A new fast fourier method for evaluating fourier spectra at arbitrary frequencies     

Karl Wodnar 《Celestial Mechanics and Dynamical Astronomy》1996,65(1-2):85-94

This paper deals with some recent problems of frequency determination in dynamical systems. As a main result a new Fast Fourier Transform (FIT) method, the High Resolution Fast Fourier Transform (HRFFT) is presented, which allows for economic evaluation of discrete Fourier spectra at arbitrary frequencies, not just at the evenly spaced points of the rigid frequency grid the ordinary FFT is restricted to (continuous evaluation). Comparison is made to existing methods in what regards continuous evaluation, computational speed, memory requirements and precision, evidencing the high efficiency of the HRFFT. Possible applications of the new technique are indicated, showing that existing methods, as e.g. that of Laskar (1990, Icarus 88) and its extension by idlichovský and Nesvorný (1996, this volume), may strongly benefit from the HRFFT.  相似文献   

Zero-frequency tidal distrotion due to the orbital elements of tide-forming bodies     

Viliam Vatrt 《Studia Geophysica et Geodaetica》1996,40(2):119-124

Summary It has been proved that orbital elements of perturbing bodies should be taken into account when 10^–10 accuracy is required for zero-frequency tidal distortion in the second zonal Stokes parameter of the geopotential. A solution at the 10^–15 level of magnitude has been presented. The zero-frequency tidal distortion in the fourth zonal Stokes parameter has been derived as 1·3×10^–10 if the secular Love number is unity. It should be reflected in the geopotential models respecting the 10^–10 level of magnitude.  相似文献   

Nonlinear three- wave interaction among barotropic rossby waves in a large- scale forced barotropic flow     

Luo Dehai 《大气科学进展》1999,16(3):451-466

In this paper, the coupling equations describing nonlinear three-wave interaction among Rossby waves including the forcing of an external vorticity source are obtained. Under certain conditions, the coupling equations with a constant amplitude forcing, the stability analysis indi-cates that when the amplitude of the external forcing increases to a certain extent, a pitchfork bifurcation occurs. Also, it is shown from numerical results that the bifurcation can lead to chaotic behavior of “strange” attractor. For the obtained three-variable equation, when the amplitude of modulated external forcing gradually increases, a period-doubling bifurcation is found to lead to chaotic behavior. Thus, in a nonlinear three-wave coupling model in the large-scale forced barotropic atmospheric flow, chaotic behavior can be observed. This chaotic behavior can explain in part 30-60-day low-frequency oscillations observed in mid-high latitudes.  相似文献   

Audio frequency magneto-telluric survey of Norikura Volcano in central Japan     

Kiyoshi Fuji-ta  Yasuo Ogawa  Masahiro Ichiki  Satoru Yamaguchi  Yutaka Makino 《Journal of Volcanology and Geothermal Research》1999,90(3-4)

Norikura Volcano has not been active during the last 10,000 years in spite of the activity of the surrounding volcanic mountains. To study past volcanic activities, geological studies were carried out extensively. However, quite a few geophysical investigations were conducted to contribute to volcanology. Our objective is to detect the present subsurface structure of Norikura Volcano and to define volcanic stratifications. In the vicinity of Norikura Volcano, geothermal fields are still active. Subsurface volcanic rocks in this area have been exposed to geothermal activity and altered. To comprehend volcanic stratifications of Norikura and geothermal activity, we conducted audio frequency magneto-telluric (AMT) surveys around Norikura Volcano. AMT survey is useful in clearly defining the resistivity structure related to volcanic regions. The AMT data were acquired over a frequency range 10 Hz–10 kHz. Decomposition analysis was applied to the tensor impedance data. Subsequently, apparent resistivity and phase data were inverted using a two-dimensional magneto-telluric (MT) inversion and a model of Norikura was derived. The final model manifests that the surface resistors are in agreement with andesite lava or dacite lava. As for the deeper structure, a horizontal conductor is situated above resistive basements. The alteration of the conductor was weak, while basement rocks were strongly altered and/or heated through the thermal activity. The existence of these layers seems to indicate the degree of thermal activity of Norikura Volcano.  相似文献   

