The University of Southampton
University of Southampton Institutional Repository

A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island

Record type: Article

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 km2 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.

Full text not available from this repository.

Citation

Hobro, J.W.D., Minshull, T.A., Singh, S.C. and Chand, S. (2005) A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island Journal of Geophysical Research, 110, (B9), B09102-[14pp]. (doi:10.1029/2004JB003477).

More information

Published date: September 2005

Identifiers

Local EPrints ID: 18169
URI: http://eprints.soton.ac.uk/id/eprint/18169
ISSN: 0148-0227
PURE UUID: 35593403-e64f-4bd2-a55f-964cbcbceff4
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

Catalogue record

Date deposited: 06 Dec 2005
Last modified: 17 Jul 2017 16:36

Export record

Altmetrics

Contributors

Author: J.W.D. Hobro
Author: T.A. Minshull ORCID iD
Author: S.C. Singh
Author: S. Chand

University divisions


Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×