IMAGING OF REFLECTION MOHO IN THE SOUTHWEST SUB-BASIN OF SOUTH CHINA SEA AND ITS GEOLOGICAL IMPLICATIONS

Deep crust structure is important to understand the dynamic origin of a marginal sea basin. However, reflection Moho has been poorly imaged in the Southwest Sub-basin of the South China Sea so far. So we reprocessed a portion of the seismic line NH973-1, which was collected with a 6 km streamer, to improve the Moho imaging. This data is rich of peg-leg multiples, thus the Moho is masked. For this, Parabolic Radon transform filtering is firstly applied to suppress the peg-leg multiples to get a initial velocity of the deep reflections. Then, velocity filtering and inner muting are carried out to further attenuate the multiples. Consequently, peg-leg multiples are attenuated effectively, and the discontinuous strong reflections, likely Moho, appear clearly. The interpreted crust (except sediments) is about 2.3 to 3.9 km thick, which is different from the normal oceanic crust, but more like the crust created by tectonic dominated seafloor spreading.