14 research outputs found

    Quantifying Coseismic normal fault rupture at the seafloor: the 2004 Les Saintes Earthquake (Mw 6.3) along the Roseau Fault (French Antilles)

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    While >70% of Earth’s seismicity is submarine, almost all observations of earthquake-related ruptures and surface deformation are restricted to subaerial environments. Such observations are critical for understanding fault behavior and associated hazards (including tsunamis), but are not routinely conducted at the seafloor due to obvious constraints. During the 2013 ODEMAR cruise we used autonomous and remotely operated vehicles to map the Roseau normal Fault (Lesser Antilles), source of the 2004 Mw6.3 earthquake and associated tsunami (<3.5m run-up). These vehicles acquired acoustic (multibeam bathymetry) and optical data (video and electronic images) spanning from regional (>1 km) to outcrop (<1 m) scales. These high-resolution submarine observations, analogous to those routinely conducted subaerially, rely on advanced image and video processing techniques, such as mosaicking and structure-from-motion (SFM).We identify sub-vertical fault slip planes along the Roseau scarp, displaying coseismic deformation structures undoubtedly due to the 2004 event. First, video mosaicking allows us to identify the freshly exposed fault plane at the base of one of these scarps. A maximum vertical coseismic displacement of ~0.9 m can be measured from the video-derived terrain models and the texture-mapped imagery, which have better resolution than any available acoustic systems (<10 cm). Second, seafloor photomosaics allow us to identify and map both additional sub-vertical fault scarps, and cracks and fissures at their base, recording hangingwall damage from the same event. These observations provide critical parameters to understand the seismic cycle and long-term seismic behavior of this submarine fault.Our work demonstrates the feasibility of extensive, high-resolution underwater surveys using underwater vehicles and novel imaging techniques, thereby opening new possibilities to study recent seafloor changes associated with tectonic, volcanic, or hydrothermal activity

    Laccase/HBT and laccase-CBM/HBT treatment of softwood kraft pulp: impact on pulp bleachability and physical properties

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    Pycnoporus cinnabarinus laccase and a chimeric laccase-CBM were applied in softwood kraft pulp biobleaching in the presence of 1-hydroxybenzotriazole (HBT). The presence of CBM could enhance the laccase biobleaching potential as a decrease in the enzymatic charge and chlorine dioxide consumption, as well as an increase in pulp brightness were observed. Laccase/HBT treatment could be improved by increasing oxygen pressure from 1 to 3bar and pulp consistency from 5% to 10%. Conversely, under the same conditions, no improvement of laccase-CBM/HBT treatment was observed, indicating a different behavior of both systems. However, laccase-CBM/HBT treatment led to a better preservation of pulp properties. This effect was probably due to fiber surface modifications involving the action of the CBM. Transmission electron microscopy examination of pulp fibers indicated a retention of laccase-CBM inside the pulp fibers due to CBM binding and an increased external microfibrillation of the fibers due to enzymatic treatments

    Seafloor earthquake ruptures and mass wasting from the 2004 Mw 6.3 Les Saintes submarine earthquake

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    Abstract The seismic hazard posed by submarine faults and the capacity of submarine earthquakes to trigger mass wasting are poorly understood because we lack detailed characterizations of coseismic ruptures at the seafloor. Here, we present comprehensive mapping of a seafloor rupture caused by the 2004 M w 6.3 Les Saintes earthquake on the Roseau normal fault in the Lesser Antilles. We report the visual characteristics, displacement profile, and note pronounced asymmetry of the rupture that bears similarities with well-studied subaerial normal fault ruptures. We also identify footwall-derived mass wasted debris that locally cover the coseismic rupture, and show that ground accelerations of 0.1–0.2 g can trigger submarine mass wasting events in well consolidated bedrock along unstable, over-steepened, scarps. Our study demonstrates the potential of underwater vehicles for detailed mapping of seafloor ruptures and hints at a key role for earthquakes in shaping submarine bedrock landscapes by triggering mass wasting events

    Cohort Creation and Visualization Using Graph Model in the PREDIMED Health Data Warehouse

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    International audienceGrenoble Alpes University Hospital (CHUGA) is currently deploying a health data warehouse called PREDIMED [1], a platform designed to integrate and analyze for research, education and institutional management the data of patients treated at CHUGA. PREDIMED contains healthcare data, administrative data and, potentially, data from external databases. PREDIMED is hosted by the CHUGA Information Systems Department and benefits from its strict security rules. CHUGA’s institutional project PREDIMED aims to collaborate with similar projects in France and worldwide. In this paper, we present how the data model defined to implement PREDIMED at CHUGA is useful for medical experts to interactively build a cohort of patients and to visualize this cohort

    First direct observation of coseismic slip and seafloor rupture along a submarine normal fault and implications for fault slip history

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    Properly assessing the extent and magnitude of fault ruptures associated with large earthquakes is critical for understanding fault behavior and associated hazard. Submarine faults can trigger tsunamis, whose characteristics are defined by the geometry of seafloor displacement, studied primarily through indirect observations (e.g., seismic event parameters, seismic profiles, shipboard bathymetry, coring) rather than direct ones. Using deep-sea vehicles, we identify for the first time a marker of coseismic slip on a submarine fault plane along the Roseau Fault (Lesser Antilles), and measure its vertical displacement of ∌0.9 m in situ. We also map recent fissuring and faulting of sediments on the hangingwall, along ∌3 km of rupture in close proximity to the fault's base, and document the reactivation of erosion and sedimentation within and downslope of the scarp. These deformation structures were caused by the 2004 Mw 6.3 Les Saintes earthquake, which triggered a subsequent tsunami. Their characterization informs estimates of earthquake recurrence on this fault and provides new constraints on the geometry of fault rupture, which is both shorter and displays locally larger coseismic displacements than available model predictions that lack field constraints. This methodology of detailed field observations coupled with near-bottom geophysical surveying can be readily applied to numerous submarine fault systems, and should prove useful in evaluating seismic and tsunamigenic hazard in all geodynamic contexts

    Spatial synchronies in the seasonal occurrence of larvae of oysters (Crassostrea gigas) and mussels (Mytilus edulis/galloprovincalis) in European coastal waters

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