A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island
International audience Methane hydrate bottom-simulating reflectors (BSRs) are widespread on the northern Cascadia margin offshore Vancouver Island. We conducted a three-dimensional tomographic seismic study of the hydrate stability zone in an area around Ocean Drilling Program Site 889 using two de...
Published in: | Journal of Geophysical Research: Solid Earth |
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Online Access: | https://insu.hal.science/insu-03601110 https://insu.hal.science/insu-03601110/document https://insu.hal.science/insu-03601110/file/Journal%20of%20Geophysical%20Research%20Solid%20Earth%20-%202005%20-%20Hobro%20-%20A%20three%25u2010dimensional%20seismic%20tomographic%20study%20of%20the%20gas.pdf https://doi.org/10.1029/2004JB003477 |
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ftunivparis:oai:HAL:insu-03601110v1 2024-05-19T07:44:02+00:00 A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island Hobro, J. W. D. Minshull, T. A. Singh, S. C. Chand, S. Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) 2005 https://insu.hal.science/insu-03601110 https://insu.hal.science/insu-03601110/document https://insu.hal.science/insu-03601110/file/Journal%20of%20Geophysical%20Research%20Solid%20Earth%20-%202005%20-%20Hobro%20-%20A%20three%25u2010dimensional%20seismic%20tomographic%20study%20of%20the%20gas.pdf https://doi.org/10.1029/2004JB003477 en eng HAL CCSD American Geophysical Union info:eu-repo/semantics/altIdentifier/doi/10.1029/2004JB003477 insu-03601110 https://insu.hal.science/insu-03601110 https://insu.hal.science/insu-03601110/document https://insu.hal.science/insu-03601110/file/Journal%20of%20Geophysical%20Research%20Solid%20Earth%20-%202005%20-%20Hobro%20-%20A%20three%25u2010dimensional%20seismic%20tomographic%20study%20of%20the%20gas.pdf BIBCODE: 2005JGRB.110.9102H doi:10.1029/2004JB003477 http://hal.archives-ouvertes.fr/licences/copyright/ info:eu-repo/semantics/OpenAccess ISSN: 2169-9313 EISSN: 2169-9356 Journal of Geophysical Research : Solid Earth https://insu.hal.science/insu-03601110 Journal of Geophysical Research : Solid Earth, 2005, 110, pp. 639-646. ⟨10.1029/2004JB003477⟩ [SDU]Sciences of the Universe [physics] info:eu-repo/semantics/article Journal articles 2005 ftunivparis https://doi.org/10.1029/2004JB003477 2024-04-30T02:58:07Z International audience Methane hydrate bottom-simulating reflectors (BSRs) are widespread on the northern Cascadia margin offshore Vancouver Island. We conducted a three-dimensional tomographic seismic study of the hydrate stability zone in an area around Ocean Drilling Program Site 889 using two deployments of five ocean bottom hydrophones and air gun shots along a series of closely spaced profiles in various orientations. Further constraints on reflector geometry come from coincident single-channel reflection profiles. Travel times of reflected and refracted phases were inverted with a regularized three-dimensional inversion using perturbation ray tracing through smooth isotropic media for the forward step. The seismic data allow us to constrain the velocity structure in a ∼6 km 2 area around the drill site. Mean velocities range from 1.50 km s -1 at the seabed to 1.84 km s -1 at the BSR, and velocities at Site 889 match well those measured using a vertical seismic profile. At equivalent depths below the seafloor, velocities vary laterally by typically ∼0.15 km s -1 . Close to the seafloor, velocities may be controlled primarily by lithology, but close to the BSR we infer hydrate contents of up to 15% of the pore space from effective medium modeling. The mean hydrate saturation in the well-constrained volume of the velocity model is estimated to be 2.2%. There is no correlation between the seismic velocity above the BSR and the reflection coefficient at the BSR, so the latter is likely controlled primarily by the distribution of free gas beneath the hydrate stability zone. Article in Journal/Newspaper Methane hydrate Université de Paris: Portail HAL Journal of Geophysical Research: Solid Earth 110 B9 |
institution |
Open Polar |
