噪声水平上的爆炸余震信号提取   总被引：2，自引：0，他引：2  

李学政  杨选辉  胡毓良  雷军 《地震地磁观测与研究》2001,22(1):9-17

文中采用窄带滤波、傅里叶反变换及小波分析在噪声水平上提取弱余震信号。窄带滤波能够在背景噪声水平上以及（－10）－（20）dB记录中提取有用信息，但是往往产生截断误差，如果数字序列具有较大的初始幅值，所提取的波形在截断处发生畸变。傅氏反变换从负信噪比的记录中提取的信号质量较差，伴有高频干扰成分，对于信噪比为正数的记录，傅氏反变换提取的波形是良好的，该种方法同滤波方法一样，也存在截断误差。小波分析从信噪比为负数的记录中提取的信号不理想，而从信噪比为正数的记录中提取的信号质量最好，波形完整，首尾清晰，基线平直，无截断误差。窄带滤波，傅氏反变换及小波分析有两个共同点，基一，都能够从强背景噪声中提取有用信息；其二，信噪比越大，获取的信号质量越高。  相似文献   

Non-linear filter, using the wavelet transform, applied to seismological records   总被引：1，自引：0，他引：1  

A. Pazos  M.J. González  G. Alguacil 《Journal of Seismology》2003,7(4):413-429

As any process in Nature, seismic recordsare affected by noise that the analystwould want to eliminate. One of the mostcommon techniques used to minimise thisnoise effect is the application of linearfilters, which reduce the bandwidth of thesignal. This method is based on the FourierTransform, and therefore any perturbationon the coefficients affects the entirerecord.We have developed a non-linear filter basedon the multiresolution analysis of theDiscrete Time Wavelet Transform (DTWT). Themain idea is to use the time-frequencylocalisation properties of the waveletdecomposition. Each coefficient isassociated to a window on thetime-frequency plane, so any perturbationwould only affect the time and frequencyrange of the correspondent window.The procedure we propose has three stages:periodic noise elimination, spikesreduction and, finally, the non-linearfiltering. The non-linear filter acts bythresholding the wavelet coefficients. Thethresholding estimator will depend on thesignal-noise ratio (SNR) in each of thefrequency bands associated to the waveletdecomposition.We have compared the proposed method to thecoherent structures method (Mallat, 1998)and to two 4^th order linear filterbanks (Butterworth and Elliptic filters),applying all of them to a syntheticdatabase, and a real earthquake databaserecorded by the Short Period ROA Network.The proposed method improves the SNR in the87% of the tested events, being therelative rms error less than three, and themaximum amplitude relative error less than10% in the 90% of the synthetic database.  相似文献   

Low-Frequency Variations, Chandler and Annual Wobbles of Polar Motion as Observed Over One Century   总被引：1，自引：0，他引：1  

Joachim Höpfner 《Surveys in Geophysics》2004,25(1):1-54

Polar motion data are available from the mid-19th century to the present. Basedon time series with a variety of sampling intervals (monthly, 0.05-year, 5-day anddaily), we have separated the low-frequency terms by low-pass filtering and theChandler and annual terms by recursive band-pass filtering of the pole coordinates.Using a simple unweighted least-squares fit to the filtered low-frequency terms, thelinear trends of the rotation pole were estimated. Assessing the estimates based onintercomparisons, the most reliable trend estimate was found. Using a Fast FourierTransform, we have computed the prograde, retrograde and total amplitude spectraof the low-frequency part of polar motion in order to reveal the long-periodic signals.The characteristics and time evolution of the Chandler and annual wobbles aredescribed by changes in their parameters (radii, directions and period lengths) overone century.  相似文献   

Seasonal and secular positional variations at eight co-located GPS and VLBI stations   总被引：2，自引：0，他引：2  

X.L. Ding  D.W. Zheng  D.N. Dong  C. Ma  Y.Q. Chen  G.L. Wang 《Journal of Geodesy》2005,79(1-3):71-81

