3D gravity modelling for Anyongbok Seamount in the East Sea     

Moo Hee Kang  Hyun-Chul Han  Hyesu Yun  Gee Soo Kong  Kyong O. Kim  Youn Soo Lee 《Marine Geophysical Researches》2007,28(3):257-269

A seamount chain with an approximately WNW trend is observed in the northeastern Ulleung Basin. It has been argued that these seamounts, including two islands called Ulleung and Dok islands, were formed by a hotspot process or by ridge related volcanism. Many geological and geophysical studies have been done for all the seamounts and islands in the chain except Anyongbok Seamount, which is close to the proposed spreading ridge. We first report morphological characteristics, sediment distribution patterns, and the crustal thickness of Anyongbok Seamount using multibeam bathymetry data, seismic reflection profiles, and 3D gravity modeling. The morphology of Anyongbok Seamount shows a cone shaped feature and is characterized by the development of many flank cones and flank rift zones. The estimated surface volume is about 60 km³, and implies that the seamount is smaller than the other seamounts in the chain. No sediments have been observed on the seamount except the lower slope, which is covered by more than 1,000 m of strata. The crustal structure obtained from a 3D gravity modeling (GFR = 3.11, SD 3.82 = mGal) suggests that the seamount was formed around the boundary of the Ulleung Plateau and the Ulleung Basin, and the estimated crustal thickness is about 20 km, which is a little thicker than other nearby seamounts distributed along the northeastern boundary of the Ulleung Basin. This significant crustal thickness also implies that Anyongbok Seamount might not be related to ridge volcanism.  相似文献   

无舵翼水下机器人路径跟踪控制研究   总被引：1，自引：0，他引：1  

甘永  万磊  陆雯雯  庞永杰 《海洋工程》2007,25(1):70-75

针对无舵翼水下机器人的各种不同任务要求下的路径跟踪控制进行研究。通过模拟人的运动行为,建立了虚拟避碰声纳模型。根据地形跟踪的方法提出基于虚拟声纳的路径跟踪控制方法,并通过考虑纵向速度对于其他各个自由度运动的影响设计了运动控制器。通过海上试验验证了所提出的路径跟踪控制方法对于无舵翼水下机器人是可以满足实际需要的。  相似文献   

Modelling morphological processes in the vicinity of shore-parallel breakwaters     

Julio A. Zyserman  Hakeem K. Johnson 《Coastal Engineering》2002,45(3-4)

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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   

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   

基于多源数据的三维城市建模方法     

叶秋果  滕惠忠  郭思海  李军  辛宪会 《海洋测绘》2006,26(6):62-64

以天津新港三维城市建模为例,介绍了基于二维数据、DEM和3D模型等多源数据的三维城市建模的方法和关键技术。为有效利用现有数据资源快速、准确建立三维城市模型提供了一种经济、灵活、省时、高效的方法。  相似文献   

Design of a 3D Chirp Sub-bottom Imaging System     

Jonathan M. Bull  Martin Gutowski  Justin K. Dix  Timothy J. Henstock  Peter Hogarth  Timothy G. Leighton  Paul R. White 《Marine Geophysical Researches》2005,26(2-4):157-169

Chirp sub-bottom profilers are marine acoustic devices that use a known and repeatable source signature (1–24 kHz) to produce decimetre vertical resolution cross-sections of the sub-seabed. Here the design and development of the first true 3D Chirp system is described. When developing the design, critical factors that had to be considered included spatial aliasing, and precise positioning of sources and receivers. Full 3D numerical modelling of the combined source and receiver directivity was completed to determine optimal source and receiver geometries. The design incorporates four source transducers (1.5–13 kHz) that can be arranged into different configurations, including Maltese Cross, a square and two separated pairs. The receive array comprises 240 hydrophones in 60 groups whose group-centres are separated by 25 cm in both horizontal directions, with each hydrophone group containing four individual elements and a pre-amplifier. After careful consideration, it was concluded that the only way to determine with sufficient accuracy the source–receiver geometry, was to fix the sources and receivers within a rigid array. Positional information for the array is given by a Real Time Kinematic GPS and attitude system incorporating four antennas to give position, heading, pitch and roll. It is shown that this system offers vertical positioning accuracy with a root-mean-square (rms) error less than 2.6 cm, while the horizontal positioning rms error was less than 2.0 cm. The system is configured so that the Chirp source signature can be chosen by software aboard the acquisition vessel. The complete system is described and initial navigational and seismic data results are presented. These data demonstrate that the approach of using fixed source-receiver geometry combined with RTK navigation can provide complete 3D imaging of the sub-surface.  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   

Comparison of two three-dimensional hydrodynamic modeling systems for coastal tidal motion     

Q.Y. Zhang   《Ocean Engineering》2006,33(2):137-151

A comparison of two three-dimensional numerical modeling systems for tidal elevations and velocities in the coastal waters is presented. The two modeling systems are: (1) the Princeton Ocean Model (POM) and (2) the MIKE 3 flow model. The model performance results for Singapore's coastal waters show that the predicted tidal elevations from the two hydrodynamic modeling systems are almost identical and are in very good agreement with field measurement data. The simulated tidal current velocities match well with field measurement data at the selected stations, but it seems that the POM provides the slightly better simulation, compared to the MIKE 3 flow model. The depth profiles of the velocities obtained from the two modeling systems may be greatly different at some time, due to the vertical diffusion coefficient calculated from different turbulent sub-models in the two modeling systems. The POM generally predicts larger peak tidal velocities. The maximum speed differences for the model results from the two modeling systems occur in the top and differ from time to time and from location to location, reaching up to 20%.  相似文献   

三维符号构成及建模方法研究   总被引：3，自引：0，他引：3  

许敏  刘宁  丛凤波 《海洋测绘》2006,26(2):45-48

随着计算机软硬件技术和三维可视化技术的快速发展,二维平面电子地图正在向直观、形象的三维电子地图方向过渡,而原来的二维地图符号已难以满足三维场景逼真性的要求,它必然要求与之配套的三维符号理论和技术的产生。由于三维符号如何构成及怎样标注尚无标准可遵循,在对三维符号的构成、分类及建模方法进行分析的基础上,提出了实体模型符号的两种建模方法,实验表明它们切实可行,能较好地表达三维实体模型。  相似文献