery of these giant oyster banks illustrates the rich biodiversity of deep-sea canyons and their underestimation as true ecosystem hotspots (C) 2010 Elsevier Ltd All rights reserved
Deep-sea Research Part I-oceanographic Research Papers (0967-0637) (Pergamon-elsevier Science Ltd), 2010-12 , Vol. 57 , N. 12 , P. 1561-1572

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00023/13419/14034.pdf
DOI:10.1016/j.dsr.2010.09.002
http://archimer.ifremer.fr/doc/00023/13419/

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 Oxford University Press
Résumé : International audience
The BioMart Community Portal (www.biomart.org) is a community-driven effort to provide a unified interface to biomedical databases that are distributed worldwide. The portal provides access to numerous database projects supported by 30 scientific organizations. It includes over 800 different biological datasets spanning genomics, proteomics, model organisms, cancer data, ontology information and more. All resources available through the portal are independently administered and funded by their host organizations. The BioMart data federation technology provides a unified interface to all the available data. The latest version of the portal comes with many new databases that have been created by our ever-growing community. It also comes with better support and extensibility for data analysis and visualization tools. A new addition to our toolbox, the enrichment analysis tool is now accessible through graphical and web service interface. The BioMart community portal averages over one million requests per day. Building on this level of service and the wealth of information that has become available, the BioMart Community Portal has introduced a new, more scalable and cheaper alternative to the large data stores maintained by specialized organizations.
ISSN: 0305-1048

hal-01146849
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01146849
DOI : 10.1093/nar/gkv350
PUBMED : 25897122

Éditeur(s) : HAL CCSD Linnean Society of London
Résumé : International audience
The circumscription of Salicaceae has recently been enlarged to include a majority of the species formerly placed in the polyphyletic tropical family Flacourtiaceae. Several studies have reported a peculiar and infrequently formed multilayered structure of tension wood in four of the tropical genera. Tension wood is a tissue produced by trees to restore their vertical orientation, and most studies have focused on trees developing tension wood by means of cellulose-rich, gelatinous fibres, as is known in Populus L. and Salix L. (Salicaceae s.s.). This study aims to determine if the multilayered structure of tension wood is an anatomical characteristic common in other Salicaceae, and if so, how its distribution correlates to phylogenetic relationships. Therefore, we studied the tension wood of 14 genera of Salicaceae as well as two genera of Achariaceae, one genus of Goupiaceae, and one genus of Lacistemataceae, families closely related to Salicaceae or formerly placed in Flacourtiaceae. Opposite wood and tension wood were compared with light microscopy and 3D Laser Scanning Confocal Microscopy. The results indicate that a multilayered structure of tension wood is common in the family except in Salix, Populus, and one of their closest relatives, Idesia polycarpa Maxim. We suggest that tension wood may be a useful anatomical character in understanding phylogenetic relationships in Salicaceae. Further investigation is still needed on the tension wood of several other putatively close relatives of Salix and Populus, in particular Bennettiodendron Merr., Macrohasseltia L.O.Williams and Itoa Hemsl.
ISSN: 0024-4074

hal-01392845
https://hal.archives-ouvertes.fr/hal-01392845
https://hal.archives-ouvertes.fr/hal-01392845/document
https://hal.archives-ouvertes.fr/hal-01392845/file/GhislainEtAl2016_MultylayerTWSalicaceae_Bot_Jsur the_Lin_Soc_HALssfig.pdf
DOI : 10.1111/boj.12471

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
An exploration 3D seismic data set from the Gjallar Ridge off mid-Norway images a giant fluid seep structure 3 × 5 km wide, which connects to late Palaeocene magmatic sills at depth. Two of the pipes that have developed as hydrothermal vents reach all the way to the modern seafloor implying that they either were active much longer than the original hydrothermal activity or have been reactivated. We combine detailed seismic analysis of the northern pipe and sandbox modeling to constrain pipe initiation and propagation. Although both the seismic data and the sandbox models suggest that fluids at depth are focused through a vertical conduit, sandbox models show that fluids ascend and reach a critical depth migration where focused migration abruptly transforms into distributed fluid flow through unconsolidated sediments. This indicates that at this level the sediments are intensely deformed during pipe propagation, creating a V-shaped structure, i.e. an inverted cone at depth and a positive relief anomaly, 5 to 10 m high, at the seafloor, which is clearly identified on 3D seismic data. Comparison of the geometries observed in sandbox modeling with the seismically observed geometries of the Giant Gjallar Vent suggests that the Giant Gjallar Vent may be a proto-fluid seep at an early stage of its development, preceding the future collapse of the structure forming a seafloor depression. Our results imply that the Gjallar Giant Vent can be used as a window into the geological processes active in the deep parts of the Vøring Basin.
ISSN: 0025-3227

hal-00772465
https://hal.archives-ouvertes.fr/hal-00772465
DOI : 10.1016/j.margeo.2012.08.010

