| 南海东北部内孤立波包的地震海洋学和遥感研究 |
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| 引用本文： | 邝芸艳,王亚龙,宋海斌,关永贤,范文豪,龚屹,张锟.南海东北部内孤立波包的地震海洋学和遥感研究[J].地球物理学报,2021,64(2):597-611. |
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| 作者姓名： | 邝芸艳 王亚龙 宋海斌 关永贤 范文豪 龚屹 张锟 |
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| 作者单位： | 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;同济大学国家海底科学观测系统项目办公室,上海200092;广州海洋地质调查局,广州510075 |
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| 基金项目： | 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;国家重点研发计划;国家自然科学基金 |
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| 摘 要： | 在南海东北部东沙环礁附近,内孤立波被大量地观测报道.在该地区内孤立波的传播和演化过程仍然存在许多待解决的问题.利用改进的地震海洋学处理方法对2009年夏的一段海洋勘探地震测线进行了重新处理,获得了50 m水深之下的水层反射图像,发现了包含8个内孤立波的下沉型内孤立波包.遥感仪器中分辨率成像光谱仪(MODIS)图像在该段地震测量的3 h内,捕捉到同一个内孤立波包,经处理分析,获得前5个内孤立波的清晰图像.本文采用了两种方法计算内孤立波相速度,方法一是利用不同的叠前共偏移距道集剖面估算内孤立波的视相速度,并根据MODIS图像上内孤立波的传播方向对其进行校正;方法二是利用地震与MODIS图像联测直接获得传播相速度.将这两种方法得到的相速度分别进行对比,发现它们在数值大体一致.地震海洋学剖面可直接获得内孤立波包中8个内孤立波的特征参数,包括振幅、视半高宽和视波间距.该内孤立波包的最大振幅为117 m,最大视半高宽为1020 m,最大视波间距为4100 m.由于地震采集船和内孤立波之间存在类多普勒效应,且二者前进方向存在夹角,所以利用地震与MODIS图像联测得到的传播相速度,结合MODIS图像所推断的内孤立波传播方向对视半高宽和视波间距进行校正.首波的半高宽与遥感估算的特征半波宽的比值是1.75,接近理论比值的1.763;校正后的真波间距和遥感量测波间距数值基本一致.最后,结合地震观测前后的遥感图像和潮流数据推断这一内孤立波包为Type-b型.结果表明,将地震海洋学和遥感方法结合,可以更好地研究内孤立波的特征.
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| 关 键 词： | 地震海洋学 MODIS图像 内孤立波包 内孤立波相速度 内孤立波的特征 |
Study of internal solitary wave packets in the northeastern South China Sea based on seismic oceanography and remote sensing |
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| KUANG YunYan,WANG YaLong,SONG HaiBin,GUAN YongXian,FAN WenHao,GONG Yi,ZHANG Kun.Study of internal solitary wave packets in the northeastern South China Sea based on seismic oceanography and remote sensing[J].Chinese Journal of Geophysics,2021,64(2):597-611. |
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| Authors: | KUANG YunYan WANG YaLong SONG HaiBin GUAN YongXian FAN WenHao GONG Yi ZHANG Kun |
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| Affiliation: | (State Key laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai 200092,China;Guangzhou Marine Geological Survey,Guangzhou 510075,China;Project Management Office of China National Scientific Seafloor Observatory,Tongji University,Shanghai 200092,China) |
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| Abstract: | Numerous Internal Solitary Waves(ISWs)have been observed and reported around the Dongsha Atoll in the northeastern South China Sea.The propagation and evolution processes of ISWs in this area remain debated.Here,a marine seismic exploration line carried out near the Dongsha Atoll in July 2009 is reprocessed by an advanced method of seismic oceanography.After seismic data processing,an internal solitary wave packet containing 8 well-shaped first-mode depression ISWs is identified in the water below depth 50 m.On the same day of seismic exploration,the Moderate-resolution Imaging Spectroradiometer(MODIS)image captured the same ISW packet.After processing of this MODIS image,the first 5 of the ISWs packet were clearly identified.Two methods are used to calculate ISWs phase speeds.According to the first method,the ISWs apparent phase speeds are estimated by pre-stack migration profiles using the Common Offset Gather(COG),then the apparent phase speeds are adjusted in terms of ISWs propagation direction on the MODIS image.While the second method can directly obtain the first 5 ISWs phase speeds by locations and times revealed by seismic data and the MODIS image.The results of these two methods consistent well accordingly.Three waveform characteristic parameters,i.e.amplitude,apparent full width of the trough at half amplitude and apparent wave length,can be directly revealed by the seismic oceanography image.The internal solitary wave packet maximum amplitude is 117 m,maximum apparent full width of the trough at half amplitude is 1020 m,and maximum apparent wave interval is 4100 m.Because of the Doppler-like effect and the angle between ISWs propagation and direction of ship travel,horizontal information provided by the MODIS image and phase speeds calculated by the second method should be considered to correct the last two parameters.The ratio of the first ISW wave maximum full width of the trough at half amplitude to the full width half maximum(estimated by remote sensing)is 1.75,which is close to the theoretical ratio 1.763;the true wave intervals are consistent with the wave intervals estimated by the MODIS image.Finally,MODIS images and tide data gathered before and after seismic observation permit to infer the ISW pocket is Type-b.The results show that the combination of seismic oceanography and remote sensing can help better characterize ISWs. |
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| Keywords: | Seismic oceanography MODIS image Internal solitary wave packet ISWs phase velocity Characteristics of ISWs waveform |
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