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Chinese Journal of Oceanology and Limnology 2012年第2期30卷 352-359页

作者：曹俊和刘秦玉 Physical Oceanography Laboratory Key Laboratory of Ocean-Atmosphere Interaction and Climate in Universities of ShandongOcean University of China

The sea surface height oscillation with a quasi-four-month period （SSHO4） along continental slope in the northern South China Sea （NSCS） is detected using satellite altimeter data and an ocean model simulation. The SSHO4 is at southwest of Dongsha Island, and is characterized by a wavelength of-600 km and a southwestward phase speed of-0.1 m/s. Crossing the climatological background SST front, geostrophic currents corresponding to the SSHO4 generally induce sea surface temperature （SST）＂tongues＂ during January-March. The cold and warm SST tongues appear southwest of cyclonic and anticyclonic eddies, respectively. The distance between the warm and cold SST tongues is about half the wavelength of the SSHO4. The geostrophic currents play an important role in lateral mixing, as manifested by the SST tongue phenomena in the NSCS.

关键词： sea surface height heat advection eddies continental slope

Distribution and generic composition of culturable marine actinomycetes from the sediments of Indian continental slope of Bay of Bengal

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Chinese Journal of Oceanology and Limnology 2008年第2期26卷 166-177页

作者： Surajit DAS P. S. LYLA S. AJMAL KHAN Centre of Advanced Study in Marine Biology Annamalai University Parangipettai-608 502 Tamil Nadu India

Actinomycetes population from continental slope sediment of the Bay of Bengal was studied. Samples were collected during two voyages of FORV Sagar Sampada in 2004 （May-June） and 2005 （July） respectively from 11 transects （each transect had ca. 200 m, 500 m, and 1 000 m depth stations）. The physicochemical parameters of overlying water, and sediment samples were also recorded. The actinomycete population ranged from 5.17 to 51.94 CFU/g dry sediment weight and 9.38 to 45.22 CFU/g dry sediment weight during the two cruises respectively. No actinomycete colony was isolated from stations in 1 000 m depth. Two-way analysis of variance showed significant variation among stations （ANOVA two-way, P〈0.05）, but no significance was found between the two cruises （ANOVA two-way, P〈0.05）. Populations in stations in 500 m depth in both cruises were higher than that of 200 m depth stations with statistically insignificant difference （ANOVA two-way, P〉0.05）. Three actinomycetes genera were identified. Streptomyces was found to be the dominating one in both the cruises, followed by Micromonospora, and Actinomyces. The spore of Streptomyces isolates showed the abundance in spiral spore chain. Spore surface was smooth. Multiple regression analysis revealed that the influencing physico-chemical factors were sediment pH, sediment temperature, TOC, porosity, salinity, and pressure. The media used in the present study was prepared with seawater. Thus, they may represent an autochthonous marine flora and deny the theory of land runoff carriage into the sea for adaptation to the salinity of the seawater and sediments.

关键词： marine actinomycetes generic composition physico-chemical parameters continental slope Bay of Bengal

Bottom Currents Observed in and Around a Submarine Valley on the continental slope of the Northern South China Sea

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Journal of Ocean University of China 2016年第6期15卷 947-957页

作者： WU Lunyu XIONG Xuejun LI Xiaolong SHI Maochong GUO Yongqing CHEN Liang First Institute of Oceanography State Oceanic Administration Qingdao 266061 P. R. China CNOOC Deepwater Exploitation Co. Ltd. Shenzhen 518067 P. R. China College of Physical and Environmental Oceanography Ocean University of China Qingdao 266100 P. R. China

