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71.
晚更新世末期南海北部陆架的古地理探讨 总被引:7,自引:3,他引:7
根据地球物理综合调查,沉积物的粒度、矿物成分、石英砂粒扫描电镜分析,14T测年,以及微体古生物等成果,表明南海北部外陆架地区在更新世末期,冬半年气候干寒,东北风强劲,风沙活动强烈,砂丘广布,为干寒多风沙的自然环境。 相似文献
72.
73.
瞬变电磁法应用于浅海底进行资源勘探或工程地质勘查时,需要将仪器系统和观测装置置于海底,以克服海水屏蔽效应。因此,要求能够远程控制仪器进行自动化数据采集;同时,受工作环境影响,需要将观测装置小型化;另外,通过拖曳式测量提高工作效率。总结课题组目前的研究成果,就仪器系统研制、观测装置小型化、拖曳式测量及海水影响等内容的研究进展进行了简要叙述。 相似文献
74.
SCICEX Investigations of the Arctic Ocean System 总被引:1,自引:0,他引:1
75.
Late amagmatic extension along the central and eastern segments of the West Philippine Basin fossil spreading axis 总被引:2,自引:0,他引:2
The spreading processes within the West Philippine Basin (WPB) remain partly unknown. This study presents an analysis of the tectono-magmatic processes that happened along its spreading axis during the conclusion of the last spreading phase at 33/30 Ma. We demonstrate that the late episode of N-S opening from an E-W-trending spreading system has been followed by a late tectonic event occurring in the central and eastern parts of the basin. This event was responsible for transtensional strain accommodated along the NW-SE faults cutting through the former E-W rift valley in the central part of the basin. In its eastern part, the same event occurred at a larger extent and led to the creation of a new NW-SE axis, obliquely cutting the older E-W spreading segments and their associated spreading fabrics. At this location, several tens of kilometers of slightly oblique amagmatic extension occurred following a ∼60° direction. We propose that this late event is associated with the onset of E-W opening of the Parece-Vela Basin located along the eastern border of the WPB at 30 Ma. Extensive stresses within this basin were probably transmitted to the hot and easily deformable rift zone of the WPB. The newly-created NW-SE axis most likely propagated from east to west, being responsible for scissors opening within the WPB. NE-SW extension ceased when well-organized spreading started at 26 Ma in Parece-Vela Basin, accommodating entirely the global extensive stress pattern. 相似文献
76.
77.
地球物理资料表明,莺歌海盆地区麻坑众多,浅层气发育,在高分辨率地震剖面上可以识别出到达海底的地震模糊带,在3.5 kHz的浅层剖面上可见穿透到海底的气体聚集带,在声呐图像可以识别出麻坑.莺歌海盆地不仅在其边缘隆起带沉积层较薄的地区存在海底天然气渗漏现象,而且在中央坳陷带沉积层巨厚的地区也存在海底天然气渗漏,海底天然气渗漏在莺歌海盆地是广泛分布的.莺歌海盆地广泛分布的海底天然气渗漏是全球海底天然气渗漏系统的重要组成部分,海底天然气渗漏系统排出的大量甲烷气体的一部分可能穿越水层到达海面. 相似文献
78.
A convection-conduction model for analysis of the freeze-thaw conditions in the surrounding rock wall of a tunnel in permafrost regions 总被引:1,自引:0,他引:1
The results of simulated tidal current field, wave field and storm-induced current field are employed to interpret the depositional
dynamic mechanism of formation and evolution of the radial sand ridges on the Yellow Sea door. The anticlockwise rotary tidal
wave to the south of Shandong Peninsula meets the following progressive tidal wave from the South Yellow Sea, forming a radial
current field outside Jianggang. This current field provides a necessary dynamic condition for the formation and existence
of the radial sand ridges on the Yellow Sea seafloor. The results of simulated “old current field (holocene)” show that there
existed a convergent-divergent tidal zone just outside the palaeo-Yangtze River estuary where a palaeo-underwater accumulation
was developed. The calculated results from wave models indicate that the wave impact on the topography, under the condition
of high water level and strong winds, is significant. The storm current induced by typhoons landing in the Yangtze River estuary
and turning away to the sea can have an obvious influence, too, on the sand ridges. The depmitional dynamic mechanism of formation
and evolution of the radial sand ridges on the Yellow Sea seafloor is “tidal current-induced formation—storm-induced chang—tidal
current-induced recovery”.
Project supported by the National Natural Science Foundation of China (Grant No. 49236120). 相似文献
79.
80.
As the soil traction of the track system consisting of a track plate and protruded grousers is generally higher than that of a comparable wheel system, underwater tracked vehicles are the favored platforms for heavy-weight remotely operated vehicles (ROVs). When an underwater tracked vehicle moves on the seafloor, the track system laterally transmits an engine torque to the soil-track interface, resulting in slip displacement and an associated soil thrust acting as a traction force. Therefore, to evaluate the mobility of underwater tracked vehicle, it is critical to evaluate the soil thrust of the track system based on the soil-track interaction. Unlike the soil thrust of sandy soils, a reliable soil thrust assessment method accounting for the failure mechanism of clayey soil has yet to be developed in spite of its significance. An experimental study on the mechanism of the soil thrust of clayey soil was thus performed. Model track experiments were conducted on a model track system with clayey soil. Based on the experiment results, the mechanism of the soil thrust of clayey soil was investigated and was compared with the mechanism of soil thrust derived from the previous soil thrust assessment methods using sandy soil. Particular attention was given to the development of a new soil thrust prediction model for the track system on clayey soil using the limit equilibrium analysis technique. 相似文献