The crustal structure under Sanjiang and its dynamic implications: Revealed by seismic reflection/refraction profile between Zhefang and Binchuan,Yunnan   总被引：6，自引：0，他引：6  

ZHANG Zhongjie  BAI Zhiming  WANG Chunyong  TENG Jiwen  Lü Qingtian  LI Jiliang  LIU Yifeng & LIU Zhenkuan . Institute of Geology  Geophysics  Chinese Academy of Sciences  Beijing  China  . Institute of Geophysics  China Seismological Bureau  Beijing  China  . Institute of Deposition Resource  Chinese Academy of Geosciences  Beijing  China  . School of Exploration  Information  China University of Geosciences  Beijing  China 《中国科学D辑(英文版)》2005,48(9):1329-1336

The Sanjiang area in southwest China is considered as a tectonic intersection belt between the Tethys-Alps and the western Pacific, and has endured three-phase evolution processes: Proto-Tethys,Paleo-Tethys and Meso-Tethys[1―4]. In this area, its tectonics and struc- ture are extremely complicated, and intensively extru-sive deformation and faults are widely developed[1―3]. For that, the area is considered as the ideal na- ture-laboratory to study the evolution of Paleo-Tethys and also …  相似文献   

Geophysical Field Pattern in The West Bohemian Geodynamic Active Area     

Švancara  Jan  Gnojek  Ivan  Hubatka  František  Dědáček  Karel 《Studia Geophysica et Geodaetica》2000,44(2):307-326

Regional geophysical data from detailed gravity survey, airborne magnetometry and gamma-ray spectrometry were analysed in order to determine the subsurface extent of contrasting geological bodies and to highlight subtle anomalies which can be related to the occurrence of earthquake swarms. Potential field data were compiled into contour and colour-shaded relief maps suitable for detecting structural tectonic elements. A shaded relief map of the horizontal gradient of gravity was used to detect considerable structural and tectonic features. The results of airborne gamma-ray spectrometry, showing the regional total gamma-ray activity, abundance of uranium, thorium and potassium, were included in this study. Only the two most instructive maps – the total gamma-ray activity and the abundance of potassium are shown. The main line of epicentres Nový Kostel – Poátky coincides well with the N-S configuration of abundances of these natural radioactive elements. The epicentres of micro-earthquakes detected by the local seismological network KRASLICE for the 1991 to 1998 period were plotted in the geophysical maps. The hypocentres of earthquakes in the main epicentral zone at Nový Kostel were projected onto the crustal density model based on the interpretation of seismic reflection profile 9HR and gravity data. The average distance between the Nový Kostel epicentral zone and the seismic profile was 4-5 km. Based on the interpretation of gravity data the hypocentres of the main epicentral zone seem to be associated with the western margin of the Eibenstock - Nejdek (Karlovy Vary) Pluton and, beside that, they follow the depth level where the allochthonnous part of the Saxothuringian Zone is thrust over the European parautochton. A drawing of the geodynamic model of the area is also shown.  相似文献   

宣城第四纪红色粘土剖面的发育特征   总被引：14，自引：6，他引：8       下载免费PDF全文

刘良梧  龚子同 《第四纪研究》2000,20(5):464-468

宣城第四纪红色粘土14层土体硅铝率、风化淋溶系数,以及阳离子交换量、盐基饱和 度和粘粒含量等风化、成土作用指标表明,该剖面各层次之间仅显示出一定程度沉积作用和成土作用的差别。它们是边沉积边成土作用的产物。上覆lm左右厚下蜀黄土,且由均质红土层、铁锰焦斑层和网纹层构成的宣城第四纪红色粘土应归属于埋藏类型古土壤。  相似文献   

农田蒸散量计算方法的比较研究   总被引：9，自引：1，他引：8  

孙卫国  申双和 《南京气象学院学报》2000,23(1):101-105

根据观测资料,采用波文比法、廓线梯度法和综合阻地等分别计算了农田植被层上的蒸散量,并对比分析了不同方法之间的相对误差和相关程度。结果表明,用波文比法计算的潜热通量存在系统性偏小的现象,而工法和综合阻抗法的计算结果比较一致。文中还讨论了不同方法的优缺点和产生误差的可能原因。  相似文献   

