Éditeur(s) : HAL CCSD Springer-Verlag
Résumé : The Chile-Argentina Patagonian Cordillera is a natural laboratory to study the interactions between oceanic and continental lithosphere during the subduction of an active spreading ridge beneath a continent. Subduction of the South Chile spreading ridge, which separates the Nazca plate from the Antarctic plate, started around 15–14 Ma at the southern tip of Patagonia. Presently, the southernmost segment of the Chile Ridge enters the Peru-Chile trench at 46°S, at the site of the Chile Triple Junction (CTJ). We review the main events which occurred on land in the CTJ region (46–47°S), related with processes of ridge subduction. We summarize tectonic, sedimentary, and magmatic features in a 30 Ma-to Present chronological table. A preridge subduction stage, from 30 to 15 Ma, is characterized by the onset and growth of Patagonian relief and by a shift from marine to continental detrital sedimentation in the foreland at 20–22 Ma. The change from pre-ridge subduction to ridge subduction is marked on land by a transition from calc-alkaline to alkaline volcanism, at 14–12 Ma, and by the onset of eruption of very large fl ood basalt provinces (future volcanic plateaus) following rapid erosion of the eastern foreland belt. Post-plateau basaltic volcanism (<4 Ma) is coeval with a period of tectonic and morphological rejuvenation during which the eastern foreland of the Cordillera has been affected by extensional/transtensional tectonics. We place these events in the framework of a tectonomagmatic model involving the opening of slab windows due to both slab tear and ridge axis subduction.
Subduction Zone Geodynamics

hal-00421053
https://hal.archives-ouvertes.fr/hal-00421053
DOI : 10.1007/978-3-540-87974-9_12

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Northwest Iran is characterized by a high level of historical and instrumental seismicity related to the ongoing convergence between the Arabian and Eurasian plates. In this region, the main right-lateral strike-slip fault known as the North Tabriz fault (NTF) forms the central portion of a large crustal fault system called the Tabriz fault system (TFS). The NTF is a major seismic source along which at least three strong and destructive earthquakes have occurred since 858 AD. The two most recent destructive seismic events occurred in 1721 AD and 1780 AD, rupturing the SE and NW fault segments, respectively. This paper reports paleoseismological and quantitative geomorphologic investigations on the SE segment of the NTF, between the cities of Bostanabad and Tabriz. These observations help to improve our understanding of the seismic hazard for Tabriz city and its surrounding areas. Our field investigations revealed evidence of successive faulting events since the Late Quaternary. Paleoseismic investigations indicate that since 33.5 kyr, the SE segment of the NTF has experienced at least three major (M>7.5) seismic events, including the 1721 AD earthquake (M=7.6–7.7). Along the NW segment of the fault, however, our results suggest that the amount of strong (M~7.5) seismic events during the same period is significantly greater than along the SE segment. One possible explanation of such a difference in seismic activity is that the Late Quaternary-Holocene coseismic slip rate is decreasing along the NTF from the northwest to the southeast. This explanation contradicts the former hypothesis of a constant slip rate along the whole length of the NTF. In addition, more distributed deformation along several parallel fault branches, in a wider fault zone of the SE segment of the NTF may be considered as additional evidence for the estimation of lower rate of deformation along the fault segment. Such a slip distribution pattern can explain the existence of smaller (~300 m) Pliocene-Quaternary cumulative dextral offsets along the SE fault segment than the measured cumulative offsets along the NW segment (~800 m) of the NTF.
ISSN: 0040-1951

hal-01089420
http://hal.upmc.fr/hal-01089420
http://hal.upmc.fr/hal-01089420/document
http://hal.upmc.fr/hal-01089420/file/Solaymani%20Azad%20et%20al.%2C%202014%20%28accepted%29.pdf
DOI : 10.1016/j.tecto.2014.11.010

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
The Calabro-Peloritan belt constitutes the eastward termination of the southern segment of the Alpine Mediterranean belt. This orogenic system was built up during the convergence between the Eurasian and the African plates, roughly directed North-South since the Upper Cretaceous. It was subsequently fragmented during the opening of the Western Mediterranean basins since Oligocene times. The curved shape of the Calabro-Peloritan belt was acquired during the opening of the Tyrrhenian basin since Tortonian. The origin, kinematics and significance of the Calabro-Peloritan tectonic pile are still debated. Our data in the Aspromonte Massif of Southern Calabria reveal an Alpine history marked by two main superimposed kinematic regimes. (i) A first phase corresponds to the piling up of basement nappes with a top-to-the-SE vergence, i.e in a direction orthogonal to the belt trend and towards the Adriatic foreland. This external vergence is similar to what is observed in both Northeastern Sicily and Northern Calabria. In Sicily, the age of nappe piling is Alpine, as evidenced by pinched slices of Mesozoïc sediments. In the Aspromonte Massif, thrusting age is less constrained. Our data suggest remnants of late Hercynian structuration before the Alpine stacking. (ii) A second phase corresponds to the thinning of the continental crust, dated at around 30 Ma by both geochronological and stratigraphical data. This extension is mainly localized on two low-angle detachment contacts, with top-to-the-NE displacement. The lower one corresponds to the reworking of the former main nappe contact. The upper one is a large detachment fault cutting across the pile from upper sedimentary levels down to metamorphic basement. Extension of similar Alpine age and similar internal vergence has been already recognized in other parts of the Calabro-Peloritan Arc: in the basement nappes of Northeastern Sicily and in the ophiolitic units of Northern Calabria. Coming back to the original geometry and position of the Calabro-Peloritan belt, before its bending and the opening of the Liguro-Provençal and Tyrrhenian basins, we evidence a homogeneous Oligocene NE-SW extension all along the Calabro-Peloritan segment of the Alpine Mediterranean belt. This tectonometamorphic history is best explained within the framework of the continuous Tertiary westward dipping subduction of the Tethyan oceanic domain below the European active margin and the progressive eastward retreat of the Apennine trench since Oligocene times.
ISSN: 0278-7407

