大陆架科学钻探CSDP-2井的垂直地震剖面测量   总被引：1，自引：0，他引：1       下载免费PDF全文

吴志强  祁江豪  张训华  郭兴伟  丘学林  张雪飞  谭云龙  黄聿晓  李文强  庞玉茂 《地球物理学报》2019,62(9):3492-3508

南黄海海相地层的地震波场特征和层位标定一直是困扰地震勘探的重要问题.为了近距离、高精度和高分辨率地观测井周围构造特征和岩石性质引起的波场变化，为地震资料的采集、处理与解释提供地震波衰减规律、速度与层位标定等信息，对大陆架科学钻探CSDP-2井实施了近零偏移距垂直地震剖面（VSP）观测.针对海相地层顶部强反射界面地震波穿透难的问题，采用了大容量气枪震源并设计了气枪阵列组合方式，提高了激发地震波的能量，获得了强反射界面之下清晰的PP、PS下行波和上行波信号.采用了三分量偏振合成、组合滤波和波场分离等处理方法，对VSP观测数据进行处理，获得了海相三叠系—志留系的精细的纵波、横波速度结构和地层吸收因子等物性数据，建立了钻井地层、测井、VSP上行波和多道地震剖面对应关系，实现了不同尺度的地质和地球物理属性资料的有效衔接，标定了钻井地质剖面上各深度地质体的地震反射特性，厘定了过井地震剖面上反射同相轴的地质属性.此次观测取得的纵波、横波速度信息，成为建立南黄海海相地层速度模型主要的资料来源，也是地震资料的岩性反演处理不可缺少的信息.  相似文献   

基于多源卫星遥感数据的安达曼海及其邻近海域内波分布特征分析          下载免费PDF全文

王隽  杨劲松  周礼英  贺双颜  贺治国  肖清梅  刘安国  许明光 《海洋学研究》2019,37(3):1-11

安达曼海是内波频繁发生的海区之一,对其内波的研究是当今海洋研究的热点。本文利用2013—2016年间覆盖整个安达曼海的3 000多幅Terra/Aqua MODIS、GF-1、Landsat-8、Sentinel-1 等卫星遥感图像,从中提取和解译了内波波列线和波向信息,得到安达曼海海洋内波的时间分布特征,并绘制了内波空间分布图。结果表明,安达曼海及其邻近海域内波主要出现在4个区域:苏门答腊岛以北海域、安达曼海中部海域、安达曼海北部海域以及尼科巴群岛以西海域,尺度较大的内波主要分布在苏门答腊岛以北海域和安达曼海中部海域。在时间分布上,2013—2016年间安达曼海内波的年发生次数相近;在热季、雨季及冬季遥感都能观测到内波的发生;2-4月遥感观测到的内波最多,其次为8、9月,7月遥感观测到的内波较少,这可能是由于雨季光学影像受云影响,安达曼海海域晴空影像过少造成,还需要借助更多的遥感影像进一步证明。在波向上,安达曼海多数内波向岸传播,在苏门答腊岛北部、安达曼海中部海域,内波向东或向东南传播;在安达曼群岛东部,内波向东传播,传播一定距离后与海底地形交互作用,一部分继续向前传播,一部分产生反射,向西南方向传播至安达曼群岛;在尼科巴群岛以西海域,内波由尼科巴群岛向孟加拉湾传播。  相似文献   

波浪溢流作用下海堤内坡高性能加筋草皮护坡防侵蚀特征研究     

潘毅  张同鑫  周子骏  陈永平 《海洋工程》2019,37(1):29-36

基于1∶1的大型水槽试验结果,分析了波浪溢流过程中位于海堤内坡的高性能加筋草皮护面的侵蚀特征。试验观察表明试验期间有一定土壤的损失,但护坡无明显的破坏;土面高度测量表明,当土壤流失发展到一定深度后,如果水动力强度变化不大,侵蚀趋于逐渐停止,这种现象称为侵蚀上限;结合试验现象对侵蚀上限进行了初步解释,并讨论了侵蚀上限达到前的侵蚀速率特征;植株密度监测表明,试验期间的草茎密度基本不变,草叶密度在开始几次试验期间持续减小,而后达到一个稳定值,这对于海堤的可持续防护有重要意义。研究成果能够为波浪溢流期间海堤内坡防御的相关研究和工程措施提供参考依据。  相似文献   