南半球对流层中部大气环流的若干特点     

曲维政  金华  黄菲  王燕宾 《热带气象学报》2000,16(2):155-163

分析了南半球对流层５００ｈＰａ平均地转西风随纬度的分布特点,平均地转西风季节变化特点,计算分析了南半球位势高度对纬向平均的偏差,分析了超长波的分布特征。以上结果均与北半球同期计算结果作了对比比较,指出了南北半球大气环流的异同点。  相似文献   

Understanding the effect of a static driving shear stress on the liquefaction resistance of medium dense granular soils     

M. E. Rahhal  G. Lefebvre 《Soil Dynamics and Earthquake Engineering》2000,20(5-8):397-404

The influence of a driving static shear stress on the liquefaction resistance of medium dense granular soils is investigated. A laboratory study of the behavior of five sands (percentage of silt varying between 2 and 42%, and D₅₀ varying between 0.55 and 0.09 mm) was undertaken. These five sands were sampled from the foundations of two dams in Quebec (Canada). Sixty cyclic direct simple shear (DSS) tests were performed with and without a driving static shear stress. Relative densities D_r varied between 60 and 70%, and static shear stress ratios =τ_st/σ′_vc varied between 0.2 and 0.6. The presence of static shear stress increased the cyclic strength of these soils. A relation between and K() factor giving the effect of preshearing on cyclic shear resistance is obtained. The mechanical competence is examined as a function of D₅₀ and percentage of fines. The observed dilatancy yielded rather cyclic mobility than liquefaction.  相似文献   

ERODIBILITY CRITERION FOR AUXILIARY SPILLWAYS OF DAMS     

《国际泥沙研究》2000,(1)

lINTRoDUCTIONDamshavebeendesignedtraditionallynottobeovertoppedduringprobablemaximumfloodevents.AccordingtoPowledgeet.aI.(l989),manytensofthousandsofdamshave,however,becomepotentiallysubjecttoovertoppingasaresuItofimprovementsinthequalityofflooddataandinthemethodsfordeterminingprobablemaximumfloodsforwhichitisnotpossiblenoreconomicallyfeasibletoconsidermodificationstopreventovertopping.SomedamshavemoreoverbeenobservedtohavewithstoodmoderateoveFtopping.Effortshaveasaresultbeenconcentrated…  相似文献   

Ⅳ度区多层砖房的抗震设防问题探讨     

徐进华  杜娟 《山西地震》2000,(2):26-27

针对处于地震基本烈度为 度区的有些设计人员对多层砖房的抗震设防重视不够 ,超越规范的使用范围等问题 ,结合设计实践 ,对 度区多层砖房的有关抗震设防问题作了探讨 ,并对如何加强 度区的抗震设防问题提出了几点认识  相似文献   

Intrusions and exclusions: Democratization in Thailand in the context of environmental discourses and resource conflicts*     

R. Buergin  Chr. Kessler 《GeoJournal》2000,52(1):71-80

This article sketches the process of democratization in Thailand, focusing on shifting relations between civil society and state actors. Environmental discourse and conflicts about natural resources, specifically forests, during the last two decades, have been one of the main fields of social controversy and change. In the context of these controversies, civil society actors, in resistance to and alliance with state agencies, drove forward democratization by intruding into power domains of the state. State agents, increasingly forced to justify their actions according to democratic norms in the expanding space of public debate, had to search for allies and majorities within civil society. The successful establishment of public debate as an integral part of political decision making, on the one hand, resulted in a diversification of civil society, on the other hand, forced powerful segments of society to organize and defend their interests within the new public political space. Strategies of exclusion, referring to nationalism and ethnicism, have become an important instrument to secure positions and power, threatened in the process of democratization and emancipation of discriminated social groups.  相似文献   

东秦岭深地震剖面上莫霍基本特征的研究   总被引：7，自引：2，他引：5  

徐明才  高景华 《地质与勘探》2000,36(1):40-43

东秦岭深地震剖面上反映的华北、秦岭和扬子莫霍地震波组的特征具有明显差异。对莫霍地震波组特征的研究,指出秦岭壳幔过渡带的不均匀程度和厚度大于华北和扬子壳幔过渡带。受地壳均衡作用的影响,已形成的秦岭壳幔过渡带起了通常所说的“山根”作用。  相似文献