hal-00283182
https://hal.archives-ouvertes.fr/hal-00283182
https://hal.archives-ouvertes.fr/hal-00283182/document
https://hal.archives-ouvertes.fr/hal-00283182/file/Heymes_et_al_2008.pdf
DOI : 10.1029/2007TC002157

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : Gravity data and P-wave teleseismic traveltime residuals from 29 temporary broad-band stations spread over the northern margin of the Gulf of Aden (Dhofar region, Oman) were used to image lithospheric structure. We apply a linear relationship between density and velocity to provide consistent density and velocity models from mid-crust down to about 250 km depth. The accuracy of the resulting models is investigated through a series of synthetic tests. The analysis of our resulting models shows: (1) crustal heterogeneities that match the main geological features at the surface; (2) the gravity edge effect and disparity in anomaly depth locations for layers at 20 and 50 km; (3) two low-velocity anomalies along the continuation of Socotra-Hadbeen and Alula-Fartak fracture zones between 60 and 200 km depth; and (4) evidence for partial melting (3-6 per cent) within these two negative anomalies. We discuss the presence of partial melting in terms of interaction between the Sheba ridge melts and its along-axis segmentation.
ISSN: 0956-540X

hal-00456048
https://hal.archives-ouvertes.fr/hal-00456048
DOI : 10.1111/j.1365-246X.2009.04438.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Evidence of anomalous volcanism is readily observed in the Gulf of Aden, although, much of this oceanic basin remains as yet unmapped. In this paper, we investigate the possible connection of the Afar hotspot with a major off-axis volcanic structure and its interpretation as a consequence of a the anomalous presence of melt by integrating several data sets, both published and unpublished, from the Encens-Sheba cruise, the Aden New Century (ANC) cruise and several other onshore and marine surveys. These include bathymetric, gravity, magnetic, magneto-telluric data, and rock samples. Based upon these observations, interpretations were made of seafloor morphology, gravity and magnetic models, seafloor age, geochemical analyses and tectonic setting. We discuss the possible existence of a regional melting anomaly in the Gulf of Aden area and of the probability of its connection to the Afar plume. Several models that might explain the anomalous volcanism are taken into account, such as a local melting anomaly unrelated to the Afar plume, an anomalously large volume of melt associated with seafloor spreading, and interaction of the ridge with the Afar plume. A local melting anomaly and atypical seafloor spreading prove inconsistent with our observations. Two previously proposed models of plume-ridge interactions are examined: the diffuse plume dispersion called pancaked flow and channelized along-axis flow. We conclude that the configuration and structure of this young ocean basin may have the effect of channeling material away from the Afar plume along the Aden and Sheba Ridges to produce the off-axis volcanism observed on the ridge flanks. This interpretation implies that the influence of the Afar hotspot may extend much farther eastwards into the Gulf of Aden than previously believed. The segmentation of the Gulf of Aden and the configuration of the Aden-Sheba system may provide a potential opportunity to study channeled flow of solid plume mantle from the plume along a segmented ridge and nearby continental margins.
ISSN: 0012-821X

hal-00486140
https://hal.archives-ouvertes.fr/hal-00486140
DOI : 10.1016/j.epsl.2010.02.036

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Paleostress orientations were calculated from fault populations at 24 sites along the SW-NE segment and five sites along the E-W. Yasin segment of the Karakoram-Kohistan Suture Zone in NW Pakistan They demonstrate the importance of combined thrusting and strike-slip faulting. However, several paleostress tensor directions are distinguished, a dominant NW-SE compression and a minor E-W compression are compatible with the recent evolution of this part of the Hindu Kush. From the lack of both systematic overprinting-relationships and spatial trend (the two tensors were obtained at different locations) we conclude that in each location any of these two shortening directions can dominate Heterogeneously distributed extension is found in some places and is likely due to local conditions These paleostress tensors substantiate a transpressional regime due to far-field Himalayan compression and document the long-term background of the seismogenic deformation in this region.
ISSN: 0743-9547

hal-00496459
https://hal.archives-ouvertes.fr/hal-00496459
DOI : 10.1016/j.jseaes.2010.01.004

