检索结果-南通市图书馆

On the siltation of the middle Yangtze River

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Earth Sciences 2004年第5期47卷 463-480页

作者： YIN Hongfu1, CHEN Guojin2, LI Chang抋n1 & WEI Yuan3.1. School of Earth Sciences, china University of Geosciences, Wuhan 4.0074. china 2. Hydrogeological Team, Hubei bureau of Geology and Mineral Resources, Jingzhou 4.4.00, china 3. geological Survey of Jiangxi Province, Nanchang 3.0201, china china Univ Geosci Sch Earth Sci Wuhan 430074 Peoples R China Hubei Bur Geol & Mineral Resources Hydrogeol Team Jinzhou 434100 Peoples R China Geol Survey Jiangxi Province Nanchang 3300201 Peoples R China

About 5.2×108 t/a of silts from the upper reach of the Yangtze River are transported through Yichang into the middle Yangtze River. The middle Yangtze itself and its tributaries yield ca. 0.8×108 t silts annually. Of this total 6×108 t/a input of silts, ca. 1.2×108 t/a are deposited within the river artery and lakes, while ca 4.83.108 t/a are at first transported into the lower reach through Datong, and then either deposited along the river and the Yangtze Delta, or output into the sea. Along the middle Yangtze River silting generally exceeds scouring, but the spatial and temporal distributions of scour-and-fill, as well as its distribution in the river valley transections, are uneven. Along the Yichang-Chenglingji and Jiujiang-Datong Segments of the middle Yangtze, scouring exceeds or equals silting. Silting mainly occurs along the Luoshan-Wuhan-Huangshi Segments with Wuhan as the pivotal point, as well as in the Dongting and Poyang Lakes. Even in these silting-dominated areas, there are times and parts of segments that scouring prevails. As to the transections, generally the river channel of main stream is scouring-dominated, forming V-shaped sections to a depth of 203. m or more, whereas the floodplains and bar islands are silting-dominated, forming wide and relatively high flats, which are often artificially transformed into protected embankments. Because the Jingjiang Levee separates the Jianghan Plain from Yangtze to the south, little has been deposited in that plain except a few sediments from the Han River—a tributary of the middle Yangtze. This factor plus the tectonic sag of that plain has made the altitude of plain surface several meters lower than that of the levee in most of the areas. Sil-tation along the Luoshan-Wuhan-Huangshi Segments has resulted in the elevation of flood level in this and upstream segments. River channel scouring plus floodplain silting have caused the transections of the middle Yangtze valley typically with deep channel and height

关键词： the middle Yangtze, scour-and-fill, siltation, silt utilization.

National 2000' GPS control network of china

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第8期17卷 983-987页

作者： Yang Yuanxi~(1**) Tang Yingzhe~1 Chen Chuanlu~2 Wang Min~3.Zhang Peng~4.Wang Xiaorui~2 Song Lijie~5 Zhang Zusheng~6 (1.Xi'an Research institute of Surveying and Mapping,Xi'an 710054.{3. 2.Geodetic Data Processing Center,Xi'an 710054.{3. 3.Center of Earthquake Analysis and Prediction,{3. {4. bureau,Beijing 10003.,{3. 4.National Geomatics Center of china,Beijing 10004.,{3. 5.institute of Surveying and Mapping,Zhengzhou University of Information Engineering,Zhengzhou 4.0052,{3. 6.First Crustal Deformation Monitoring Center,{3. {4. bureau,Tianjin 3.0180,{3.) [a]Xi' an Research institute of Surveying and Mapping Xi' an China [b]Geodetic Data Processing Center Xi'an China [c]Center of Earthquake Analysis and Prediction China Seismological Bureau Beijing China [d]National Geomatics Center of Chinna Beijing China [e]institute of Surveying and Mapping Zhengzhou University of Information Engineering Zhengzhou China [f]First Crustal Deformation Monitoring Center China Seimological Bureau Tianjin China

