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Jiuxun Yin, Marine A. Denolle, Huajian Yao. (2018). Spatial and Temporal Evolution of Earthquake Dynamics: Case Study of the Mw 8.3 Illapel Earthquake, Chile (Vol. 123).
Abstract: We develop a methodology that combines compressive sensing backprojection (CS-BP) and source spectral analysis of teleseismic P waves to provide metrics relevant to earthquake dynamics of large events. We improve the CS-BP method by an autoadaptive source grid refinement as well as a reference source adjustment technique to gain better spatial and temporal resolution of the locations of the radiated bursts. We also use a two-step source spectral analysis based on (i) simple theoretical Green's functions that include depth phases and water reverberations and on (ii) empirical P wave Green's functions. Furthermore, we propose a source spectrogram methodology that provides the temporal evolution of dynamic parameters such as radiated energy and falloff rates. Bridging backprojection and spectrogram analysis provides a spatial and temporal evolution of these dynamic source parameters. We apply our technique to the recent 2015 Mw 8.3 megathrust Illapel earthquake (Chile). The results from both techniques are consistent and reveal a depth-varying seismic radiation that is also found in other megathrust earthquakes. The low-frequency content of the seismic radiation is located in the shallow part of the megathrust, propagating unilaterally from the hypocenter toward the trench while most of the high-frequency content comes from the downdip part of the fault. Interpretation of multiple rupture stages in the radiation is also supported by the temporal variations of radiated energy and falloff rates. Finally, we discuss the possible mechanisms, either from prestress, fault geometry, and/or frictional properties to explain our observables. Our methodology is an attempt to bridge kinematic observations with earthquake dynamics.
Keywords: backprojection earthquake dynamics Illapel Earthquake radiated energy
Programme: 133
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Mazé C., Tixier P., Boulinier T., Gamble A., Guinet C., Robin J.-p. Et J. Labonne. (2020). La transformation vers la soutenabilité, de la théorie à la pratique : la ZATA, un modèle d'étude et d'action pertinent et efficace. Le cas des pêcheries et de la conservation des oiseaux et mammifères marins.
Abstract: L'horizon de transformation vers la soutenabilité fondée sur le concept de résilience en écologie est décrit de manière normative dans la littérature en sciences de l'environnement ou mis en valeur à partir de cas d'étude isolés. S'ils constituent d'importantes « semences pour un bon Anthropocène » ces exemples restent encore trop rares, alors que la transformation devrait d'être entreprise à plus grande échelle et à vitesse rapide. Cette transformation nécessite urgemment d'être mise en pratique de manière plus systématique et étayée à partir de cas d'action-recherche efficaces. Pour ce faire, ceux-ci doivent être conçus et mis en œuvre grâce à de nouvelles configurations, représentations et pratiques des relations entre chercheurs et autres acteurs du territoire, publics comme privés. Autrement dit, la transformation implique un changement de gouvernance, pour aller vers une gestion adaptative des territoires, des ressources naturelles et des sociétés qui en dépendent. Elle doit faire une plus grande place aux interactions entre humains et non-humains, redéfinir en profondeur le rapport homme / nature et passer par un rééquilibrage des pouvoirs entre groupes d'acteurs et institutions, dans le processus de décision en matière de gestion environnementale. Les sciences sociales et en particulier l'anthropologie des relations homme / milieu, la sociologie politique des sciences, la sociologie politique et l'économie écologique doivent être mobilisées à cette fin, en étroite interaction avec l'écologie. Les zones-ateliers fournissent à ce titre des cas privilégiés, permettant d'opérer ce changement de paradigme, en donnant une plus grande place à l'action collective, à l'hybridation des savoirs et à l'articulation équilibrée entre intérêts divergents. Elles permettent d'identifier les paramètres déterminants pour générer de manière efficace la transformation. La ZATA, zone atelier Antarctique et Terres Australes, malgré une pression anthropique directe limitée, offre un cadre de travail privilégié pour identifier les paramètres nécessaires à la mise en œuvre d'une gouvernance propice à une gestion adaptative permettant d'augmenter la résilience des SES. La pression du changement global y est très forte, tout comme les interactions entre les diverses catégories d'acteurs et d'institutions historiquement situées. La présence des scientifiques y est très installée et mêlée à des enjeux politiques, économiques et géostratégiques auxquels contribuent la conservation de la biodiversité. A partir de deux modèles d'étude (pêcheries à Kerguelen et interactions avec la mégafaune marine/ conservation des oiseaux marins, pathogènes et dératisation à Amsterdam) faisant intervenir des chercheurs, des décideurs, des gestionnaires et les acteurs économiques dans le processus de décision multi-échelles (e.g. État français / CCAMLAR-RCTA) en termes de gestion environnementale, nous présenterons une méthode de modélisation des socio-écosystèmes en systèmes dynamiques. Les modèles produits permettent d'envisager leurs trajectoires de résilience en fonction des choix de gestion et peuvent ainsi servir d'outil d'aide à la décision et d'instrument inédit en matière de construction des mesures de gestion adaptative. Cette communication, élaborée au fil des interactions avec les gestionnaires, alliera ainsi réflexion théorique et retours sur des cas concrets pouvant permettre une montée en généralité utile pour aller vers une gouvernance des SES effective et efficace en termes de résilience et de soutenabilité.
