Shear Wave Speed Dispersion Characteristics of Seafloor Sediments in the Northern South China Sea

To accurately characterize the shear wave speed dispersion of seafloor sediments in the northern South China Sea,five types of sediments including silty clay,clayey silt,sandy silt,silty sand,and clayey sand were selected,on which the measurements of the shear wave speed at 0.5-2.0 kHz and related physical properties were performed.Results reveal that the shear wave speed of sediments increases as the frequency increases,and the dispersion enhanced in the sediments in the order of silty clay,clayey silt,sandy silt,silty sand,and clayey sand,at a linear change rate of 0.727,0.787,3.32,4.893,and 6.967 m s−1 kHz−1,respectively.Through regression analysis,linear and logarithmic regression equations for the correlation between shear wave speed and frequency were established for each sediment type and the determination coefficients of regression equations indicate that the correlation is closer to a logarithmic relationship.The Grain-Shearing(GS)and Biot-Stoll models were used to calculate the shear wave speed dispersion of the five sediment types,and the comparison between theoretical prediction and measured results of shear wave speeds shows that the GS model can more accurately describe the shear wave speed dispersion characteristics of these sediments in the frequency band of 0.5-2.0 kHz.In the same band,the predictions obtained by using the Biot-Stoll model are significantly different from the measured data.

A preliminary study on the acoustic properties of seafloor sediment in the southern U-boundary of the South China Sea

The acoustic properties of seafloor sediment are essential parameters in the exploration of marine resources,ocean scientific research and ocean engineering.Seafloor sediment samples were collected at the southern U-boundary of the South China Sea(SCS),and the acoustic and physical properties were measured in the laboratory.The correlation between physical and sound speed ratio(SSR)was discussed,and SSR-physical property empirical regressions in the Sunda Shelf were established for the first time.Compared with the northern continental shelf of SCS,the Sunda Shelf are mainly silty and sand sediment,and the SSR ranges from 0.9949 to 1.0944,which has higher SSR than the northern continental shelf,implies that the Sunda Shelf is a high SSR area.Since the same kind of sediment has different physical properties,the single physical parameter of sediment cannot fully represent the acoustic properties of sediment,therefore,the multiple parameter prediction model should develop in the future to improve the prediction precision.

Physical-mechanical properties of sediments and their correlation with near seafloor seismic amplitude in the Liwan canyon area, northern South China Sea

Before the implementation of offshore oil and gas exploitation,it is essential to understand the various factors that influence the stability of submarine sediments surrounding the project.Considering the factors such as cost and operability,it is not feasible to assess the physical-mechanical properties of sediments covering the entire region by borehole sampling.In this study,the correlation between near seafloor seismic amplitude and the mean shear strength of shallow sediments was explored using seismic and core testing data from the northern continental slope area of the South China Sea.Results showed that the mean water content of sediments in the layer up to 12 m below the seafloor(mbsf)gradually increased with increasing water depth,and the mean shear strength tended to decrease rapidly near the 1000 m depth contour.The near seafloor seismic amplitude could reflect the mean shear strength of sediments in the 12 mbsf layer under seismic frequency of 65 Hz and wave velocity of 1600 m/s.When the mean shear strength was greater than 10 kPa or the water depth was less than 1000 m,there was a significant linear positive correlation between mean shear strength and near seafloor seismic amplitude.Otherwise,there was a significant linear negative correlation between mean shear strength and near seafloor seismic amplitude.On the basis of these correlations,the pattern of shear strength was estimated from near seafloor seismic amplitude and mapped.The mean shear strength of sediments above 12 mbsf gradually decreased with increasing water depth in the continental slope area,whereas little change occurred in the continental shelf and the end of the canyon.Within the canyon area,the mean shear strength of sediments was characterized by larger values in both sides of the canyon walls and smaller values in the canyon bottom,which was consistent with the infinite slope stability theory.The study provides a method for using near seafloor seismic amplitude data to guide sediment sampling design,and presents a continuous dataset of sediment strength for the simulation of regional sediment stability.

