02397nas a2200277   4500000000100000000000100001008004100002260000800043653006400051653008200115653006700197653005900264653006600323653002000389653000900409653002100418100001900439700001500458700002400473245009500497856004300592300001100635490000800646520145100654020001402105       2005                            d  bAGU10a3004 Marine Geology and Geophysics: Gas and hydrate systems10a3022 Marine Geology and Geophysics: Marine sediments: processes and transport10a3094 Marine Geology and Geophysics: Instruments and techniques10a5102 Physical Properties of Rocks: Acoustic properties10a5194 Physical Properties of Rocks: Instruments and techniques10amethane hydrate10asand10aseismic velocity1 aJeffrey Priest1 aAngus Best1 aChristopher Clayton00aA laboratory investigation into the seismic velocities of methane gas hydrate-bearing sand  uhttp://dx.doi.org/10.1029/2004JB003259  aB041020 v1103 aRemote seismic methods, which measure the compressional wave (P wave) velocity (V p ) and shear wave (S wave) velocity (V s ), can be used to assess the distribution and concentration of marine gas hydrates in situ. However, interpreting seismic data requires an understanding of the seismic properties of hydrate-bearing sediments, which has proved problematic because of difficulties in recovering intact hydrate-bearing sediment samples and in performing valid laboratory tests. Therefore a dedicated gas hydrate resonant column (GHRC) was developed to allow pressure and temperature conditions suitable for hydrate formation to be applied to a specimen with subsequent measurement of both V p and V s made at frequencies and strains relevant to marine seismic investigations. Thirteen sand specimens containing differing amounts of evenly dispersed hydrate were tested. The results show a bipartite relationship between velocities and hydrate pore saturation, with a marked transition between 3 and 5\% hydrate pore saturation for both V p and V s . This suggests that methane hydrate initially cements sand grain contacts then infills the pore space. These results show in detail for the first time, using a resonant column, how hydrate cementation affects elastic wave properties in quartz sand. This information is valuable for validating theoretical models relating seismic wave propagation in marine sediments to hydrate pore saturation.  a0148-0227