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991.
孙建刚 《地震工程与工程振动》1996,16(1):110-115
本文从拟协调元列式出发,建立板弯曲弹塑性分析单元,给出了分层和不分层的板弹塑性问题的Tresca屈服准则下,由切线刚度法进行求解的方法。 相似文献
992.
给出了“广义信息维”的计算公式和计算方法,研究了首都圈和周期地区的广义时间分维和华北地区的广义空间分维。结果表明,在该地区Ms≥5.3地震前0.5-3a,时间分维都有一个较明显的降维过程;空间分维也有较好的对应效果,但是存在漏现象。 相似文献
993.
Based on the long period surface wave data recorded by the China Digital Seismograph Network (CDSN), theQ
R
of fundamental mode Rayleigh wave with periods from 10 s to 146 s is determined for the eastern Sino-Korean paraplatform
in this paper. TheQ
β
models of the crust and upper mantle are respectively obtained for the 4 paths, with the aid of stochastic inverse method.
It shows that in the eastern Sino-Korean paraplatform, the average crustalQ
β
is about 200, and that there exists a weak attenuation layer in the middle crust (about 10–20 km deep) which is possibly
related to earthquake-prone layer. A strong attenuation layer (lowQ) of 70 km thick extensively exists in the uppermost mantle, with the buried depth about 80 km. The averageQ
R
of fundamental mode Rayleigh wave is between the value of stable tectonic region and that of active tectonic region, and
much close to the latter.
Contribution No. 96A0001, Institute of Geophysics, SSB, China.
Funded by the Chinese Joint Seismological Science Foundation. 相似文献
994.
Summary Based on observational data at Beijing since 1940, trends in daily maximum, mimimum and mean temperatures are studied. It is shown that the linear rate of increase in minimum temperature is 4.08 °C/100 yr; whereas the maximum temperature decreases with a linear rate of — 0.245 °C/100 yr. Consequently, the diurnal temperature range (DTR) becomes smaller.Warming in Beijing occurred mainly in the daytime in the 1940s; but in the night in the 1980s. Although the latter has been found in other studies, the former is a new discovery. The difference of temperature and the diurnal temperature range between urban and surburban areas in Beijing are also analysed. The results show that the urban heat island effect (UHIE) has been becoming larger, and during 1960–1989 the change in UHIE in summer is larger than that in winter. Since the warning trend does not match the change of UHIE in last two decades, it is thought that UHIE is not the main factor contributing to climatic warming.With 2 Figures 相似文献
995.
The wavelets and hierarchies of the climate system 总被引:1,自引:0,他引:1
Summary Wavelet analysis of global mean temperature data, the drought-flood data of the past 500 years in China, and the temperature time series of Shanghai, highlights the following: (1) the climatic wavelets depend on the hierarchies of a climate system; (2) for different time scales or hierarchies, a climate system may have different catastrophic points and periods; (3) for different time scales or hierarchies, variation of the Southern Hemisphere temperature has an obvious phase-lag compared with that of the Northern Hemisphere and the catastrophe points also lag behind; (4) in a cold-warm period, the cold semi-period of the Northern Hemisphere is obviously longer than the warm one; (5) for different hierarchies or time scales, there exists a phase-lag for the droughtflood variation in China moving gradually with latitude from north to south. Finally, a new technique of climate diagnosis, the phase curve of wavelets, is put forward in this paper.With 6 FiguresSupported by Chinese NKPFR. 相似文献
996.
997.
Jianguo Sun 《Geophysical Prospecting》1996,44(3):351-374
Conventionally, the Fresnel zone and the geometrical spreading factor are investigated separately, because they belong to different theories of wave propagation. However, if the paraxial ray method is used for establishing the Fresnel–Kirchhoff diffraction formula for a laterally inhomogeneous multilayered medium, it can be shown that the normalized geometrical spreading factor is inversely proportional to the area of the first Fresnel zone associated with the reflection point. Therefore, if no diffracting edge cuts the first Fresnel zone, the geometrical optics approximation represents the principal part of the wavefield obtained by Fresnel–Kirchhoff diffraction theory. Otherwise, the geometrical optics approximation has to be corrected by adding edge diffractions. It is also shown that Kirchhoff-type migration and geometrical spreading factor correction both reduce the first Fresnel zone to a zone with unit area. 相似文献
998.
利用模糊聚类分析和灰色聚类分析提出了预测水库诱发地震上限震级的方法,并以新丰江水库地震为例进行了讨论。研究表明,预测的上限震级与实际发震情况相符 相似文献
999.
长白山近代火山活动与地震 总被引:5,自引:0,他引:5
概述了长白山火山区的构造环境及其构造的活动性,以天池火山为主体的长白山火山区近代喷发的构造的活动,表现有继承与新生的构造双重性和不均衡的脉动性,区内的火山地震与区域性构造地震趋于同步活动。 相似文献
1000.
“七五”期间,黄淮海平原农业开发禹城试区,成功地推广了鱼塘-台田生态系统。为挖掘开发潜力及寻求最佳系统模式,本文结合渔业生产环境条件进行鱼塘不同深度的温度分析,认为,在该区的气候条件下,水深一般保持在1.5 ̄2.0m较为适宜。 相似文献