Seismic tomography study of a bottom simulating reflector off the South Shetland Islands (Antarctica)
Tinivella, U.; Lodolo, E.; Camerlenghi, A.; Boehm, G. (1998). Seismic tomography study of a bottom simulating reflector off the South Shetland Islands (Antarctica), in: Henriet, J.-P. et al. Gas hydrates: relevance to world margin stability and climate change. Geological Society Special Publication, 137: pp. 141-151. https://dx.doi.org/10.1144/GSL.SP.1998.137.01.11 In: Henriet, J.-P.; Mienert, J. (1998). Gas hydrates: Relevance to world margin stability and climate change. Geological Society Special Publication, 137. The Geological Society: London. ISBN 1-86239-010-X. 338 pp., more In: Hartley, A.J. et al. (Ed.) Geological Society Special Publication. Geological Society of London: Oxford; London; Edinburgh; Boston, Mass.; Carlton, Vic.. ISSN 0305-8719; e-ISSN 2041-4927, more |
| Keywords | Chemical compounds > Organic compounds > Hydrocarbons > Gas hydrates
Plate margins
Reflection
Reflection > Seismic reflection
PSW, Antarctica, South Shetland I. [Marine Regions]
Marine/Coastal |
| Authors | | Top | - Tinivella, U.
- Lodolo, E.
- Camerlenghi, A.
- Boehm, G.
| | |
| Abstract | Reflection tomography techniques have been applied to two multi-channel seismic profiles, acquired across the accretionary prism of the South Sheltand margin, in order to reconstruct the velocity field associated with gas hydrate and free gas layers in the sedimentary sequence. Data show the presence of a strong bottom simulating reflector (BSR), running along the slope in water depths ranging from 1000 to 4600 m, locally underlain by a weak normal polarity reflector about 80 ms deeper in the section. The analysis indicates a velocity trend from the sea floor to the BSR generally consistent with that of normally compacted marine sediments, with an abrupt decrement between the BSR and the underlying reflector, indicating the presence of free gas in the sediment pore spaces. The calculated thickness of this gas-bearing layer is approximately 50 m. Local increments of tomographic velocity above the BSR can be related either to gas hydrate abundances in normally compacted slope basin sediments or to overcompaction in accreted sediments, as imaged by the pre-stack depth migrated sections. We conclude that clathrates and free gas distribution on the South Shetland continental slope are strongly controlled by the structural setting of the accretionary prism, where faults act as conduits for migration of natural gas towards the surface. A brief description of the adopted tomography method is also presented. |
|
