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  • 1
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    PANGAEA
    In:  Supplement to: Tréhu, Anne M; Long, Philip E; Torres, Marta E; Bohrmann, Gerhard; Rack, Frank R; Collett, Tim S; Goldberg, D S; Milkov, Alexei V; Riedel, Michael; Schultheiss, P; Bangs, N L; Barr, Samantha R; Borowski, Walter S; Claypool, George E; Delwiche, Mark E; Dickens, Gerald Roy; Gràcia, Eulàlia; Guerin, Gilles; Holland, M; Johnson, J E; Lee, Young-Joo; Liu, C-S; Su, Xin; Teichert, Barbara M A; Tomaru, Hitoshi; Vanneste, M; Watanabe, Mahito; Weinberger, J L (2004): Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: constraints from ODP Leg 204. Earth and Planetary Science Letters, 222(3-4), 845-862, https://doi.org/10.1016/j.epsl.2004.03.035
    Publication Date: 2024-01-09
    Description: Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30–40% of pore space or 20–26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs. Elsewhere, the average gas hydrate content of the sediments in the gas hydrate stability zone is generally 〈2% of the pore space, although this estimate may increase by a factor of 2 when patchy zones of locally higher gas hydrate content are included in the calculation. These patchy zones are structurally and stratigraphically controlled, contain up to 20% hydrate in the pore space when averaged over zones ~10 m thick, and may occur in up to ~20% of the region imaged by 3D seismic data. This heterogeneous gas hydrate distribution is an important constraint on models of gas hydrate formation in marine sediments and the response of the sediments to tectonic and environmental change.
    Keywords: 204-1244B; 204-1244C; 204-1244E; 204-1245A; 204-1245B; 204-1245C; 204-1246A; 204-1246B; 204-1247A; 204-1247B; 204-1248A; 204-1248C; 204-1249A; 204-1249F; 204-1250A; 204-1250C; 204-1250D; 204-1251A; 204-1251B; 204-1251D; 204-1252A; Calculated; Comment; Comment 2 (continued); Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; DRILL; Drilling/drill rig; Elevation of event; Event label; Hydrate; Joides Resolution; Latitude of event; Leg204; Length, difference; Longitude of event; North Pacific Ocean; Number; Ocean Drilling Program; ODP; Recovery; Spacing; Temperature, difference
    Type: Dataset
    Format: text/tab-separated-values, 194 data points
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  • 2
    Publication Date: 2016-01-06
    Description: Log and core data document gas saturations as high as 90% in a coarse-grained turbidite sequence beneath the gas hydrate stability zone (GHSZ) at south Hydrate Ridge, in the Cascadia accretionary complex. The geometry of this gas-saturated bed is defined by a strong, negative-polarity reflection in 3D seismic data. Because of the gas buoyancy, gas pressure equals or exceeds the overburden stress immediately beneath the GHSZ at the summit. We conclude that gas is focused into the coarse-grained sequence from a large volume of the accretionary complex and is trapped until high gas pressure forces the gas to migrate through the GHSZ to seafloor vents. This focused flow provides methane to the GHSZ in excess of its proportion in gas hydrate, thus providing a mechanism to explain the observed coexistence of massive gas hydrate, saline pore water and free gas near the summit.
    Type: Article , PeerReviewed
    Format: text
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  • 3
    Publication Date: 2020-07-10
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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  • 4
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    GSL (Geological Society of London)
    In:  In: Subaqueous Mass Movements and their Consequences: Advances in Process Understanding, Monitoring and Hazard Assessments. , ed. by Georgiopoulou, A. Special Publications Geological Society London, 500 . GSL (Geological Society of London), London, pp. 289-300.
    Publication Date: 2020-07-21
    Description: The development of overpressure in continental margins is typically evaluated with hydrogeological models. Such approaches are used to both identify fluid flow patterns and to evaluate the development of high pore pressures within layers with particular physical properties that may promote slope instability. In some instances, these models are defined with sediment properties based on facies characterization and proxy values of porosity, permeability or compressibility are derived from the existing literature as direct measurements are rarely available. This study uses finite-element models to quantify the differences in computed overpressure generated by fine-grained hemipelagic sediments from Gulf of Cadiz, offshore Martinique and Gulf of Mexico, and their consequences in terms of submarine slope stability. By comparing our simulation results with in-situ pore pressure data measured in the Gulf of Mexico, we demonstrated that physical properties measured on volcanic-influenced hemipelagic sediments underestimate the computed stability of a submarine slope. Physical properties measured on sediments from the study area are key to improving the reliability and accuracy of overpressure models, and when that information is not available literature data from samples with similar lithologies, composition and depositional settings enable better assessment of the overpressure role as a pre-conditioning factor in submarine landslide initiation.
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 5
    Publication Date: 2021-05-12
    Description: The H2020 Project SERA (WP25-JRA3; http://www.sera-eu.org) is committed to updating and extending the 2013 European Seismic Hazard Model (ESHM13; Woessner et al., 2015, Bull. Earthquake Eng.) to form the basis of the next revision of the European seismic design code (CEN-EC8). Following the probabilistic framework established for ESHM13, the 2020 update (ESHM20) requires a continent-wide seismogenic model based on input from earthquake catalogs, tectonic information, and active faulting. The development of the European Fault-Source Model (EFSM20) fulfills the requirements related to active faulting. EFSM20 has two main categories of seismogenic faults: crustal faults and subduction systems. Crustal faults are meant to provide the hazard model with seismicity rates in a variety of tectonic contexts, including onshore and offshore active plate margins and plate interiors. Subduction systems are meant to provide the hazard model with both slab interface and intraslab seismicity rates. The model covers an area that encompasses a buffer of 300 km around all target European countries (except for Overseas Countries and Territories, OTCs), and a maximum of 300 km depth for slabs. The compilation of EFSM20 relies heavily on publicly available datasets and voluntarily contributed datasets spanning large regions, as well as solicited local contributions in specific areas of interest. The current status of the EFSM20 compilation includes 1,256 records of crustal faults for a total length of ~92,906 km and four subduction systems, namely the Gibraltar Arc, Calabrian Arc, Hellenic Arc, and Cyprus Arc. In this contribution, we present the curation of the main datasets and their associated information, the criteria for the prioritization and harmonization across the region, and the main strategy for transferring the earthquake fault-source input to the hazard modelers. The final version of EFSM20 will be made available through standard web services published in the EFEHR (http://www.efehr.org) and EPOS (https://www.seismofaults.eu) platforms adopting FAIR data principles. The SERA project received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No.730900.
    Description: European Union's Horizon 2020 research and innovation programme under grant agreement No.730900
    Description: Published
    Description: Online
    Description: 3T. Sorgente sismica
    Keywords: Seismic Hazard Assessment ; SHA ; Seismogenic fault ; EFSM20 ; SERA ; Solid Earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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