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231.
全球、中国大陆和华北地区地震活动韵律性时变特征及趋势分析 总被引:4,自引:0,他引:4
基于Morlet小波变换,提出一种新的定量划分地震活跃期或平静期的分析方法,形成了根据复小波变换得到不同周期累加能谱极大值点变化、实小波变换振动周期谱时频分布以及指定周期的小波振动周期随时间变化的极值分布规律来研究地震活动韵律性及其时变特征的物理思路。通过对全球、中国大陆和华北地区浅源地震年释放能量的时间序列分析。对研究区强震活动的韵律性及其时变特征有了新的认识。根据目前强震活动具有的韵律性,结合历史地震活动情况,对未来研究区地震趋势进行了初步分析。 相似文献
232.
川藏公路二郎山隧道和平沟泥石流特征研究与治理设计 总被引:1,自引:0,他引:1
泥石流作为地质环境较差的山区的主要自然灾害之一,对于泥石流的研究思路的进一步发展和完善,在很大程度上将对山区的工程建设有很重要的指导意义。从工程地质研究思路的角度出发,对位于川藏公路二郎山隧道西口和平沟泥石流进行了研究。采用工程地质分析的方法对和平沟泥石流的形成环境(地层岩性条件、构造条件、地貌条件、气象条件、植被发育及人类活动)、基本特征(泥石流沟的基本特征、泥石流的堆积特征)进行了系统的研究,并在此基础上对泥石流沟沿岸的岸坡稳定性(可能泥石流的物源)等进行了评价分析。对泥石流的活动趋势以及可能泥石流的方量做出了较为科学的评价预测。经过这样的系统分析对工程建设中的泥石流防治提出了治理设计方案。 相似文献
233.
234.
简要叙述了柳林泉域岩溶地下水水文地质结构,明确了奥陶系上马家沟组为最主要的含水层,通过对柳林泉水及泉域内“奥灰”钻孔水质分析化验资料的主要水化学特征进行对比,确定了柳林泉南北两岸的补给来源不同,南岸来自东部子系统,北岸来自北部子系统。 相似文献
235.
藏南特提斯喜马拉雅带中段二叠纪-白垩纪的火山活动(Ⅰ):分布特点及其意义 总被引:12,自引:1,他引:12
在野外实地考察和追索的基础上,详细厘定了特提斯喜马拉雅带中段晚古生代以来火山岩的分布特点和迁移规律。结果表明,在特提斯喜马拉雅带中段晚古生代以来的地层系统中,从二叠纪→三叠纪→侏罗纪→白垩纪,共有11个层位含规模不等的火山岩,它们以透镜体、薄夹层或以块状玄武岩、玄武质安山岩等形式产出于不同地层系统中;从二叠纪→早中三叠世→晚三叠世→侏罗纪和白垩纪,具有由西向东、从南→北→南→北的迁移规律。这些火山活动的发现和厘定,对填补特提斯喜马拉雅带火山岩研究的空白,了解陆下岩石圈地幔和软流圈地幔之间的相互作用和新特提斯洋盆的形成演化都具有一定的指示意义。 相似文献
236.
237.
ZHAGN Yijun DONG Wansheng ZHAO Yang ZHANG Guangshu Zhang Hongfa CHEN Chengpin ZHANG Tong 《中国科学D辑(英文版)》2004,47(Z1)
The comprehensive observations on lightning discharges were conducted in Naqu area of Qinghai-Tibet Plateau in summer of 2002. The electric structures of thunderstorms and the characteristics of lightning discharges at initial stage were analyzed by using the observation data. The results show that most of intracloud (IC) lightning flashes were polarities inverted in thunderstorms with tripole electric charge structure and occurred between negative charge region located in the middle of the thunderstorm and positive charge region located at the bottom of the thunderstorm. The radiation characteristics of discharge processes in cloud with longer lasting time involved in Cloud-to-Ground (CG) lightning flashes were similar to that of IC discharges.A lot of radiation pulses were produced in these discharge processes. Because the IC discharges took place at the bottom of thundercloud and were near the ground, they may produce more serious damage to equipment on the ground therefore should not be neglected in lightning protection. 相似文献
238.
