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| | Abstract | | A high-resolution 3D seismic survey with short cables was carried out off Joetsu, Niigata Prefecture, using "SoundArray 3D (SA3D)" System developed by Sound Oceanics, Inc. This survey was conducted to delineate detailed gas chimney structures in which shallow methane hydrates deposit. Additionally 2D lines with a longer cable were also acquired for velocity analysis because SA3D with short cables is not suitable to have accurate velocity structure. The original data were heavily contaminated with swell and induction noises, etc., then a comprehensive noise suppression was applied to eliminate such noises. The footprint noises caused by variation of cable depth and other water column statics were also suppressed to enhance S/N ratio. Thanks to the elaborate processing, a high resolution 3D data volume was obtained and the data have been used to reveal the fine structure of the gas-chimneys and BSR in this region. |
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