Imaging the P‐Wave Velocity Structure of Arctic Subsea Permafrost Using Laplace‐Domain Full‐Waveform Inversion

Kang, Seung‐Goo; Jin, Young Keun; Jang, Ugeun; Duchesne, Mathieu J.; Shin, Changsoo; Kim, Sookwan; Riedel, Michael; Dallimore, S. R.; Paull, C. K.; Choi, Yong-Hwa; Hong, Jong Kuk

doi:10.1029/2020jf005941

Cited by 8 publications

(2 citation statements)

References 35 publications

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“…Ice‐bonded and partially ice‐bonded states of permafrost both generally hamper this, because the top and bottom boundaries are very reflective and attenuative, respectively. Moreover, because permafrost is often characterized by rapid lateral changes in seismic properties, thickness and distribution, it adds another challenge to the optimization of the parameters of the source (Kang et al., 2021; Pullan et al., 1987).…”

Section: Discussionmentioning

confidence: 99%

Detecting subsea permafrost layers on marine seismic data: An appraisal from forward modelling

Duchesne

Fabien‐Ouellet

Bustamante

2022

Near Surface Geophysics

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Detecting the top and base subsea permafrost from 2D seismic reflection data in shallow marine settings is a non‐trivial task due to the occurrence of strong free surface multiples. The potential to accurately detect permafrost layers on conventional 2D seismic reflection data is assessed through viscoelastic modelling. Reflection imaging of permafrost layers is examined through the evaluation of specific characteristics of the subsurface, acquisition parameters and their impact. Results show that limitations are related to the principles of the method, the intrinsic nature of the permafrost layers, and the acquisition geometry. The biggest challenge is the occurrence of free surface multiples that overprint the base permafrost reflection, with the worst‐case scenario the case of a thin layer of ice‐bonded sand. Wedge models suggest that if the base permafrost is dipping, it would intersect internal and free surface multiples of the seafloor and the top permafrost and be detected. Also, the amplitude ratio of the base permafrost reflection and the multiples decreases with the increasing thickness of permafrost. Therefore, the crosscutting relationship between the reflection at base permafrost reflection and the multiples might not be enough to detect the base permafrost for thicker permafrost layers. Finally, the experiment results show that, for partially ice‐bonded layers, the attenuation combined with the low reflectivity of the basal interface limits the likelihood to resolve the base permafrost, especially for thick permafrost layers.

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Section: Discussionmentioning

confidence: 99%

Detecting subsea permafrost layers on marine seismic data: An appraisal from forward modelling

Duchesne

Fabien‐Ouellet

Bustamante

2022

Near Surface Geophysics

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“…Seismic indications for permafrost and gas hydrates are frequently reported in the literature. Evidence for IBPF in seismic data mainly stems from velocity analyses of refractions (e.g., Brothers et al., 2012; Draebing, 2016; MacAulay & Hunter, 1982; Pullan et al., 1987; Riedel et al., 2016), analysis from stacking velocities (Brothers et al., 2016), inversion applications (e.g., Kang et al., 2021; Ramachandran et al., 2011) or imaging‐effects like an increased reflectivity (Hinz et al., 1998), amplitude anomalies, or travel time pull‐up effects (e.g., Matson et al., 2013; Portnov et al., 2013). Reflections from the top of IBPF were noted, for example, in the Kara and Laptev Sea (Rekant & Vasiliev, 2011; Rekant et al., 2005, 2015).…”

Section: Introductionmentioning

confidence: 99%

Revealing the Extent of Submarine Permafrost and Gas Hydrates in the Canadian Arctic Beaufort Sea Using Seismic Reflection Indicators

Grob

Riedel

Duchesne

et al. 2023

Geochem Geophys Geosyst

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The Canadian Arctic Southern Beaufort Sea is characterized by prominent relict submarine permafrost and gas hydrate occurrences formed by subaerial exposure during extensive glaciations in Pliocene and Pleistocene. Submarine permafrost is still responding to the thermal change as a consequence of the marine transgression that followed the last glaciation. Submarine permafrost is still underexplored and is currently the focus of several research projects as its degradation releases greenhouse gases that contribute to climate change. In this study, seismic reflection indicators are used to investigate the presence of submarine permafrost and gas hydrates on the outer continental shelf where the base of permafrost is expected to cross‐cut geological layers. To address the challenges of marine seismic data collected in shallow water environments, we utilize a representative synthetic model to assess the data processing and the detection of submarine permafrost and gas hydrate by seismic data. The synthetic model allows us to minimize the misinterpretation of acquisition and processing artifacts. In the field data, we identify features along with characteristics arising from the top and base of submarine permafrost and the base of the gas hydrate stability zone. This work shows the distribution of the present submarine permafrost along the southern Canadian Beaufort Sea region and confirms its extension to the outer continental shelf. It supports the general shape suggested by previous works and previously published numerical models.

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Massive Ice Outcrops and Thermokarst Along the Arctic Shelf Edge: By‐Products of Ongoing Groundwater Freezing and Thawing in the Sub‐Surface

Paull,

Hong,

Caress

et al. 2024

JGR Earth Surface

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Substantial seafloor morphological changes are rapidly occurring along the Canadian Arctic shelf edge. Five multibeam bathymetric mapping surveys, each partially covering a 15 km2 study area between 120‐ and 200‐m water depth, were conducted over a 12‐year time period. These surveys reveal that 65 new craters have developed between 2010 and 2022, averaging 6.5 m and reaching up to 30 m deep. Remotely operated vehicle investigations revealed massive ice outcrops exposed on two newly formed crater flanks. This ice is not relict subaerially formed Pleistocene permafrost because it is hosted in sediments which were deposited in a submarine setting post‐deglaciation. Low salinity porewater and sediment core ice samples with depleted oxygen isotopic compositions indicate waters with a meteoric signature are discharging and freezing in this area. These ascending brackish groundwaters are likely derived in part from thawed relict permafrost hundreds of meters under the continental shelf. They refreeze as they approach the −1.4°C seafloor, leading to the development of widespread, near seafloor, sub‐bottom ice layers. Conditions appropriate for ice melting also exist nearby where ice is exposed to seawater or warmed by ascending groundwater. Small variations in temperature and salinity lead to shifts between freezing of ascending brackish groundwater or melting of near seafloor ice layers. These conditions have produced a dramatic submarine thermokarst morphology riddled with multi‐aged depressions. Thermokarst geohazards may exist, unmapped, on other Arctic margins with groundwater channeled toward the shelf edge by a relict permafrost cap, and sufficiently cold shelf edge bottom water temperatures.

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Imaging the P‐Wave Velocity Structure of Arctic Subsea Permafrost Using Laplace‐Domain Full‐Waveform Inversion

Cited by 8 publications

References 35 publications

Detecting subsea permafrost layers on marine seismic data: An appraisal from forward modelling

Detecting subsea permafrost layers on marine seismic data: An appraisal from forward modelling

Revealing the Extent of Submarine Permafrost and Gas Hydrates in the Canadian Arctic Beaufort Sea Using Seismic Reflection Indicators

Massive Ice Outcrops and Thermokarst Along the Arctic Shelf Edge: By‐Products of Ongoing Groundwater Freezing and Thawing in the Sub‐Surface

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