Programme: 119
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. (2010). Provenance of freshwater pulses in the Gulf of Mexico during the last deglaciation
. Quaternary Research, 74(2), 235–245.
Abstract: During the last deglaciation, the decaying Laurentide Ice Sheet (LIS) delivered huge volumes of meltwater toward the Gulf of Mexico. The present investigation of clay mineralogy and grain-size characteristics of terrigenous sediments deposited in the Orca Basin (Gulf of Mexico) offers a unique opportunity to link the marine record of these meltwater floods with the reconstructed continental glacial history and the modeled drainage patterns. Five peculiar sedimentary levels, characterized by high smectite content and low CaCO3 content, were identified and occurred simultaneously with major meltwater floods. According to recently published clay mineral distribution maps for North America, these results help to pinpoint the southwestern margin of the LIS as a main contributor to most of the meltwater discharges. In addition, the peculiar mineralogical composition (illite and chlorite-rich) of the sediments characterizing the meltwater episode associated with Heinrich event 1 suggests a provenance from the Great Lakes area, supporting the interpretation of destabilization of the LIS southeastern margin during this event. Decreased terrigenous contribution associated with changing provenance of sediments after 12.9 cal ka BP suggests strong modifications of the continental hydrography in relation to Lake Agassiz history and changes in the morphology of Mississippi delta due to rising sea level.
Keywords: Deglaciation, Meltwater pulse, Laurentide Ice Sheet, Clay minerals, Orca Basin, Mississippi River,
Programme: 316
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. (2011). Sr/Ca and Mg/Ca ratios of ontogenetically old, long-lived bivalve shells (Arctica islandica) and their function as paleotemperature proxies
. Palaeogeography, Palaeoclimatology, Palaeoecology, 302(12), 52–64.
Abstract: The Sr/Ca and Mg/Ca ratios of many biogenic skeletons provide useful paleotemperature estimates. As yet however, it has remained largely impossible to obtain such information from bivalve shells. In the present study, metal-to-calcium values in the hinge plate (aragonite, outer shell layer) of four ontogenetically old (85 to 374 year-old) specimens of the long-lived bivalve, Arctica islandica, were measured on a LAICPMS. The shells were collected alive in 1868, 1986 and 2003 from three different localities around Iceland. With increasing ontogenetic age and decreasing growth rate, a distinct trend toward increasing Sr/Ca (max. 5.17 mmol/mol) and Mg/Ca values (max. 0.89 mmol/mol) and greater variance were observed. Three potential explanations for these trends include a reduced capacity for element selection due to cell ageing, changing metabolism and/or a relative increase in the number of organic-rich (= Mg-rich) and organic-poor (= Sr-rich) shell portions through ontogeny. Partition coefficients however, remained far below 1, indicating that physiology exerted a strong control over the element partitioning between the shells and the ambient water. After mathematical elimination of these vital effects, residuals exhibited a highly significant negative correlation (e.g., age-detrended Sr/Ca data: R = 0.64, R2 = 0.41, p < 0.0001, growth rate-detrended Mg/Ca data: R = 0.52, R2 = 0.27, p < 0.0001) with sea surface temperature. These results are in good agreement with results obtained from the precipitation of abiogenic aragonite. The results of the present study can help to develop new techniques to extract environmental signals from the metal-to-calcium ratios of bivalve shells.
Keywords: Metal-to-calcium ratio, Bivalve shell, Vital effect, Sea surface temperature, Longevity,
Programme: 1090
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. (2011). Annually resolved 13Cshell chronologies of long-lived bivalve mollusks (Arctica islandica) reveal oceanic carbon dynamics in the temperate North Atlantic during recent centuries
. Palaeogeogr Palaeoclimatol Palaeoecol, 302(12), 31–42.
Keywords: Sclerochronology, Stable carbon isotope ratio, Carbon dioxide, Dissolved inorganic carbon, Oceanic Suess effect,
Programme: 1090
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Dettai A, Berkani M, Lautredou A-C, Couloux A, Lecointre G, Ozouf-Costaz C, Gallut C, . (2012). Tracking the elusive monophyly of nototheniid fishes (Teleostei) with multiple mitochondrial and nuclear markers
. Marine Genomics, 8, 49–58.
