中美洲海域第二模态内孤立波的地震海洋学研究  

Seismic oceanography study of mode-2 internal solitary waves offshore Central America

作　　者：范文豪 宋海斌[1] 龚屹 张锟 孙绍箐 FAN WenHao;SONG HaiBin;GONG Yi;ZHANG Kun;SUN ShaoQing(State Key Laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai 200092,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

出　　处：《地球物理学报》2021年第1期195-208,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41976048);全球变化专项国际合作项目“东亚大陆边缘现代地质过程与致灾机理”(GASI-GEOGE-05);国家重点研发计划(2018YFC0310000)资助.

摘　　要：以往利用地震海洋学方法发现的内孤立波大多是第一模态内孤立波,本文利用地震海洋学方法首次在中美洲太平洋沿岸海域发现了第二模态内孤立波群.通过叠前偏移观察该第二模态内孤立波群细结构的变化,发现位于陆坡上的第二模态内孤立波ISW4在大约50 s的采集过程中,出现反射同相轴分叉、合并以及密跃层中心深度变化.利用共偏移距道集叠前偏移剖面计算的这些第二模态内孤立波视相速度在0.5 m·s^-1左右,其视传播方向都是沿地震测线从SW到NE(44°N方向,0°指向北).通过对视相速度误差相对较小的三个第二模态内孤立波(ISW1、ISW3和ISW5)的视相速度进行分析,发现总体上第二模态内孤立波视相速度随着水深的增加而增加,另外一般情况下具有较大最大振幅的第二模态内孤立波的视相速度较大.In previous work,most of the internal solitary waves(ISWs)found by seismic oceanography were mode-1 ISWs.In this study,mode-2 ISWs group was found for the first time in the Pacific coast of Central America using seismic oceanography.Observation to changes in the fine structure of mode-2 ISWs group through pre-stack migration found that as to the mode-2 ISWs ISW4 located on the continental slope,during the acquisition of about 50 seconds,the bifurcation and merger of the reflection events appear and the mid-depths of the pycnocline change.The apparent phase speeds of these mode-2 ISWs calculated by the pre-stack migration profile using the Common Offset Gather(COG)are about 0.5 m·s^-1,and their apparent propagation directions are from SW to NE along the seismic line(44°N,0°pointing north).Analysis of the apparent phase speeds of the three mode-2 ISWs(ISW1,ISW3,and ISW5)with relatively small apparent phase speed errors found that the apparent phase speed of mode-2 ISWs generally increases with the increasing depth of water.In addition,the apparent phase speed of the mode-2 ISWs with a larger maximum amplitude is generally larger.

关 键 词：地震海洋学 第二模态内孤立波 中美洲太平洋沿岸 结构特征 传播特征 

分 类 号：P738[天文地球—海洋地质] P631[天文地球—海洋科学]