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Zandjan province is situated in the NW of Iran, at the junction between the southern termination of the Tabriz right-lateral strike-slip fault and the western end of the Alborz active mountain range. Despite this key location, in terms of active tectonics, there is no destructive earthquake reported in available historical seismicity catalogues. Even if a few low magnitude instrumental earthquakes have been recorded indicating that this area is actively deforming, the Zandjan region can be considered as a seismic gap. Based on detailed field investigations, digital elevation models (DEMs), satellite image and aerial photo interpretations, we have identified a major active fault network affecting this regions. It is mainly constituted by several west and est verging thrust faults, trending NW-SE to N-S, that clearly cut Late Quaternary to Holocene deposits. Evidences in the morphology indicate also that they accommodate some right-lateral slip component. This fault network can be divided into four major fault zones affecting Zandjan city (present day population over 500,000) and part of the Zandjan-Mianeh basin more to the west. Based on fault geometrical characteristics (fault length, segmentation ... ) and kinematics, the Zandjan fault system is certainly capable to produce moderate to large earthquakes (Mw = 6.5-7.0) and serious damages in the Zandjan city and surrounding areas. The study of these faults is, then, of major interest for seismic hazard assessment in Zandjan province where total population exceed 1.5 million but also to better understand present day geodynamic of NW Iran.
ISSN: 0040-1951

hal-00617526
https://hal.archives-ouvertes.fr/hal-00617526
DOI : 10.1016/j.tecto.2011.04.012

Éditeur(s) : HAL CCSD
Résumé : In SW Yukon – SE Alaska, the boundary between the Pacific and North America plates is characterized by a syntaxis at the transition between the Aleutian subduction to the W and the Fairweather – Queen Charlotte strike-slip faults to the SE. The relative motion is oblique to the main fault structures, and the area is marked by the Yakutat block collision. From the Chugach – Saint Elias mountains in the plate boundary zone (up to 6 000 m high) to the intraplate strike-slip faults, markers of the present-day deformation give information on its partition in the system.During my PhD, I first measure surface deformation using a dense GPS network, deployed up to 500 km inland the North America plate. After precise processing and corrections of transient effects in the area (postseismic and glacial isostatic rebound), a new residual velocity field is produced for the syntaxis area, from which I derive strain rates. Those data allow me to quantify the fault slip rates for Fairweather and southern Denali strike-slip faults, and to characterize a bi-modal deformation pattern: Along the plate boundary, the deformation is localized on large-scale structures (accretionary prism to the W, Fairweather to the E); In the syntaxis area, strain rates are the highest and the GPS data shows a diffuse intraplate deformation, similar to an indentor pattern. The Yakutat block seems to strongly drive the North America plate deformation.This indentor pattern induces strong lateral variations on the large intraplate faults: the Denali – Totschunda – Duke River system. In a second part, I realize a regional geomorphological study to characterize the role and slip rate of those faults. From very high-resolution Digital Elevation Models (~ 1 m), a detailed cartography is done. On the basis of fieldwork observations, I measure offsets of fluvial and glacial markers, which are sampled for dating. A dextral cumulative deformation is highlighted on the northern Denali Fault, where as all southern Denali is marked by vertical deformation. This study allows me to quantify new slip rates for the system Denali – Totschunda – Duke River, and to show the leading role of the Totschunda (~ 14 mm/a) and Duke River (~ 6 mm/a) faults, contrary to the Denali Fault (~ 1 mm/a) North of the syntaxis.The new tectonic model for the Yakutat collision provides an important case study for the understanding of indentor systems. The concomitance of a rigid-block deformation (to the West) and diffuse deformation (to the East), as well as the near-zero slip rate on the lithospheric-scale southern Denali Fault highlight the major control of boundary conditions and the structural heritage on the orogen deformation.
Au SO Yukon – SE Alaska, la frontière entre les plaques Pacifique et Nord-Amérique est marquée par une syntaxe à la transition entre la subduction des Aléoutiennes à l’O et le décrochement de Fairweather – Queen Charlotte au SE. Le mouvement relatif est oblique et la région est marquée par la collision du bloc Yakutat. De la chaine des Chugach – Saint Elias en frontière de plaque (jusqu’à 6 000 m d’altitude) aux grands décrochements intraplaque, les marqueurs de la déformation actuelle apportent des informations sur sa partition dans ce système.Au cours de cette thèse, je m’intéresse dans un premier temps à mesurer la déformation de surface à l’aide d’un réseau GPS dense, déployé jusqu’à 500 km à l’intérieur de la plaque Nord-Amérique. Après un travail minutieux de traitement des données et de correction des effets transitoires (rebond post-glaciaire et post-sismique), un champ de vitesses résiduelles robuste et inédit est produit au niveau de la syntaxe, dont je dérive des taux de déformation. Ces données me permettent de quantifier les vitesses de glissement les failles décrochantes de Fairweather et Denali au Sud, et également de caractériser une déformation bimodale : En frontière de plaques, la déformation est localisée sur les grandes structures (prisme d’accrétion à l’O, Fairweather à l’E) ; Au niveau de la syntaxe, les taux de déformation sont les plus importants et les données GPS mettent en évidence une déformation intraplaque diffuse, similaire à un champ attendu à l’aplomb d’un indenteur. Le bloc Yakutat semble donc contrôler fortement la déformation de la plaque Nord-Amérique.Ce champ de déformation induit des variations latérales fortes sur les grandes failles intraplaque : le système Denali-Totschunda-Duke River. Dans une seconde partie, je réalise une étude géomorphologique régionale pour caractériser le rôle et la vitesse de ces failles. À partir de Modèles Numériques de Terrain très haute résolution (~ 1 m), une cartographie de détail est réalisée. Puis une mission de terrain me permet de mesurer des décalages sur des marqueurs fluviatiles et glaciaires et collecter des échantillons pour les dater. Je mets en évidence une déformation cumulée dextre sur le segment Nord de la faille de Denali, alors que toute la partie Sud déforme verticalement la surface. Cette étude me permet de quantifier de nouvelles vitesses de failles sur le système Denali-Totschunda-Duke River, et de montrer le rôle prépondérant des failles de Totschunda (~ 14 mm/a) et Duke River (~ 6 mm/a) contrairement à la faille de Denali (~ 1 mm/a) au Nord de la syntaxe.Le nouveau modèle cinématique proposé pour la région de collision Yakutat permet d’apporter un nouvel exemple à la compréhension des systèmes d’indenteur. La concomitance d’une déformation de blocs (à l’Ouest) et diffuse (à l’Est), ainsi que l’absence de déformation sur la faille lithosphérique de Denali Sud met en évidence le contrôle majeur des conditions aux limites et de l’héritage structural dans la déformation des orogènes.
https://hal.archives-ouvertes.fr/tel-01241688