Abstract: Since the first molecular study of the suborder Notothenioidei in 1994, many phylogenetic studies have been published. Among these, those with a sufficient number of taxa have all suggested that the Nototheniidae, as currently defined, is monophyletic only with the inclusion of the Channichthyidae, Artedidraconidae, Bathydraconidae and Harpagiferidae. This is corroborated by more recent studies including more taxa, but in these studies either the number of nuclear markers or the number of taxa included remained low. We obtained sequences for a large sampling covering most nototheniid genera for five markers described previously for other samplings (COI, Rhodopsin retrogene, Pkd1, HECW2, and SSRP1) and one nuclear marker never used before in phylogenetic inference (PPM1d). The topology for the combined analysis of the nuclear coding genes, as well as the topology for SSRP1 (non-coding) and the combined analysis for all markers all support the paraphyly of Nototheniidae, the genus Notothenia (including Paranotothenia) is the sister group of the clade Channichthyidae, Artedidraconidae, Bathydraconidae and Harpagiferidae, and genus Gobionotothen is a sister group to both. As in previous studies, Trematomus, Lepidonotothen and Patagonotothen form a clade that also includes Indonotothenia cyanobrancha. The position of Pleuragramma antarctica, Dissostichus species and Aethotaxis mitopteryx remains unstable and dependant on markers and analyses.
Keywords: Cytochrome oxidase 1, Phylogeny, Congruence, Simultaneous analysis,
Programme: 1124
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. (2010). Experimental growth pattern calibration of Antarctic scallop shells (Adamussium colbecki, Smith 1902) to provide a biogenic archive of high-resolution records of environmental and climatic changes
. J. Exp. Mar. Biol. Ecol., 393(12), 158–167.
Abstract: To determine the potential of Antarctic bivalve shells as biomonitors for environmental and climatic variations in polar marine areas, we developed a growth model for juvenile Adamussium colbecki Smith, 1902 based on the use of in situ temporal calcein markings to calibrate growth patterns in the external striae formation. To minimize scallop stress caused by excessive handling, in situ benthic chambers were used for the marking experiment, during an exposure time of 6 h. Once marked, scallops remained on site in a benthic cage and were collected 18, 26, and 41 days later. Apart from a few specimens affected by possible calcein toxicity effects, the detectable mark in all shells revealed a higher austral summer growth rate for A. colbecki compared to other Antarctic bivalves. Using calcein labeling, we identified a near 14-day periodicity in the striae formation associated with the fortnightly seawater level regime. Striae counting and increment width measurements showed an annual cycle, with no clear cessation of growth in juvenile specimens, allowing age determination. Because of the relatively high growth rate for a polar species and easily recognizable sclerochronological calendar in the shell striae formation, A. colbecki is an appropriate species for high-resolution (infra-monthly) geochemical sampling. Comparison between LA-ICP-MS analyses (Li, B, Mg, Mn, Co, Sr, Ba, Pb) from one shell and hydrological parameters (sea level, temperature, salinity) measured in seawater suggests, however, that more work is needed to calibrate the trace element proxies. Nevertheless, the shell of the Antarctic scallop A. colbecki has tremendous potential for recording environmental conditions from time periods covering months to a few years in polar waters, notably the ice melting date.
Keywords: Adamussium colbecki, Antarctic scallop, Calcein marking, Growth pattern, LA-ICP-MS,
Programme: 1090
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. (2013). Two new species of aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) from the high arctic (Spitsbergen, Svalbard)
. Zoologischer Anzeiger – A Journal of Comparative Zoology, 252(1), 34–40.
Abstract: The high arctic Svalbard archipelago is characterized by a low insect species richness explained by both extreme living conditions and insularity. Here, we described two new species of Hymenopteran parasitoids found in Spitsbergen, the main island of Svalbard, using aphids as hosts. We named the first one Diaeretellus svalbardicum (Hymenoptera: Braconidae) because of morphological similarities with other European members of the Diaeretellus genus. D. svalbardicum parasitizes exclusively the aphid Acyrthosiphon svalbardicum, a species endemic to Svalbard. We also reported in D. svalbardicum a unique case of wing polymorphism with macropterous and micropterous forms in both genders. We named the second newly described parasitoid species Aphidius leclanti because of morphological similarities with other members of the Aphidius genus. Contrarily to D. svalbardicum, A. leclanti exploits the only two aphid species regularly found in Spitsbergen, A. svalbardicum and Sitobion calvulum.
Keywords: Arctic environments, Insect biodiversity, Aphid parasitoids, New species, Spitsbergen,
Programme: 426
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Spilmont Nicolas, Seuront Laurent, Meziane Tarik, Welsh David T, . (2011). Theres more to the picture than meets the eye: Sampling microphytobenthos in a heterogeneous environment
. Estuar Coast Shelf Sci, 95(4), 470–476.
Keywords: intertidal environment, chlorophyll, sediment sampling, spatial variations, sampling strategy,
Programme: 1090
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. (2011). QUBIC: The QU bolometric interferometer for cosmology
. 0927-6505, 34(9), 705–716.
Abstract: One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the Cosmic Microwave Background. These originate from tensor fluctuations of the metric produced during the inflationary phase. Their detection would therefore constitute a major step towards understanding the primordial Universe. The expected level of these anisotropies is however so small that it requires a new generation of instruments with high sensitivity and extremely good control of systematic effects.
Keywords: Cosmology, Cosmic Microwave Background, Inflation, Instrumentation, Bolometric interferometry,
Programme: 915
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