THE MICROTOPOGRAPHIC FEATURES AND GAS SEEP MODEL ON THE SLOPE IN THE NORTHEASTERN SOUTH CHINA SEA

Submarine gas seepage is rather popular in marine environment. It has been found almost in all the oceans. Submarine gas seep could greatly alter the seafloor topography and produce the seeping-related microtopographies. Submarine gas seepage is an indicator of gas hydrate occurrence. Shallowly buried gas hydrate always occur in submarine gas seepage areas. Sub-bottom profiles,multi-beam geomorphologic data, and seismic data on the slope in northeastern South China Sea were interpreted together, and pockmarks, submarine domes, Large-scale submarine hummocks, Mud volcanoes and Authigenic carbonate mounds were identified. Our studies show that the pockmark may indicate a thin-bed and high-speed gas seepagee, the submarine dome or large-scale submarine hummock may indicate a thin-bed and midium-speed gas seepage, and the mud volcano may indicate a thick-bed and high-speed gas seeage. Submarine domes together with acoustic blank indicate the areas where gas accumulated in shallow strata and may be favorable for formation of the block-hydrate.