P-T stability conditions of methane hydrate in sediment from South China Sea

For reasonable assessment and safe exploitation of marine gas hydrate resource, it is important to determine the stability conditions of gas hydrates in marine sediment. In this paper, the seafloor water sample and sediment sample （saturated with pore water） from Shenhu Area of South China Sea were used to synthesize methane hydrates, and the stability conditions of methane hydrates were investigated by multi-step heating dissociation method. Preliminary experimental results show that the dissociation temperature of methane hydrate both in seafloor water and marine sediment, under any given pressure, is depressed by approximately -1.4 K relative to the pure water system. This phenomenon indicates that hydrate stability in marine sediment is mainly affected by pore water ions.

Empirical Equations of P-Wave Velocity in the Shallow and Semi-Deep Sea Sediments from the South China Sea

Three-hundred and thirty-one sediment cores,including six sediment types(clayey-and sandy-silt,silty-and sandy-clay,clayey-and silty-sand)were collected from the shallow and semi-deep seas of the South China Sea,and the P-wave velocities and physical properties of core sediments were measured under standard laboratory conditions.To eliminate the influence of environ-mental factors,the empirical sound speed ratio equations were established.Compared with several equations from literature,the po-rosity and wet bulk density empirical equations established in this paper agree well with Richardson and Briggs(2004)’s in-situ equations,which implies that our empirical equations can be used in the similar region of world’s oceans under certain conditions and will be useful in areas lacking first-hand P-wave speed data.However,the mean grain size equations established in this study,similar to the previous studies,have low accuracy,which may be due to the different particle arrangements and degrees of compac-tion in sediments.The results also show that for different sediment types,the equation based on all sediment data is in good agree-ment with the measured data in the study area,as there are both siliciclastic and carbonate sediments on the studied seabed.It is sug-gested that appropriate empirical equations should be selected according to sediment types and sedimentary environment in future works,and the empirical equation of porosity or the two-parameter equation of porosity and grain size should be preferred.

Bias correction of sea surface temperature retrospective forecasts in the South China Sea

Offline bias correction of numerical marine forecast products is an effective post-processing means to improve forecast accuracy. Two offline bias correction methods for sea surface temperature(SST) forecasts have been developed in this study: a backpropagation neural network(BPNN) algorithm, and a hybrid algorithm of empirical orthogonal function(EOF) analysis and BPNN(named EOF-BPNN). The performances of these two methods are validated using bias correction experiments implemented in the South China Sea(SCS), in which the target dataset is a six-year(2003–2008) daily mean time series of SST retrospective forecasts for one-day in advance, obtained from a regional ocean forecast and analysis system called the China Ocean Reanalysis(CORA),and the reference time series is the gridded satellite-based SST. The bias-correction results show that the two methods have similar good skills;however, the EOF-BPNN method is more than five times faster than the BPNN method. Before applying the bias correction, the basin-wide climatological error of the daily mean CORA SST retrospective forecasts in the SCS is up to-3°C;now, it is minimized substantially, falling within the error range(±0.5°C) of the satellite SST data.

Stratal Carbonate Content Inversion Using Seismic Data and Its Applications to the Northern South China Sea

On the basis of the relationship between the carbonate content and the stratal velocity and density, an exercise has been attempted using an artificial neural network on high-resolution seismic data for inversion of carbonate content with limited well measarements as a control. The method was applied to the slope area of the northern South China Sea near ODP Sites 1146 and 1148, and the results are satisfaetory. Before inversion calculation, a stepwise regression method was applied to obtain six properties related most closely to the carbonate content variations among the various properties on the seismic profiles across or near the wells. These include the average frequency, the integrated absolute amplitude, the dominant frequency, the reflection time, the derivative instantaneous amplitude, and the instantaneous frequency. The results, with carbonate content errors of mostly ±5 % relative to those measured from sediment samples, show a relatively accurate picture of carbonate distribution along the slope profile. This method pioneers a new quantitative model to acquire carbonate content variations directly from high-resolution seismic data. It will provide a new approach toward obtaining substitutive high-resolution sediment data for earth system studies related to basin evolution, especially in discussing the coupling between regional sedimentation and climate change.

