电磁波CT技术在探测堤坝工程中的应用   总被引：4，自引：0，他引：4  

欧阳立胜 《华南地震》2002,22(1):64-69

应用电磁波CT探测技术对流溪何竹料段大堤和丰顺县虎局水库大坝渗水通道进行了探测研究，由于电磁波的吸收系数和地层结构有密切关系，因此，电磁波CT是通过能量的变化观测反演吸收系数的分布，进而推测地下构造的分布，利用电磁波的吸收系数为层析物理量，在钻孔中进行透射观测，以优于0.5m的分辨率清楚地揭示了测区内渗水层位的分布情况。  相似文献   

A quantitative investigation into the temporal and spatial variations in the emergence of adult blackflies (Diptera: Simuliidae) from the Breitenbach, a small upland stream in Germany     

Joachim Reidelbach  Heino Christl 《Limnologica》2002,32(3)

As a contribution to the long-term emergence studies carried out as part of the “Breitenbach ecosystem project”, this paper presents the results obtained on emergence patterns and population dynamics of blackflies from 1984 to 1988. The Breitenbach is a small first order stream near Schlitz/Hesse, running into the Fulda river. Adult blackflies were caught in 4 greenhouse emergence traps, each spanning the whole width of the stream for a length of 6 m. A manual and then a partly automated method for collecting trapped insects was applied for three years and one year, respectively. Sixteen blackfly-species of different origin were found in the traps: a) autochthonous species: Prosimulium tomosvaryi, Simulium vernum s.l., S. cryophilum s.l., S. ornatum s.l. (common); S. costatum, S. trifasciatum, S. monticola, S. argyreatum (rare); b) species of doubtful origin: S. lundstromi, S. angustitarse, S. angustipes, S. aureum (very rare); c) allochthonous species: S. lineatum, S. equinum, S. erythrocephalum, S. noelleri. It was shown that the last 4 species had not emerged from the Breitenbach but had flown into the traps as adults. In addition, females of autochthonous species with blood or with mature eggs were trapped, which were also considered to have flown in. Besides revealing a limitation of the trap construction, they supported the detailed interpretation of some intricated patterns of appearance. Variations in emergence patterns and specimen numbers between years and traps were pronounced, but only in a few cases could they be attributed to changes in abiotic factors such as water temperature or discharge. P. tomosvaryi had the most simple and regular life cycle, with one well synchronised emergence peak annually from April to May (or even to June). No gradient of specimen numbers along the stream was evident. The two closely related species S. vernum and S. cryophilum had quite similar emergence patterns: There were two broad peaks per year, extending mainly from March to June and from July to October or November. In some cases the number and separation of consecutive generations was not clear. The abundance of both species clearly decreased downstream, more so for S. cryophilum than for S. vernum. In a trap closest to a tributary spring, S. cryophilum was the dominant species during three of the four years examined. The adults of S. ornatum displayed an intricate pattern of appearance, with very low specimen numbers in spring and medium to very high numbers in July/August and September/October. S. ornatum is the only blackfly species that inhabits both the Breitenbach and the adjacent section of the Fulda river. It was shown that females emerging from the Fulda river regularly invade the Breitenbach valley in greatly varying numbers and oviposit there. This leads to overlapping larval cohorts with corresponding emergence peaks. Although S. ornatum was the most abundant species in one year in the lower traps (60 to 80% of all individuals), it remains uncertain whether it is a long-term, permanent member of the autochthonous blackfly fauna of the Breitenbach. Estimates of total numbers of flown-in adults, actual emergence, dry weight biomass, the ecological separation of the species and their life cycle strategies are discussed.  相似文献   

3D shear-wave velocity structure of the Eifel plume, Germany     

Matthias KeyserJoachim R.R. Ritter  Michael Jordan 《Earth and Planetary Science Letters》2002,203(1):59-82