Bottom currents at about 1000m depth in and around a submarine valley on the continental slope of the northern South China Sea were studied by a 14-month long experiment from July 2013 to September 2014. The observations reveal that bottom currents are strongly influenced by the topography, being along valley axis or isobaths. Power density spectrum analysis shows that all the currents have significant peaks at diurnal and semi-diurnal frequencies. Diurnal energy is dominant at the open slope site, which is consistent with many previous studies. However, at the site inside the valley the semi-diurnal energy dominates, although the distance between the two sites of observation is quite small （11 kin） compared to a typical horizontal first-mode internal tide wavelength （200 km）. We found this phenomenon is caused by the focusing of internal waves of certain frequencies in the valley. The inertial peak is found only at the open slope site in the first deployment but missing at the inside valley site and the rest of the de- ployments. Monthly averaged residual currents reveal that the near-bottom currents on the slope flow southwestward throughout the year except in August and September, 2013, from which we speculate that this is a result of the interaction between a mesoscale eddy and the canyon/sag topography. Currents inside the valley within about 10mab basically flow along slope and in the layers above the 10mab the currents are northwestward, that is, from the deep ocean to the shelf. The monthly mean current vectors manifest an Ek- man layer-like vertical structure at both sites, which rotate counter-clockwise looking from above.

关键词： bottom currents valley continental slope South China Sea

Episodic Carbonate Deposits on the Triassic continental slope in Southern China

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Acta Geologica Sinica(English Edition) 1999年第1期73卷 93-103,129页

作者： Bao Zhidong Department of Geosciences,University of Petroleum,Changping District, Beijing,102200 Univ Petr Dept Geosci Beijing 102200 Peoples R China

Abstract Episodic carbonate deposits on the Triassic continental slope in southern China are mainly composed of gravity-flow limestones and contourite limestones. Gravity-flow limestones were well developed in the lower and middle Yangtze area in the Early Triassic and in the Yunnan-Guizhou-Guangxi area in the Early and Middle Triassic. Five fundamental types of gravity-flow limestones are recognized: slide limestone, debris-flow limestone, grain-flow limestone, turbidite limestone and rockfall limestone. They form six types of assemblage beds: slide-debris-flow limestones, slide-debris-flow-turbidite limestone, slide-debris-flow-grain-flow-turbidite limestone, rockfall-debris-flow limestone, debris-flow-turbidite limestone, and debris-flow-grain-flow-turbidite limestone. The first two were formed mainly in the Early Triassic slopes. The Middle Triassic slopes were characterized by widespread rockfall limestone. Growth faults, storms, earthquakes and oversteepened slopes are considered to be the probable triggers of the gravity flows.

关键词： continental slope episodic deposition gravity flow contour current Triassic southern China

Energy Spectrum of Linear Internal Wave Field in the Vicinity of continental slope

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Journal of Applied Mathematics and Physics 2020年第10期8卷 2256-2274页

作者： Ranis N. Ibragimov Austin Biondi Nathan Arndt Maria Castillo Guang Lin Vesselin Vatchev Sheng Zhang Wenatchee Valley College Wenatchee WA USA University of Wisconsin-Parkside Kenosha WI USA Purdue University West Lafayette IN USA University of Texas Rio Grande Edinburg TX USA

The purpose of the research was to investigate two-dimensional modeling of efficiency of mixing, resulting from the reflection of a linear internal wave field (IWF) off a continental slope. Efficiency of deep ocean mixing was associated with the energy balance of the radiating IWF into an interior of the ocean in the vicinity of a sloping bottom topography. Since waves are generated not only at the fundamental frequency but also at all of its harmonics ωn = nω less than buoyancy frequency N and greater than Coriolis frequency f, our analysis includes, in general, an infinite number of discrete internal wave modes n satisfying the dispersion relationship for internal waves. However, since we are interested only in the radiating part of the field, the mode numbers are limited. Due to multiple singularities of order two caused by resonance in the vicinity of critical slope, the energy is visualized in Lδ -norm with δ > 2. Research results include the visualization of the effects of the continental slope and the Earth’s rotation on resulting energy in the vicinity of the slope.

