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1.
海南岛西南海底沙波形态和活动性的空间差异分析 总被引：1，自引：0，他引：1
利用GeoSwath Plus和Seabat8101多波束测深系统于2007年10月和2009年9月对海南岛西南沙波区进行了高精度水深测量,利用所得数据对近岸区和远岸区两个水深相差较大区域的沙波几何形态和沙波迁移速率做了对比分析,探讨了沙波几何形态和活动性的空间差异及其控制因素。远岸研究区与近岸研究区沙波几何形态和沙波迁移速率体现在沙波规模及形态、陡坡倾角和倾向、沙波迁移速率和沙波迁移方向及偏转角度。远岸区域沙波为近于对称的直线型沙波,波高0.5～2.3 m,波长13.2～69.1 m,陡坡倾角4.3°～7.4°;近岸区域沙波为新月形沙波,波高3.1～6.5 m,波长41.5～216.6 m,沙波陡坡倾向南,陡坡倾角8.7°～12.9°。远岸研究区沙波向西北方向迁移,沙波迁移速率多为15.0～20.0 m/a,最大34.9 m/a;近岸区域沙波向南迁移,沙波迁移速率0～12.65 m/a。沙波的迁移速率主要受底流流速和沙波波高控制,在两者的综合作用下,近岸研究区沙波迁移速率小于远岸研究区沙波迁移速率。在频繁的热带气旋作用下,近岸研究区沙波迁移方向发生逆时针偏转。 相似文献
2.
海南东方岸外海底沙波活动性研究 总被引：5，自引：0，他引：5
对海南东方岸外 2 0～ 50 m水深海底沙波形成的动力环境、形态特征、剖面结构及其分布特征进行了描述和分析。根据环境参数 ,对其活动性进行了计算 ,并将计算结果与发育环境相类似的 Surtainville沙波进行了类比。认为研究区沙波主要系在潮流作用下形成。研究区沙波迁移速率为每年数米。东区 (水深 2 0～ 40 m)是沙波发育的主体 ,受落潮流作用 ,沙波自北向南迁移 ;西区 (水深 36～ 52 m)沙波受涨潮流控制自南向北迁移 ;中区为过渡区 ,沙波相对稳定 相似文献
3.
《海洋地质与第四纪地质》2021,41(4)
海南东方近岸海底发育有大量沙波,利用多波束测深、侧扫声呐、浅地层剖面、单道地震资料综合分析了活动沙波的地球物理特征,探讨了沙波的分布特征、迁移机制、活动性及形态演变特征。结果表明,研究区海底沙波分布和规模具有显著空间差异性,大中型沙波主要发育于沙脊上,小型沙波主要发育于沙脊两侧,坑槽区发育近对称沙波,研究区西南部沙波不发育。受潮流和科氏力约束,在海底沙脊西侧沙波迁移方向主要为向北(略偏东),在沙脊东侧主要为向南(略偏西);受地形制约,坑槽区近对称沙波迁移可能停止或方向发生改变。沙波活动性强的标志主要包括:(1)形态呈不对称的"脊尖槽缓",(2)叠置小沙波与沙纹发育,(3)浅部有透明层,(4)陡坡面反射模糊,(5)内部斜交前积结构。分析认为,沙波活动性与其形态密切相关,包括弱运动、强运动、不运动3个演变阶段。 相似文献
4.
海南岛西部岸外沙波的高分辨率形态特征 总被引：12，自引：1，他引：12
利用SIMRAD-EM3000多波束探测系统和DGPS定位系统,对海南岛东方岸外的沙波沙脊区进行了高精度探测,分析结果表明:从海岸到陆架底形具有明显的分带性,依次出现弱侵蚀底形段、沙波沙脊底形段和平坦底形段。沙波仅发育于沙波沙脊段,介于水深20~50 m之间,沙波形态有二维与三维两种,沙波波高多为0.7~2.5 m,波长20~70 m,沙波指数(L/H)为20~60,对称指数为1~3;沙波沙脊区沉积物的搬运方向有明显的规律性,在沙脊的西侧,沉积物主要向北搬运;在沙脊的东侧,沉积物主要向南搬运;沙波的形成和发育主要受潮流场控制,热带风暴对其有改造作用。 相似文献
5.
第五次北极科学考察在北极区的白令海首次进行了高分辨率单道地震作业。Navarinsky峡谷头部测线BL11-12剖面中部识别出不对称沙波,陡的一面朝向陆架,波高约为9m、波长约为882m。结合站位U1345的沉积速率及站位U1344表层纵波速率推测沙波沉积可以追溯到中更新世(距今约0.258Ma),同时近陆架的洼地逐渐填平。将地层分为3个沉积层,分析沉积物变化情况,结合0.25Ma以来白令海海平面变化历史,推测最大海退事件对应的界面。结合沙波的地理位置及海平面变化情况,认为内波对沙波的形成起主要作用。 相似文献
6.
