南海东北部东沙海域海水层反射特征分析  

Analyzing seismic reflection characteristics of seawater layer in the Dongsha region of the northeastern South China Sea

作　　者：李豪 关永贤[2] 宋海斌[1] 张锟 范文豪 LI Hao;GUAN Yong-xian;SONG Hai-bin;ZHANG Kun;FAN Wen-hao(State Key laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai 200092,China;Key Laboratory of Marine Mineral Resources,Ministry of Natural Resources,Guangzhou Marine Geological Survey,China Geological Survey,Guangzhou 510760,China)

机构地区：[1]海洋地质国家重点实验室,同济大学海洋与地球科学学院,上海200092 [2]自然资源部海底矿产资源重点实验室,广州海洋地质调查局,广州510760

出　　处：《地球物理学进展》2020年第1期303-312,共10页Progress in Geophysics

基　　金：国家重点研发计划(2018YFC0310002);国家自然科学基金(41576047);“全球变化与海气相互作用”专项(GASI-GEOGE-05)资助.

摘　　要：本文基于对南海东北部东沙海域近期采集的多道反射地震资料进行重新处理获得新的地震海洋学数据,分析了该海域内孤立波/内孤立波包、沙丘上方和陡坎附近特殊反射结构特征,从而提供了新的海水层与海底相互作用依据.研究结果表明,除之前已发表文章中地震海洋学资料显示存在的第一模态内孤立波/波包和沙丘上方常见的反射样式-披毛状发射外,地震海洋学资料上还发现了第二模态内孤立波、陡坎上方的上抬型波动反射结构样式.在新的地震海洋学数据中,第一模态内孤立波振幅均小于50 m,宽度上都小于5 km,单个内孤立波的最大振幅约为45 m.内孤立波包的内孤立波振幅都相对较小,均小于40 m,并且与之前不同的是,彼此之间振幅相差不大,没有明显的排列规律.此次地震海洋学数据记录到的第二模态内孤立波,形态较为完整,上层和下层反射的振幅相差不大,在30 m左右;中间层大约在水深130 m位置处,垂向结构的整体大小大于200 m.沙丘上方反射结构普遍存在弱反射层,可能是湍流边界层,并且存在特殊反射样式-披毛状反射.但并不是沙丘上方都存在披毛状反射样式,本文分析它出现在地震海洋学资料上可能是受测线与沙丘走向之间夹角的影响.陡坎区域的水层反射结构则表现为上抬型波动,并常常伴随着同相轴连续性的变化.该波动的大小及反射同相轴的连续性可能取决于陡坎的高度/坡度及水层动力的强度,新数据中出现的一个上抬型波动,高度达20~30 m,它的附近水层还存在一个形态不完整的内孤立波.陡坎附近的水层反射也常常出现弱反射带和小的波动.We reprocess some Multi-Channel Seismic(MCS)data which is acquired recently in the Dongsha region of the northeastern South China Sea and we obtain new seismic oceanography data including the information about seawater layer.According to these new seismic images,we want to provide new evidence about the interaction between seawater layer and sea floor by analyzing some special reflection structures,such as:internal solitary wave or internal solitary wave packets,seawater layer above sand dunes and steep slope(scarp).The research suggest that there are the mode-2 Internal Solitary Wave(ISWs)not just the mode-1 ISWs and a special reflection pattern(hair reflection configuration)usually above sand dunes,meanwhile,the reflection pattern of water column above scarp embodies the elevation fluctuation in the seismic images.In new seismic oceanography data,there are some mode-1 ISWs with amplitudes less than 50 m and wavelength of 1~5 km and the biggest mode-1 ISWs have the amplitude about 45 m.The internal solitary waves packets are not prototypical rank-ordered ISW packets,their soliton amplitudes are smaller than 40 and there is no obvious principle about the rank of the amplitudes.The mode-2 ISWs is well-shaped and its'amplitude is approximate 30 m,the vertical structure height is about 200 m.The reflection configuration of water column above sand dunes usually include weak reflection layer-maybe called turbulent bottom boundary layer,and there is hair reflection configuration that must not appear.Whether there will be hair reflection configuration or not may depend on the angle between the seismic line and the sand dunes.The reflection configurations usually appear up-lift fluctuation,and continuity of the seismic reflections is not good,which is controlled by the height of scarp and the strength of seawater motion.In these new data,we find a special elevation fluctuation whose height is 20~30 m,with a bad-shaped the Internal Solitary Wave(ISW)near it.And there are lots of small waves and weak reflection layer in th

关 键 词：地震海洋学 内孤立波 沙丘 陡坡 南海东北部 

分 类 号：P631[天文地球—地质矿产勘探] P738[天文地球—地质学]