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41.
The incidence of lung cancer in the Gejiu area of Yunnan Province ranks the first in the world.The radon level(indoor,soil) was measured in the Gejiu area by the SSNTD method from 1990 to 1996,The result indicates an extensive high-level of indoor radon in that area though U and Th are lower in local limestones,The indoor radon level of houses located in the geologic fault zone is 6 times high that 2km far from the fault zone.The reason probably is that the radon level of soil in the fault is 6-8 times high that 1 km far from the faults.our data indicate that a lower range of radon levels,0-100Bq.m^-3,exists in healthy families.However,a higher radon level,over 800 Bq.m^-3,is often found corresponding to that of cancer patients‘ homes(the house-owners are suffering from either lung cancer or leukaemia or liver cancer),Obviously,an increase in lung cancer incidence follows an increase in indoor radon level,The risk of cancer induced by indoor radon is no longer an inference,but a fact. 相似文献
42.
Johannes Bruining Diederik van Batenburg Larry W. Lake An Ping Yang 《Mathematical Geology》1997,29(6):823-848
Random field generators serve as a tool to model heterogeneous media for applications in hydrocarbon recovery and groundwater
flow. Random fields with a power-law variogram structure, also termed fractional Brownian motion (fBm) fields, are of interest
to study scale dependent heterogeneity effects on one-phase and two-phase flow. We show that such fields generated by the
spectral method and the Inverse Fast Fourier Transform (IFFT) have an incorrect variogram structure and variance. To illustrate
this we derive the prefactor of the fBm spectral density function, which is required to generate the fBm fields. We propose
a new method to generate fBm fields that introduces weighting functions into the spectral method. It leads to a flexible and
efficient algorithm. The flexibility permits an optimal choice of summation points (that is points in frequency space at which
the weighting function is calculated) specific for the autocovariance structure of the field. As an illustration of the method,
comparisons between estimated and expected statistics of fields with an exponential variogram and of fBm fields are presented.
For power-law semivariograms, the proposed spectral method with a cylindrical distribution of the summation points gives optimal
results. 相似文献
43.
Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau 总被引:5,自引:0,他引:5
Two Red Clay profiles near Xi’an and Xifeng were investigated in an attempt to determine magnetostratigraphic and palaeoclimatic
records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma,
and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic
history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5–2.5 Ma. Stepwise
increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the
Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global
ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences
from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan
Plateau, solar radiation, global ice volume, etc.
Project supported by the National Natural Science Foundation of China and the Foundation of Xi’an Laboratory of Loess and
Quaternary Geology, Chinese Academy of Sciences. 相似文献
44.
在地震预报研究中,地电阻率变化形态被作为地震预报的一种前兆手段.迄今为止,国内外已经做了许多不同加载方式的室内和室外岩石或样品的电阻率变化实验,积累了相当丰富的承载岩石或样品的电阻率变化资料.本文介绍部分不相似的实验结果,以促使此项研究进一步深入发展. 相似文献
45.
用冲绳海槽地区地质、地球物理、地球化学数据与资料,对横跨大陆边缘—大洋板块的中国东部—冲绳海槽—琉球岛弧地区进行综合研究. 根据地震体波、面波成像结果,空间与布格重力异常及磁力异常的综合解释等结果,利用调和系数法对该研究区的地壳厚度进行了计算,并对地壳属性进行分析. 同时,选择中国东部东北地区的宽甸、华北地区的汉诺坝、华南的闵溪和台湾海峡的澎湖列岛与冲绳海槽和日本岛弧的新生代玄武岩开展元素—同位素对比研究. 结果认为冲绳海槽岩石层明显减薄,上地幔低速层已达到莫霍面,在地幔中已形成交代软流层. 元素—同位素研究表明:它不同于中国东部,与琉球岛弧地区的特点也不相同. 综合分析认为:冲绳海槽地壳属于过渡型地壳,与大洋地壳的许多特点颇为相似. 相似文献
46.
In this study, the relationship between fluorine in drinking water and that in urine of urban residents in China is assessed. Fluorine concentrations in tap water and those in urine show a good correlation with a linear regression coefficient of 0. 9798, indicating that the fluorine concentrations in big cities under investigation are extremely low, and the main source of fluorine is tap water. The weather effect on the intake amount of fluorine is also discussed. When air temperature is above 15℃, people would intake more fluorine through drinking water with the rise of air temperature. When temperature is below 15℃, no remarkable relationship is observed between air temperature and the intake amount of fluorine. This phenomenon indicates that the main source of fluorine in China is tap water instead of foodstuff. 相似文献
47.
The geography information system of the 1303 Hongton M=8 earthquake has been established. Using the spatial analysis function of GIS, the spatial distribution characteristics of
damage and isoseismal of the earthquake are studies. By comparing with the standard earthquake intensity attenuation relationship,
the abnormal damage distribution of the earthquake is found, so the relationship of the abnormal distribution with tectonics,
site condition and basin are analyzed. In this paper, the influence on the ground motion generated by earthquake source and
the underground structures near source also are studied. The influence on seismic zonation, anti-earthquake design, earthquake
prediction and earthquake emergency responding produced by the abnormal density distribution are discussed.
Foundation item: National important fundamental research “The Basic Research of Important Project in Damage Environment” and The important
project “The Seismic Hazard Assessment Research and Anti-earthquake Structure Research” from China Earthquake Administration
during the 10th Five-year Plan.
Contribution No. 04FE1008, Institute of Geophysics, China Earthquake Administration. 相似文献
48.
Marcelo Assumpo Meijian An Marcelo Bianchi George S.L. Frana Marcelo Rocha Jos Roberto Barbosa Jesús Berrocal 《Tectonophysics》2004,388(1-4):173
The Tocantins Province in Central Brazil is composed of a series of SSW–NNE trending terranes of mainly Proterozoic ages, which stabilized in the Neoproterozoic in the final collision between the Amazon and São Francisco cratons. No previous information on crustal seismic properties was available for this region. Several broadband stations were used to study the regional patterns of crustal and upper mantle structure, extending the results of a recent E–W seismic refraction profile. Receiver functions and surface wave dispersion showed a thin crust (33–37 km) in the Neoproterozoic Magmatic Arc terrane. High average crustal Vp/Vs ratios (1.74–1.76) were consistently observed in this unit. The foreland domain of the Brasília foldbelt, on the other hand, is characterized by thicker crust (42–43 km). Low Vp/Vs ratios (1.70–1.72) were observed in the low-grade foreland fold and thrust zone of the Brasília belt adjacent to the São Francisco craton. Teleseismic P-wave tomography shows that the lithospheric upper mantle has lower velocities beneath the Magmatic Arc and Goiás Massif compared with the foreland zone of the belt and São Francisco craton. The variations in crustal thickness and upper mantle velocities observed with the broadband stations correlate well with the measurements along the seismic refraction profile. The integration of all seismic observations and gravity data indicates a strong lithospheric contrast between the Goiás Massif and the foreland domain of the Brasília belt, whereas little variation was found across the foldbelt/craton surface boundary. These results support the hypothesis that the Brasília foreland domain and the São Francisco craton were part of a larger São Francisco-Congo continental plate in the final collision with the Amazon plate. 相似文献
49.
50.