The Role of Bottom Currents on the Morphological Development Around a Drowned Carbonate Platform,NW South China Sea

The seafloor around carbonate platforms is largely shaped and modified by downslope processes.However,the role of alongslope processes,including bottom currents,on the morphological development of carbonate platforms remains poorly understood.Here,we use high-resolution multibeam bathymetric data and two-dimensional seismic profiles to investigate the detailed sea-floor morphology around the Zhongjianbei carbonate platform(ZCP)in the northwest South China Sea.A series of depositional bodies and erosional channels are identified to the south of the ZCP and are interpreted as contourite drifts and channels resulted from the interaction between bottom currents and bathymetric features.In addition,active fluid seepages have led to the formation of widespread pockmarks on the seafloor.Importantly,the contourite channels and widespread pockmarks also show a close relationship in their distribution.We propose that the contourite channels around the ZCP are evolved from the coalescence of pockmarks under the persistent erosion of bottom currents.Based on the morphological analysis,we reconstruct the past bottom-current pathways around the ZCP that are parallel to the platform slopes and heading to the south.This study provides new insights into the formation of complex bathymetry and helps understanding how bottom currents and active fluid seepages can influence the morphological development around carbonate platforms.

Source Ranging Using Ensemble Convolutional Networks in the Direct Zone of Deep Water

Using deep convolutional neural networks as primary learners and a deep neural network as meta-learner, source ranging is solved as a regression problem with the ensemble learning method. Simulated acoustic data from the acoustic propagation model are used as the training data. Real data from an experiment in the South China Sea are used as the test data to demonstrate the performance. The results indicate that in the direct zone of deep water, signals received by a very deep receiver can be used to estimate the range of underwater sound source.Within 30 km, the mean absolute error of the range predictions is 1.0 km and the mean absolute percentage error is 7.9%.

The propagation of seafloor spreading in the southwestern subbasin,South China Sea

On the basis of the summary of basic characteristics of propagation, the dynamic model of the tectonic evolution in the South-western Subbasin (SWSB), South China Sea (SCS), has been established through high resolution multi-beam swatch bathymetry and multi-channel seismic profiles, combined with magnetic anomaly analysis. Spreading propagates from NE to SW and shows a transition from steady seafloor spreading, to initial seafloor spreading, and to continental rifting in the southwest end. The spreading in SWSB (SCS) is tectonic dominated, with a series of phenomena of inhomogeneous tectonics and sedimentation.

Coastal seafloor observatory at Xiaoqushan in the East China Sea

The seafloor observation system is becoming an important infrastructure for marine research because it is transforming oceanic research from temporal investigation to long term observation.The East China Sea coastal seafloor observatory,located between 30°31′44″N,122°15′12″E and 30°31′34″N,122°14′40″E,is constructed near the Xiaoqushan Island outside the Hangzhou Bay on the inner continental shelf of the East China Sea.The observatory is connected by a submarine optical fiber composite power cable that is more than one kilometer long and consists of a special junction box that transmits power and communication signals to different instruments.The special junction box has a variety of waterproof plugs and connects to three different instruments installed in a trawl preventer.The submarine optical fiber composite power cable is landed on the platform by The East China Sea Branch,State Oceanic Administration and the power is continuously supplied by the solar panels and solar battery on the top of the platform.The real time data are directly sent through the cable to the platform and are transmitted by CDMA wireless to the receiver at the State Key Laboratory of Marine Geology of Tongji University.Measurements at the observatory have been taken since April 20,2009 after installation and the results have been interpreted.The characteristics of the near bottom boundary are constrained by a sediment suspension model using portion of the observed data.In particular,discussion is provided on the sea surface height anomaly at Xiaoqushan Island influenced by the tsunami driven by the 2010 Earthquake in Chile.The successful establishment of the coastal seafloor observatory is the first step toward future development of seafloor observation systems in China.It not only accumulates experiences in technology and engineering,but also paves the way for performing important oceanic research using the long term continuous observation platform.

Long-term seismic network in South China Sea by floating MERMAIDs

Seismic data coverage in ocean regions is sparse,and it is highly challenging to build long-term continuous seismic networks in the oceans due to the restrictions related to the shortage of instruments and great costs.The lack of data coverage limits effective seismic imaging of deep mantle structures beneath the oceans,which cover 70%of the Earth’s surface.The newly developed Mobile Earthquake Recorder in Marine Areas by Independent Drivers(MERMAID)can drift with ocean currents at a specified depth while recording seismic signals.The Southern University of Science and Technology(SUSTech)launched 10 MERMAIDs in the South China Sea(SCS)in May 2021 that formed the South China Sea Floating Seismic Network(SCS-FSN).We analyzed the one-year-long records of the SCS-FSN,identifying 372 cataloged earthquakes and acquiring 1,015 high-quality travel time data.By analyzing the records of earthquakes with magnitudes above 7.0 and conducting synthetic waveform calculation,we found that,in addition to the epicentral distance and earthquake magnitude,the earthquake identification ability of the network is also affected by the focal mechanism,sea condition,seafloor relief,and MERMAID working state.Although the recognition rate of the SCS-FSN is only 16%for earthquakes with magnitudes above 5.5 and epicentral distances less than 90°,this network is expected to collect more than 5,000 high-quality travel time data during its five-year battery life.These new data will significantly improve the seismic data coverage,compensating for the lack of long-term continuous seismic network observations in the SCS.Most importantly,with this experiment,we are confident that setting up well-designed floating seismic networks in the world’s three oceans could solve the world-class problem of the lack of effective seismic data coverage beneath ocean regions.

