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501.
通过对期刊方阵构成,科学指数数据库的介绍,认识科技期刊引证及评价指标;了解地球科学类期刊的划分排序及中国地震局数据中心的科学查新。 相似文献
502.
GPS在现代高技术条件下的局部战争和人们的日常生活中的重要性日益明显,从军用和民用方面考虑均有必要研究各种有意的和无意的对GPS的干扰,以及相应的抗干扰技术。从空域处理出发给出了一种自适应天线调零干扰抑制方案,并分析了相应的技术难点和可行性,该方案可以有效地抵消干扰,同时具有很高的推广应用价值。 相似文献
503.
Soil amplification characteristics are investigated using data from the Chibaken‐Toho‐Oki earthquake and its aftershocks recorded at Chiba dense array in Japan. The frequency‐dependent amplification function of soil is calculated using uphole‐to‐downhole spectral ratio analysis, considering the horizontal components of shear wave. The identified spectral ratios consistently demonstrate the splitting of peaks in their resonance frequencies and low amplification values in comparison with a 1D model. The torsional behaviour and horizontal ground motion coupling are clarified as the reasons for these phenomena at the site. To prove the hypothesis, the torsional motion is directly evaluated using the data of the horizontal dense array in different depths at the site. The comparison between Fourier spectra of torsional motion and identified transfer functions reveals the peaks at the same frequencies. The wave equation including torsion and horizontal motion coupling is introduced and solved for the layered media by applying wave propagation theory. Using the developed model, the effects of torsional motion with horizontal motion coupling on soil transfer function are numerically examined. Splitting and low amplification at resonance frequencies are confirmed by the results of numerical analysis. Furthermore, the ground motion in two horizontal directions at the site is simulated using site geotechnical specification and optimizing the model parameters. The simulated and recorded motions demonstrate good agreement that is used to validate the hypothesis. In addition, the spectral density of torsional ground motions are compared with the calculated one and found to be well predicted by the model. Finally, the results are used to explain the overestimation of damping in back‐calculation of dynamic soil properties using vertical array data in small strain level. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
504.
Gary D. Egbert 《Surveys in Geophysics》2002,23(2-3):207-249
The simultaneous nature of array data can be exploitedin electromagnetic induction studiesfor three general purposes.First, one or more reference sites can be usedto reduce bias, improve signal-to-noise ratios, and provide bettercontrol over source complications and coherent noisein estimates of MT impedances and otherEM transfer functions (TFs).Although a single good reference site can dramatically improveTF estimates, improvements due to multiple sites are often rather modest, because local noise is the limiting factor.Secondly, arrays allow for estimation of inter-station transfer functions, and maps of anomalous horizontal field variations. Relatively straightforward modifications to inversion codes wouldallow quantitative interpretation of these additionalconstraints on resistivity variations.Finally, with arrays it is possible to estimate the response of theEarth to a richer spectrum of external source excitations. In particular,the natural extension to the usual uniform source assumption implicit inthe MT method allows for three curl-free magnetic gradient sources.Quantitative interpretation of the response of a three-dimensionalEarth to these sources could provide additionalconstraints on large scale variations in crustal and uppermantle resistivity, and might help to overcome problemsdue to aliasing of near surface distortion in widely spaced MT data. 相似文献
505.
506.
利用残差绝对值和最小法进行单线阵CCD卫星影像的后方交会,一般来说,不仅可以克服外方位元素之间的强相关性,而且可以有效地剔除粗差。实验证明该方法简便、稳健、有效。 相似文献
507.
介绍了上海地震台阵观测系统,该观测系统是由地震台阵、佘山数据中心、上海信息中心等部分组成,对各部分的功能及设备系统结构作了较为翔实的分析,并简要描述了台阵数据处理软件系统。上海地震台阵投入并网运行后表明,从根本上改善了地震波形、特别是远震波形的记录,并从总体下提出了上海地震台网的地震综合监测能力。 相似文献
508.
上海地震台阵的标定方法 总被引:1,自引:0,他引:1
地震台阵标定可以校正视慢度和后方位角,从而进一步校正震源位置,有助于提高地震定位精度及地震类型鉴别研究等。此外,台阵标定也可校正由于台阵接收系统而导致视慢度和后方位角的偏差。 相似文献
509.
R. de Franco G. Biella G. Boniolo A. Corsi M. Demartin M. Maistrello A. Morrone 《Geophysical Journal International》1997,128(3):723-736
A seismic-array study of the continental crust and upper mantle in the Ivrea-Yerbano and Strona-Ceneri zones (northwestern Italy) is presented. A short-period network is used to define crustal P - and S -wave velocity models from earthquakes. The analysis of the seismic-refraction profile LOND of the CROP-ECORS project provided independent information and control on the array-data interpretation.
Apparent-velocity measurements from both local and regional earthquakes, and time-term analysis are used to estimate the velocity in the lower crust and in the upper mantle. The geometry of the upper-lower crust and Moho boundaries is determined from the station delay times.
We have obtained a three-layer crustal seismic model. The P -wave velocity in the upper crust, lower crust and upper mantle is 6.1±0.2 km s−1 , 6.5±0.3 km s−1 and 7.8±0.3 km s−1 respectively. Pronounced low-velocity zones in the upper and lower crust are not observed. A clear change in the velocity structure between the upper and lower crust is documented, constraining the petrological interpretation of the Ivrea-type reflective lower continental crust derived from small-scale petrophysical data. Moreover, we found a V P / V S ratio of 1.69±0.04 for the upper crust and 1.82±0.08 for the lower crust and upper mantle. This is consistent with the structural and petrophysical differences between a compositionally uniform and seismically transparent upper crust and a layered and reflective lower crust. The thickness of the lower crust ranges from about 8 km in front of the Ivrea body (ARVO, Arvonio station) in the northern part of the array to a maximum of about 15 km in the southern part of the array. The lower crust reaches a minimum depth of 5 km below the PROV (Provola) station. 相似文献
Apparent-velocity measurements from both local and regional earthquakes, and time-term analysis are used to estimate the velocity in the lower crust and in the upper mantle. The geometry of the upper-lower crust and Moho boundaries is determined from the station delay times.
We have obtained a three-layer crustal seismic model. The P -wave velocity in the upper crust, lower crust and upper mantle is 6.1±0.2 km s
510.