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Seismic anisotropy in gas‐hydrate‐ and gas‐bearing sediments on the Blake Ridge, from a walkaway vertical seismic profile
Author(s) -
Pecher Ingo A.,
Holbrook W. Steven,
Sen Mrinal K.,
Lizarralde Daniel,
Wood Warren T.,
Hutchinson Deborah R.,
Dillon William P.,
Hoskins Hartley,
Stephen Ralph A.
Publication year - 2003
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2003gl017477
Subject(s) - clathrate hydrate , anisotropy , geology , ridge , isotropy , submarine pipeline , transverse isotropy , vertical seismic profile , mineralogy , sediment , seismic anisotropy , seabed , hydrate , bearing (navigation) , petrology , seismology , geophysics , geotechnical engineering , geomorphology , oceanography , chemistry , optics , paleontology , physics , cartography , organic chemistry , mantle (geology) , geography
We present results from an analysis of anisotropy in marine sediments using walkaway vertical seismic profiles from the Blake Ridge, offshore South Carolina. We encountered transverse isotropy (TI) with a vertical symmetry axis in a gas‐hydrate‐bearing unit of clay and claystone with Thomsen parameters ε = 0.05 ± 0.02 and δ = 0.04 ± 0.06. TI increased to ε = 0.16 ± 0.04 and δ = 0.19 ± 0.12 in the underlying gas zone. Rock physics modeling suggests that the observed TI is caused by a partial alignment of clay particles rather than high‐velocity gas‐hydrate veins. Similarly, the increase of TI in the gas zone is not caused by thin low‐velocity gas layers but rather, we speculate, by the sharp contrast between seismic properties of an anisotropic sediment frame and elongated gas‐bearing pore voids. Our results underscore the significance of anisotropy for integrating near‐vertical and wide‐angle seismic data.