An accurately unified national GPS network with more than 2500 stations,named"National 2000' GPS Control Net- work",signed the epoch 2000.0,has been established by integrating the existing six nationwide GPS networks of china set up by differ- ent departments with different *** paper presents the characteristics of the existing GPS networks,summarizes the strategies in the integrated adjustment of the GPS network,including functional model,stochastic model as well as the adjustment principle modifi- *** modifying the adjustment strategies according to the characteristics of the existing GPS networks and under the support of the IGS stations,the accuracy of the integrated national GPS network is greatly *** datum differences among the sub networks disappear,the systematic error influences are weakened,and the effects of the outliers on the estimated coordinates and their variances are *** is shown that the average standard deviation for the horizontal component is smaller than 1.0 cm,the vertical component is smaller than 2.0 cm,and the three-dimensional (3.D) position of geocenter coordinates is smaller than 3.0 *** exterior checking ac- curacy for the 3.D position is averagely better than 1.0 cm.

关键词： GPS control network adjustment systematic errors robust estimation variance component estimation coordinate system

Assessment of time-dependent seismic hazards on segments of active fault, and its problems

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1998年第23期43卷 1937-1950页

作者： WEN Xueze seismological bureau of Sichuan Province, Chengdu 61004.,{3. seismological bureau of Sichuan Province Chengdu China

Assessment of time dependent seismic hazards on segments of active fault is one of the important techniques of long term earthquake forecast for specific locations. It is based on the data from quantitatively seismo geologic investigation in active faults and expresses seismic hazards of a fault segment with both the earthquake occurrence probability, which increases as the elapsed time increases, and the magnitude predicted. Through summing up and analyzing main technical steps in research of the recent decade, some defects in the current theory and model of this technique are pointed out. For instance, the probabilistic models for recurrence interval are based solely on the quasi periodic behavior of earthquake recurrence, ignoring behavior’s diversity that possibly exists. Variability of repeated rupture dimensions in various cycles is considered inadequately in fault segmentation research, etc. It is most important for improving the reliability of the result of seismic hazard assessment to reveal actual earthquake recurrence behavior and its generalities, and to update relevant models for evaluating probabilistic earthquake hazard based on the behavior and generalities.

关键词： active fault rupture segmentation time dependent hazard probabilistic model long term forecast.

δD values of escaped H_2 from hot springs at the Tengchong Rehai geothermal area and its origin

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2002年第2期47卷 146-149页

作者： SHANGGUAN Zhiguan & HUO Weiguo institute of Geology, china seismological bureau, Beijing 10002.,{3. institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 10002.,{3. institute of Geology China Seismological Bureau Beijing 100029 China

Here we give the δD values of escaped H2 from hot springs at the Tengchong Rehai and adjacent regions, and deal with a genetic correlation between the increment H2 in escaped gases from middle-shallow reservoirs and the H2S, CH4.derived from deep sources. Isotopic compositions of H2 indicate that the generation of increment H2 may be related to recent strong activity of N-W trending fault at the Rehai area. Trace monitoring the H2 release could be significant in order to keep watch on present activity of that fault.

关键词： Rehai geothermal area hydrogen stable isotopic composition.

Partial Melting and Its Implications for Understanding the Seismic Velocity Structure within the Southern Tibetan Crust

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2003年第1期77卷 64-71页

作者： YANG Xiaosong, MA Jin, JIN Zhenmin, GAO Shan and MA Shengli Geology institute, china seismological bureau, Beijing 10002. Laboratory of Tectonophysics, china seismological bureau, Beijing 10002. Faculty of Earth Sciences, china University of Geosciences, Wuhan, Hubei 4.0074 china Seismol Bur Inst Geol Beijing 100029 Peoples R China china Seismol Bur Lab Tectonophys Beijing 100029 Peoples R China china Univ Geosci Fac Earth Sci Wuhan 430074 Hubei Peoples R China

