周期和振幅相结合检测地震方法研究     

张念印苏文  张志俊 《大地测量与地球动力学》2007,27(F06):133-135

分析了单纯用地震波振幅作为报警阈值的缺点,通过数字地震仪与模拟地震仪报警机制的对比,提出用检测周期和振幅相结合的方法来实现地震报警。  相似文献   

A Hamiltonian theory for an elastic earth: First order analytical integration     

Juan Getino  José M. Ferrándiz 《Celestial Mechanics and Dynamical Astronomy》1991,51(1):35-65

In this article an approximate analytical integration is performed of the Hamiltonian corresponding to the rotational motion of an Earth whose elastic mantle is deformed by rotation and lunisolar attraction, using Deprit's perturbation method for the first order. Besides the usual terms, this Hamiltonian includes the perturbation of the kinetic energy and the elastic energy produced with the deformation, as well as their causes, the tidal and the centrifugal potential; these new terms have already been studied for the tidal deformation in previous articles (Getino and Ferrándiz, 1990a, 1990b). The effects of the deformation due to the centrifugal potential are studied in this article, following the same method as that used for the tidal deformation. Numerical tables of the periodic perturbations corresponding to the nutation in obliquity and longitude are obtained. As for the secular effects, a theoretical value of 457 days is obtained for Chandler's period.  相似文献   

AGB stars in the Magellanic Clouds     

P. R. Wood 《Astrophysics and Space Science》1994,217(1-2):121-130

The stars that will be detectable in the Magellanic Clouds by the DENIS and 2MASS near infrared surveys are enumerated. All thermally-pulsing AGB stars will be observable in I, J, H and K, along with the top two magnitudes of both the early-AGB and the first giant branch. All carbon stars will be visible, and normal (N type) C stars will be easily distinguished by their large J-K colours. However, it will not be possible to separate faint, warm C stars from K and M stars using the photometry alone. Photometry of AGB stars in clusters will allow an accurate evaluation of the AGB tip luminosities as a function of initial mass. Random phase K magnitudes of LPVs and Cepheids should provide a better measure of the LMC tilt and distortions in the SMC. The K survey should turn up 100 to 150 objects undergoing superwind mass loss, these objects being OH/IR stars and the dust-enshrouded C star equivalents of OH/IR stars. It is shown that crowding should not be a problem even in the LMC bar.  相似文献   

21世纪云南第1次大震活跃期的趋势预测     

罗葆荣 《天文研究与技术》2003,(3):69-72

在太阳活动与地震活动相关研究的基础上指出:在周期性太阳活动的调控下,地震活动也显示出与太阳活动相关的周期性变化。云南22年的地震周期在20世纪形成了4个大震活跃期和4个相对平静期。根据地震活动和太阳活动的若干相关规律,对云南地区在本世纪第1次大震活跃期的到来作了趋势性预测:云南在本世纪第1次大震活跃期的第1个大震(M=7.0左右)将于2012年到来,那时正是太阳活动第24周下降段的开始,离上次大震活跃期的最后一个大震(丽江,M=7.0,1996年)恰好是16年。在该大震活跃期里,还将发生若干个M=7.0左右的大震和一些较小的地震,其大震爆发的时间将遵循Tx=(Tn-Tn-1)1/2(a年)的非线性经验规律发生。  相似文献   

Variability and trends in the annual snow‐cover cycle in Northern Hemisphere land areas, 1972–2000     

Dennis G. Dye 《水文研究》2002,16(15):3065-3077

This study investigated variability and trends in the annual snow‐cover cycle in regions covering high‐latitude and high‐elevation land areas in the Northern Hemisphere. The annual snow‐cover cycle was examined with respect to the week of the last‐observed snow cover in spring (WLS), the week of the first‐observed snow cover in autumn (WFS), and the duration of the snow‐free period (DSF). The analysis used a 29‐year time‐series (1972–2000) of weekly, visible‐band satellite observations of Northern Hemisphere snow cover from NOAA with corrections applied by D. Robinson of Rutgers University Climate Laboratory. Substantial interannual variability was observed in WLS, WFS and DSF (standard deviations of 0·8–1·1, 0·7–0·9 and 1·0–1·4 weeks, respectively), which is related directly to interannual variability in snow‐cover area in the regions and time periods of snow‐cover transition. Over the nearly three‐decade study period, WLS shifted earlier by 3–5 days/decade as determined by linear regression analysis. The observed shifts in the annual snow‐cover cycle underlie a significant trend toward a longer annual snow‐free period. The DSF increased by 5–6 days/decade over the study period, primarily as a result of earlier snow cover disappearance in spring. The observed trends are consistent with reported trends in the timing and length of the active growing season as determined from satellite observations of vegetation greenness and the atmospheric CO₂ record. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