融合多源海洋大地测量数据的南海海底地形多层感知机反演

本文融合SIO(Scripps Institution of Oceanography)发布的垂线偏差、重力异常和垂直重力梯度数据及NCEI(National Centers for Environmental Information)发布的船载测深数据,利用多层感知机神经网络(Multi-Layer Perceptron,MLP)建立南海海域(108°E—121°E,6°N—23°N)分辨率为1'×1'的海底地形模型(MLP_Depth).首先,将642716个船载测深控制点的位置信息与周围4'×4'格网点处的地球重力信息(垂线偏差、重力异常、垂直重力梯度)作为输入数据,将船载测深控制点处实测水深值作为输出数据,训练MLP神经网络模型,训练结束时决定系数R2为99%,平均绝对误差MAE为39.33 m.然后,将研究区域内1'×1'格网正中心点处的输入数据输入于MLP模型中,可得格网正中心点处的预测海深值.最后,根据预测海深值建立研究区域范围内分辨率为1'×1'的MLP_Depth模型.将MLP_Depth模型预测水深与160679个检核点处实测水深对比,其差值的标准差STD(75.38 m)、平均绝对百分比误差MAPE(5.89%)与平均绝对误差MAE(42.91 m)皆优于GEBCO_2021模型、topo_23.1模型、ETOPO1模型与检核点实测水深差值的STD(108.88 m、113.41 m、229.67 m)、MAPE(6.11%、6.94%、18.37%)与MAE(47.33 m、52.24 m、130.08 m).同时,为了研究不同区域内利用该方法建立的海底地形模型的精度,本文在研究区域内分别建立了A、B区域的海底地形模型(MLP_Depth_A、MLP_Depth_B).经过验证得:MLP_Depth_A、MLP_Depth_B相比于MLP_Depth模型具有更高的精度,更能反应海底地形的变化趋势.

环南海区域航空网络空间演化及影响机制研究

环南海地区作为中国“21世纪海上丝绸之路”倡议的起锚之地,厘清其区域的航空连通性及其发育机制对促进各国经贸合作具有重要意义。为此,本文通过构建航空连通性指数并运用优势流和TERGM模型,尝试刻画环南海区域航空网络的空间演化规律并揭示其自组织发育机制。研究发现:①环南海区域内航空枢纽等级体系保持基本恒定性和一定突变性,新加坡、吉隆坡、雅加达、曼谷、马尼拉、中国香港、广州等城市是环南海区域航空联系的关键枢纽。②环南海区域内航空联系稳定于印尼–马来西亚–泰国三角区,并呈现向东部中国沿海城市及菲律宾蔓延态势,轴辐组织呈现出多中心演化态势,遵循区域集聚规律。③在影响机制方面,网络演化主要受到内生结构、城市属性与城际关系的共同作用。闭合三元结构对航空联系具有正向促进作用,非核心城市的航空联系扩张迅速,低等级节点在网络演化过程中愈发呈现主动扩张趋势。经济发展水平、城市规模、制度邻近性、文化邻近性以及合作事件对航空客运均具有正向促进作用,地理距离和冲突事件对航空联系产生负向影响,网络整体呈现稳定发展态势。