Distribution characteristics and petroleum geological significance of the Silurian asphaltic sandstones in Tarim Basin 总被引:1,自引:0,他引:1
The Tarim Basin is a typical superimposed basin in which there have occurred multiphase adjustment and destruction of the reservoirs. The widely distributed asphaltic sandstones of the Silurian are the very product after destruction of the reservoirs. Studies show that the Silurian asphaltic sandstones distributed in both the middle and western parts on the basin are controlled chiefly by the Caledonian oil source area and by the Tazhong, Tabei and Bachu uplifts, whereas the distribution of the asphaltic sandstones on local structural belts is controlled by the reservoir's sedimentary system. Vertically, most of the asphaltic sandstones are under the regional caprock of red mudstones and the upper sandstone section of compact lithology. Due to the difference of hydrocarbon destruction in the early stage and the influence of hydrocarbon recharge in the late stage, the asphaltic sandstones and oil-bearing sandstones in the Tazhong area can be vertically divided into the upper and lower sections and they have an interactive distribution relationship as well. Asphaltic sandstones exist not only in intergranular pores but also inside the grains of sand and between the crevices, proving the destruction of early reservoirs due to uplifting. The existence of asphaltic sandstones over a large area reveals that the large-scale migration and accumulation and the subsequent destruction of hydrocarbons in the Craton area. The destruction caused a loss of the reserve resources of the Palaeozoic amounting to nearly 13.3 billion tons. Asphaltic sandstones formed after the destruction of oil and gas may serve as an effective caprock which is beneficial to accumulation of hydrocarbons and formation of the pool sealed by asphaltic sandstones in the later stage. The destruction of the early Silurian hydrocarbons depends on the stratigraphic burial depth. The deep part under the northern slope of Tazhong is an area favorable to search of undestroyed Silurian oil reservoirs. 相似文献
239.
Alluvial fan development in Alpine areas is often affected by catastrophic sedimentary processes associated with extreme ?oods events, causing serious risks for people living on the fans. Hazard assessment in these areas depends on proper identi?cation of the dominant sedimentary processes on the fans. Data from a set of 209 alluvial fans from the central Alps of Italy are presented in this paper and analysed with the help of various statistical techniques (linear regression, principal components analysis, cluster analysis, discriminant analysis and logistic regression). First, we used modern sedimentary facies and historical records (?ood events since 15th century), to distinguish between the two dominant sedimentary processes on alluvial fans: debris ?ows and stream?ows. Then, in order to analyse the main controls on past and present fan processes, 36 morphological, geological and land‐use variables were analysed. As with observations for arid‐environment fans, catchment morphology is the most in?uential factor in the study area, whereas geology and land use are minor controls. The role of climatic change and landsliding within the catchments also seems to be very important and is discussed. Statistical techniques also help in differentiating groups of alluvial fans by sets of controlling factors, including stage and type of evolution. Finally, by using discriminant analysis and logistic regression, we classi?ed alluvial fans according to the dominant sedimentary process, with a success rate ranging between 75 and 92 per cent. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
240.
Development characteristics of interlayer oxidation zone type of sandstone uranium deposits in the southwestern Turfan-Hami basin 总被引:3,自引:0,他引:3
YANG Dianzhong XIA Bin & WU Guogan Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China 《中国科学D辑(英文版)》2004,47(5)
The known uranium ore and anomaly occur-rences are distributed mainly in the southwestern part of the Turfan-Hami basin. The focus of current explo-ration is placed on the leachable interlayered oxidation zone type of sandstone uranium deposits. Uranium deposits in the sedimentary basin can be classified into three types in accordance with their host rock types, i.e. the sandstone-type uranium deposits, the coal rock-type uranium deposits and the mud-stone-type uranium deposits. The sandstone… 相似文献