Wood, Warren T.; Holbrook, W. Steven; Hoskins, Hartley (2000): In situ measurements of P-wave attenuation in the methane hydrate- and gas-bearing sediments of the Blake Ridge. Texas A & M University, Ocean Drilling Program, College Station, TX, United States, In: Paull, Charles K., Matsumoto, Ryo, Wallace, Paul J., Black, Nancy R., Borowski, Walter S., Collett, Timothy S., Damuth, John E., Dickens, Gerald R., Egeberg, Per Kristian, Goodman, Kim, Hesse, Reinhard F., Hiroki, Yoshihisa, Holbrook, W. Steven, Hoskins, Hartley, Ladd, John, Lodolo, Emanuele, Lorenson, Thomas D., Musgrave, Robert J., Naehr, Thomas H., Okada, Hisatake, Pierre, Catherine, Ruppel, Carolyn D., Satoh, Mikio, Thiery, Regis, Watanabe, Yoshio, Wehner, Hermann, Winters, William J., Wood, Warren T., Miller, Christine M. (editor), Reigel, Ruth (editor), Proceedings of the Ocean Drilling Program; volume 164; scientific results; gas hydrate sampling on the Blake Ridge and Carolina Rise; covering Leg 164 of the cruises of the drilling vessel JOIDES Resolution, Halifax, Nova Scotia, to Miami, Florida, sites 991-997, 31 October-19 December 1995, 164, 265-272, georefid:2001-025822

Abstract:
Recent drilling on the crest of the Blake Ridge during Ocean Drilling Program Leg 164 has provided an opportunity to compare estimates of attenuation from seismic data with direct samples of hydrate and gas in this region with the objective of using attenuation to remotely quantify hydrate and gas. Hydrate formation at the sediment grain contacts rather than in the pore spaces may significantly decrease the seismic attenuation. Because attenuation may be estimated from single-channel data, it would be more useful in hydrate detection than velocity, which requires more expensive multichannel data. In this analysis both single-channel seismic data and vertical seismic profile (VSP) data were inverted using a spectral modeling technique. For the single-channel data, this was performed using a simulated annealing algorithm, and for VSP data, the model updates were implemented manually. The results from both independent data sets are consistent with each other in each of the hydrate-and gas-stability zones. Values of the quality factor Q for hydrate-bearing sediments fall within the range expected of nonhydrate-bearing, fine-grained marine sediments, ranging from approximately 90 to 600, suggesting that small amounts of hydrate do not significantly affect Q. All values of Q less than approximately 90 were associated with gassy sediments; some were as low as Q = 6. Q within the hydrate stability field changes systematically, reaching a minimum directly below the ridge crest. As expected, Q in the gassy sediments appears to correlate inversely with reflection strength.
Coverage:
West: -75.3245 East: -75.2500 North: 31.5200 South: 31.4600
Relations:
Expedition: 164
Site: 164-994
Site: 164-997
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.164.246.2000 (c.f. for more detailed metadata)
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