Exploring the deep South China Sea: Retrospects and prospects

Rapid developments of deep-sea researches in China over the past 20 years have promoted the South China Sea(SCS) into the international deep-sea frontiers. The 'three deep technologies', namely scientific drilling, long-term seafloor observation and deep submersible vehicles implemented successively in SCS studies helped to achieve a number of scientific breakthroughs. Over the 20 years, five international ocean drilling expeditions to the SCS recovered nearly 10 km of sediment cores from sites at 3–4 km water depths, and drilling into the magmatic basement at 6 sites shed light on the genesis of the SCS basin. Coupled with other deep-sea short core sediments from the SCS, these records demonstrate evidence that water and carbon cycling in the low latitude regions can directly respond to the orbital forcing, and subsequently nurture a new concept of lowlatitude forcing of climate changes, which challenges the classical wisdom of the overwhelming role played by the Arctic icesheet in climate changes. The exploration in the continent-ocean transition zone also reveals a number of specific features that characterize the SCS as a marginal basin formed at the subduction zone in the Western Pacific. The features include active magmatism and rapid rupture of lithosphere through the basin formation process, and imply that 'the SCS is not a mini-Atlantic'as they can be distinguished as 'plate-edge rifting' and 'inner-plate rifting' respectively, thus challenging the universality of the Atlantic model for passive margins. Many more discoveries can be assembled from long-term mooring observations and deep diving cruises in the deep SCS, such as the cyclonic nature of the deep-water circulation, deep-water sediment transport by contour currents and turbidites, manganese nodules, extinct hydrothermal vents, and cold-water coral forests. In addition,prominent progress achieved in microbiology and biogeochemistry includes the microbial carbon pump and the coupling of carbon and nitrogen cycles. Clearly, most achievements of the deep-sea explorations in the SCS over the last 20 years have always been of international scale and impact. However, the contributions from Chinese scientists are most prominent, particularly with the research activities undertaken from the major program 'Deep Sea Processes and Evolution of the South China Sea(2011–2018)' supported by the National Natural Science Foundation of China.

Relationship between Formation of Zhongyebei Basin and Spreading of Southwest Subbasin, South China Sea

The Zhongyebei （中业北） basin （ZYBB） is an NE-striking, narrow and small sedimentary basin superimposing the southern 1/2 segment of the proposed spreading axes of the SW subbasin of the South China Sea （SCS）. More than 4 500 m strata were identified in the Zhongyebei basin, including the Paleogene lower structure layer and the Neogene upper structure layer. The SW subbasin of the South China Sea has been regarded as an oceanic basin opened by seafloor spreading, as evidenced by the flat and deep （〉 4 000 m mostly） seafloor with linear magnetic anomalies, and by the shallow Moho depth of 〈 12 km as estimated from gravity modeling. The classic model of seafloor spreading predicts that sediments on the oceanic crust are younger and thinner towards the spreading axes. But in the southwestern segment of the SW subbasin, contradictions appear. Firstly, the thick sedimentation in the ZYBB is along the proposed spreading axes. Secondly, the sediments are thinner （500-1 500 m） and younger away from the proposed spreading axes. Thirdly, geological elements of the two sides of spreading axes develop asymmetrically in the southwestern SW subbasin. Two models, the early opening model and the limited modeling model, are suggested for resolving this paradox. The former suggests that the opening of the SW subbasin was in Late Eocene and earlier than the oldest sediment in the ZYBB. The latter proposes that the opening of the SW subbasin was limited to its northeastern portion, and did not extend to the southwest portion. The ZYBB is a rift basin survived from the spreading but subjected to severe syn-spreading magmatic disturbance. The SW subbasin and the ZYBB of the SCS provide a unique opportunity for studying the structural evolution and dynamic mechanism at the tip of a propagating seafloor spreading. Both models have unresolved questions, and further studies are needed.

Magnetic recording of the Cenozoic oceanic crustal accretion and evolution of the South China Sea basin

