This paper presents results of a seismic tomography experiment carried out at the Bullseye cold
vent site offshore Vancouver Island. In the experiment, a seismic air gun survey was recorded on
an array of five ocean bottom seismometers (OBS) deployed around the vent. The locations of the
shots and the OBSs were determined to high accuracy by an inversion based on the shot travel
times. A three-dimensional tomographic inversion was then carried out to determine the velocity
structure around the vent, using the localized source and receiver positions. The inversion
indicates a relatively uniform velocity field around and inside the vent. The velocities are close to
the values expected for sediments containing no hydrate, which supports previous claims that the
bulk concentrations of gas hydrates are low at the site. However, the largest resolved velocity
anomalies of + 25 m/s are spatially within the limits of the acoustic blank zone seen in
multichannel seismic data near the Bullseye vent. The velocity inversion is consistent with zones
of high concentration (15-20 % of the pore space) in the top 50-100 m of sediment.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/1381 |
| Date | 07 1900 |
| Creators | Zykov, Mykhail M., Chapman, N. Ross, Spence, G.D. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Rights | Chapman, N. Ross |
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