In order to constrain the crustal wave velocity structure in the southernTibetan crust and provide insight into the contribution of crustal composition, geothermal gradientand partial melting to the velocity structure, which is characterized by low average crustalvelocities and widespread presence of low-velocity zone(s), the authors model the crustal velocityand density as functions of depth corresponding to various heat flow values in light of velocitymeasurements at high temperature and high pressure. The modeled velocity and density are regarded ascomparison standards. The comparison of the standards with seismic observations in southern Tibetimplies that the predominantly felsic composition at high heat flow cannot explain the observedvelocity structure there. Hence, the authors are in favor of attributing low average crustalvelocities and low-velocity zone(s) observed in southern Tibet mainly to partial melting. Modelingbased on the experimental results suggests that a melting percentage of 7-12 could account for thelow-velocity zone(s).

关键词： partial melting intracrustal low-velocity zone high-pressure andhigh-temperature experiments Tibetan plateau

DYNAMIC STRESS CONCENTRATION AROUND A CIRCULAR HOLE DUE TO SH-WAVE IN ANISOTROPIC MEDIA

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 1988年第2期4卷 146-155页

作者： Liu Diankui, institute of Engineering Mechanics, State seismological bureau, Harbin,{3. 1. institute of Engineering Mechanics State Seismological Bureau Harbin China

A new approach based on complex function to solve the SH-wave scattering problemaround a circular hole in anisotropic media is introduced in this paper. It is found that the dynamicstress concentration factor is dependent on the incident wave number and the hole radius. Finally,some numerical results of dynamic stress concentration factor of a circular hole in anisotropic mediaare given.

关键词： SH-wave scattering of elastic wave dynarnic stress concentration sleady-state wave

Ecological response to the climate change on the northern slope of the Tianshan Mountains in Xinjiang

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Earth Sciences 2005年第6期48卷 765-777页

作者： CHEN Xi1, LUO Geping1, XIA Jun2, ZHOU Kefa1, LOU Shaoping3.& YE Minquan4.1. Xinjiang institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 83.011, china 2. institute of Geographical and Resources Sciences, Chinese Academy of Sciences, Beijing 100101, china 3. Urumqi Meteorological-satellite Land Station, Urumqi 83.011, china 4. seismological bureau of Xinjiang Uygur Autonomous Region, Urümqi 83.011, china Correspondence should be addressed to Chen Xi 1. Xinjiang institute of Ecology and Geography Chinese Academy of Sciences 830011 Urumqi China 2. institute of Geographical and Resources Sciences Chinese Academy of Sciences 100101 Beijing China 3. Urumqi Meteorological-satellite Land Station 830011 Urumqi China 4. seismological bureau of Xinjiang Uygur Autonomous Region 830011 Urümqi China

The Tianshan Mountains is a high and huge mountain body lying across the central part of Xinjiang, china, and is also the main area where the runoff forms in Xinjiang. In this paper, a set of RS-based study methods is put forward for deriving the information about the natural change of the ecology in arid areas, and the relationship between the climate change trend and the corresponding ecological response on the northern slope of the Tianshan Mountains since recent 4. years is analyzed from the scales of the land cover ecosystems and landscapes based on the observed data of climate, hydrology, modern glaciers and lakes on the northern slopes of the Tianshan Mountains since recent 4. years and the satellite RS data since recent 10 years by using the RS and GIS technologies. The results are as follows: (1) The overall trend of climate change on the northern slope of the Tianshan Mountains since recent 4. years is that both air temperature and precipitation are increased, especially the increase amplitudes of air tempera-ture, precipitation and annual runoff volume are high since the decade of the 1990s; (2) the in-tegrated indexes of the vegetation in all the geographical divisions on the northern slope of the Tianshan Mountains are obviously increased since recent 10 years, especially in the artificial oases and the foothill belts, such a change trend is advantageous for improving the vegetation ecology; and (3. the vegetation ecology in the arid areas is extremely sensitive to the climate change, the vegetation coverage and the biomass on the northern slope of the Tianshan Moun-tains are continuously increased because of the climate change since recent 10 years, their in-crease amplitudes in the plains and during the late stage are obviously higher than that in the mountainous regions and during the early stage.