我们考察并且讨论一些在华南海(SCS ) 在磁性的数据上做的最近的科学调查结果。磁性的异例在中生代和新生代上忍受极其富有的信息构造进化。从磁性的异例计算的分析信号振幅很精确揭示的 3D 二上的中生代沉积序列的寡妇分布结合大陆人边缘，和他们也在在 SCS 海洋的外壳以内描绘以后阶段的 magmatism 和构造转变和带状配列被发现很有效。通过综合分析磁性，严肃和思考地震数据，我们在华南海大陆人边缘附近定义大陆海洋边界(圆块) ，并且发现圆块与一个转变地区与一致很好从对否定免费空气的严肃异例主要积极。COB 的这精确构画出为更好跟踪海洋的外壳导致的磁性的异例是批评的。几何上复杂的圆块和内部磁性的带状配列要求一个阵发性的洞模型，以及一个变换差错的介绍(这里作为 Zhongnan 差错制造了)在东方和西南亚盆之间在东方和西南亚盆以内，磁性的异例旁边地是相当连续的，在这些亚盆以内显示大变换差错的不存在。我们提高浅玄武岩的层经由一个通带过滤器引起的磁性的异例，并且认识到北大陆人边缘附近的多半最旧的磁性的异例根据磁性的时间规模 CK95 是 C12。在南部的大陆人边缘附近，磁性的异例是不太可认识的，异例 C12 看起来失踪。这些差别证明关于散布中心的寡妇的一种不均匀的开始式样，和北部分看起来比到南方有稍微更快传播的率。磁性的异例 C8 (M1 和 M2， 26 妈) 在海洋的盆以内代表重要磁性的边界，并且可能与在散布率和 magmatic 紧张的变化有关。为一条以前建议的山脉的磁性的证据在异例 C7 不是清楚的以后，跳。西南亚盆的年龄还得进一步被检验，最有利地与深拖引磁性的调查并且海洋钻。我们的磁性光谱最浅的居里削尖的学习表演在西南的亚盆的东方部分附近被定位，而在东方亚盆居里以内深度对传播的寡妇的北方更小，比到南方集中。居里深度的这个模式对地区性的热流动大小和以后阶段的暴烈的海底山分布一致，并且我们因此推想居里深度变化仔细与以后阶段的 magmatism，而非与外壳的年龄被联系。尽管在北大陆海洋转变地区(简易窄床) 附近定位的磁性的异例是相对安静的，自从概念上它与一个海洋的磁性的安静地区显著地不同，这个区域不是一个典型磁性的安静地区。相对安静的磁性的异例看起来在居里等温线与 shallowing 被联系并且在磁性的层，而是我们的全面观察变瘦建议保存得很好的厚中生代沉积岩石是为有磁力地安静的地区的主要原因。各种各样的低通行证的过滤水兵和在空中的磁性的异例和卫星的高类似磁性的异例清楚地证实那更深磁性的来源(在更低的外壳中并且最高披风) 有贡献到长波长的表面在区域的磁性的异例，当已经推断了从有磁力地 inversed 居里深度。近海华南磁性的异例(SCMA ) 在低通行证的过滤水兵和在空中的磁性的异例和卫星上变得更突出磁性的异例，在它下面显示很深深地埋葬的磁性的来源。

Passive-source ocean bottom seismograph(OBS) array experiment in South China Sea and data quality analyses

Long-term passive source ocean bottom seismograph(OBS) observatory is challenging due to various technical difficulties. In order to gain experience in this field, and to reveal the lithospheric structure beneath the extinct ridge in the central South China Sea(SCS), we carried out a passive source OBS array experiment, which includes 18 OBSs, in the deep portion of SCS. Here we present the instrumentation, the OBS deployment and recovery of this experiment, and more importantly, the data quality evaluated by a number of approaches. Through processing and inspecting waveforms from global, regional and local earthquakes, we find that most of recovered OBSs have good data quality with discernible main phases. The ambient noise analyses of OBS recordings show that their noise is higher than the global average, and the horizontal component is noisier than the vertical, indicating current impacts on horizontal components are more severe. In the period range of 5–10 s, there is a noise notch for the SCS OBSs, and noise levels of horizontal components are comparable to the vertical. This feature, which is not seen at OBS stations in open ocean, suggests the distant sources for double frequency microseism in this marginal sea are not significant. In addition, we successfully determined the orientations for 7 OBSs by investigating their Rayleigh wave polarizations; and we demonstrated the dispersion feature of Rayleigh waves through the frequency-time analysis. Finally, we summarized lessons learned from this experiment regarding the passive source OBS investigations in SCS.

琼东南盆地古近纪沉积充填演化及其区域构造意义

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南海北部海底沙波研究

南海北部水深100-250m的陆架和陆坡斜坡海底分布着大片沙波地貌，本文采用底形相图参数近似计算和泥沙起动流速2种计算方法，结合海底微地貌的实际形态，研究了沙波的沉积特征及其成因机理。研究认为，区内的沙波为现代沉积地貌；控制沙波形成发育的主要水动力因素是潮流与风暴条件下风海流的叠加；区内泥沙颗粒粒径适宜，海底坡度平缓，有利于海底沙波的发育。