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : A study combining very high resolution seismic and sediment core data has been carried out on the Thau lagoon (Mediterranean coast, microtidal setting, SE France) in order to understand more clearly the dynamics and Holocene chronology of its closure through the different stages of its filling. One main seismic unit (U2) has been defined into the infill, above the rocky basement (U0) and a composite unit U1, which is interpreted as remnants of Pleistocene fluvial terraces or/and to early marine Holocene deposits. Unit U2, that reaches locally 9 m in thickness, rests conformably on U1 in the central part of the lagoon and onlaps U0 or U1 close to the edge of the lagoon. It is divided in two sub-units, U2-1 and U2-2. U2-2 rests paraconformably on U2-1 in the central part of the lagoon where the infill is the thickest, while a marked erosional unconformity is observed between U2-1 and U2-2 on topographic highs of the basement and on the seaward edge of the lagoon. A total of seven elementary sequences have been observed in U2-1 and U2-2.;According to core data, U2 consists in a series of mud-dominated sequences, with shell fragments dispersed at the base. The vertical distribution of the fauna into U2-1 and U2-2 reveals a lagoonal environment. However in U2-1, marine species are more abundant in the south of the lagoon. C-14 AMS dating provides three ages: similar to 6000 cal yr B.P. in the lower part of U2-1 on CAL1, 5400 cal yr B.P. just above the boundary between U2-1 and U2-2 on CAL4, similar to 3000 cal yr B.P. in the middle of U2-2 on CAL4.;A scenario to explain the lagoon infill stratigraphy and geometry is proposed. The beginning of the lagoon infill occurred with the initiation of the barrier construction, as soon as the sea-level rise slowed down significantly, i.e. between 7000-6000 yr B.P. The sediment-fill began into the back-barrier system, with a high rate of sedimentation for U2-1, according to the radiocarbon data. At 5400 yr B.P., the barrier is assumed to be totally closed leading to the deposition of the fully lagoonal U2-2 succession. The unconformity between U2-1 and U2-2 is interpreted as the result of a rapid landward retreat of the barrier. This severe retreat could be related to climate forcing and/or brutal change in sediment discharge driven by the Rhone River, which is the main sediment source of the longshore drift. In this scenario, the last sub-unit, U2-2, represents most of the late Holocene infill. In this framework, the elementary sequences observed in U2-2 could be related to high frequency climate changes of about 1000-1500 years periodicity according to C-14 dates.
EISSN: 1777-5817

hal-00486386
https://hal.archives-ouvertes.fr/hal-00486386
DOI : 10.2113/gssgfbull.181.2.197

Éditeur(s) : HAL CCSD Copernicus Publications on behalf of the European Geosciences Union
Résumé : International audience
During the GWADASEIS cruise (Lesser Antilles volcanic arc, February–March 2009) a very high resolution (VHR) seismic-reflection survey was performed in order to constrain Late Quaternary to Present faulting. The profiles we obtained evidence frequent " ponding " of reworked sediments in the deepest areas, similar to the deposition of Mediterranean " homogenites ". These bodies are acoustically transparent (few ms t.w.t. thick) and are often deposited on the hanging walls of dominantly normal faults, at the base of scarps. Their thickness appears sufficient to compensate (i.e. bury) co-seismic scarps between successive earthquakes, resulting in a flat and horizontal sea floor through time. In a selected area (offshore Montserrat and Nevis islands), piston coring (4 to 7 m long) was dedicated to a sedimento-logical analysis of the most recent of these particular layers. It corresponds to non-stratified homogenous calcareous silty sand (reworked calcareous plankton and minor volcanoclas-tics). This layer can be up to 2 m thick, and overlies fine-grained hemipelagites. The upper centimeters of the latter represent the normal RedOx water/sediment interface. 210 Pb and 137 Cs activities lack in the massive sands, while a normal profile of unsupported 210 Pb decrease is observed in the hemipelagite below, together with a 137 Cs peak corresponding to the Atmospheric Nuclear Experiments (1962). The RedOx level was thus capped by a recent instantaneous major sedimentary event considered as post-1970 AD; candidate seismic events to explain this sedimentary deposits are either the 16 March 1985 earthquake or the 8 October 1974 one (M w = 6.3 and M w = 7.4, respectively). This leads to consider that the syntectonic sedimentation in this area is not continuous but results from accumulation of thick homogen-ites deposited after the earthquakes (as observed in the following weeks after Haiti January 2010 event, McHugh et al., 2011). The existence of such deposits suggests that, in the area of study, vertical throw likely results from cu-mulated effects of separated earthquakes rather than from aseismic creep. Examination of VHR profiles shows that all major co-seismic offsets are recorded in the fault growth sequence and that co-seismic offsets can be precisely estimated. By using a sedimentation rate deduced from 210 Pb decrease curve (0.5 mm yr −1) and taking into account minor reworking events detected in cores, we show that the Redonda system may have been responsible for five > M 6 events during the last 34 000 yr. The approach presented in this work differs from fault activity analyses using displaced sets of isochronous surfaces and postulating co-seismic offsets. Combining VHR seismic imagery and coring we can decipher co-seismic vs. slow continuous displacement, and thus actually estimate the amplitude and the time distribution of major co-seismic offsets.
Natural Hazards and Earth System Science

insu-01585969
https://hal-insu.archives-ouvertes.fr/insu-01585969
https://hal-insu.archives-ouvertes.fr/insu-01585969/document
https://hal-insu.archives-ouvertes.fr/insu-01585969/file/nhess-12-1755-2012-beck.pdf
DOI : 10.5194/nhess-12-1755-2012

