Relationship between Shot-Induced Noise and Shot Interval in Seismic Refraction Experiments at Sea     

Herber  R.  Weigel  W.  Wong  H. K. 《Marine Geophysical Researches》1997,19(3):257-265

Seismic noise induced by the seismic source during continuous profiling reduces the signal-to-noise ratio and hence the data quality. This noise is largely dependent on the shot interval. In this paper, the noise amplitude of refraction seismic records from a special experiment is analysed as a function of the shot interval. An empirical exponential relationship between mean peak noise amplitude and shot interval is deduced. By increasing the shot interval, the induced noise can be minimized on all successive records. This results in an improvement of the data, predominantly the signal-to-noise ratio. Because the seismic signal and the shot-induced noise have nearly the same spectra, the chance of improving the signal-to-noise ratio by stacking is significantly reduced.  相似文献   

Recent changes in the winter distribution and movements of northern Atlantic cod (Gadus morhua Linnaeus, 1758) on the Newfoundland-Labrador Shelf     

Kulka  David W.; Wroblewski  J. S.; Narayanan  Savi 《ICES Journal of Marine Science》1995,52(6):889-902

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Seasonal methyltin and (3-dimethylsulphonio)propionate concentrations in leaf tissue of Spartina alterniflora of the Great Bay estuary (NH)     

James H. Weber  Marilyn R. Billings  Anne M. Falke 《Estuarine, Coastal and Shelf Science》1991,33(6)

Concentrations of total recoverable inorganic tin (TRISn), monomethyltin (MeSn³⁺), dimethyltin (Me₂Sn²⁺), trimethyltin (Me₃Sn⁺) and (3-dimethylsulphonio)propionate (DMSP) were determined in leaves of Spartina alterniflora from three sites in the Great Bay estuary (NH) from 8 May to 15 September 1989. Total methyltin concentration increased from 8·9 ng g⁻¹ (fresh weight) on 8 May to 472 ng g⁻¹ on 23 May, decreased to 52 ng g⁻¹ on 7 June and 16ng g⁻¹ on 20 June, and remained low until the last sample on 18 September. Statistical calculations showed that methyltin concentrations varied significantly with sampling week, but not with site. DMSP concentrations showed very different behaviour. During the same sampling period DMSP concentrations varied only from 7·5 to 26 μmol g⁻¹ (fresh weight). DMSP concentrations varied significantly for site, but not sampling week.  相似文献   

Seasonal and interannual variations in the East Sakhalin current revealed by TOPEX/POSEIDON altimeter data     

Naoto Ebuchi 《Journal of Oceanography》2006,62(2):171-183

Seasonal and interannual variations in the East Sakhalin Current (ESC) are investigated using ten-year records of the sea level anomaly (SLA) observed by the TOPEX/POSEIDON (T/P) altimeter. The T/P SLA clearly documents seasonal and interannual variations in the ESC along the east coast of Sakhalin Island, although sea ice masks the region from January to April. Estimates of surface current velocity anomaly derived from T/P SLA are in good agreement with drifting buoy observations. The ESC is strong in winter, with a typical current velocity of 30–40 cm s⁻¹ in December, and almost disappears in summer. Southward flow of the ESC is confined to the shelf and slope region and consists of two velocity cores. These features of the ESC are consistent with short-term observations reported in previous studies. Analysis of the ten-year records of T/P SLA confirms that the structure of the ESC is maintained each winter and the seasonal cycle is repeated every year, although the strength of the ESC shows large interannual variations. Seasonal and interannual variations in the ESC are discussed in relation to wind-driven circulation in the Sea of Okhotsk, using wind stress and wind stress curl fields derived from European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis data and a scatterometer-derived wind product. Seasonal and interannual variations of the anticyclonic eddy in the Kuril Basin are also revealed using T/P SLA.  相似文献   

Metabolites from mangrove endophytic fungus Dothiorella sp.     

XU Qingyan  WANG Jianfeng  HUANG Yaojian  ZHENG Zhonghui  SONG Siyang  ZHANG Yongmin  SU Wenjin 《海洋学报(英文版)》2004,23(3):541-547

Mangroves are special woody plant communities in the intertidal zone of tropical and subtropical coasts. They prove to be a natural microorganisms and new metabolites storage. In the study of mangrove endophytic fungi metabolites, four new compounds, Compounds 1, 2, 3 and 4, as well as a known octaketide, cytosporone B (5), are isolated from an endophytic fungus, Dothiorella sp., HTF3. They all show cytotoxic activities. The elucidation of these structures is mainly based on 1D/2D NMR and ESI-MS spectral analyses.  相似文献   

Variability of organic δC and C/N in the Mersey Estuary, U.K. and its implications for sea-level reconstruction studies     

Graham P. Wilson  Angela L. Lamb  Melanie J. Leng  Silvia Gonzalez  David Huddart 《Estuarine, Coastal and Shelf Science》2005,64(4):685-698

