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Registros recuperados: 10
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A joint electromagnetic and seismic study of an active pockmark within the hydrate stability field at the Vestnesa Ridge, West Svalbard margin ArchiMer
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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Fine-scale gas distribution in marine sediments assessed from deep-towed seismic data ArchiMer
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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Gas and seismicity within the Istanbul seismic gap ArchiMer
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...
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Ano: 2018 URL: https://archimer.ifremer.fr/doc/00439/55072/56500.pdf
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How wide is the seismogenic zone of the Lesser Antilles forearc? ArchiMer
Gutscher, Marc-andre; Westbrook, Graham; Marcaillou, Boris; Graindorge, David; Gailler, Audrey; Pichot, Thibaud; Maury, Rene.
The Lesser Antilles subduction zone has produced no recent strong thrust earthquakes, making it difficult to quantify the seismic hazard from such events. The Lesser Antilles arc has a low subduction rate and an accretionary wedge that is very wide at its southern end. To investigate the effect of the wedge on seismogenesis, numerical models of forearc thermal structure were constructed along six transects perpendicular to the arc in order to determine the thermally predicted width of the seismogenic zone. The geometry of each section is constrained by published seismic profiles and crustal models derived from gravity and seismic data and by earthquake hypocenters at depth. A major constraint on the deep part of the model is that mantle temperature beneath...
Tipo: Text Palavras-chave: Zone sismogène; Séisme chevauchant; Modélisation thermique; Prisme d’accrétion; Petites Antilles; Seismogenic zone; Thrust earthquake; Thermal modeling; Accretionary wedge; Lesser Antilles.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00140/25140/29432.pdf
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Leaking methane reservoirs offshore Svalbard ArchiMer
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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Methane in shallow subsurface sediments at the landward limit of the gas hydrate stability zone offshore Western Svalbard ArchiMer
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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Methane release from warming-induced hydrate dissociation in the West Svalbard continental margin: Timing, rates, and geological controls ArchiMer
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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Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope ArchiMer
Goswami, Bedanta K.; Weitemeyer, Karen A.; Minshull, Timothy A.; Sinha, Martin C.; Westbrook, Graham; Marin-moreno, Hector.
The Arctic continental margin contains large amounts of methane in the form of methane hydrates. The west Svalbard continental slope is an area where active methane seeps have been reported near the landward limit of the hydrate stability zone. The presence of bottom simulating reflectors (BSR) on seismic reflection data in water depths greater than 600 m suggests the presence of free gas beneath gas hydrates in the area. Resistivity obtained from marine controlled source electromagnetic (CSEM) data provides a useful complement to seismic methods for detecting shallow hydrate and gas as they are more resistive than surrounding water saturated sediments. We acquired two CSEM lines in the west Svalbard continental slope, extending from the edge of the...
Tipo: Text Palavras-chave: Electrical properties; Marine electromagnetics; Gas and hydrate systems; Arctic region.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00350/46081/45740.pdf
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Slip rate estimation along the western segment of the Main Marmara Fault over the last 405–490 ka by correlating mass transport deposits ArchiMer
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...
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Ano: 2013 URL: http://archimer.ifremer.fr/doc/00169/28074/26289.pdf
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Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data ArchiMer
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
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00372/48348/48515.pdf
Registros recuperados: 10
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