tel-01241688
https://hal.archives-ouvertes.fr/tel-01241688
https://hal.archives-ouvertes.fr/tel-01241688/document
https://hal.archives-ouvertes.fr/tel-01241688/file/manuscrit_anais_v2_optimise.pdf

Éditeur(s) : Amer Geophysical Union
Résumé : Recent ROV dives and high-resolution bathymetric data acquired over the Ashadze fields on the Mid-Atlantic Ridge (13 degrees N) allow us to derive constraints on the regional and local geological setting of ultramafic-hosted hydrothermal fields. The active vent fields of Ashadze hydrothermal fields are located in the western axial valley wall, downslope from the termination of a prominent corrugated surface and in a transitional domain with respect to ridge segmentation. The study of the shipboard and ROV bathymetry shows that decameter (100 m by 60 m) to kilometer-scaled rockslides shape the axial valley wall slopes in this region. The Ashadze 1 vent field occurs on a coherent granular landslide rock mass that is elongated in an E-W direction. The Ashadze 1 vent field comprises hundreds of active and inactive sulfide chimneys. The Ashadze 2 vent field is located in a NNE-trending linear depression which separates outcrops of gabbros and serpentinized peridotites. Active black smokers in the Ashadze 2 field are located on ultramafic substratum in a 40-m diameter crater, 5-m deep. This crater recalls similar structures described at some vents of the Logatchev hydrothermal field (Mid-Atlantic Ridge 15 degrees N). We discuss the mode of formation for these craters, as well as that for a breadcrust-like array of radial fissures identified at Ashadze 1. We propose that hydrothermalism at Ashadze can be an explosive phenomena associated with geyser-like explosions. Our study also constrains the geological and geophysical context of the ultramafic-hosted Ashadze hydrothermal system that may use the oceanic detachment fault as a preferred permeability conduit.
Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2012-11 , Vol. 13 , N. 1 , P. Q0AG14

Droits : 2012. American Geophysical Union. All Rights Reserved.
http://archimer.ifremer.fr/doc/00111/22223/19895.pdf
DOI:10.1029/2012GC004433
http://archimer.ifremer.fr/doc/00111/22223/

Éditeur(s) : HAL CCSD
Résumé : International audience
The fusion of regions from segmentation is often a required step in order to analyze objects in the scene. It allows to group under a same closure property the partitions of an image, which denote the same object. In this way, several studies have been made. Most of the algorithms are based on global information to evaluate the relevance of region combinations and fusion. In this paper, we propose a merging process based on Gestalt vision's theory. The particularity of our method is to preserve photographer's region of interest thanks to the definition of a new criterion based on Di Zenzo gradient. Thus, region fusion preserves photographer's relevant objects of the scene. The performance of the proposed method is evaluated using various natural images, including Berkeley image database and its accuracy is shown.
Color and Imaging Conference
San Jose, CA, United States

hal-00637144
https://hal.archives-ouvertes.fr/hal-00637144

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : La prolifération récente des résidences secondaires, observée récemment sur la côte Pacifique Sud du Nicaragua, s’inscrit dans une perspective de développement ayant trait à l’hébergement touristique. Or, le caractère immobilier prédominant de ce type d’hébergement, ainsi que les modes de consommation de ces résidents temporaires nous mettent en garde quant aux risques socioéconomiques et environnementaux encourus par les communautés autochtones. Parmi ces risques, notons les problèmes découlant de l’amplitude des variations saisonnières, de privatisation et de destruction des espaces naturels, ainsi que les perspectives de pérennisation des retombées économiques à moyen et long terme. Les auteurs de cet article remettent donc en question les prouesses attribuées à ce secteur d’activité et invitent à considérer des alternatives de développement durable du tourisme plus respectueuses des territoires d’accueil.
In recent years, there has been a proliferation of second home developments on attractive coastal regions of Central and South America. Based on the assumed benefits of second home tourism to regional economies, public authorities - accompanied by private investors – have capitalised on this sector as part of their tourism development strategies. This paper first examines the nature of recent second home tourism developments and then presents the socio-economic and environmental impacts of this phenomenon as experienced by local communities on the South Pacific Coast of Nicaragua. The main impacts include conflicts with local and indigenous communities over land use and ownership, seasonal and low-income employment generation, an increased burden on municipal budget to provide public infrastructure, and environmental degradation. It is argued that the second home tourism sector, strongly driven by private real estate investors, fails to generate tourism activities which are expected to sustain community development. Furthermore, this study indicates that municipalities concentrating on the second home tourism segment may deprive themselves of access to resources for more sustainable forms of tourism activities.
Amérique centrale
Nicaragua