Active channel width as a proxy of sediment supply from mining sites in New Caledonia     

Mélanie Bertrand  Frédéric Liébault 《地球表面变化过程与地形》2019,44(1):67-76

Although the channel morphology of upland fluvial systems is known to be strongly controlled by sediment supply from hillslopes, it is still difficult to isolate this effect from the other controlling factors of channel forms, such as the sediment transport capacity (depending notably on the size of the catchment) and local conditions (e.g. confinement, riparian vegetation, valley-floor slope). The rivers in New Caledonia offer an interesting field laboratory to isolate the morphological effect of contrasted sediment supply conditions. Some of these rivers are known to be highly impacted by the coarse sediment waves induced by the mining of nickel deposits that started in the early 1870s, which was particularly intensive between the 1940s and 1970s. The propagation of the sediment pulses from the mining sites can be traced by the presence of wide and aggraded active channels along the stream network of nickel-rich peridotite massifs. A first set of 63 undisturbed catchments in peridotite massifs distributed across the Grande Terre was used to fit a classic scaling law between active channel width and drainage area. A second set of 86 impacted sites, where the presence of sediment waves was clearly attested by recent aerial imagery, showed systematically wider active channels, with a width ratio around 5 (established from the intercept ratio of width–area power laws). More importantly, this second set of disturbed sites confirmed that the residual of active channel widths, computed from the scaling law of undisturbed sites, is statistically positively related to the catchment-scale relative area of major mining sediment sources. It is therefore confirmed that the characterization of sediment supply conditions is crucial for the understanding of spatial patterns of active channel width, and this should be more thoroughly considered in morphological studies of rivers draining environments with contrasted geomorphic activities on hillslopes. © 2018 John Wiley & Sons, Ltd.  相似文献   

南海北部台风海浪谱的双峰性和成长性     

莫冬雪  刘亚豪  侯一筠  刘泽 《海洋学报(英文版)》2019,38(11):70-80

本论文通过对南海北部三次台风过境期间基于浮标观测的海浪谱进行分析，发现虽然大部分成熟的台风海浪谱为单峰结构，但实际上在台风海浪的成长和衰减阶段，双峰谱占据了很大的比例。双峰谱的形成主要是由于风浪和涌浪的叠加以及不同波分量之间的非线性相互作用，我们可以通过能量密度的成长率对谱型变化进行高效的预报。此外，台风海浪的主要波向依赖于台风中心相对观测点的位置，而波向的分散情况在相距台风中心较远的区域无明显规律。本文提出了一个新的六参数波浪谱型拟合双峰谱，其拟合效果相较于前人的谱型更好。通过验证，形状参数和谱宽度之间的理论关系依然适用于单个谱峰。通过分析谱参量的变化特征，证明了谱参量不仅与台风强度和台风路径相关，还存在很强的交互相关。最后通过拟合海浪谱数据，本文得到了台风影响下海浪有效波高和有效周期之间的成长关系，这对海洋工程实际应用具有重要意义。  相似文献   

长江口横沙东滩典型海堤越浪量现场和试验研究   总被引：3，自引：3，他引：0  

孙鹏  陈海英  周益人  田鹏 《海洋工程》2019,37(4):27-34

越浪量是允许越浪海堤设计的重要参数。在对以往相关研究成果进行回顾和分析基础上,结合长江口横沙东滩促淤圈围五期工程现场波浪和越浪量实测资料,通过对横沙东滩典型断面型式进行整体和断面物理模型试验,研究结构各参数对越浪量的影响,进而提出适合长江口海堤的越浪量计算公式。公式计算结果与试验数据吻合良好,与Van der Meer公式相比具有较好的一致性。  相似文献   

