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991.
992.
993.
Introduction The Great North China, located at longitude 106E to 124E and latitude 31N to 42N, in-cludes three secondary active tectonic blocks, Ordos, Yanshan and North China plain (Figure 1). The geological tectonics of these three secondary blocks is much different from each other. As a stable block with high rigidity, the Ordos block is mostly surrounded by down-faulted basins with an inactive interior since Cenozoic, although the fault zones along its boundary are strongly active wi… 相似文献
994.
Introduction In recent years, with the development of earthquake observation technology, increasing ofobservation stations and improvement of observation instruments which are digitalized and con-nected by network, a great deal of data is recorded, to some extend, which brings difficulty for usto manage and store them. It leads to traditional methods, which use the file system to managemass data, could not satisfy our requirement, and it is necessary to find a new method in place oftradit… 相似文献
995.
Introduction The acceleration response spectrum and peak ground acceleration are the necessary and im-portant parameters in earthquake-resistant design at present. They are still active research field. With the increase of digital high accurate strong motion observation data, especially the earth-quakes of Loma Prieta (M=7.0) in 1989; Landers (M=7.3) in 1992; Big Bear (M=6.4) in 1994 and Northridge (M=6.7) in 1994 in USA; Kozani (M=6.6) earthquake and afteshocks in 1995 in Greece; Dinar… 相似文献
996.
Thermodynamic conditions of framework grain dissolution of clastic rocks and its application in Kela 2 gas field 总被引:2,自引:2,他引:2
LAI Xingyun YU Bingsong CHEN Junyuan CHEN Xiaolin LIU Jianqing MEI Mingxiang JING Weiguang & CHENG Suhua School of Earth Sciences Mineral Resources China University of Geosciences Beijing China Key Laboratory of Lithospheric Tectonics Deep-level Process Exploration of Ministry of Education Beijing China 《中国科学D辑(英文版)》2005,48(1):21-31
Feldspar and clastic debris are the most important constituent framework grains of sedimentary clastic rocks and their chemical dissolution plays an essential role in the formation and evolution of the secondary pore in the reservoir rocks. On the basis of thermodynamic phase equilibrium, this study investigates the chemical equilibrium relationships between fluid and various plagioclase and K-feldspar in diagenesis of the sediments, particularly, the impact of temperature and fluid compositions (pH, activity of K+, Na+, Ca2+ and so on) on precipitation and dissolution equilibria of feldspars. Feldspar is extremely easily dissolved in the acid pore water with a low salinity when temperature decreases. The dissolution of anorthite end-member of plagioclase is related to the Ca content of the mineral and the fluid, higher Ca either in the mineral or in the fluid, easier dissolution of the feldspar. Moreover, the dissolution of albite end-member of plagioclase is related to Na of both the mineral and fluid, 相似文献
997.
Distribution of chlorophyll-a off the Changjiang River and its dynamic cause interpretation 总被引:1,自引:1,他引:1
ZHU Jianrong State Key Laboratory of Estuarine Coastal Research East China Normal University Shanghai China 《中国科学D辑(英文版)》2005,48(7)
Red tide,also called harmful algal bloom interna-tionally,is a disaster abnormal phenomenon of oceanecology with an explosive breed or dense assemble ofone or several phytoplanktons in a specific ocean en-vironment condition,colors the seawater,influencesand harms ocean living things.The formation of redtide is controlled mainly by a complex interplay ofbiological,physical and chemical processes,but themost main cause influencing the occurrence of red tideis the seawater eutrophication,i.e.,the… 相似文献
998.
WU Yaping ZHU Yuanlin GUO Chunxiang SU Qiang & MA Wei . School of Civil Engineering Lanzhou Jiaotong University Lanzhou China . State Key Laboratory of Frozen Soil Engineering Cold Arid Regions Environmental Engineering Research Institute Chinese Academy of Sciences Lanzhou China 《中国科学D辑(英文版)》2005,48(7)
In the construction of Qinghai-Tibet railway,to avoid diseases caused by frost heave and thaw col-lapse of frozen ground,besides the normal bridges over the rivers,a lot of dry bridge structures have been built to replace subgrade in the regions of high tem-perature and high ice content frozen soil.So,the problems on forming mechanism of bearing capacity of pile foundation in cold regions already become one of hot spot problems in frozen soil engineering.Freezing force and frost heave force ar… 相似文献
999.
HE Yongfeng & CHEN Xiaofei . Department of Geophysics School of Earth & Space Sciences Peking University Beijing China . North-West Institute of Nuclear Technology Xi’an China 《中国科学D辑(英文版)》2005,48(12):2118-2122
Since the sign up of CTBT (Comprehensive Test Ban Treaty), the nuclear monitoring and distinguishing has gained great attention by the treaty countries. Seismology is one of the primary technical means available for monitoring compliance to a CTBT. However, there does not exist a single criterion, so far, that can effectively distinguish explorations from earthquakes. It has been known that source time function (abbreviated to STF) of an underground nuclear explosion contains important p… 相似文献
1000.
LIU Jihua SHI Xuefa Chen Lirong HUANG Yongyang Wang Yinxi Cui Yingchun BU Wenrui 《中国科学D辑(英文版)》2005,48(5)
Clay fractions in the non-calcareous surface sediments from the eastern Pacific were analyzed for clay minerals, REE and 143Nd/144Nd. Montmorillonite/illite ratio (M/I ratio), total REE contents ((REE), LREE/HREE ratio and cerium anomaly (бCe) may effectively indicate the genesis of clay minerals. Clay fractions with M/I ratio >1, бCe (0.85, (REE (400 μg/g, LREE/HREE ratio (4, and REE patterns similar to those of pelagic sediments are terrigenous and autogenetic mixed clay fractions and contain more autogenetic montmorillonite. Clay fractions with M/I ratio <1, бCe=0.86 to 1.5, ΣREE=200 to 350 μg/g, LREE/HREE ratio (6 and REE distribution patterns similar to that of China loess are identified as terrigenous clay fraction. The 143Nd/144Nd ratios or (э)Nd values of clay fractions inherit the features of terrigenous sources of clay minerals. Clay fractions are divided into 4 types according to (э)Nd values. Terrigenous clay minerals of type I with the (э)Nd values of -8 to -6 originate mainly from North American fluvial deposits. Those of type II with the (э)Nd values of -9 to -7 are mainly from the East Asia and North American fluvial deposits. Those of type III with (э)Nd values of -6 to -3 could come from the central and eastern Pacific volcanic islands. Those of type IV with (э)Nd values of -13 to -12 may be from East Asia eolian. The terrigenous and autogenetic mixed clay fractions show patchy distributions, indicating that there are volcanic or hot-spot activities in the eastern Pacific plate, while the terrigenous clay fractions cover a large part of the study area, proving that the terrigenous clay minerals are dominant in the eastern Pacific. 相似文献