Controls on the formation and stability of gas hydrate‐related bottom‐simulating reflectors (BSRs): A case study from the west Svalbard continental slope

Haacke, R.; Westbrook, G. K.; Riley, Michael S.

doi:10.1029/2007jb005200

Cited by 50 publications

(62 citation statements)

References 87 publications

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“…Heterogeneity of the hydrate layer is not considered in this study for lack of coring data or profiles. Sediment porosity, 8 = 0.55, reflects deeper locations further offshore [Haacke et al, 2008], and an intrinsic sediment permeability of k = 10 À15 m 2 (1 mD) is representative of unconsolidated ocean sediments and similar to previously simulated arctic scenarios [Reagan and Moridis, 2008]. Other physical properties of the sediments and porous-media system are summarized elsewhere [Reagan and Moridis, 2008]; however, this work uses a full 2-D representation of the model system.…”

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confidence: 99%

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Large‐scale simulation of methane hydrate dissociation along the West Spitsbergen Margin

Reagan

Moridis

2009

Geophysical Research Letters

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[1] Vast quantities of methane are trapped in oceanic hydrate deposits, and there is concern that a rise in the ocean temperature will induce dissociation of these hydrate accumulations, potentially releasing large amounts of methane into the atmosphere. The recent discovery of active methane gas venting along the landward limit of the gas hydrate stability zone (GHSZ) on the shallow continental slope west of Spitsbergen could be an indication of this process, if the source of the methane can be confidently attributed to dissociating hydrates. In the first large-scale simulation study of its kind, we simulate shallow hydrate dissociation in conditions representative of the West Spitsbergen margin to test the hypothesis that the observed gas release originated from hydrates. The simulation results are consistent with this hypothesis, and are in remarkable agreement with the recently published observations. They show that shallow, low-saturation hydrate deposits, when subjected to temperature increases at the seafloor, can release significant quantities of methane, and that the releases will be localized near the landward limit of the top of the GHSZ. These results indicate the possibility that hydrate dissociation and methane release may be both a consequence and a cause of climate change.

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“…[7] The initial conditions involve a geothermal gradient of 8.7°C/100 m as taken from measurements further downslope [Haacke et al, 2008], 3.5 wt% initial salinity, and a uniform initial hydrate saturation of 3% between z = À5 m and the base of the GHSZ. Heterogeneity of the hydrate layer is not considered in this study for lack of coring data or profiles.…”

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confidence: 99%

Large‐scale simulation of methane hydrate dissociation along the West Spitsbergen Margin

Reagan

Moridis

2009

Geophysical Research Letters

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“…The presence of gas-hydrate in the submarine sediment could vary its physical properties. The gas-hydrate dissociation induced by the human or non-human activities, such as gas hydrate exploration, change of temperature, pressure and sea level, etc., may weaken the marine sedimentary strength and cause serious slope instability problems (Kayen and Lee 1991;Sultan et al 2004;Mienert et al 2005;Haacke et al 2008). In addition, the SW Taiwan lies at the northern termination of the Manila Trench active tectonic zone and is affected by the present-day geodynamic processes (Lin et al 2008(Lin et al , 2009.…”

Section: Introductionmentioning

confidence: 99%

Seismic site response of submarine slope offshore southwestern Taiwan

Lin¹,

Chen²,

Su³

et al. 2018

Terr. Atmos. Ocean. Sci.

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Widely distributed Bottom-Simulating Reflectors (BSRs) have been observed in the area offshore of southwestern Taiwan where the active accretionary complex meets with the passive China continental margin. In order to clarify the link between seismic site response and sedimentary properties of submarine slope, we evaluate the response of seafloor sediments in regard to passive dynamic loads. The local site effect produced by shallow marine sediments was characterized by estimating the horizontal-to-vertical (H/V) spectral ratios of data recorded by the short-period Ocean Bottom Seismometers (OBSs). The results show that the maximal H/V ratios appeared in the range of 3.66 -9.28 Hz, suggesting that the fundamental frequency is dominated by the effect related to the very shallow sediments. For most stations, the H/V ratios estimated based on the earthquakes and noise records were characterized by different patterns. Relatively broad H/V pattern was obtained when the signals were extracted from earthquakes. This phenomenon may be related to soil nonlinearity when a stronger motion applies. In comparison with the available geological structures and bulk density distribution obtained from coring experiments, we found a relatively higher fundamental frequency of about 8 -9 Hz for the more rigid material, such as mud diapir and folding axes. For most of the area along the slope, the fundamental frequency shows a relatively low value, about 6 -8 Hz. Finally, when a site is characterized by thick or lowest bulk density sedimentary layer, we observed a fundamental frequency lower than 5 Hz, which is the lowest in our assessment.

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“…It represents the boundary between gas hydrates and free gas [7,15]. In the gas-filled zone, if there is any below the hydrates, P-wave velocities decrease [16,17].…”

Section: Introductionmentioning

confidence: 99%

Indications for the Occurrence of Gas Hydrates in the Fram Strait from Heat Flow and Multichannel Seismic Reflection Data

Geissler

Pulm

Jokat

et al. 2014

Journal of Geological Research

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The distribution of gas hydrates recently raised increased attention, especially along glaciated continental margins, due to its potential importance for slope stability and global climate. We present new heat flow data together with multichannel reflection seismic data from the central Fram Strait in-between Northeast Greenland and Svalbard. This area is only accessible by icebreaking vessels, and, therefore, knowledge about this area is still sparse. The new heat flow data concur with previous measurements in the region. High temperature gradients of >200 mK/m were recorded along the active spreading zone in the Fram Strait, and gradients of 75 mK/m along the western slope of Yermak Plateau. Along the Northeast Greenland slope, the measured gradients reach 54 mK/m at maximum. Seismic data image bottom-simulating reflections proofing that the known gas-hydrate province spreads much further north along the western slope of the Yermak Plateau than previously known. Existing slide scars indicate that there might be a causal relationship between the occurrence of gas hydrates and slope instability in that area. Along the Northeast Greenland continental margin and in the adjacent abyssal plain, strong indications for the occurrence of gas within the sedimentary basins and for its migration along fault zones and chimney-like structures are found.

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Controls on the formation and stability of gas hydrate‐related bottom‐simulating reflectors (BSRs): A case study from the west Svalbard continental slope

Cited by 50 publications

References 87 publications

Large‐scale simulation of methane hydrate dissociation along the West Spitsbergen Margin

Large‐scale simulation of methane hydrate dissociation along the West Spitsbergen Margin

Seismic site response of submarine slope offshore southwestern Taiwan

Indications for the Occurrence of Gas Hydrates in the Fram Strait from Heat Flow and Multichannel Seismic Reflection Data

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