峨眉山玄武岩的岩相与岩体结构   总被引：16，自引：0，他引：16  

沈军辉  王兰生  徐林生  李天斌 《水文地质工程地质》2001,28(6):1-4

峨眉山玄武岩是西南地区水电工程的主要建基岩体，其岩体结构明显受其建造的控制，不同地区，不同岩相的玄武岩，由于岩石组合及原生结构特征等的差异，而具有不同的岩体结构特征。本文结合拟建金沙江溪洛渡水电工程，雅砻江官地水电工程等实例，从岩相角度分析了玄武岩岩相及原生结构及原生结构对其岩体结构的控制作用。  相似文献   

遥感在新疆淖毛湖戈壁找矿中的应用     

张守林  傅水兴  杨自安 《铀矿地质》2001,17(6):365-367,373

根据不同地质体在不同波段上的光谱特征，选择不同波段的TM数据进行假彩色合成，主成分分析，匹配滤波及多种处理方法，对淖毛湖戈壁琼河坝地区的线环构造特征，赋矿岩层，矿化蚀变等示矿要素进行增强处理和特征提取，取得较好效果，为在戈壁地区快速追踪找矿信息，指导成矿预测提供了重要的基本资料。  相似文献   

Crustal structure in and around the region of the 1995 Kobe Earthquake deduced from a wide-angle and refraction seismic exploration     

Takeshi Ohmura  Takeo Moriya  Chengshi Piao  Takaya Iwasaki  Toshikastu Yoshi  Shin'ichi Sakai  Tetsuya Takeda  Kaoru Miyashita  Humihito Yamazaki  Kiyoshi Ito  Akira Yamazaki  Yoji Shimada  Katsuya Tashiro  Hiroki Miyamachi 《Island Arc》2001,10(3-4):215-227

Abstract The 1995 Kobe (Hyogo-ken Nanbu) earthquake (M_JMA 7.2, M_w 6.9) occurred on Jan. 17, 1995, at a depth of 17 km, beneath the areas of southern part of Hyogo prefecture and Awaji Island. To investigate P-wave velocity distribution and seismological characteristics in the aftershock area of this great earthquake, a wide-angle and refraction seismic exploration was carried out by the Research Group for Explosion Seismology (RGES) . The profile including 6 shot points and 205 observations was 135 km in length, extending from Keihoku, Northern Kyoto prefecture, through Kobe, to Seidan on Awaji Island. The charge of each shot was 350–700 kg. The P-wave velocity structure model showed a complicated sedimentary layer which is shallower than 2.5 km, a 2.5 km-thick basement layer whose velocity is 5.5 km/s, overlying the crystalline upper crust, and the boundary between the upper and lower crust.
Almost all aftershock hypocenters were located in the upper crust. However, the structure model suggests that the hypocenters of the main shock and some aftershock clusters were situated deeper than the boundary between the upper and lower crust. We found that the P-velocity in the upper crust beneath the northern part of Awaji Island is 5.64 km/s which is 3% lower than that of the surrounding area. The low-velocity zone coincides with the region where the high stress moment release was observed.  相似文献   

Characteristics and Implication of the Earthquake Swarm Occurred in Fuzhou in September 1999     

Yuan Dingqiang  Wang Jian 《中国地震研究》2001,15(2):146-154

on Septmeber 23,1999,an earthquake swarm occured in Fuzhou,Because the swarm occurred in the region where earthquaks occurred scarcely before and very close to the center of the city as well as shortly after the Jiji earthquake with Ms7.6 in Taiwan,September 21,1999,has aroused interest broadly.In this paper,we analyzed the characteristics of spatial and temporal distribution of the earthquake swarm and validated magnitude-number constituent of the swarm is special.In present theory,the earthquake swarm means that a small scale macro original rupture has formed in the layer of the crust in Fuzhou region where moderately strong earthquake risk exists.  相似文献   

Centralized power and divided space: `Fractured regions' in the Israeli `ethnocracy'     