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.3869
http://journals.openedition.org/etudescaribeennes/3869

Éditeur(s) : HAL CCSD
Résumé : contient des versions PDF d'articles scientifiques (versions éditeur)
Spectrins are actin binding proteins that constitute the main components of membrane skeletons, the protein network located under the plasma membrane. Erythroid or non erythroid (in this case, they are called fodrins), spectrins play an important structural function in the membrane as demonstrated in the red blood cell. Spectrins are composed of two long α and β chains, associated in tetramers (αβ)2, forming the long flexible filaments of the network. Both chains are composed of repeating units which are folded in a triple helical arrangement (A, B and C helices), except for segment α10 which corresponds to a Src Homology 3 domain (SH3). The head-to-head interaction between dimers implies the N-terminal end of α chain and the C-terminal end of β chain. A model was proposed for the tetramerization site of spectrin : the two A and B helices of the last repeat of α chain interact with the C helix of the β chain in order to constitute a triple-helical structure similar to the repeats along the remainder of spectrin molecule. This model was first inferred from the relationship between the severity of the spectrin self-association defect and the location of the underlying mutations found in hereditary elliptocytosis (HE). Using recombinant peptides we defined the region, on both chains, which was sufficient and necessary to generate a fully functional tetramerization site. Producing peptides carrying a βHE mutation, we reproduced the tetramerization defect as observed in red blood cells of patients.
Finally, the presence of an SH3 domain probably gives to spectrins new functions which are different from the stability of the membrane. After contesting the existence of interaction between the fodrin SH3 domain and the α subunit of epithelial sodium channel sensitive to amiloride, we searched for partners of this domain, by screening a rat kidney library with the yeast two-hybrid system. We identified severals proteins implicated in the actin polymerization asoociated with motility or cell differenciation, suggesting that SH3 domain could play a part in this process.
Les spectrines, protéines liant l'actine, sont des constituants majeurs du squelette membranaire, réseau multiprotéique localisé sous la membrane plasmique. Érythroïdes ou non érythroïdes (dans ce cas, on les appelle fodrines), les spectrines ont un rôle structural important dans la membrane comme cela a déjà été démontré, pour la spectrine, dans le globule rouge. Elles sont constituées de deux longues chaînes a et ß associées côte à côte en tétramères (aß)2 qui forment les longs filaments du réseau. Chacune des chaînes est composée par la répétition de segments homologues, 22 pour a et 17 pour ß. Ces segments sont constitués de trois hélices a (hélices A, B et C) repliées sur elles-mêmes. Cette succession de structures trihélicoïdales est parfois interrompue par un domaine particulier comme le domaine SH3 (Src Homology 3) présent au milieu de la chaîne a. Les tétramères (aß)2 de spectrine constituent les filaments du squelette membranaire. L'interaction tête-à-tête de deux dimères aß implique les extrémités NH2 de la chaîne a et COOH de la chaîne ß. D'une part la sévérité du défaut d'auto-association et la localisation des mutations associées à celui-ci et d'autre part, les séquences en acides aminés des extrémités impliquées dans le site d'auto-association ont permis de proposer un modèle : la première hélice C isolée de la chaîne a pourrait s'associer aux deux dernières hélices A et B de la chaîne ß pour reconstituer une unité conformationnelle trihélicoïdale semblable à celles observées le long de la molécule. Un défaut dans la formation du tétramère est le support moléculaire le plus fréquemment observé dans les elliptocytoses héréditaires (HE). À l'aide de peptides recombinants, nous avons défini, sur les deux chaînes, les régions nécessaires et suffisantes possédant les caractéristiques pleinement fonctionnelles du site de tétramérisation. Nous avons ensuite, par mutagenèse dirigée, reproduit le lien entre la présence de mutations HE localisées dans les hélices A ou B et le défaut d'auto-association observé dans les globules rouges de patients HE. La présence d'un domaine SH3 localisé au milieu de la chaîne a confère probablement aux spectrine des fonctions autres que le maintien et la stabilité de la membrane. Les SH3, petits domaines protéiques, participent aux interactions protéine/protéine. Le seul partenaire connu du domaine SH3 de la fodrine était la sous-unité a du canal sodium sensible à l'amiloride (ENaC) mais la fonction de ce complexe n'était pas encore caractérisée. À l'aide de différentes méthodes, nous avons remis en cause l'interaction directe entre ENaC et le SH3 de la fodrine. La fonction de ce domaine SH3 étant liée à la nature de son ligand, nous avons donc recherché les partenaires putatifs du domaine SH3 de la fodrine par la technique du double-hybride. 29 partenaires ont été identifiés, regroupés en 19 familles et 10 clones isolés. La spécificité des interactions a été étudiée à la fois par double-hybride, à l'aide de mutants du domaine SH3 de la fodrine produits par mutagenèse dirigée. Les interactions vis-à-vis d'autres domaines SH3 (spectrine ou une protéine de levure non relatée Scd2) ont été également analysées. Enfin, la spécificité de certains partenaires a été confirmée par des études d'interactions in vitro. Deux des protéines les plus spécifiques du domaine SH3 de la fodrine sont des protéines tyrosine-phosphatase PTP. La première est l'isoforme A de PTP de faible poids moléculaire (LMPTPA) mais l'interaction n'a pas été confirmée in vitro. La deuxième, TD14, est une nouvelle PTP dont la seule fonction connue est d'inhiber la formation des foyers tumoraux des cellules surexprimant l'oncogène Ha-ras. Ces PTP pourraient soit déphosphoryler la fodrine, soit être recrutées sous la membrane pour déphosphoryler une autre cible. Nous avons également identifié trois partenaires (N-WASP, Evl et une protéine de la famille des formines) suggérant que les domaines SH3 des spectrines pourraient être impliqués dans les processus de polymérisation de l'actine liés à la mobilité ou la différenciation cellulaire. Mot clés : spectrine, fodrine, tétramérisation, SH3, double-hybride, polymérisation de l'actine
https://tel.archives-ouvertes.fr/tel-00284819

