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| Registros recuperados: 10 | |
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| Goswami, Bedanta K.; Weitemeyer, Karen A.; Minshull, Timothy A.; Sinha, Martin C.; Westbrook, Graham; Chabert, Anne; Henstock, Timothy J.; Ker, Stephan. |
| We acquired coincident marine controlled-source electromagnetic (CSEM), high-resolution seismic reflection and ocean-bottom seismometer (OBS) data over an active pockmark in the crest of the southern part of the Vestnesa Ridge, to estimate fluid composition within an underlying fluid-migration chimney. Synthetic model studies suggest resistivity obtained from CSEM data can resolve gas or hydrate saturation greater than 5% within the chimney. Acoustic chimneys imaged by seismic reflection data beneath the pockmark and on the ridge flanks, were found to be associated with high-resistivity anomalies (+2-4 m). High-velocity anomalies (+0.3 km/s), within the gas hydrate stability zone (GHSZ) and low-velocity anomalies (-0.2 km/s) underlying the GHSZ, were also... |
| Tipo: Text |
Palavras-chave: Gas hydrate; Svalbard; CSEM; Saturation; Pockmark; Vestnesa. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00283/39458/37928.pdf |
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| Graves, Carolyn A.; James, Rachael H.; Sapart, Celia Julia; Stott, Andrew W.; Wright, Ian C.; Berndt, Christian; Westbrook, Graham; Connelly, Douglas P.. |
| Offshore western Svalbard plumes of gas bubbles rise from the seafloor at the landward limit of the gas hydrate stability zone (LLGHSZ; ∼400 m water depth). It is hypothesized that this methane may, in part, come from dissociation of gas hydrate in the underlying sediments in response to recent warming of ocean bottom waters. To evaluate the potential role of gas hydrate in the supply of methane to the shallow subsurface sediments, and the role of anaerobic oxidation in regulating methane fluxes across the sediment-seawater interface, we have characterised the chemical and isotopic compositions of the gases and sediment pore waters. The molecular and isotopic signatures of gas in the bubble plumes (C1/C2+ = 1 × 104; δ13C-CH4 = -55 to -51 ‰; δD-CH4 = -187... |
| Tipo: Text |
Palavras-chave: Methane; Seafloor sediments; Gas hydrate; Offshore Svalbard; Seabed fluxes; Anaerobic oxidation. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00358/46914/46819.pdf |
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| Grall, Celine; Henry, P.; Thomas, Yannick; Westbrook, Graham; Cagatay, M. N.; Marsset, Bruno; Saritas, H.; Cifci, G.; Geli, Louis. |
| [1] High-resolution 3-D seismic data acquired in the Sea of Marmara on the Western High, along the northwestern branch of the North Anatolian Fault (also known as the Main Marmara Fault), shed new light on the evolution of the deformation over the last 500–600 ka. Sedimentary sequences in ponded basins are correlated with glacioeustatic cycles and transitions between marine and low sea/lake environments in the Sea of Marmara. In the 3 × 11 km2 of the 3-D seismic survey, deformation over the last 405–490 ka is localized along the main fault branch and north of it, where N130°–N140° trending normal faults and N40°–N50° folding accommodated strike-slip deformation associated with active argillokinesis. There is some evidence that deformation was more... |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00169/28074/26289.pdf |
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| Thatcher, K. E.; Westbrook, Graham; Sarkar, S.; Minshull, T. A.. |
| Hundreds of plumes of methane bubbles, first observed in 2008, emanate from an area of the seabed off West Svalbard that has become 1 degrees C warmer over the past 30 years. The distribution of the plumes, lying close to and upslope from the present upper limit of the methane hydrate stability zone, indicates that methane in the plumes could come from warming-induced hydrate dissociation, a process commonly invoked as contributing to rapid climate change. We used numerical modeling to investigate the response of hydrate beneath the seabed to changes in bottom-water temperature over periods of up to 1000 years B. P. The delay between the onset of warming and emission of gas, resulting from the time taken for thermal diffusion, hydrate dissociation, and gas... |
| Tipo: Text |
