ACTIVITY OF SUBMARINE SAND WAVES AND SEAFLOOR EROSION AND DEPOSITION IN THE SEA AREA TO THE SOUTHWEST OF HAINAN ISLAND

Sand wave migration has an important effect on seafloor stability.Based on multi-beam system, repetitive submarine micro-geomorphic features from 2004 to 2006 are analyzed to research the relationship between them. The investigated results show that in the study area, the wavelength of sand wave ranges from 5.8 to 91.8 m, wave height from 0.1 to 4.3 m, steepness from 0.013 to 0.12, and symmetry from 0.32 to 6.52. The sand wave migration velocity is up to 48.8 m/a, migration direction is oriented SE in the west of the study area, NW in the east, and to and fro in the middle.The migration velocity varies in different sections, and commonly the end of the sand wave migrates more rapidly. Reverse migration exists in sets of sand waves, and the axis line lies near the crest of the sand ridge, upon which the sand waves are superimposed, indicating that the reverse migration is not only related to bottom current but also to submarine topography. From 2004 to 2006, the seafloor is under erosion in the west and the erosion is up to 1.3 m, while the seafloor is under deposition in the east and the deposition is up to 2.8 m.