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
We analyze the kinematics of fault tip folding at the front of a fold-and-thrust wedge using a sandbox experiment. The analog model consists of sand layers intercalated with low-friction glass bead layers, deposited in a glass-sided experimental device and with a total thickness h = 4.8 cm. A computerized mobile backstop induces progressive horizontal shortening of the sand layers and therefore thrust fault propagation. Active deformation at the tip of the forward propagating basal décollement is monitored along the cross section with a high-resolution CCD camera, and the displacement field between pairs of images is measured from the optical flow technique. In the early stage, when cumulative shortening is less than about h/10, slip along the décollement tapers gradually to zero and the displacement gradient is absorbed by distributed deformation of the overlying medium. In this stage of detachment tip folding, horizontal displacements decrease linearly with distance toward the foreland. Vertical displacements reflect a nearly symmetrical mode of folding, with displacements varying linearly between relatively well defined axial surfaces. When the cumulative slip on the décollement exceeds about h/10, deformation tends to localize on a few discrete shear bands at the front of the system, until shortening exceeds h/8 and deformation gets fully localized on a single emergent frontal ramp. The fault geometry subsequently evolves to a sigmoid shape and the hanging wall deforms by simple shear as it overthrusts the flat ramp system. As long as strain localization is not fully established, the sand layers experience a combination of thickening and horizontal shortening, which induces gradual limb rotation. The observed kinematics can be reduced to simple analytical expressions that can be used to restore fault tip folds, relate finite deformation to incremental folding, and derive shortening rates from deformed geomorphic markers or growth strata.
ISSN: 2169-9313

hal-00138061
https://hal.archives-ouvertes.fr/hal-00138061
https://hal.archives-ouvertes.fr/hal-00138061/document
https://hal.archives-ouvertes.fr/hal-00138061/file/Bernard_et_al-2007-Journalsur Geophysical_Research__Solid_Earth_%281978-2012%29.pdf
DOI : 10.1029/2005JB004149

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : The volcanic island of Mayotte (374 km super(2)) is part of the Comoros Archipelago, which is situated on the North of Mozambic's Canal (Indian Ocean). Mayotte is composed of two islands and some thirty small islands distributed in a lagoon of more than 1,000 km super(2). Being one of the French Republic's Territorial Collectivity, this island is characterized by a very fast demographic evolution (growth rate : 5.8 %), which constitutes the foundation of the development problematic. Most of local halieutic production comes from the reef (nearly 2,000 t in 1999), the technic of "palangrotte" (deep line) is still dominating. The fishing fleet is composed of monoxyl pirogues and polyester fishing boats for the 1,200 fishermen. The first FADs (Fish Aggregating Devices) were installed in 1989. Now, 5 FADs are situated in the lagoon whereas 10 others have been installed out of it. If it is very hard to evaluate economic impact of FAD in Mayotte, their success seems to be limited because of several local constraints : fear to fish out of the lagoon, little interest in tuna, lack of formation. Nevertheless, faced to the demographic evolution and the decrease of the reef ressources, a program of fishing development on FAD has been initiated in 1998, with those following themes : realization of a new prototype of FAD, experimental fishing program with vertical drift "long line", teaching programs for the local fishermen. Today, it is too early to analyze the informations already collected, but the results are very promising, and validate the technical improvement of the new prototype.Original Abstract: L'ile volcanique de Mayotte (374 km super(2)) fait partie de l'archipel des Comores situe au Nord du canal du Mozambique (ocean Indien). Mayotte comprend deux iles et une trentaine d'ilots repartis dans un lagon de plus de 1 000 km super(2). Collectivite territoriale de la Republique francaise, l'ile se caracterise par une evolution demographique tres rapide (taux de croissance: 5,8 %), qui constitue le socle de toutes les problematiques de developpement. L'essentiel de la production halieutique provient du milieu recifal (environ 2 000 t en 1999), la peche a la ligne de fond reste la technique dominante. La flottille de peche est constituee de pirogues monoxyles et de barques polyester pour une population de 1 200 pecheurs. Les premiers DCP mahorais furent installes en 1989. A ce jour, on denombre cinq DCP dans le lagon et dix hors lagon. Il semble que leur succes soit reste limite en raison de plusieurs contraintes locales : peur de la peche hors lagon, peu d'interet pour les poissons pelagiques, manque de formation. Neanmoins, face a l'explosion demographique et a l'appauvrissement des ressources lagonaires, un nouveau programme de developpement de la peche sur DCP a ete initie en 1998. Ce programme comporte trois axes : realisation d'un nouveau prototype de DCP, lancement d'un programme de peches experimentales a la palangre verticale derivante et formation des pecheurs. A ce jour, les informations obtenues sont trop parcellaires pour etre analysees mais les donnees et observations realisees sur les nouveaux dispositifs permettent de valider leur conception technique.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15290/12647.pdf
http://archimer.ifremer.fr/doc/00042/15290/