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231.
232.
全国自动地震速报系统介绍 总被引:2,自引:0,他引:2
对全国自动地震速报系统进行简要介绍。根据《自动地震速报技术管理规定》,全国自动地震速报系统由5个区域自动地震速报分中心(辽宁、河北、福建、陕西及云南)和国家地震速报备份中心(广东省地震局)组成。通过十五国家测震台网的建设,利用全国1 000多个地震台站和200多个境外地震台站,现阶段自动地震速报能力达到国内地区1 min左右、周边地区2 5 min、国外其他地区3—30 min的水平。 相似文献
233.
Zhou Jian Jiang Tong Wang Yanjun Su Buda Tao Hui Qin Jiancheng Zhai Jianqing 《地理学报(英文版)》2020,30(1):37-52
Journal of Geographical Sciences - Aridity index reflects the exchanges of energy and water between the land surface and the atmosphere, and its variation can be used to forecast drought and flood... 相似文献
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236.
研究表明新疆富蕴盆地早石炭世黑山头组、南明水组主要为一套滨、浅海相沉积,地层之间发育多套砾岩层,呈透镜体状,横向上延伸不远,为河流入海时形成的一系列水下河道沉积,而并非前人所认为的萨吾尔造山运动形成的构造底砾岩。砾岩层横向特征的对比及交错层理、波痕等古流向数据,表明地层沉积时期水体古流向总体自北西向南东(介于93°~125°),物源区位于盆地北西方向。研究区内黑山头组与南明水组之间为连续沉积,整合接触,并非准噶尔地块与西伯利亚板块的碰撞形成的构造不整合面。 相似文献
237.
Genesis and Geological—Geochemical Characters of the ushan Gold Deposit,Shandong,China 总被引:3,自引:0,他引:3
The Rushan gold deposit, explored in recent years in the Jiaodong area, Shandong Province, is a quartz vein-type gold deposit
hosted in granite. The temperature of its major mineralization episode is between 220°C and 280°C. The salinity of the ore-forming
fluid is 5 % to 9% NaCl equivalent, with H2O and CO2 as the dominant gas constituents. The fluid is rich in Na+, Ca2+ and Cl−, but relatively impoverished in K+ and F−, characterized by either Ca2+ > Na+ > K+ (in three samples) or Na+ > Ca2+ > K+ (in six samples). Hydrogen and oxygen isotopes in the ore-forming fluid are highly variable with δ18
ranging between − 7.70‰ and 5. 97‰ and
between − 128‰ and − 71‰. The possibility of lamprophyre serving as the source of gold can be excluded in view of its low
gold content on the order of 2.5 × 10−9. Rb-Sr isochron ages of the deposit and the host Kunyushan granite are ( 104.8 ± 1.5) Ma and 134.6 Ma respectively with the
respective initial Sr ratios of 0. 71307 and 0.7096. It is considered that the emplacement of the lamprophyre under a tensile
environment had provided sufficient heat energy to facilitate deep circulation of meteoric water by which ore metals were
extracted from the Kunyushan granite through long-term water-rock reaction.
This project was financially supported by the National Natural Science Foundation of China. 相似文献
238.
Runoff at the three time scales(non-flooding season,flooding season and annual period) was simulated and tested from 1958 to 2005 at Tangnaihai(Yellow River Source Region:YeSR),Zhimenda(Yangtze River Source Region:YaSR) and Changdu(Lancang River Source Region:LcSR) by hydrological modeling,trend detection and comparative analysis.Also,future runoff variations from 2010 to 2039 at the three outlets were analyzed in A1B and B1 scenarios of CSIRO and NCAR climate model and the impact of climate change was tested.The results showed that the annual and non-flooding season runoff decreased significantly in YeSR,which decreased the water discharge to the midstream and downstream of the Yellow River,and intensified the water shortage in the Yellow River Basin,but the other two regions were not statistically significant in the last 48 years.Compared with the runoff in baseline(1990s),the runoff in YeSR would decrease in the following 30 years(2010-2039),especially in the non-flooding season.Thus the water shortage in the midstream and downstream of the Yellow River Basin would be serious continuously.The runoff in YaSR would increase,especially in the flooding season,thus the flood control situation would be severe.The runoff in LcSR would also be greater than the current runoff,and the annual and flooding season runoff would not change significantly,while the runoff variation in the non-flooding season is uncertain.It would increase significantly in the B1 scenario of CSIRO model but decrease significantly in B1 scenario of NCAR model.Furthermore,the most sensitive region to climate change is YaSR,followed by YeSR and LcSR. 相似文献
239.
The marine risers are often subjected to parametric excitations from the fluctuation top tension. The top tension on the riser may fluctuate with multiple frequencies caused by irregular waves. In this paper, the influence between different frequency components in the top tension on the riser system is theoretically simulated and analyzed. With the Euler-Bernoulli beam theory, a dynamic model for the vibrations of the riser is established. The top tension is set as fluctuating with time and it has two different frequencies. The influences from the fluctuation amplitudes, circular frequencies and phase angles of these frequency components on the riser system are analyzed in detail. When these two frequencies are fluctuating in the stable regions, the riser system may become unstable because ω_1+ω_2≈2Ωn. The fluctuation amplitudes of these frequencies have little effect on the components of the vibration frequencies of the riser. For different phase angles, the stability and dynamic behaviors of the riser would be different. 相似文献
240.
中国蛇绿岩的分布、时代及其形成环境 总被引:23,自引:22,他引:23
中国蛇绿岩分布很广,主要在中国的西部,西南部和北部,中部和南部较少,蛇绿岩形成的时代可分为元古宙,早古生代、晚古生代和中-新生代四个时期,中国元古宙蛇绿岩分布零星。星生宙蛇绿岩主要分布在古亚洲洋,秦祁昆洋,古特提斯洋,新特提斯洋和和环太平洋等5个区域,古亚洲洋蛇绿岩位于塔里木和华北地块之北的中国北方,秦祁昆洋位于塔里木、华北和扬子地块之间,古特提斯洋和新特提斯洋位于中国的西南地区,环太平洋带有东北和台湾的蛇绿岩,中国蛇绿岩的地和玻安岩产出,指示产于消减带之上的构造环境,在这些蛇绿岩中也有MORB产出,可能是弧后盆地环境的,也可能有正常大洋岩石圈碎片的残留。古特提斯蛇绿岩MORB发育,而减少与消减作用有关的岩石组(IAT和玻安岩),推测形成在陆间洋盆环境。 相似文献