南海海盆东北部内孤立波的地震海洋学研究

Seismic oceanography study of internal solitary waves in the northeastern South China Sea Basin

以往利用地震海洋学方法发现的内孤立波大多在东沙岛附近,本文在南海海盆东北部首次利用地震海洋学方法发现了海盆中的内孤立波.通过叠前偏移观察该内孤立波细结构的变化,发现内孤立波波形在采集时间段内整体较稳定,内孤立波浅层反射相对深层变化较大.通过改进前人的方法,利用共偏移距道集叠前偏移剖面计算内孤立波视相速度.该方法比直接使用共偏移距道集拟合的共中心点-炮点对曲线线性更好,其计算的内孤立波视相速度为0.82m·s^-1,内孤立波视传播方向为从NW向SE(172°N方向,0°指向北).

In previous work,the internal solitary waves(ISWs)discovered by seismic oceanography are mostly near the Dongsha Island.This paper uses the method of seismic oceanography to find the ISWs in the basin for the first time in the northeastern South China Sea.The pre-stack migration is used to examine the changes of the ISWs structure.It is found that the ISWs waveforms are stable overall during the acquisition period.The shallow reflection of the ISWs has a relatively larger change than the deep.By improving the methods of the predecessors,the ISWs apparent phase velocity is calculated by pre-stack migration profile using the Common Offset Gather(COG).The fitting curve of CMP(Common Mid-Point)-shot point pairs using this method has a better linearity than that using Common Offset Gather directly.The apparent phase velocity of this ISWs using the improved method is 0.82 m·s^-1,and the apparent direction of the ISWs propagation is from NW to SE(172°N,0°pointing north).