关键词： north slope of the Tianshan Mountains, climate change, hydrological change, natural change of ecology,RS and GIS, vegetation index.

THE NORTHWARD PROPAGATION OF THE ARC TECTONICS OF THE NORTHEAST PAMIR AND NORTHWEST TARIM BASIN

在线全文

学校读者我要写书评

暂无评论

地学前缘 2000年第S1期7卷 90-91页

作者： Li Yingzhen 1,Shen Jun 2 (1 Xinjiang seismological bureau, Urumqi 83.011,china 2 {3. bureau of china seismological bureau, Beijing 10002.,china)

The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north. In addition to these three belts, there are two nascent arc tectonic belts developed in its fore\|deep depression, the Kashi depression in the northwest Tarim basin, which is the northward propagation of the arc tectonics of northeast *** south Pamir is an ancient folded belt, composed of the Proterozoic metamorphic layers and igneous complex. It was pushed northward since the collision between the India and Asia, and uplifted since the end of the early Tertiary. The elevation of the Plateau is 4.00～53.0m, and several intermontane basins distributed in the plateau. At its northeast boundary is the Kalakorum right lateral strike slip fault. Strong strike slip earthquakes occurred along this fault. In the hinterland of the plateau, several normal faulting earthquakes occurred,which are consistent with the extensional dynamic environment of the south Pamir. Deep earthquakes occurred under the 70km depth crust of south Pamir. The N—S cross section of the focal depth show that the earthquake occurred within the south Pamir crust are lower than 70km, and the deep earthquakes with depth of 100～200km occurred in the crystal basement of Tarim basin which are under\|thrusting southward into the root of the south Pamir.

关键词： Pamir Tarim basin arc tectonics seismicity

THE GLOBAL TECTONIC SYSTEMS AND A LATITUDINAL MOUNTAIN-PLATEAU CHAIN ON THE NORTH HEMISPHERE

在线全文

学校读者我要写书评

暂无评论

地学前缘 2000年第S1期7卷 344-345页

作者： Ma Zongjin(institute of Geology,china seismological {3.,Beijing {4.,china)

Three global tectonic systems that formed since the middle Jurassic (160Ma ago)are outlined based on the global map of the Cenozoic and Mesozoic tectonics edited by Ma Zongjin et al.(1996).They are the circum\|Pacific tectonic system,the mid\|ocean ridge tectonic system and the intra\|continental tectonic system of the north *** map shows that about 80% of the total length of the continental orogens are concentrate on the north hemisphere of the earth,of which a latitudinal mountain\|plateau chain occur within a zone between north latitude 20°and 50°.Seismic and volcanic activities demonstrate that the intracontinental tectonic system on the north hemisphere is still *** distribution of the continental deep\|focus earthquakes and almost ultra high\|pressure rock found so far over the World,that are assumed both related to recent or previous deep subduction of continent,along with this *** latitudinal mountain\|plateau chain is subdivided into four active tectonic region of Qinghai—Xizang(Tibet),Iranian,eastern mediterranean and North American,both characterized by an individual similar mountain\|plateau\|basin structure with major active boundaries or controlling faults (Fig.1).These active regions are all close to primary dynamic boundaries of continent\|continent *** of source mechanisms shows that regional tectonic stress field in these regions are dominated by a nearly NS or NNE—SSW direction compression corresponding to a local plate motions and a global compressive *** between the formation of the continental latitudinal mountain\|plateau chain on north hemisphere and the oceanic plate tectonics is discussed using the information of the “Map of Magnetic Lineations of the World’s Ocean Basins (Cande et al.,1989)”and the Cenozoic and Mesozoic tectonic evolution in the *** 4. accretion units formed during 6 accretion stages of the ocean spreading in three chief oceans (the Pacific,the India and th

关键词： global asymmetrical system geodynamics mountain\| plateau chain seismotectonic system latitudinal tectonic zone