Droits : info:eu-repo/semantics/OpenAccess
tel-00284819
https://tel.archives-ouvertes.fr/tel-00284819
https://tel.archives-ouvertes.fr/tel-00284819/document
https://tel.archives-ouvertes.fr/tel-00284819/file/Nicolas_1999_-_These.pdf

Éditeur(s) : HAL CCSD Blackwell Publishing
Résumé : International audience
In the Causses platform (south-east France), Late Hettangian to Sinemurian deposits were interpreted previously as shallow-water carbonate ramp deposits. A new look at these deposits has shown a fault-controlled mosaic carbonate platform that is different from the carbonate ramp models. Within the platform mosaic, 15 lithofacies have been recognized, which are organized in four facies associations, including peritidal, restricted shallow sub-tidal, sand dunes and sub-tidal shelf facies associations. The rapid lateral and vertical facies changes, and the lack of consistent landward or seaward direction indicated by the pattern of facies changes, question the existence of a shoreline suggested by the traditional models for this region. Instead, the facies organization and cycle stacking pattern suggest deposition in a mosaic of intertidal islands between which sub-tidal restricted or open conditions could coexist in very close proximity. Such a platform mosaic would have been defined by tectonic activities along normal faults which segmented the shallow-water Causses platform. The facies and facies associations are arranged into metre-scale, peritidal and sub-tidal cycles that are also variable. Certain cycles show the same stacking pattern in all the sections and seem to be traceable over tens of kilometres. On the contrary, other cycles cannot be correlated; they are present only in specific sections and have a maximum lateral extension of 1 or 2 km. These metre-scale cycles stack to form four medium-scale cycles bounded by surfaces that display sub-aerial exposure features. Medium-scale cycles stack into two larger-scale cycles (tens of metres thick) and are bounded by well-defined karstic surfaces. Based on their lateral continuity and their stacking pattern, the metre-scale cycles are controlled probably by high frequency eustatic variations overprinting the topographic irregularities formed by differential subsidence of fault-bounded blocks. Episodic fault activities may reorganize the topography so that, even if eustatic changes may still be the major control of cycles, the expression and number of cycles could be different. Cycles of medium and large-scale are interpreted as being allogenic, controlled by changes in eustasy and/or subsidence rates as evidenced by their lateral continuity and the correlations of the large-scale cycles with third-order depositional sequences.
ISSN: 1469-3496

hal-00411940
https://hal.archives-ouvertes.fr/hal-00411940
DOI : 10.1111/j.1365-3091.2007.00896.x