Calculation of the h-value during Superposing of Strong Earthquake Sequences and Its Application in Earthquake Prediction     

Yang Xin  Yu XingbaoSeismological Bureau of Xinjiang Uygur Autonomous Region  Urumqi  China 《中国地震研究》1999,(3)

For a strong earthquake swarm, the key to estimate the frequency attenuation coefficient h-value of ensuing strong earthquake sequence accurately lies in quantitative calculation and subtraction of the foreshock sequence effect.Taking the Jiashi strong earthquake swarm sequence as an example, we analyzed and compared the h-values when foreshock effect has been subtracted or not subtracted. The result shows that the boundary between the two great difference is the M56.6 earthquake on April 11,1997. The h-values with foreshock effect subtracted are all Iess than 1 before the moderately strong earthquakes, but after the earthquake, the h-values are all greater than 1. On the contrary, the h-values with foreshock effect do not show this kind of turning variation.Practical test results shows that quantitatively subtracting foreshock effect is beneficial to the judgement of the trend of the activity of the Jiashi strong earthquake swarm. This provides the basis for accurately grasping sequence development and  相似文献   

前兆异常与强震时空点的研究   总被引：2，自引：0，他引：2  

杨桂芬  王华林 《地震研究》1999,22(3):221-227

本文研究了云南三次７ 级以上强震前的小震活动, 前兆异常总台项频数变化, 地下水时空特征。得出在大震前３ ～６ 个月前兆异常台项总频数的升高现象与３０ ～３９ 级小震向震中区收缩的时间大致同步, 可能是大震前的异常从短期向短期临震过渡的时间标志。震前１ ～３ 个月出现的前兆台项总频数异常峰值和水位、水氡的场兆现象则是异常进入短期临震的时间; 峰值回落是震源区进入临震状态的时间。  相似文献   

关于地震震级-频度关系式及其非线性项的讨论   总被引：2，自引：0，他引：2       下载免费PDF全文

敖力布 《地震工程学报》1999,21(1):94-98

研究了震级频度关系式中非线性项产生的原因,指出由于地震孕育过程是非线性的,很多地震现象都服从分形和混沌规律,因此传统的震级频度关系式中应含有非线性项,才能全面描述地震过程的非线性规律．得出了新的含有非线性项的震级频度关系式．讨论了该公式中非线性项的含义．  相似文献   

振动频率对原状黄土动本构关系的影响   总被引：7，自引：0，他引：7  

王建荣  张振中  王峻  李兰 《地震工程学报》1999,21(3):310-314

对原状黄土（ Ｑ４） 施加４ 种频率的等幅正弦波荷载进行动三轴试验,研究振动频率对原状黄土动本构关系的影响．结果表明,对应于４ 种频率的原状黄土的动本构关系均服从双曲线模型,但试验常数ａ 、ｂ 均随振动频率的增大而略有减小．讨论了试验常数、动弹性模量和阻尼比等随振动频率的变化规律  相似文献   

安全钻探新途径──交流变频调速动力系统应用前景展望   总被引：1，自引：1，他引：0       下载免费PDF全文

桂暖银  刘宝林  郑黎明 《探矿工程》1999,(4):1-3

在对钻机交流变频调速动力系统的研究基础上,对该动力系统在钻探过程中如何控制和减少钻探事故的发方面做了些探索,为安全钻探提供了一条有效的新途径。  相似文献   

焉耆盆地低信噪比地震资料处理方法   总被引：7，自引：3，他引：4  

段洪有  朱丕跃 《物探与化探》1999,23(4):265-270,276

根据焉耆盆地低信噪比地震资料的特点,进行了大量的分析、试验,设计了一套以交互迭代静校正技术、随机干扰和线性干扰的压制技术、地表一致性振幅处理技术、子波归一化处理及叠后fx域预测去噪技术等处理方法为主的低信噪比地震资料处理框架.通过实际资料的处理见到了明显的效果.  相似文献