GRB 170817A的洛伦兹因子和观测角          下载免费PDF全文

林一清 《天文学报》2020,61(1):6

伴随着引力波事件GW170817的短暴GRB (Gamma-Ray Burst) 170817A首次提供了双中子星并合与短暴相联系的直接证据.但是短暴GRB 170817A具有非常弱的光度,意味着观测的视线方向可能偏离喷流轴方向.根据短暴静止系的峰值能量E_(p,i)和各向同性光度L_(iso)。之间的关系以及洛伦兹因子Γ和L_(iso)。之间的关系估算了短暴GRB 170817A以及长短暴GRB 060614观测角与喷流边缘的夹角θ'_(obs)和洛伦兹因子Γ,结果表明GRB 170817A的Γ=45±27,θ'_(obs)=2.2±0.5°,而GRB 060614的Γ=214±93,θ'_(obs)=0.5±0.1°.这个结果相当于GRB 170817A的正轴各向同性光度L_(iso,on)=(2.1±0.7)×10~(49) erg·s~(-1),比典型的短暴少2-3个数量级.GRB 060614的L_(iso,on)=(5.12±1.91)×10~(51) erg·s~(-1)与典型短暴相当.这意味着GRB 060614可能属于短暴类型,而GRB 170817A可能本质上就是一个弱暴.  相似文献   

Risk Analysis of Breakwater Caisson Under Wave Attack Using Load Surface Approximation     

Dong Hyawn KIM 《中国海洋工程》2014,(6):739-748

A new load surface based approach to the reliability analysis of caisson-type breakwater is proposed. Uncertainties of the horizontal and vertical wave loads acting on breakwater are considered by using the so-called load surfaces, which can be estimated as functions of wave height, water level, and so on. Then, the first-order reliability method（FORM） can be applied to determine the probability of failure under the wave action. In this way, the reliability analysis of breakwaters with uncertainties both in wave height and in water level is possible. Moreover, the uncertainty in wave breaking can be taken into account by considering a random variable for wave height ratio which relates the significant wave height to the maximum wave height. The proposed approach is applied numerically to the reliability analysis of caisson breakwater under wave attack that may undergo partial or full wave breaking.  相似文献   

Conditional statistics of Reynolds shear stress in flow over 2D dunes in the presence of surface waves          下载免费PDF全文

Satya P. Ojha 《水文研究》2014,28(18):4829-4842

This study presents the analysis of the velocity fluctuations to describe the conditional statistics of Reynolds shear stress in flow over two‐dimensional dunes in the presence of surface waves of varying frequency. The flow velocity measurements over the dunes are made using a 16‐MHz 3D acoustic Doppler velocimeter. The joint probability distributions of the normalized stream‐wise and vertical velocity fluctuations at different vertical locations are calculated in the trough region of a selected dune in quasi‐steady region of the flow. Third‐order moments of the stream‐wise and vertical velocity components over one dune length are also calculated throughout the flow depth for understanding the effect of surface waves on relative contributions to the Reynolds shear stress due to the four quadrant events. The structure of instantaneous Reynolds stresses is analysed using quadrant analysis technique. It has been shown that the contributions of second and fourth quadrant events to the Reynolds shear stress increase with increase in the frequency of surface waves. In fact, the largest contribution to turbulent stresses comes from the second quadrant. The cumulant discard method is applied to describe the statistical properties of the covariance term u′w′. Conditional statistics and conditional sampling are used to compare the experimental and theoretical relative contributions to the Reynolds shear stress from the four quadrant events. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Hydrodynamic Performance of the Arc-Shaped Bottom-Mounted Breakwater     

楚玉川  程建生  王景全  李志刚  江克斌 《中国海洋工程》2014,(6):749-760

The problem of the hydrodynamic interaction with the arc-shaped bottom-mounted breakwaters is investigated theoretically. The breakwater is assumed to be rigid, thin, impermeable and vertically located in a finite water depth. The fluid domain is divided into two sub-regions of inner and outer by an auxiliary circular interface. Linear theory is assumed and the eigenfunction expansion approach is used to determine the wave field. In order to examine the validity of the theoretical model, the analytical solutions are compared to agree well with published results with the same parameters. Numerical results including wave amplitude, surge pressure, and wave force are presented with different model parameters. The major factors including wave parameters, structure configuration, and water depth that affect the surge pressure, wave forces, and wave amplitudes are discussed and illustrated by some graphs and cloud maps.  相似文献