海南岛西南海底沙波活动及底床冲淤变化

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

为了研究沙波迁移对底床稳定性的影响,通过对比分析2004—2006年连续3年的多波束海底地貌扫描数据,得出研究区域海底沙波的波长为5.8-91.8 m,波高0.1-4.3 m,陡峭度0.013-0.12,对称指数0.32-6.52。沙波的移动速率最大48.8 m/a,移动方向在研究区域西部为SE向,中部呈往复迁移,东部为NW向;沙波不同部位的迁移速率不同,一般的沙波尾翼迁移速率较大;同一组沙波存在反向扭转迁移的现象,反向扭转迁移的轴线位于研究区域沙脊的脊线附近,这种反向迁移不仅与底层流作用有关,还与海底地形关系密切;西部海底底床处于侵蚀状态,局部最大侵蚀量可达1.3 m,东部处于堆积状态,最大堆积量达2.8 m。

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.