云南地区4级地震频度异常特征与强震关系研究   总被引：2，自引：0，他引：2  

王兰兰  刘丽芳 《内陆地震》2004,18(4):359-364

对云南地区18次MS≥6强震事件前中、小地震活动过程进行了分析,发现在这些地震发生前1—3年近场区2°×2°范围内4级地震频度基本上出现了显著增强现象,可以用4级地震年累计频度进行定量描述。通过全时空的扫描,确定年累计频度N≥4为异常阈值,该指标通过了置信度97.5%的R值内符检验。并用调整单元对强震附近4级地震活动增强现象给予了物理解释。  相似文献   

地脉动测试技术若干问题的讨论   总被引：1，自引：0，他引：1  

李友鹏  邹桂高 《岩土工程技术》2004,18(4):199-203

讨论了地脉动的测试技术以及测试工作中应该重视而且容易被忽视的问题 ,并就地脉动幅值域和频率域特性参数提出不同的看法  相似文献   

多功能水文频率分析计算软件的研制和应用   总被引：2，自引：0，他引：2  

关志成黎书铨  袁国臣 《水文》2004,24(1):39-41,9

介绍了多功能水文频率分析计算软件的设计及功能扩充，尤其是增加了采用鼠标拉动曲线直接屏幕适线的功能。本软件在生产实践中，获得了较好的应用效果，不仅功能多，而且实用方便。  相似文献   

The effect of an interface boundary layer on the resonance properties of a buried structure     

Y. S. Karinski  V. V. Shershnev  D. Z. Yankelevsky 《地震工程与结构动力学》2004,33(2):227-247

This paper presents a model for the analysis of the diffraction of plane waves at a cavity in an infinite homogeneous linear elastic medium supported by a segmented lining. An elastic boundary layer is introduced between the cavity lining and the infinite medium. The boundary layer is simulated by ‘elastic boundary conditions’ in which the stress is proportional to the relative displacement of the lining and of the surrounding medium boundary. A closed‐form analytical solution of the problem was obtained using the Fourier–Bessel series, the convergence of which was proven. It was shown that the number of series terms required to obtain a desired level of accuracy can be determined in advance. Using amplitude–frequency response analysis it was shown that the boundary layer produces additional ‘pseudo‐resonance’ frequencies that depend on the layer properties. These frequencies are almost identical to the eigenvalues obtained from the simple analysis of a segmented elastically supported lining. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Frequency domain modal analysis of earthquake input energy to highly damped passive control structures     

Izuru Takewaki 《地震工程与结构动力学》2004,33(5):575-590

A new complex modal analysis‐based method is developed in the frequency domain for efficient computation of the earthquake input energy to a highly damped linear elastic passive control structure. The input energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non‐linear structures, the earthquake input energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake input energy in the frequency domain is essential for deriving a bound on the earthquake input energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis‐based method is developed. The importance of overdamped modes in the energy computation of specific non‐proportionally damped models is demonstrated by comparing the energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis‐based method in the frequency domain is very efficient in the computation of the earthquake input energy. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

近间距并行管线探测方法的效果对比   总被引：4，自引：0，他引：4  

赵献军  伍卓鹤 《物探与化探》2004,28(2):133-135

介绍了管线探测的几种方法,结合实例,对近间距并行管线的几种探测方法的效果进行了比较。  相似文献   

枯水研究进展   总被引：20，自引：0，他引：20       下载免费PDF全文

殷福才  王在高  梁虹 《水科学进展》2004,15(2):249-254

枯水和洪水是水文学中极值范畴,自20世纪七八十年代以来,大规模地开展河流枯水研究工作,但枯水研究的深度远远低于洪水。总结前人研究的成果可以发现,人类对枯水研究的内容主要集中在以下3点:①对不同区域影响枯水的主要因素进行识别;②枯水频率分析以及有关枯水资料的处理方法;③分析枯水径流的计算方法及系统预测。从研究方法来看,过去,对于枯水研究中所采用的方法主要是以概率统计学和时间序列分析等为主的传统方法。随着信息时代的到来,一些新的技术、新的方法纷纷地应用于枯水研究,如"3S"技术(RS、GIS、GPS)。通过枯水研究综述,对我国进一步开展枯水研究以及合理利用枯水资源提供了科学依据,为我国开展系统综合分析应用研究,特别是对西部的干旱、半干旱地区具有深远的科学现实意义。  相似文献   

Low-frequency 3-D seismic survey of upper crustal magmatic intrusions in the northeastern Pannonian basin of Hungary     

Zoltn Hajnal  Endre Heged&#x;s  G. Randy Keller  Tams Fancsik  Attila Cs. Kovcs  Rbert Csabafi 《Tectonophysics》2004,388(1-4):239

A specially designed 700-km² grid survey, deploying 1000 regularly distributed low-frequency seismic recording systems, successfully investigated one of the most complex geologic environments of the Pannonian basin. The wide-angle signals penetrated through over 1000 m of multi-phase igneous lithology and recognized, for the first time, the underlying enigmatic Permian to Early Triassic basement rocks. Tomographic inversion of the first arrival grid data resulted in determination of an accurate three-dimensional (3-D) velocity field, to a depth of 4 km. The anomalous changes of the spatial velocity data outline the regional extent of the Late Miocene magmatic intrusions, which are covered by over 2000 m of Mid-Miocene to Pleistocene clastics. Complex relationship was found between the surface potential data and the intrusive bodies. This multi-faceted geophysical data analysis established a functional technique for mapping a subsurface with intricate acoustic and structural complexity.  相似文献   

用GPS秒信号锁定高频振荡器的方法研究   总被引：1，自引：0，他引：1  

郭芳 《时间频率学报》2004,27(2):94-102

对用远距离传输的GPS秒信号锁定本地高频晶体振荡器的方法进行了探讨。介绍了高精度的时间数字转换器TDC(Time to Digital Converter)和对滤波的方法进行了探讨。为了降低成本又能够满足设计要求的精度，还考虑了双D／A转换的方法。有关的硬件系统已经通过了调试和一系列的测试和实验，在测量和控制精度方面，能达到设计的要求。此外，提出了这个系统有待解决的问题，如双D／A转换的非线性问题，Kalman滤波抗野值及继续提高精度的问题。  相似文献   

Spectral element modelling of three-dimensional wave propagation in a self-gravitating Earth with an arbitrarily stratified outer core     

Emmanuel Chaljub  Bernard Valette 《Geophysical Journal International》2004,158(1):131-141

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