Oren Yiftachel 《GeoJournal》2001,53(3):283-293

This paper uses a critical political-geographical perspective to account for the high centrality of power found in Israel. It suggests that the concentration of power have not been solely caused by national solidarity and integration or by metropolitan development, as commonly explained, but also by the territorial `fracturing' of the main social and ethnic groups in Israel/Palestine. This has prevented the emergence of effective pressure for regional devolution. Israel's character as a settler and settling state, and its central project of Judaizing contested territories, enabled the Israeli `ethnocracy' and its (mainly Ashkenazi and secular) elites to create a political geography of `fractured ethnic and social regions'. Dispersing minorities and legitimizing segregation and inequality, all in the name of the `national interest', achieved this. The Israeli political landscape is therefore organized as `fractured regions', each representing a distinct and interconnected, yet geographically dispersed, set of localities, and resembling a `chain of beads'. The logic of dispersal and segregation, in turn, has also influenced patterns of development and residential separation within Israel's main urban areas. Thus, ethnic and social fragmentation and conflict, and not a putative process of national or metropolitan integration, can explain much of Israel's highly centralized power structure.  相似文献   

3–D Tomographic Images and Deep Ore-Control in Northern Margin of the North China Plate     

Yike LIU  Xu CHANG 《Resource Geology》2001,51(4):401-406

Abstract: 3–D velocity images of the crust beneath the northern margin of the North China Plate have been constructed using P-wave travel time residuals of the latest earthquakes, with the data supplied by Chinese seismic networks.
The seismic image results indicate that there is a lateral heterogeneity in the crust beneath the northern part of the North China block. The velocity images of the upper crust show features closely related to the tectonic features on the surface. It can be seen from these velocity images of the vertical sections, and from the horizontal slice images at depths of 11 and 16 km that there exist East-West and North-East structures. The images indicate that the juncture zone of basin–and–range terrain is between the blue-colored high–velocity block corresponding to the Yanshan mountain range that developed during the Yanshan period in northwest Beijing and the green low-velocity area corresponding to the North China basin in southeast Beijing (Fig. 5). The juncture zone between high-velocity and low–velocity, and EW and NE fault zones have significant ore-control effects. From the chart of epicenters in the northern region of North China, we find that the epicenters of earthquakes are almost entirely distributed within the NE strip. Almost all major earthquakes took place in the transition strip between the high and low-velocity zones in the crust. The distribution of epicenters also reflects the strikes of known NE–faults. From the image sections along the latitude, we find that in the area between 114.0 E –118.0 E , there is a blue high-velocity block standing upright from the Moho to the upper crust (Fig. 6), from which can be deduced that some materials such as magma moved upward from the upper mantle during the history of its geological development.  相似文献   

SOURCE RADIATION AND RESPONSES OF WAVE PROPAGATION   总被引：2，自引：0，他引：2  

CHEN Sheng-zao  Gail M Atkinson 《大地构造与成矿学(英文版)》2001,25(1)

Recordings of seismic waves propagating from earthquake source to a station at the earth's surface are a system response function.The convolution operator in time domain can be simplified as a multiplication operator in frequency domain.We discuss in frequency domain the separation of source,path and site effects for global scaling of earthquake source radiation.Also discussed are source scaling model,faulting mechanism,and the H/V inversion problems with crustal and near surface structures.Gross features of apparent source spectra appear to be not much region-dependent although there may be difference between tectonic styles within a region of tectonic mixture for which we need further study as data accumulate.Vertical spectra may be a better approach to approximate source radiation,as it has less crustal amplification effects than horizontal spectra.The H/V ratio is evidently a comprehensive indicator of amplification effects from near surface to deep structure.This gives it potential as an inversion tool to deduce site crustal structure.  相似文献   

Structural and vibrational behaviour of fluorapatite with pressure. Part I: in situ single-crystal X-ray diffraction investigation     