南海北部海底沙波地貌动态研究 总被引：9，自引：1，他引：9
南海北部水深80～250m的外陆架和上陆坡海底,有大片沙波地貌分布,它们主要是晚更新世末次冰期低海面时遗留下来的滨海沙波、沿岸沙丘、沙堤和沙垄,属残留沙体地貌,它们的分布规律明显沿着末次冰期时形成的最低海岸线两侧分布,但在现代海底底流作用下,其两翼及沙波谷部发育有次一级的小型沙波或沙纹,它们的形态细小、排列紧密,与残留沙体地貌组成复式海底沙波。人们称这些沙体地貌为流动沙波,它们是不稳定的地质因素,对海底工程有一定危害。但根据外陆架实侧底流数据,运用计算机数学模型方法计算,表明在细砂和中细砂大面积覆盖区,其海底沙波每年均以0.168～0.534m的速度向深海方向迁移,其移动速度相当缓慢,对海底工程实施不会造成直接危害。 相似文献
7.
海南岛西南海底沙波活动及底床冲淤变化 总被引：17，自引：0，他引：17
为了研究沙波迁移对底床稳定性的影响,通过对比分析2004—2006年连续3年的多波束海底地貌扫描数据,得出研究区域海底沙波的波长为5.8~91.8 m,波高0.1~4.3 m,陡峭度0.013~0.12,对称指数0.32~6.52。沙波的移动速率最大48.8 m/a,移动方向在研究区域西部为SE向,中部呈往复迁移,东部为NW向;沙波不同部位的迁移速率不同,一般的沙波尾翼迁移速率较大;同一组沙波存在反向扭转迁移的现象,反向扭转迁移的轴线位于研究区域沙脊的脊线附近,这种反向迁移不仅与底层流作用有关,还与海底地形关系密切;西部海底底床处于侵蚀状态,局部最大侵蚀量可达1.3 m,东部处于堆积状态,最大堆积量达2.8 m。 相似文献
8.
长江口南港航道沙波群研究 总被引：19，自引：2，他引：17
本文利用Innerspace449热敏式双频测深仪和GPS(全球定位系统)在长江口南港和南北槽主航道走航观测结果,确认南港(吴淞口以下)上段航道在洪季正常风况下存在尺度较大的沙波群,并对沙波的几何特征、形成条件、迁移速率以及台风后的变化做了初步分析.结果表明:(1)在统计的652个沙波中,平均和最大波长分别为21m和105m.平均和最大波高分别为0.8m和2.7m,波高和波长间具有明显的正相关关系;沙波中72%为单一沙波,复合沙波的波长和沙波指数较大;单一沙波最大、最小和平均沙波指数分别为36.5、11.2和21.8(复合沙波最大可达69.3);随着沙波度的增大,沙波指数呈增大趋势;绝大多数沙波(波高＜1m)是对称或近于对称的,但波高＞1m的沙波通常向海倾斜.(2)沙波沉积物为分选好的细沙,Φ50为2.70.(3)沙波现场水流费劳德数Fr小于0.2,与某些理论相符而与某些水槽实验结果相冲突.(4)大潮和寻常潮一个涨(落)潮过程沙波来回迁移的距离约为1～5m;小潮期间沙波的迁移距离接近0;落潮迁移距离总是大于涨潮.(5)台风后沙波有被掩埋的迹象.结果包括:①沙质床底是形成沙波的重要基础.南北槽虽具有沙波形成的动力条件,但因最大浑浊带发育而造成淤泥质床底,故沙波不发育.②潮汐河口双向流环境下沙波的对称性较好,频繁的水动力变化使沙波的消长和迁移过程更加复杂,但沙波的基本特征和形成条件与单向流河流环境相似. 相似文献
9.
海南东方岸外海底沙波活动性研究 总被引：14，自引：0，他引：14
对海南东方岸外20－50m水深海底沙波形成的动力环境、形态特征、剖面结构及其分布特征进行了描述和分析，根据环境参数，对其活动性进行了计算，并将计算结果与发育环境相类似的Surtainville沙波进行了类比，认为研究区沙波主要系在潮流作用下形成。研究区沙波迁移速率为每年数米。东区（水深20－40m）是沙波发育的主体，受落潮流作用，沙波自北向南迁移；西区（水深36－52m）沙波受涨潮流控制自南向北迁移；中区为过渡区，沙波相对稳定。 相似文献
10.
陆架沙丘(波)形成发育的环境条件 总被引：9，自引：0，他引：9
陆架大、中、小、巨沙丘(沙波)发育的动力机制与河流沙波有相似之处，也有许多差异，前者含定时多向的潮流、持续定向的洋流和偶发性的暴风浪流，后者为单向持续水流。20～100cm／s的底流速是发育沙丘的动力因素，水流的多向性和浪流的偶发性又常常制约沙丘发育的强度和迁移的速度；陆架浅水区(小于18m)受破浪的影响，沙丘尺度与水深呈微弱负相关，深水区水深的影响甚微。陆架输沙量是沙丘发育的物质条件，特别是细、中砂底质，在此粒度范围内沙波尺度与粒径呈微弱正相关，平缓广阔的地形在沙丘发育中也起一定的作用。 相似文献
11.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
13.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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15.
《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
16.
The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
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18.
The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献
19.
Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
20.
Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献