关键词： Internal Wave Field Effects of Rotation continental slope Energy Radiation

Double-Frequency Microseisms on the Thick Unconsolidated Sediments in Eastern and Southeastern Coasts of United States: Sources and Applications on Seismic Site Effect Evaluation

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Journal of Earth Science 2021年第5期32卷 1190-1201页

作者： Zhen Guo Yu Huang Adnan Aydin College of Civil Engineering Tongji UniversityShanghai 200092China Shanghai Sheshan National Geophysical Observatory Shanghai 201602China Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education Tongji UniversityShanghai 200092China Department of Geology and Geological Engineering the University of MississippiMS 38677USA

This study presents a systematic analysis of double-frequency(DF) microseisms recorded on the unconsolidated sediments in the eastern and southeastern coasts of United States. For all recordings, the site effect parameters(predominant frequency(f_(0)), amplification factor and unconsolidated sediment thickness(UST)) are obtained by Nakamura method and the DF spectra are classified into five groups in terms of the DF peak patterns and the recording locations relative to the coastline. The frequencies and energy levels of the DF peaks in horizontal direction and the amplification factors are associated with the UST which is resulted from seismic site effect. By polarization analysis, the primary vibration directions of the DF peaks are identified and presented as great circles passing through the recording stations intersecting mainly along the continental slope. Correlation analyses of time histories of the DF energy and the ocean wave climate observed at buoys show that the low(0.2 Hz) frequency DF microseisms are generated in the deep ocean and the continental shelf respectively. It is concluded that the continental slope plays a significant role in the generation of DF microseisms as it causes reflection of waves from the open ocean, initiating standing waves.

关键词： seismic site effect double-frequency microseisms unconsolidated sediments continental slope ocean wave

Velocity model and time-depth conversion for the northwestern South China Sea deepwater areas

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Acta Oceanologica Sinica 2015年第4期34卷 56-61页

作者： LIU Aiqun CHEN Dianyuan LI Wentuo FAN Caiwei HE Jianwei Zhanjiang Branch of China National Offshore Oil Corporation Limited

There are rich natural gas resources in the northwestern South China Sea deepwater areas, with poor degree of exploration. Because of the unique tectonic, sedimentary background of the region, velocity model building and time-depth conversion have been an important and difficult problem for a long time. Recent researches in this direction have revealed three major problems for deepwater areas, i.e., the way to determine error correction for drilling velocity, the optimization of velocity modeling, and the understanding and analysis of velocity variations in the slope areas. The present contribution proposes technical solutions to the problems：（1） velocity correction version can be established by analyzing the geology, reservoir, water depths and velocity spectrum characteristics;（2） a unified method can be adopted to analyze the velocity variation patterns in drilled pale structural positions;and （3） across-layer velocity is analyzed to establish the velocity model individually for each of the layers. Such a solution is applicable, as shown in an example from the northwestern South China Sea deepwater areas, in which an improved prediction precision is obtained.

关键词： time-depth conversion velocity modeling deepwater areas continental slope South China Sea

Estimation of the Reflection of Internal Tides on a slope

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Journal of Ocean University of China 2020年第3期19卷 489-496页

作者： WANG Shuya CAO Anzhou CHEN Xu LI Qiang SONG Jinbao MENG Jing Key Laboratory of Physical Oceanography Qingdao Collaborative Innovation Center of Marine Science and Technology(CIMST)Ocean University of Chinaand Qingdao National Laboratory for Marine Science and TechnologyQingdao 266100China Ocean College Zhejiang UniversityZhoushan 316021China Graduate School at Shenzhen Tsinghua UniversityShenzhen 518055China College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao 266100China

Reflection occurs when internal tides impact on a steep continental slope. Separating reflected internal tide signals from incident ones is crucial to develop the parameterization of internal tide-driven turbulent mixing on the continental slopes. In this study, the performances of three different methods for estimating internal tide reflections are examined by using two different cases. The Hilbert transform-based method is found to be more suitable than two other methods for both cases considered in this study. The two other methods are effective for westward-propagating mode-1 internal tides impacting a slope, but inappropriate in the case where internal tides radiate from a Gaussian ridge impact the slope because of their inaccurate estimation of incident internal tides in the latter case. Such inaccurate estimation further influences the extraction of reflected signals and calculation of the reflected and cross term of energy fluxes. In addition, it should be noted that, due to the use of filtering, the method based on Hilbert transform may result in slight bias when assessing the incident and reflected signals near topographic features.

关键词： internal tide reflection continental slope Hilbert transform energy flux filtering