Time series of daily position solutions at eight co-located GPS and VLBI stations are used to assess the frequency features in the solutions over various time-scales. This study shows that there are seasonal and inter-annual signals in all three coordinate components of the GPS and VLBI solutions. The power and frequency of the signals vary with time, the station considered and the coordinate components, and between the GPS and VLBI solutions. In general, the magnitudes of the signals in the horizontal coordinate components (latitude and longitude) are weaker than those in the height component. The weighted means of the estimated annual amplitudes from the eight GPS stations are, respectively, 1.0, 0.8 and 3.6 mm for the latitude, longitude and height components, and are, respectively, 1.5, 0.7 and 2.2 mm for the VLBI solutions. The phases of the annual signals estimated from the GPS and VLBI solutions are consistent for most of the co-located stations. The seasonal signals estimated from the VLBI solutions are, in general, more stable than those estimated from the GPS solutions. Fluctuations at inter-annual time-scales are also found in the series. The inter-annual fluctuations are up to ∼5 mm for the latitude and longitude components, and up to ∼10 mm for the height component. The effects of the seasonal and inter-annual variations on the estimated linear rates of movement of the stations are also evaluated.  相似文献   

苏北盆地部分古生界原油来自第三系源岩的证据     

陈安定 《江苏地质》2005,29(4):193-197

苏北盆地LT1井、D7井、7．43井和L1井等古生界原油的地球化学特征研究表明，它们来自古新统阜宁组源岩。“新生石储”现象主要是新生界源岩与古生界储层呈断层接触造成的。  相似文献   

THE APPLICATION OF TIDAL SIGNAL EXCLUSION SCHEME FROM INITIALIZATION IN A GENERAL CIRCULATION MODEL     

杨学胜  王军  陈谊 《热带气象学报(英文版)》2004,10(2):210-215

In this paper, some corrections was made to the assumption that the forcing is quasi-static, which is the basis of the nonlinear diabatic initialization scheme adopted by a global model T106L19. Thus the tidal signal is expressed and excluded from the i…  相似文献   

Seismic Signals Induced by Snow Avalanche Flow     

Kishimura  K.  Izumi  K. 《Natural Hazards》1997,15(1):89-100

In this paper some observations and their analysis are presented dealing with the link between seismic signals and avalanche flow. The measurements during the passage of avalanches showed a specific spindle pattern which was quite different from the one of natural earthquakes. The general trend strongly depended on the topographic features of the avalanche path, and as a result we could estimate avalanche velocity. The running power spectrum showed a meaningful shift of the dominant peak from the front to the rear part of the flow.  相似文献   

微弱光信号检测方法的初步研究     

Chai Wenquan 《地球科学》1989,(6)

本文介绍了微弱信号检测方法在微光检测方面的应用,详细讨论了三个方面的问题:(1)由于光电倍增管的动态特性不同,可将其分为两种类型,即多光电子情况和单光电子情况,而且决定了检测系统的不同方式;(2)为了提高检测灵敏度和信噪比,介绍了8种检测方式结构图,并对每种检测方式的工作原理和信噪比做了详细说明;(3)从理论上分析了检测方式的动态特性,推出主要检测方式的表达式,并进一步讨论了各种检测方式的适用范围。  相似文献   

关于微动信息基本性质的初步研究     

Liu Cai  Han Wenming  Zhou Hui  Tang Dayi  Yang Baojun 《吉林大学学报(地球科学版)》1994,(2)

在简述微动信息的采集技术后，以随机信号的基本理论为基础，详细分析了微动信息的数字特征与物理性质。微动信息的功率谱密度具有分立性与主频特征，道间的规则信息具有同相性，道内信息具有一定的重复性与稳定性，在空间上各分量表现出传播性。这些物理性质表明微动信息虽然不是来源于特定震源，却呈现不是任意随机的特征。带通滤波后的微动信息在高频范围内，相位谱出现分叉现象，即由微动频带内混沌状态经过一个简短的过渡进入了有规则的变化带。  相似文献   

EXPERT SYSTEM FOR THE CHARACTERIZATION OF LABORATORY SAMPLE INPUT SIGNALS:AUTOCORR     

P.MIJLAND  J.KLAESSENS  B.VANDEGINSTE  G.KATEMAN 《地理学报(英文版)》1989,(2)

An expert system is presented for automated time series analysis of laboratory sample input signals.Thesystem,AUTOCORR,builds a model of the time series by identifying the processes that are present.These are an uncorrelated random process and,underlying this,possibly one or more of the following:a first-order autoregressive process,a trend and a periodic process.AUTOCORR has a knowledge baseof 44 rules and 41 facts for this purpose.The employed shell,INFER,allows the use of algorithmicprocedures.Elaborate tests with simulated signals show that AUTOCORR has a very low false positivescore and is successful in describing time series for laboratory simulation models.  相似文献