甘肃黄土高原作物生长期土壤干旱及气候生产力特征分析   总被引：5，自引：0，他引：5  

王毅荣  姚玉璧  张秀云 《成都信息工程学院学报》2004,19(4):558-563

分析了近40年甘肃黄土高原区域作物生长期土壤干旱和气候生产力特征,结果表明:(1) 土壤干旱和气候生产力在空间上表现为全区一致,区域内相关性很好.(2) 时间演变规律上,土壤干旱有加重的趋势、气候生产力呈下降的趋势.(3) 土壤干旱和气候生产力变化阶段性明显,年际变化具有3～5a的振荡,4a周期最为明显.  相似文献   

人工冻结梁构件中不同加筋作用的对比试验研究     

牛富俊  夏慧民 《地球科学与环境学报》2002,24(2):1-3

考虑土层冻结构件中冻结管的加筋作用,对于增加冻结构件强度,减小变形量,提高人工冻结支护工程经济效益有重要作用。为研究冻结管对人工冻结构件的加筋作用,通过淤泥质粘土人工冻结梁构件三点弯试验,获得了各级载荷下构件的位移值。根据对冻土梁加筋与否,构件特定力学响应的比较,完成了冻结管加筋作用的量化分析。  相似文献   

Chandler摆动周期和Q值对激发函数估计与比较的影响     

廖德春  廖新浩  周永宏 《中国科学院上海天文台年刊》2002,(1)

用 198 4～ 1999年期间的地极坐标序列和两个大气角动量序列 ,分析了不同Chandler周期和品质因子Q的取值对Chandler摆动观测激发的功率谱密度 ,以及观测激发与大气激发之间的相干系数和相干相位的影响。结果表明 ,不同Chandler周期和品质因子Q的取值对观测激发的功率谱密度 ,以及观测激发与大气激发之间的相干系数有很大影响。因此 ,在分析Chandler摆动的观测激发与地球物理激发的关系时 ,不能仅以观测激发与某个地球物理激发序列 (如大气激发 )的更好逼近来选择Chandler摆动的最佳周期 ,因为Chandler摆动是多种地球物理激发共同作用的结果  相似文献   

甘肃党河南山北坡早古生代火山岩时代探讨   总被引：1，自引：0，他引：1  

金治鹏  党牛牛  王崇礼 《地球科学与环境学报》2001,23(3):26-29

关于甘肃省肃北县党河南山北坡火山岩的时代,前人认为属早古生代奥陶纪,但通过对火山岩分布特征、地层接触关系、区域地层对比、岩性特征以及Rb-Sr同位素年龄(基性火山岩的年龄为(684.87±71)Ma,中性火山岩的年龄为(666.63±1.6)Ma)及侵入其中的花岗闪长岩的同位素年龄(510.85±14)Ma等资料的对比分析,认为该套火山岩的时代应为震旦纪而非奥陶纪.  相似文献   

Bivariate frequency analysis: discussion of some useful concepts in hydrological application     

Sheng Yue  Peter Rasmussen 《水文研究》2002,16(14):2881-2898

Basic concepts such as conditional probability distributions, conditional return periods, and joint return periods are important to understand and to interpret multivariate hydrological events such as floods and storms. However, these concepts are not well documented in the open literature. This paper assembles and clarifies these concepts, and illustrates their practical utility. Relationships between joint return periods and univariate return periods are also derived. These concepts and relationships are demonstrated by applying a bivariate extreme value distribution to represent the joint distribution of flood peak and volume from an actual basin. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献