P. Comodi  Yu Liu  P. F. Zanazzi  M. Montagnoli 《Physics and Chemistry of Minerals》2001,28(4):219-224

Using single-crystal X-ray diffraction from a diamond anvil cell, the compressibility of a synthetic fluorapatite was determined up to about 7?GPa. The compression pattern was anisotropic, with greater change along a than c. Unit cell parameters varied linearly with β _a =3.32(8)?10^?3 and β _c =2.40(5)?10^?3 GPa^?1, giving a ratio β _a :β _c =1.38:1. Data fitted with a third-order Birch-Murnaghan EOS yielded a bulk modulus of K ₀=93(4)?GPa with K′=5.8(1.8). The evolution of the crystal structure of fluorapatite was analysed using data collected at room pressure, at 3.04 and 4.72?GPa. The bulk modulus of phosphate tetrahedron is about three times greater than the bulk modulus of calcium polyhedra. The values were 270(10), 100(4) and 86(3) GPa for P, Ca1 (nine-coordinated) and Ca2 (seven-coordinated) respectively. While the calcium polyhedra became more regular with pressure, the distortion of the phosphate tetrahedron remained unchanged. The size of the channel extending along the [001] direction represented the most compressible direction. The Ca2–Ca2 distance decreased from 3.982 to 3.897?Å on compression from 0.0001 to 4.72?GPa. The anisotropic compressional pattern may be understood in terms of the greater compressibility of the channel size over the polyhedral units. The reduction of the channel volume was measured by the evolution of the trigonal prism, having the Ca2–Ca2–Ca2 triangle as its base and the c lattice parameter as its height. This prism volume changed from 47.3?ų at room pressure to 44.78?ų at 4.72?GPa. Its relatively high bulk moduli, 86(3) GPa, indicated that the channel did not collapse with pressure and the apatite structure could remain stable at very high pressure.  相似文献   

Modeling of dioctahedral 2:1 phyllosilicates by means of transferable empirical potentials   总被引：1，自引：0，他引：1  

C. I. Sainz-Diaz  A. Hernández-Laguna  M. T. Dove 《Physics and Chemistry of Minerals》2001,28(2):130-141

 Dioctahedral 2:1 phyllosilicates with different interlayer charge have been studied theoretically by using transferable empirical interatomic potentials. The crystal structures of pyrophyllite, muscovite, margarite, beidellite, montmorillonite, and different smectites and illites have been simulated. The interatomic potentials were able to reproduce the experimental structure of phyllosilicates with high, medium and low interlayer charge. The calculated structures are in agreement with experiment for the main structural features of the crystal lattice. The effect of the cation substitution in the octahedral and tetrahedral sheets on the structural features has been also studied. Good linear relationships have been found, and the calculated effects are consistent with experimental results. Some unknown structural features of the crystal structures of clays are predicted in this work. Received: 8 March 2000 / Accepted: 19 September 2000  相似文献   

VRANCEA99—the crustal structure beneath the southeastern Carpathians and the Moesian Platform from a seismic refraction profile in Romania     

F. Hauser  V. Raileanu  W. Fielitz  A. Bala  C. Prodehl  G. Polonic  A. Schulze 《Tectonophysics》2001,340(3-4):233-256

The VRANCEA99 seismic refraction experiment is part of an international and multidisciplinary project to study the intermediate depth earthquakes of the Eastern Carpathians in Romania. As part of the seismic experiment, a 300-km-long refraction profile was recorded between the cities of Bacau and Bucharest, traversing the Vrancea epicentral region in NNE–SSW direction.

The results deduced using forward and inverse ray trace modelling indicate a multi-layered crust. The sedimentary succession comprises two to four seismic layers of variable thickness and with velocities ranging from 2.0 to 5.8 km/s. The seismic basement coincides with a velocity step up to 5.9 km/s. Velocities in the upper crystalline crust are 5.9–6.2 km/s. An intra-crustal discontinuity at 18–31 km divides the crust into an upper and a lower layer. Velocities within the lower crust are 6.7–7.0 km/s. Strong wide-angle PmP reflections indicate the existence of a first-order Moho at a depth of 30 km near the southern end of the line and 41 km near the centre. Constraints on upper mantle seismic velocities (7.9 km/s) are provided by Pn arrival times from two shot points only. Within the upper mantle a low velocity zone is interpreted. Travel times of a PLP reflection define the bottom of this low velocity layer at a depth of 55 km. The velocity beneath this interface must be at least 8.5 km/s.

Geologic interpretation of the seismic data suggests that the Neogene tectonic convergence of the Eastern Carpathians resulted in thin-skinned shortening of the sedimentary cover and in thick-skinned shortening in the crystalline crust. On the autochthonous cover of the Moesian platform several blocks can be recognised which are characterised by different lithological compositions. This could indicate a pre-structuring of the platform at Mesozoic and/or Palaeozoic times with a probable active involvement of the Intramoesian and the Capidava–Ovidiu faults. Especially the Intramoesian fault is clearly recognisable on the refraction line. No clear indications of the important Trotus fault in the north of the profile could be found. In the central part of the seismic line a thinned lower crust and the low velocity zone in the uppermost mantle point to the possibility of crustal delamination and partial melting in the upper mantle.  相似文献