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81.
Hoi-Soo Jung Young-Tak Ko Sang-Bum Chi Jai-Woon Moon 《Marine Georesources & Geotechnology》2001,19(3):167-180
Seafloor morphology and ferromanganese nodule occurrence were studied using a multibeam side scan sonar (SeaBeam, 2000) and a deep-sea camera system in the Korea Deep-sea Environmental Study (KODES) area, northeast equatorial Pacific. Seafloor morphology and nodule abundance are highly variable even in this small study area. The NNE-SSW oriented hills are parallel and about 100-200 m high. Valleys are very flat-floored, while hilltops are rugged with depressions of tens of meters. Cliffs to about 100 m bound the valleys and the hills. The study area can be classified into three types based both on nodule occurrence and seafloor morphology, mostly G- and B-types and some M-type. G-type is characterized by high nodule abundance, ubiquitous bioturbation, and flat seafloor morphology, while B-type is characterized by irregular-shaped nodules, variable nodule abundance, occurrence of giant nodules and sediment lumps, rugged bottom morphology with depressions, and white calcareous surface sediments. Medium nodule abundance and a generally flat seafloor characterize M-type. G-type occurs mostly in the valley regions, while B-type is on the hilltop areas. M-type is located between the hilltop and the valley. Tectonic movement of the Pacific plate resulted in the elongated abyssal hills and cliffs. The rugged morphology on hilltops resulted from erosion and redistribution of surface siliceous sediments on hilltops by bottom currents, outcropping of underlying calcareous sediments, and dissolution of the carbonate sediments by corrosive bottom water undersaturated with CaCO 3 . Sediment eroded from the hills, which is relatively young and organic-rich, is deposited in the valleys, and diagenetic metal supply to manganese nodules in the valley area is more active than on the hills. We suggest that tectonic movement ultimately constrains morphology, surface sediment facies, bottom currents and sediment redistribution, bioturbation, thickness of the sedimentary layer, and other conditions, which are all interrelated and control nodule occurrence. The best potential area for mining in the study area is the G-type valley zones with about 3-4 km width and NNW-SSE orientation. 相似文献
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83.
ANDREW J. WHEELER MAXIM KOZACHENKO DOUG G. MASSON VEERLE A. I. HUVENNE 《Sedimentology》2008,55(6):1875-1887
The Darwin Mounds are small (up to 70 m in diameter), discrete cold‐water coral banks found at c. 950 m water depth in the northern Rockall Trough, north‐east Atlantic. Formerly described in terms of their genesis, the Darwin Mounds are re‐evaluated here in terms of mound growth processes based on 100 and 410 kHz side‐scan sonar data. The side‐scan sonar coverage is divided into a series of acoustic facies representing increasing current speed and sediment transport/erosion from south to north: pockmark facies, ‘mounds within depressions’ facies, Darwin Mound facies, stippled seabed facies and sand wave facies. Mound morphometric changes are quantified and show a south‐to‐north divergence from an inherited morphology, reflecting the outline of coral‐colonized fluid escape structures, to developed, downstream elongated, elevated mound forms. It is postulated that increasing current speeds and bedload sand transport favour mound growth and development by a process of enhanced sand sedimentation within mounds due to current deceleration by frictional drag around coral colonies. Comparisons are made with similar growth processes attributed to comparably sized cold‐water coral mounds in the Porcupine Seabight, offshore Ireland. 相似文献
84.
基于海底管道的检测数据,讨论了起伏地形对传统侧扫声呐探测结果的影响,为起伏地形条件下应用侧扫声呐探测海底管道的调查方案设计、探测精度优化提供参考。研究表明:海底管道周边存在的冲刷槽以及堆积体等复杂地形对侧扫声呐探测有遮挡效应,测量过程中需控制拖体与目标物的相对位置,保证有效覆盖,避免漏测;根据区域地形分布特征,海底跟踪时通过手动设置符合整体地形走势的水深值,忽略小规模起伏地形对拖体高度取值的影响,可有效降低斜距改正后平面位置偏离及目标物的形态畸变;分析了地形起伏的影响因素(k)对海底管道出露及悬空高度计算结果的影响,通过几何近似和简化,提出了海底管道出露及悬空高度计算结果改进方法,并应用该方法对已知管径的海底管道进行了验证,修正后管径反演值的绝均差和均方差都减小为原来的10%左右,可供侧扫声呐数据解释借鉴。 相似文献
85.
J.V. Gardner B.R. Calder J.E. Hughes Clarke L.A. Mayer G. Elston Y. Rzhanov 《Geomorphology》2007,89(3-4):370-390
Four drowned shelf-edge delta complexes, two drowned shelf deltas, three drowned barrier islands, large areas of “hardground”, and fields of bedforms on the mid and outer continental shelf and uppermost slope north of the head of De Soto Canyon, NE Gulf of Mexico were mapped with high-resolution multibeam echosounder. Deltas formed not during the last eustatic low stand, but during one or more interstadials when eustatic sea levels were only 60 to 80 m below present sea level. The barrier islands and deltas must have been cemented prior to rapid falls of eustatic sea level that occurred during global glaciations. Cementation is necessary to have preserved the barrier islands from erosion and subsequent destruction by the rapid sea-level rise during the last deglaciation. The preservation of the relict bathymetry is so good that features that superficially resemble trough blowouts are found in association with one of the relict barrier islands. Asymmetric bedforms on the midshelf in water depths of 50 to 60 m indicate transport directions to the SW but asymmetric bedforms in water depths of the upper slope between 100 and 120 m on the S and SE flanks of the drowned shelf-edge deltas indicate a different current direction, a separate flow that is a continuation of a SW-flowing current that was previously found on the upper slope off NW Florida. 相似文献
86.
侧扫声纳系统及其在海洋环境监测和保护中的应用 总被引:3,自引:0,他引:3
总结了侧扫声纳系统在海洋环境监测和保护中的应用,介绍了侧扫声纳基本工作原理及其发展情况,并且对其以后的发展进行了简单探讨。 相似文献
87.
基于小波变换的声纳图像边缘特征检测研究 总被引:1,自引:0,他引:1
声纳图像的边缘特征检测是其目标识别技术的重要技术基础。声纳图像背景复杂、噪声污染严重,而传统的边缘检测方法对图像噪声非常敏感,所以针对这一特点,利用小波变换易于消除噪声、运算方便的数学特征,提出了一种基于小波变换的声纳图像边缘特征检测算法。由计算机仿真结果可以得到,与传统的边缘检测算法相比,此算法在有效地抑制噪声的同时,还可以得到较高的边缘定位精度,能够很好地检测到原始声纳图像的边缘。 相似文献
88.
针对影响拖曳线列阵声纳系统目标检测性能的两种典型近场强干扰源,由宽带近场阵列模型,提出了基于功率谱相关的干扰抵消方法,通过比较基元域频域信号与干扰波束信号功率谱之间的相似关系,找到与每路基元信号相匹配的干扰分量信号,最后通过频域块自适应滤波算法实现每路基元域信号中的干扰抵消。宽带仿真结果与海试表明,这种方法在强干噪比和低信噪比条件下,比最小方差无失真响应和传统基元域干扰抵消方法在阵增益方面提高约10dB。相比传统基元域干扰抵消方法,这种方法能够实现抵消拖船干扰的同时抵消邻近目标强干扰。 相似文献
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90.