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Seafloor sediment classification based on multibeam sonar data 总被引:1,自引:1,他引:0
ZHOUXinghua CHENYongqi 《地球空间信息科学学报》2004,7(4):290-296
The multibeam sonars can provide hydrographic quality depth data as well as hold the potential to provide calibrated measurements of the seafloor acoustic backscattering strength. There has been much interest in utilizing backscatters and images from multibeam sonar for seabed type identification and most results are obtained. This paper has presented a focused review of several main methods and recent developments of seafloor classification utilizing multibeam sonar data or/and images. These are including the power spectral analysis methods, the texture analysis, traditional Bayesian classification theory and the most active neural network approaches. 相似文献
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Orthogonal intersections of megatrends in the Western Pacific ocean basin: a case study of the Mid-Pacific mountains 总被引:1,自引:0,他引:1
N. Christian Smoot 《Geomorphology》1999,30(4):1
Present-day tectonic concepts of events on the western paleo-Pacific lithosphere must be assessed relative to new data. Data collected by the newer techniques of geophysical surveying reveal leaky fracture zones, trending NNW–SSE and WSW–ENE; non-sequential in-line ages on most seamount chains; and orthogonal intersections of fracture zones. The fracture zones meander, braid, merge, splay, start and stop at any place, and are generally aligned with, or contain, linear chains of seamount. The combination of these in-line features is called megatrends. When the GEOSAT data are compared to the available bathymetry, this seemingly jumbled tectonic structure is verified. As the pole of rotation changes, the stress field changes alignment to agree with the Chandler wobble of Earth. Younger megatrends, propagating ever eastward, cross the older, already imprinted megatrends. During the Cretaceous, the voluminous outpouring of igneous rock created the large Pacific plateaus and rises where the megatrends, active and inactive, orthogonally intersected. The magma floods at the intersections flowed outwardly, and the outward flooding accounts for the fanning magnetic lineations around the Manihiki, Magellan, Shatskiy, and Hess rises. A case study of the Mid-Pacific Mountains (MPM), lying in the north-central Pacific Ocean basin, shows that the MPM formed about 125–110-Ma by overprinting the orthogonal intersections of fracture zones at the Molokai and Easter/Krusenstern–Emperor megatrends and the Murray and Tubai/Mamua megatrends. The MPM have been undergoing distortion into a vortex structure, a feature which has been confirmed by updated bathymetry, GEOSAT altimetry data, and drillsite information. 相似文献
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针对多波束常梯度声线跟踪计算耗时和声速剖面简化导致计算精度下降的问题,在对多波束常梯度声线跟踪理论进行分析的基础上,提出了一种基于时间分解的常梯度声线跟踪方法。将波束在层内的传播时间分解为与波束入射角无关的固定项和有关的变化项,固定项对于每个声速剖面仅需计算一次,对变化项采用麦克劳林公式展开得到其一阶近似,简化了层内传播时间和水平位移的计算;同时仅对变化项应用简化的声速剖面,降低剩余传播时间计算误差。实验结果证明当波束角小于50°、层间距小于50 m或上下层声速差小于20 m/s时,近似模型与常梯度算法精度相当,时间分解法在声速剖面层间距增大时能显著提高声线跟踪的精度。 相似文献
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Morphological evolution of a well‐constrained,subaerial–subaqueous source to sink system: Wabush Lake 下载免费PDF全文
Since 1964, the Iron Ore Company of Canada has deposited iron tailings resulting from mining operations into Wabush Lake, Western Labrador, Canada. This activity has resulted in a continuous hyperpycnal flow flowing over the lake floor. Bathymetric surveys were carried out between 1999 and 2008 as part of the overall environmental Iron Ore Company of Canada plans to maintain safe disposal strategies of tailings into the lake. Here, this dataset is used to study the evolution of different channels present in Wabush Lake and their link with knickpoints found at the head of most of these channels. The channels show notable evolution from one survey to the next. Some knickpoints and channels may be followed throughout more than one survey; the evolution of these knickpoints is the process responsible for the creation of erosional channels. The context in which they appear, as well as the evolution of some of the subaqueous channels is analysed. Cyclic steps and sediment waves are also found in the lake. These rhythmic bedforms, also created by the passage of turbidity currents, are analysed. Sediment waves found in Wabush Lake show values for both wavelength and wave height that are approximately one order of magnitude smaller than most of those found in the marine environment. 相似文献
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Magdalena Szuman Christian Berndt Colin Jacobs Angus Best 《Marine Geophysical Researches》2006,27(3):167-180
This study uses three acoustic instruments (different in their operating frequencies, 13, 3.5, and 6–10 kHz, and deployment
type, hull-mounted, surface-towed and deep-towed) to investigate and characterize the acoustic response of seafloor NE of
Oman in a frequency-independent manner. High-resolution control was achieved by having selected areas of our acoustic transects
ground-truthed by sampling and/or sea-floor photography. On the regional scale, the greatest degree of change in backscatter
amplitude was correlated with major changes of seabed morphology and lithology. However, small-scale roughness had the biggest
effect on amplitude on the local scale, i.e. within each area of specific seafloor type. The study also shows that seafloor
reflection amplitude changes are far more easily detected by deep-towed instrument than by surface-towed or hull-mounted systems.
Whilst there are significant changes in bioturbation types and density along the transects, the suite of instruments deployed
was not able to pick up the effect of the bioturbation on acoustic signals. 相似文献
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