The Quaternary Eifel volcanic fields, situated on the Rhenish Massif in Germany, are the focus of a major interdisciplinary project. The aim is a detailed study of the crustal and mantle structure of the intraplate volcanic fields and their deep origin. Recent results from a teleseismic P-wave tomography study reveal a deep low-velocity structure which we infer to be a plume in the upper mantle underneath the volcanic area [J.R.R. Ritter et al., Earth Planet. Sci. Lett. 186 (2001) 7-14]. Here we present a travel-time investigation of 5038 teleseismic shear-wave arrivals in the same region. First, the transverse (T) and radial (R) component travel-time residuals are treated separately to identify possible effects of seismic anisotropy. A comparison of 2044 T- and 2994 R-component residuals demonstrates that anisotropy does not cause any first-order travel-time effects. The data sets reveal a deep-seated low-velocity anomaly beneath the volcanic region, causing a delay for teleseismic shear waves of about 3 s. Using 3773 combined R- and T-component residuals, an isotropic non-linear inversion is calculated. The tomographic images reveal a prominent S-wave velocity reduction in the upper mantle underneath the Eifel region. The anomaly extends down to at least 400 km depth. The velocity contrast to the surrounding mantle is depth-dependent (from −5% at 31-100 km depth to at least −1% at 400 km depth). At about 170-240 km depth the anomaly is nearly absent. The resolution of the data is sufficient to recover the described features, however the anomaly in the lower asthenosphere is underestimated due to smearing and damping. The main anomaly is similar to the P-wave model except the latter lacks the ‘hole’ near 200 km depth, and both are consistent with an upper mantle plume structure. For plausible anhydrous plume material in the uppermost 100 km of the mantle, an excess temperature as great as 200-300 K is estimated from the seismic anomaly. However, 1% partial melt reduces the required temperature anomaly to about 100 K. The temperature anomaly associated with the deeper part of the plume (250 to about 450 km depth) is at least 70 K. However, this estimate is quite uncertain, because the amplitude of the shear-wave anomaly may be larger than the modelled one. Another possibility is water in the upwelling material. The gap at 170-240 km depth could arise from an increase of the shear modulus caused by dehydration processes which would not affect P-wave velocities as much. An interaction of temperature and compositional variations, including melt and possibly water, makes it difficult to differentiate quantitatively between the causes of the deep-seated low-velocity anomaly.  相似文献   

国际地磁学与高空物理学协会和国际地震学与地球内部物理学协会联合科学大会及地震电磁研究进展   总被引：1，自引：0，他引：1  

詹志佳  赵从利  高金田  沈文志 《国际地震动态》2002,(3):11-15

简要介绍了 2 0 0 1年 8月 1 9～ 3 1日在越南河内召开的国际地磁学与高空物理学协会 ( IAGA)和国际地震学与地球内部物理学协会 ( IASPEI)联合科学大会以及地震电磁研究进展 ,表明地震电磁前兆在地震预测研究中具有一定的实际效果与良好的研究前景。我们建议在不久的将来能在北京举办 IAGA,IASPEI和 IUGG(国际大地测量学与地球物理学联合会 )大会。这将促进我国的科技进步 ,有助于加强我国在国际科学界的地位与影响。  相似文献   

关于水资源承载力理论与方法的研究   总被引：119，自引：3，他引：119  

朱一中  夏军  谈戈 《地理科学进展》2002,21(2):180-188

本文首先明确了水资源承载力的基本概念 ,指出可持续发展理论、水 -生态 -社会经济复合系统理论、二元模式下的水文循环机制和过程是水资源承载力研究的理论基础 ,对水资源承载力研究的基本内容、评价指标体系的建立和评价方法进行了较全面的概括和总结。  相似文献   

A finite‐element algorithm for electromagnetic induction in two‐dimensional anisotropic conductivity structures     

Yuguo Li 《Geophysical Journal International》2002,148(3):389-401

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Finite-difference modelling of two-dimensional elastic wave propagation in cracked media     

Vincent A. van Antwerpen  Wim A. Mulder  Gérard C. Herman 《Geophysical Journal International》2002,149(1):169-178

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Fréchet kernels for body-wave amplitudes     

F. A. Dahlen  Adam M. Baig 《Geophysical Journal International》2002,150(2):440-466

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Controlled source apparent resistivity tensors and their relationship to the magnetotelluric impedance tensor   总被引：2，自引：0，他引：2  

T. Grant Caldwell  Hugh M. Bibby  Colin Brown 《Geophysical Journal International》2002,151(3):755-770

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长白山自然保护区旅游灾害及其防治对策   总被引：3，自引：0，他引：3  

佟守正  王琦  李光  吕弼顺 《山地学报》2002,(Z1)

旅游灾害越来越受到人们的重视,文章通过对长白山自然保护区常见灾害类型的分析,建立了灾害管理系 统框架模型,为降低和消除旅游灾害,提出了防范对策。  相似文献