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

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

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : L’exploitation commerciale des produits forestiers non ligneux a animé et anime encore au plan international les débats sur la gestion durable des forêts, notamment par son apport en matière de conservation, d’amélioration des conditions d’existence des populations locales et de gestion participative. Cependant, l’exploitation commerciale des PFNL soulève la problématique de la durabilité tant au plan écologique, économique que sociopolitique. La présente recherche traite de cette problématique en prenant comme PFNL d’illustration le raphia dans la forêt marécageuse Hlanzoun. Elle vise à analyser la durabilité socio-économique et environnementale de l’exploitation du raphia dans la forêt marécageuse « Hlanzoun ». La méthodologie utilisée est une combinaison d’approches quantitatives et qualitatives. Les outils d’analyse de données utilisés sont entre autre, la statistique descriptive, l’analyse filière des revenus d’exploitation et des valeurs ajoutées et l’analyse du système socio-écologique. Nos résultats montrent que le raphia est une plante à usages multiples. Que ce soit les feuilles, les fibres, la sève ou le tronc, tout ou presque peut être valorisé sur le raphia. Au niveau des villages riverains du Hlanzoun l’exploitation de la sève du raphia et sa transformation en alcool alimentaire est de loin le type d’usage qui procure le plus de revenu malgré le fait que les autres types d’usages mobilisent un nombre plus important d’acteurs. L’exploitation commerciale de ce PFNL se déploie suivant une organisation relativement simple et avec des caractéristiques propres à la plupart des activités de la petite production marchande des économies sous-développées en crise. Cette exploitation est essentiellement articulée autour des coupeurs/collecteurs, des intermédiaires commerciaux, des agents de transformation/conditionnement et des consommateurs des produits finis. La contribution annuelle totale de la filière raphia au développement a été estimée à 192 429 633 Fr. CFA (environ 385 000 dollar) et les revenus d’exploitation de tous les acteurs ont un signe positif malgré le faible niveau de technologie et de formation. Le raphia apporte donc des revenus relativement importants aux divers acteurs en dépit des handicaps de la filière et du déficit d’équité dans la répartition des richesses produites. Au plan de la gouvernance, on note un déficit d’instances, de règles et de procédures, dont l’effectivité et la légitimité sont clairement établies. Cet état de chose laisse le parc à raphia dans un régime d’accès « libre » mais seulement pour les riverains ; nous nous retrouvons donc en présence d’un système de cueillette, caractérisé par l’exploitation de plants immatures et la surexploitation, mettant en péril la capacité de renouvellement de la ressource et même l’avenir de la filière. On note cependant un effort de contrôle de l’accès des non riverains et des tentatives d’adaptation des riverains. En effet, le nombre d’exploitants est passé de 148 à 92 entre 2008 et 2010 et le nombre de pieds de raphia saignés est passé de 15 452 à 8 832 durant la même période. Au total, l’exploitation du raphia dans le Hlanzoun s’inscrit dans un environnement défavorable par rapport aux exigences de développement durable d’une filière de PFNL. Mais les divers acteurs sont à présent conscients de la nécessité d’agir pour une meilleure réglementation de l’accès et de l’exploitation.
The commercial use of non woody forest products is a crucial issue in the international debate on the sustainable management of forests. These products are supposed to contribute to conservation by improving local populations’ livelihood and their involvement in forest management. This study lies within the scope of two South-South Cooperation projects (PSC 22P07 and PSC 03T08) implemented by the CEBEDES NGO with the financial support of the Kingdom of the Netherlands. It aims at analyzing the socioeconomic and environmental sustainability of the raffia stands management in the swamp forest "Hlanzoun ". This small forest is located in one of Benin southern Wetlands in the municipality of Zogbodomey.The methodology to assess raffia socioeconomic performances relies on the estimation of the values added within the raffia value chains. Stakeholders at every segment of the value chains have been surveyed on the incomes obtained out of raffia. The methodology to assess the sustainability of the management relies on a simple indicator measuring the ratio of younger to elder palms. Palms in stands have been counted according to their age group. The survey confirms that raffia is a multi-purpose plant used for its leaves, fibers, sap and trunk. In villages at the borders of the Hlanzoun forest, harvesting the raffia sap on standing palms and processing it into alcohol are a major income generating activity. Alcohol is then marketed through a network of collectors, wholesalers and petty traders up to the consumers. The contribution of raffia to local and regional development was estimated by the total incomes generated at 192.429.633 F CFA. All stakeholders earn positive and significant incomes in spite of the low level of technology and skills, but traders receive a large share of the wealth produced. As regard to governance, "free" access only concerns residents and efforts are made to control the access of non-residents. One notes a deficit of legitimated authorities, rules and procedures for a sustainable use: Restrictions on the harvest of immature palms are not anymore enforced and it endangers the renewal capacity of the resource. But at the same time, the number of operators seems to be decreasing (from 148 to 92 between 2008 and 2010, whereas the number of harvested raffia palms decreased from 15,452 to 8,832 during the same period). A self-regulation might occur, due to the fact that a livelihood of local people relies on a diversity of income generating activities. In total, the operation of Raffia in Hlazoun is in an unfavorable environment with the requirements of sustainable development in a sector of NTFF. But the various actors are now aware of the need for action to better regulate access and operation.
Bénin

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.5556
http://journals.openedition.org/etudescaribeennes/5556

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) : Elsevier Science Bv
Résumé : We present the results from a new grid of deep penetration multichannel seismic (MCS) profiles over the 280-km-long north-central segment of the Lesser Antilles subduction zone. The 14 dip-lines and 7 strike-lines image the topographical variations of (i) the subduction interplate décollement, (ii) the top of the arcward subducting Atlantic oceanic crust (TOC) under the huge accretionary wedge up to 7 km thick, and (iii) the trenchward dipping basement of the deeply buried forearc backstop of the Caribbean upper plate. The four northernmost long dip-lines of this new MCS grid reveal several-kilometres-high topographic variations of the TOC beneath the accretionary wedge offshore Guadeloupe and Antigua islands. They are located in the prolongation of those mapped on the Atlantic seafloor entering subduction, such as the Barracuda Ridge. This MCS grid also provides unexpected evidences on huge along-strike topographical variation of the backstop basement and of the deformation style affecting the outer forearc crust and sediments. Their mapping clearly indicates two principal areas of active deformation in the prolongation of the major Barracuda and Tiburon ridges and also other forearc basement highs that correspond to the prolongation of smaller oceanic basement highs recently mapped on the Atlantic seafloor. Although different in detail, the two main deforming forearc domains share similarities in style. The imaged deformation of the sedimentary stratification reveals a time- and space-dependent faulting by successive warping and unwarping, which deformation can be readily attributed to the forearc backstop sweeping over the two obliquely-oriented elongated and localized topographical ridges. The induced faulting producing vertical scarps in this transport does not require a regional arc-parallel extensional regime as proposed for the inner forearc domain, and may support a partitioned tectonic deformation such as in the case of an outer forearc sliver. A contrasted reflectivity of the sedimentary layering at the transition between the outer forearc and accretionary domains was resolved and used to define the seaward edge of the outer forearc basement interpreted as being possibly a proxy to the updip limit of the interplate seismogenic zone. Its mapping documents along-arc variations of some tens of kilometres the subduction backstop with respect to the negative gravity anomaly commonly taken as marking the subduction trench. With the exception of the southernmost part, the newly mapped updip limit reaches 25 km closer to the trench, thus indicating a possible wider seismogenic zone over almost the whole length of the study area.
Tectonophysics (0040-1951) (Elsevier Science Bv), 2013-09 , Vol. 603 , P. 32-54

