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| | Abstract | | Seismic wrap-around multiples which are produced by the previous shot and trapped between sea surface and flat seabed in the two-dimensional (2D) marine seismic reflection data, have a potential to provide information about oceanographic phenomena because their repetition in the water column could influence seismic wave propagation. By focusing on the disturbance of wrap-around multiples, we imply the possible presence of methane gas bubbles emitting from seafloor over several kilo-meters within a submarine canyon with a flat seabed. We observe the significant disturbance of wrap-around multiples in both pre-stacked gathers and common mid-point (CMP) stacked sections, which may be caused by methane bubbles. The existence of a bottom simulating reflector (BSR) implies the existence of methane gas, and the existence of a fault beneath the specific event, which could be a pathway of methane gas flows to the seafloor, provides an indirect evidence of gas bubble seeps. Furthermore, we conduct preliminary numerical simulations of acoustic wave propagation to investigate the cause of disturbances of wrap-around multiples. Our preliminary numerical simulations imply that the disturbance of wrap-around multiples might be associated with the internal scattering caused by an aggregation of gas bubble seeps in the water column. |
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