Microfossil analysis (e.g. diatoms, foraminifera and pollen) represents the cornerstone of Holocene relative sea-level (RSL) reconstruction because their distribution in the contemporary inter-tidal zone is principally controlled by ground elevation within the tidal frame. A combination of poor microfossil preservation and a limited range in the sediment record may severely restrict the accuracy of resulting RSL reconstructions. Organic δ¹³C and C/N analysis of inter-tidal sediments have shown some potential as coastal palaeoenvironmental proxies. Here we assess their viability for reconstructing RSL change by examining patterns of organic δ¹³C and C/N values in a modern estuarine environment. δ¹³C and C/N analysis of bulk organic inter-tidal sediments and vegetation, as well as suspended and bedload organic sediments of the Mersey Estuary, U.K., demonstrate that the two main sources of organic carbon to surface saltmarsh sediments (terrestrial vegetation and tidal-derived particulate organic matter) have distinctive δ¹³C and C/N signatures. The resulting relationship between ground elevation within the tidal frame and surface sediment δ¹³C and C/N is unaffected by decompositional changes. The potential of this technique for RSL reconstruction is demonstrated by the analysis of part of an early Holocene sediment core from the Mersey Estuary. Organic δ¹³C and C/N analysis is less time consuming than microfossil analysis and is likely to provide continuous records of RSL change.  相似文献   

南海北缘东部盆地油气资源研究   总被引：5，自引：0，他引：5  

杜德莉  王树民  陈弘  陈泓君  万玲 《海洋地质与第四纪地质》2001,21(3):67-74

南海北缘东部的珠江口盆地及台西南盆地蕴藏着十分丰富的油气资源，根据区域构造背景、盆地发育分布的特点及中、新生代的油气地质条件，结合含油气构造、油气田、油气井的分布规律，利用油气资源评价的理论、方法，对区内的油气资源进行了综合研究，并按照油气资源状况划分出油气富集区、油气潜力区、油气远景区，在此基础上，再进一步划分出4条油气富集带、11条油气潜力带、8条油气远景带，充分显示了该区石油、天然气的分布规律和油气地质特点，为商业性的勘探开发和理论研究奠定了基础。  相似文献   

3种蛏类线粒体16SrRNA和COI基因片段的序列比较及其系统学初步研究   总被引：15，自引：0，他引：15  

陈丽梅  孔晓瑜  喻子牛  于珊珊  徐晖 《海洋科学》2005,29(8):27-32

对3种蛏类大竹蛏（Solen grandis），长竹蛏（Solen strictus）和小刀蛏（Cultellus attenuatus）的线粒体16SrRNA和COI基因片段序列进行了比较并对其系统学进行了初步研究。得到的序列总长度分别为472-481bp（16S）和658bp（COI）。3种蛏序列的碱基组成均显示出较高的A＋T比例（16SrRNA基因62．1％；COI基因62．8％）。对位排序比较表明，16SrRNA片段种内个体间变异较小，3种类间存在128个碱基变异位点（其中包括127个简约信息位点）和5个插入／缺失位点，总共12个碱基长；COI片段有200个碱基存在变异，其中包括191个简约信息位点，不存在任何插入／缺失位点。数据分析结果表明16SrRNA和COI基因片段大竹蛏与长竹蛏两片段的遗传距离分别为0．0856和0．1712，两竹蛏类与小刀蛏的遗传距离分别为0．3054，0．2798和0．2662，0．2933。作者认为小刀蛏与竹蛏之间的遗传距离已达到科之间的水平，结果支持将其提升为刀蛏科的分类观点。3种蛏类线粒体16SrRNA和COI基因在种间明显的多态性，证实了16SrRNA和COI基因序列均普遍适用于蛏类种及以上阶元的系统学分析。  相似文献   

提取分潮调和常数的新方法——正交方法     

王庆业  刘志亮 《海洋科学》2003,27(9):49-53

给出了提取潮汐调和常数的一种新方法--正交方法,并应用1992～1997年的TOPEX/POSEIDON卫星高度计遥感资料,提取中国海M2分潮调和常数.同时,利用最小二乘法来提取中国海M2分潮调和常数,两种方法结果比较渤海、黄海、东海海域M2分潮振幅、迟角的均方差分别是3.3 cm,3.6°;南中国海海域M2分潮振幅、迟角均方差分别是1.1 cm,1.7°,结果表明正交方法是一种可信的具有实用性的方法.  相似文献   

1993—2001年全球海面高度变化特征   总被引：9，自引：0，他引：9       下载免费PDF全文

申辉  郭佩芳  钱成春  韩树宗 《海洋与湖沼》2003,34(2):169-178

应用TOPEX／POSEIDON（T／P）卫星高度计测高资料，对全球海洋的海面变化特征进行了分析，结果表明，1993年1月－2001年6月期间，全球海平面呈现上升的态势；全球平均海平面高度的平均上升速率约为1．2mm/a；海温的变化是引起海平面变化的重要原因，便其对海平面抬升的贡献不到50％。海平面的变化具有很强的地域特征。海平面变化的空间分布特征受风应力异常特别是纬向风应力异常的空间分布影响较大。  相似文献