Palavras-chave: Methane hydrate; Gas emission; Arctic warming; Geological controls; Thermal history. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00137/24779/22838.pdf |
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| Geli, Louis; Henry, P.; Grall, Celine; Tary, Jean-baptiste; Lomax, A.; Batsi, Evangelia; Riboulot, Vincent; Cros, Estelle; Gurbuz, C.; Isik, S. E.; Sengor, A. M. C.; Le Pichon, X.; Ruffine, Livio; Dupre, Stephanie; Thomas, Yannick; Kalafat, D.; Bayrakci, G.; Coutellier, Q.; Regnier, Thibaut; Westbrook, Graham; Saritas, H.; Cifci, G.; Cagatay, M. N.; Ozeren, M. S.; Gorur, N.; Tryon, M.; Bohnhoff, M.; Gasperini, L.; Klingelhoefer, Frauke; Scalabrin, Carla; Augustin, Jean-marie; Embriaco, D.; Marinaro, G.; Frugoni, F.; Monna, S.; Etiope, G.; Favali, P.; Becel, A.. |
| Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the “Istanbul seismic gap”) has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5–5 km depth... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00439/55072/56500.pdf |
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| Goswami, Bedanta K.; Weitemeyer, Karen A.; Bunz, Stefan; Minshull, Timothy A.; Westbrook, Graham; Ker, Stephan; Sinha, Martin C.. |
| The Vestnesa Ridge marks the northern boundary of a known submarine gas hydrate province in the west Svalbard margin. Several seafloor pockmarks at the eastern segment of the ridge are sites of active methane venting. Until recently, seismic reflection data was the main tool for imaging beneath the ridge. Coincident controlled source electromagnetic (CSEM), high-resolution two-dimensional (2D) airgun, sweep frequency SYSIF and three-dimensional (3D) p-cable seismic reflection data were acquired at the south-eastern part of the ridge between 2011 and 2013. The CSEM and seismic data contains profiles across and along the ridge, passing several active and inactive pockmarks. Joint interpretation of resistivity models obtained from CSEM and seismic reflection... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00372/48348/48515.pdf |
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| Minshull, T. A.; Westbrook, Graham; Weitemeyer, K. A.; Sinha, M. C.; Goswami, B. K.; Marsset, Bruno. |
| Methane hydrate—a solid substance in which methane is trapped within ice‐like crystals—is stable at low temperatures and high pressures and may be destabilized by ocean warming on both geological and human time scales. Methane is a powerful greenhouse gas, and methane released from hydrate provides a potential positive feedback mechanism in global climate change [e.g., Archer and Buffett, 2005]—in theory, the more methane is released by the hydrates, the warmer the climate gets, causing the ocean to warm and release more methane. However, methane escaping from the seabed is oxidized and dissolved in the ocean, and insufficient methane may reach the atmosphere to affect the climate significantly. Its importance for climate change therefore depends on... |
| Tipo: Text |
Palavras-chave: Methane hydrate; Svalbard; Sea floor; Seismic; Electromagnetic; Arctic. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00451/56262/57832.pdf |
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| Ker, Stephan; Le Gonidec, Y.; Marsset, Bruno; Westbrook, Graham; Gibert, D.; Minshull, T. A.. |
| In the context of seismic imaging of gas/gas-hydrate systems, the fine-scale structure of subseabed gas-related reflections is assessed by taking advantage of the source signature of the deep-towed high-resolution SYSIF seismic device. We demonstrate the value of an original wavelet-based method and associated multiscale seismic attributes, applied to seismic data recently acquired on the western margin of the Arctic archipelago of Svalbard. From analysis in the wavelet domain, we recognize two types of gas-related reflections associated with submetre-scale distribution of gas. We identify a thin gas-charged layer associated with an apparent normal polarity reflection, and we detect gas patches associated with a reverse-polarity bright spot with... |
| Tipo: Text |
Palavras-chave: Wavelet transform; Gas and hydrate systems; Wave propagation; Acoustic properties; Arctic region. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00175/28602/27019.pdf |
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| Registros recuperados: 10 | |
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