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Afsaneh Mohammadzaheri, Karin Sigloch, Kasra Hosseini, Mitchell G. Mihalynuk. (2021). Subducted Lithosphere Under South America From Multifrequency P Wave Tomography (Vol. 126).
Abstract: We analyze mantle structure under South America in the DETOX-P1 seismic tomography model, a global-scale, multifrequency inversion of teleseismic P waves. DETOX-P1 inverts the most extensive data set of broadband, waveform-based traveltime measurements to date, complemented by analyst-picked traveltimes from the ISC-EHB catalog. The mantle under South America is sampled by ∼665,000 cross-correlation traveltimes measured on 529 South American broadband stations and on 5,389 stations elsewhere. By their locations, depths, and geometries, we distinguish four high-velocity provinces under South America, interpreted as subducted lithosphere (“slabs”). The deepest (∼1,800–1,200 km depth) and shallowest (<600 km) slab provinces are observed beneath the Andean Cordillera near the continent’s northwest coast. At intermediate depths (1,200–900 km, 900–600 km), two slab provinces are observed farther east, under Brazil, Bolivia and Venezuela, with links to the Caribbean. We interpret the slabs relative to South America’s paleo-position over time, exploring the hypothesis that slabs sank essentially vertically after widening by viscous deformation in the mantle transition zone. The shallowest slab province carries the geometric imprint of the continental margin and represents ocean-beneath-continent subduction during Cenozoic times. The deepest, farthest west slab complex formed under intra-oceanic trenches during late Jurassic and Cretaceous times, far west of South America’s paleo-position adjoined to Africa. The two intermediate slab complexes record the Cretaceous transition from westward intra-oceanic subduction to eastward subduction beneath South America. This geophysical inference matches geologic records of the transition from Jura-Cretaceous, extensional “intra-arc” basins to basin inversion and onset of the modern Andean arc ∼85 Ma.
Keywords: Andes intra-arc intra-oceanic subduction seismic tomography South America structure of the mantel
Programme: 133
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Agabi, A.; Aristidi, E.; Azouit, M.; Fossat, E.; Martin, F.; Sadibekova, T.; Vernin, J.; Ziad, A. (2006). First Whole Atmosphere Nighttime Seeing Measurements at Dome C, Antarctica. Publ. Astron. Soc. Pac., 118(840), 344–348.
Abstract: We report site-testing results obtained in the nighttime during the polar autumn and winter at Dome C. These results were collected during the first Concordia winterover by A. Agabi. They are based on seeing and isoplanatic angle monitoring, as well as in situ balloon measurements of the refractive index structure constant profiles C2n(h). Atmosphere is divided into two regions: (1) a 36 m high surface layer responsible for 87% of the turbulence, and (2) a very stable free atmosphere above, with a median seeing of 0.36“ +/- 0.19” at an elevation of h=30 m. The median seeing measured with a differential image motion monitor placed on top of an 8.5 m high tower is 1.3“ +/- 0.8”.
Keywords: Site Testing
Programme: 908
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Aghajari N., Feller G., Gerday C. & Haser R. (2002). Structural basis of a alpha-amylase activation by chloride. Protein Sci., 11, 1435–1441.
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Aghajari N., Feller G., Gerday C. & Haser R. (1996). Crystallization and preliminary X-ray diffraction studies of a-amylase from the antarctic psychrophile Alteromonas haloplanctis A25. Protein Sci., 5, 2128–2129.
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Aghajari N., Feller G., Gerday C. & Haser R. (1998). Structures of the psychrophilic Alteromonas halop Ch. lanctis alpha-amylase give insights into cold adaptation at molecular level. Structure, 6, 1503–1516.
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Aghajari N., Feller G., Gerday C. & Haser R. (1998). Crystal structures of the psychrophilic amylases from Alteromonas haloplanctis in its native form and complexed with an inhibitor. Protein Sci., 7, 564–572.
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Aghajari N., Van Petegem F., Villeret V., Chessa J.P., Gerday C., Haser R. & VanBeeumen J. (2003). Crystal structures of a psychrophilic metalloprotease reveal new insights into catalysis by cold-adapted proteases. Proteins, 50, 636–647.
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Agnès Baltzer, Marine Bourriquen, Jérôme Fournier-Sowinski, Denis Mercier, S. Costa, Florian Tolle, Eric Bernard, Maria Jensen. (2017). Evolution of prodeltas: a print of glacier melting processes.
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Agnès Chounet, Martin Vallée. (2018). Global and Interregion Characterization of Subduction Interface Earthquakes Derived From Source Time Functions Properties (Vol. 123).
Abstract: Source time functions (STFs) describe how the seismic moment rate is released with time, and carry information on integral rupture properties, such as static stress drop and radiated energy. In this study, we systematically analyze a set of 1,433 STFs extracted from the SCARDEC method (Vallée and Douet, 2016, https://doi.org/10.1016/j.pepi.2016.05.012), containing the Mw≥5.6, shallow (z≤70 km) earthquakes with dip-slip mechanism that occurred between 1992 and 2014. At the global scale, STFs properties indicate scale invariance of stress drop and scaled radiated energy with magnitude. In a second step, these source parameters are investigated in light of the tectonic context of the earthquakes: in agreement with other approaches, we observe that subduction interface earthquakes have lower stress drop and scaled radiated energy relative to all other earthquakes (e.g., crustal earthquakes). Finally, a focus on subduction interface earthquakes (approximately 800 earthquakes) is done by considering 18 regional segments of subduction zones. We find that these segments do not have the same signature in terms of macroscopic rupture properties, which means that large-scale plate convergence and mechanical properties influence rupture behavior. In a given segment, local heterogeneities of stress drop or radiated energy can be associated with local features of the subduction zone: in particular, we find that low coupled zones generate earthquakes with low stress drop and scaled radiated energy. This last feature, also observed at a larger scale, suggests a positive correlation between coupling and stress drop.
Keywords: global earthquake seismology radiated energy seismic coupling source time functions stress drop subduction earthquakes
Programme: 133
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Agnès Lewden. (2017). Stratégies de thermorégulation liées aux contraintes physiologiques et environnementales chez le manchot royal (Aptenodytes patagonicus) (Vol. 203 pp). Ph.D. thesis, , .
Abstract: The energetic cost of foraging activities in King Penguin (Aptenodytes patagonicus) consists to reach favourable areas, realizes depth diving to attempt fish patch and resting in high latitude cold water. Several studies have shown that resting in cold water could be represent a more expensive cost than realized depth diving. Indeed, this paradox is probably linked with contrasting thermoregulation processes. During daylight, a general hypothermia occurs and is believed to reduce energy expenditure. At sunrise occurs a re-warming to normothermia, contributing to increase heat-loss during the night. We hypothesise an energetic conflict between thermoregulation and digestive processes. During daylight, the organism may be unable to assimilate the end product of prey digestion (free fatty acids) inside the peripheral subcutaneous adipose tissues (SAT), because skin is no more blood perfused. During the night, re-warming and re-connecting to blood circulation peripheral tissues could be inevitable to end the assimilation of FFA inside the SAT. In a first step, we have reproduced the conditions of a resting night at sea and events of rewarming skin temperature, using a sea water tank in which king penguins equipped with internal temperature loggers were maintained several days. In a second step, we have tested a generalisation of our hypothesis studying body temperature variations on penguins fast and feed. Finally, we have measured the cost to maintain normothermia in cold water with respirometry measures and investigated peripheral vasodilation with body temperature variations and infrared thermography. Key words: Thermoregulation – Normothermia – Seabirds – Vasodilation – Energetic
Programme: 394
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