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Université de Paris: Portail HAL |
op_collection_id |
ftunivparis |
language |
English |
topic |
[SDU]Sciences of the Universe [physics] |
spellingShingle |
[SDU]Sciences of the Universe [physics] Hobro, J. W. D. Minshull, T. A. Singh, S. C. Chand, S. A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island |
topic_facet |
[SDU]Sciences of the Universe [physics] |
description |
International audience Methane hydrate bottom-simulating reflectors (BSRs) are widespread on the northern Cascadia margin offshore Vancouver Island. We conducted a three-dimensional tomographic seismic study of the hydrate stability zone in an area around Ocean Drilling Program Site 889 using two deployments of five ocean bottom hydrophones and air gun shots along a series of closely spaced profiles in various orientations. Further constraints on reflector geometry come from coincident single-channel reflection profiles. Travel times of reflected and refracted phases were inverted with a regularized three-dimensional inversion using perturbation ray tracing through smooth isotropic media for the forward step. The seismic data allow us to constrain the velocity structure in a ∼6 km 2 area around the drill site. Mean velocities range from 1.50 km s -1 at the seabed to 1.84 km s -1 at the BSR, and velocities at Site 889 match well those measured using a vertical seismic profile. At equivalent depths below the seafloor, velocities vary laterally by typically ∼0.15 km s -1 . Close to the seafloor, velocities may be controlled primarily by lithology, but close to the BSR we infer hydrate contents of up to 15% of the pore space from effective medium modeling. The mean hydrate saturation in the well-constrained volume of the velocity model is estimated to be 2.2%. There is no correlation between the seismic velocity above the BSR and the reflection coefficient at the BSR, so the latter is likely controlled primarily by the distribution of free gas beneath the hydrate stability zone. |
author2 |
Institut de Physique du Globe de Paris (IPGP) Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Hobro, J. W. D. Minshull, T. A. Singh, S. C. Chand, S. |
author_facet |
Hobro, J. W. D. Minshull, T. A. Singh, S. C. Chand, S. |
author_sort |
Hobro, J. W. D. |
title |
A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island |
title_short |
A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island |
title_full |
A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island |
title_fullStr |
A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island |
title_full_unstemmed |
A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island |
title_sort |
three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore vancouver island |
publisher |
HAL CCSD |
publishDate |
2005 |
url |
https://insu.hal.science/insu-03601110 https://insu.hal.science/insu-03601110/document https://insu.hal.science/insu-03601110/file/Journal%20of%20Geophysical%20Research%20Solid%20Earth%20-%202005%20-%20Hobro%20-%20A%20three%25u2010dimensional%20seismic%20tomographic%20study%20of%20the%20gas.pdf https://doi.org/10.1029/2004JB003477 |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_source |
ISSN: 2169-9313 EISSN: 2169-9356 Journal of Geophysical Research : Solid Earth https://insu.hal.science/insu-03601110 Journal of Geophysical Research : Solid Earth, 2005, 110, pp. 639-646. ⟨10.1029/2004JB003477⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1029/2004JB003477 insu-03601110 https://insu.hal.science/insu-03601110 https://insu.hal.science/insu-03601110/document https://insu.hal.science/insu-03601110/file/Journal%20of%20Geophysical%20Research%20Solid%20Earth%20-%202005%20-%20Hobro%20-%20A%20three%25u2010dimensional%20seismic%20tomographic%20study%20of%20the%20gas.pdf BIBCODE: 2005JGRB.110.9102H doi:10.1029/2004JB003477 |
op_rights |
http://hal.archives-ouvertes.fr/licences/copyright/ info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.1029/2004JB003477 |
container_title |
Journal of Geophysical Research: Solid Earth |
container_volume |
110 |
container_issue |
B9 |
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1799483785720365056 |