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41.
42.
通过1850~1991年旱涝百分率的CEOF分析,研究了近百年来中国东部旱涝的分布特征、时空变化特点及年际演变规律。结果表明,我国东部主要有三种旱涝分布类型。第一种类型是以长江流域为中心全国大范围旱或涝,空间位相近似相同,且有10.7年和3.1年周期性变化,振幅强度在1923~1924年间曾发生过增强突变。第二种类型为南北旱涝趋势相反的分布,空间位相自北向南变化显著,且有4.3年周期性变化,振幅强度在1884~1885年间曾有一次减弱突变。第三种类型呈江淮流域与华北和华南旱涝趋势相反的分布,空间位相从南北两个方向向中间或相反方向移动,并有3.4年周期性变化,振幅强度在1911~1912年有过增强突变。 相似文献
43.
本文从比较文化学与文化地理学的角度,较全面、系统地分析比较了东西文化的诸多差异,侧重剖析了东西方文化差异的地理原因,评介了“东化”与“西化”之争的基本观点,说明了东西方文化的关系及其发展前景。 相似文献
44.
赣东加里东变质混合岩带 ,是以混合岩体为主体 ,受韧性剪切带控制的多相、多型、递增变质带 ,是受区域深构造控制的热变质带。该带产有茅排式金矿。通过对该带金地球化学特征和地球化学行为研究 ,认为带中金丰度 0 .83× 10 - 9,呈峰式分布 ,为对数及双对数正态分布型式 ,Au与主元素成分无关 ,与微量元素组合是Au -Zn -Li-Pb -Cs ,在韧性剪切过程中Au具活化迁移富集特点 相似文献
45.
Large tectonic movement of the Japan Arc in late Cenozoic times inferred from paleomagnetism: Review and synthesis 总被引:4,自引:0,他引:4
Abstract Paleomagnetic studies facilitate an understanding of the evolution of the Japan Arc in Cenozoic times from the perspective of tectonic movement. The Japan Arc rifted from the Asian continent in the middle Miocene, while East Asia, including the Japan Arc, moved northward at the same time. The rifting phenomenon of the Japan Arc is described by differential rotation of Southwest and Northeast Japan. Southwest Japan was rotated clockwise through about 45° and Northeast Japan was rotated counter-clockwise through about 40°. This differential rotation occurred concurrently at about 15 Ma. Eighty percent of the rotation was completed during a period of 1.8 million years. These factors lead us to propose a'double door'opening mode with a fast spreading rate of 21 cm/yr for the evolution of the Japan Sea, suggesting that the asthenosphere with a low viscosity was injected beneath the Japan Sea area. The large northward motion of East Asia in relation to Europe is expected from the apparent polar wander path constructed from the paleomagnetic data of the Japan Arc. East Asia may have moved northward by more than 1700 km between 20 Ma and 10 Ma accompanied by a slightly clockwise rotation of 10°. The eastern part of the Eurasian plate was subjected to extreme geodynamic conditions in late Cenozoic times. 相似文献
46.
本文对冀东迁安麻粒岩及有关岩石中的辉石进行了研究,结果表明:辉石的含铁度
明显受寄主岩石化学成分的制约,寄主岩石的/Mg0和=(Fe203 ×0.8999 + Fa0)
值愈高,辉石的含铁度也愈高;共存辉石对的Fe2+ 一Mg分配系数(KD劝不仅受结晶温压条件
控制,同时也受辉石其它成分的影响。但Ca-Mg-Fe 三角图解等资料研究表明:共存的二辉
石对是平衡结晶的产物,其KD平均值也符合张儒媛等(1)统计的变质辉石平均值为1.85的规
律。通过二辉石温度计计算和矿物共生组合等资料的分析,得出辉石形成的温度为869±60ºC.压力为5 ×108-9 ×108 Pa。本区与铁矿体成过渡关系的辉石岩全铁含量与工业铁矿大致相等,铁矿的成因与其有着非常密切的关系。 相似文献
47.
ABSTRACTRapid economic growth, a high degree of urbanization and the proximity of a large number of desert and semidesert landscapes can have a significant impact on the atmosphere of adjacent territories, leading to high levels of atmospheric pollution. Therefore, identifying possible sources of atmospheric pollution is one of the main tasks. In this study, we carried out an analysis of spatial and temporal characteristics of five main atmospheric pollutants (PM2.5, PM10, SO2, NO2, and CO) near potential source of natural aerosols, affecting seven cities (Wuhai, Alashan, Wuzhong, Zhongwei, Wuwei, Jinchang, Zhangye), located in immediate proximity to the South Gobi deserts. The results, obtained for the period from 1 January 2016 to 31 December 2018, demonstrate total concentrations of PM2.5 and PM10 are 38.2 ± 19.5 and 101 ± 80.7 μg/m3 exceeding the same established by the Chinese National Ambient Air Quality Standard (CNAAQS), being 35 and 70 μg/m3, respectively. Based on the data from Moderate Resolution Imaging Spectroradiometer (MODIS) for the whole period, Clean Сontinental (71.49%) and Mixed (22.29%) types of aerosols prevail in the region. In the spring and winter seasons maximum concentrations of pollutants and high values of Aerosol Optical Depth (AOD) in the region atmosphere are observed. PM2.5 and PM10 ratio shows the presence of coarse aerosols in the total content with value 0.43. The highest concentrations of pollutants were in the period of dust storms activity, when PM2.5 and PM10 content exceeded 200 and 1000 µg/m3, and AOD value exceeded 1. UV Aerosol Index (UVAI), Aerosol Absorbing Optical Depth (AAOD), and Single Scattering Albedo (SSA), obtained from Ozone Monitoring Instrument (OMI), demonstrate the high content of dust aerosols in the period of sandstorms. Analysis of backward trajectories shows that dust air masses moved from North to Northwest China, affecting large deserts such as Taklamakan, Gurbantunggut, Badain Jaran, Tengger, and Ulan Buh deserts. 相似文献
48.
The assessment of seismic hazard parameters is important in the seismically active regions. A straightforward approach is considered for the statistical estimation of the maximum values of earthquake hazard parameters. The Bayesian estimator is suggested and emphasis is given to the evaluation of the maximum possible Mmax (regional) magnitude in a future time interval T. This approach allows the uncertainty of earthquake magnitude to be accounted for. Seismic hazard parameters like the -value which is the slope of the magnitude-frequency law (where, b = loge) and the intensity (rate) of seismic activity and their uncertainties are also estimated. The quantiles of functions of distributions of true and apparent magnitude on a given time interval [0, T] are evaluated, as well. Two main assumptions are adopted for the method:(1) earthquake occurrence is Poissonian and(2) the magnitude-frequency law is of Gutenberg-Richter type with a cutoff maximum value of magnitude. It is needless to say the seismic catalog used must have a large number of events. This requirement leads to the estimation of the parameters referred to some of the most seismically active regions of the world, e.g., Chile, Peru-Equador-South Colombia,Central America and Mexico, which belong to the east part of the circum-Pacific belt. 相似文献
49.
50.
INTRODUCTIONThe east Kunlun active fault is an important NWWtrending boundary fault on the northeasternmargin of the Qinghai-Xizang(Tibet)Plateau.The fault extends fromthe northside of the Qiangtangmassif in the west,runs eastward through the Kusai Lake,Dongdatan,Xidatan,Tuosuo Lake andMaqu to the north of Zoig毢(Van Der Woerd,et al.,2002;Ma Yinsheng,et al.,2005;Seismological Bureau of Qinghai Province,et al.,1999;Li Chunfeng,et al.2004).The intenseleft-lateral strike-slip move… 相似文献