Droits : 2013 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/00139/25003/23109.pdf
DOI:10.1016/j.tecto.2013.05.028
http://archimer.ifremer.fr/doc/00139/25003/

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The region of Bhutan is thought to be the only segment of the Himalayas not having experienced a major earthquake over the past half millennium. A proposed explanation for this apparent seismic gap is partial accommodation of the India-Asia convergence further south across the Shillong Plateau, yet the seismic behavior of the Himalayan megathrust in Bhutan is unknown. Here we present historical documents from the region reporting on an earthquake in 1714 A.D. and geological evidence of surface rupture to constrain the latest large event in this area. We compute various earthquake scenarios using empirical scaling relationships relating magnitude with intensity, source location and rupture geometry. Our results constrain the 1714 A.D. earthquake to have ruptured the megathrust in Bhutan, most likely during a M7.5–8.5 event. This finding reclassifies the apparent seismic gap to a former information gap and implies that the entire Himalayan arc has a high level of earthquake potential.
ISSN: 0094-8276

hal-01467822
https://hal.archives-ouvertes.fr/hal-01467822
DOI : 10.1002/2016GL071033

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Dahomey belt in Togo and Benin is an important segment of the larger West Gondwana Orogen. Here, we review the geodynamic evolution of the Dahomey belt and discuss new U–Pb and Lu–Hf zircon data in light of similar data previously acquired on the geologically related Northern Borborema Province, in NE Brazil. Eighteen samples from different tectonic settings and regions within the belt were collected for zircon isotopic investigation. Passive margin deposits of the Atacora Structural Unit and lower units of the Volta Basin have detrital zircon signatures compatible with the flanking West Africa Craton. The arc-related magmatism resulted from the east-dipping subduction of the Goiás-Pharusian oceanic lithosphere and is represented by a variety of granitoids emplaced in the Benino-Nigerian Shield between 670 and 610 Ma. These granitoids were mainly sourced from crustal reservoirs with subordinate juvenile input. Detrital zircon ages from syn-orogenic deposits in Benino-Nigerian Shield suggest that arc development could have started as early as 780 Ma. The main period of melting in the internal part of the belt, the Benino-Nigerian Shield, is related to crustal thickening and occurs only ca. 30 m.y. after initiation of the continental collision, marked by the ca. 610 Ma ultra-high pressure (UHP) metamorphism recorded at Lato Hills. Foreland development represented by the upper units of the Volta basin developed soon after continental collision and persisted with the development of the west-verging thrust front synchronously with the main period of crustal melting due to collision at ca. 580 Ma. The subvertical Transbrasiliano Lineament in South America, that corresponds to the Kandi Lineament in Africa, provides a present-day fit between NW Africa and NE Brazil. Restoration of the movement of the Transbrasiliano-Kandi Lineament (strike-slip plate boundary) places the Dahomey belt and Borborema Province (NE Brazil) along the same section of the West Gondwana Orogen. This configuration would explain some of the misfits previously discussed in the literature and aligns the UHP eclogites in Togo and NE Brazil.
ISSN: 0301-9268

hal-01358584
https://hal.archives-ouvertes.fr/hal-01358584
DOI : 10.1016/j.precamres.2016.01.032

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The 856 A.D. Qumis earthquake (M7.9) is the most destructive earthquake to have occurred in Iran, killing more than 200,000 people and destroying the cities of Damghan and the old Parthian capital of Shahr-i Qumis (Hecatompylos). This study combines evidence of historical seismicity with observations of the geomorphology and paleoseismology to provide the first detailed description of active faulting in the Damghan region of the east Alborz mountains, Iran. Regional left-lateral shear is accommodated on the Astaneh, Damghan, and North Damghan faults. Quaternary alluvial fans have been displaced along the Astaneh fault, with 15–20 m stream offsets recording the cumulative displacement over the last two to five earthquakes. A paleoseismology study from a single trench along a 5–10 km segment of the Astaneh fault reveals a rupture prior to 1300 A.D. and significantly later than 600 B.C. Despite the limitations of a single trench in documenting the spatial and temporal evolution of the fault over the late Quaternary, we are nevertheless able to bracket the last event to a time period consistent with the 856 A.D. earthquake. Two older earthquakes were also identified during the Holocene occurring between 600 B.C. and 4600 B.C. and between 4600 B.C. and 9600 B.C. The location of our trench within a bend on the Astaneh fault, which could act as a barrier to rupture propagation, means the three earthquakes recovered from our trench over the Holocene may represent a minimum. Further trenching will reveal how the Astaneh fault ruptures over repeated earthquakes and, consequently, the magnitude and extent of slip during the 856 A.D. earthquake.
ISSN: 0148-0227

hal-00551330
https://hal.archives-ouvertes.fr/hal-00551330
https://hal.archives-ouvertes.fr/hal-00551330v2/document
https://hal.archives-ouvertes.fr/hal-00551330/file/Hollingsworth2010.pdf
DOI : 10.1029/2009JB007185