HR: 0800h
AN: OS41C-0484    [Abstracts]
TI: Examination of Marine Seismic Reflection Data for the Occurrence and Distribution of Gas Hydrate on the Continental Margin of Fiordland, New Zealand
AU: * Fohrmann, M
EM: fohmi830@student.otago.ac.nz
AF: University of Otago Department of Geology, Department of Geology, P.O. Box 56, Dunedin, 9015 New Zealand
AU: Gorman, A R
EM: andrew.gorman@otago.ac.nz
AF: University of Otago Department of Geology, Department of Geology, P.O. Box 56, Dunedin, 9015 New Zealand
AU: Pecher, I A
EM: i.pecher@gns.cri.nz
AF: Institute of Geological and Nuclear Sciences, P.O. Box 30-368, Lower Hutt, 6009 New Zealand
AB: Evaluation of seismic data on the Fiordland margin reveals a widespread zone of Bottom Simulating Reflections (BSRs) east of the incipient subduction zone. BSRs are most commonly used to infer the presence of gas hydrates in marine sediments. We have compiled the distribution of gas hydrates on the Fiordland margin based on the occurence of BSRs in an extensive database of seismic data, acquired by academic, government and petroleum research cruises over the last 30 years. BSRs can be recognised by a negative reflection-coefficient that occurs at the boundary between shallow sediments that contain gas hydrate and deeper sediments storing free gas. Further, it is characteristic for BSR structures to follow isotherms which are nearly parallel to the morphology of the sea floor. Because methane is the prevalent enclosed gas in hydrates, it becomes an important agent of climate change in the case of fast destablisation of the hydrates. We present seismic observations that suggest that hydrate instability, due to a change in water temperature and/or of hydrostatic pressure, may cause subsea landslides on the continental slope - perhaps triggering tsunamis. Thus, evaluation of the distribution of gas hydrates can contribute to natural hazard prevention. The interest in gas hydrates as a possible resource is increasing due to the vast energy potential of methane, even though the engineering challenges of producing methane from gas hydrates are daunting. Based on the distribution of BSRs, it is therefore possible to calculate the resource potential in the gas hydrate province off Fiordland.
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 0930 Oceanic structures
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting