福建沿海地区地微动的谱结构特征

在福建沿海地区的福州、泉州、莆田等地进行了场地地微动的测试 ,利用快速富里叶变换 (FFT)方法对观测到的地微动信号进行频谱分析。结果表明 ,覆盖层厚度大、有厚层的软弱夹层淤泥的场地 ,其整体刚度小 ,地微动谱能量相当分散 ,频带宽 ,峰值频率低 ,卓越频率一般为 1～ 5Hz ;覆盖层薄、土层刚度 (Vs)大的场地 ,地微动的峰值频率也大 ,卓越频率一般为8～ 11Hz,且常呈单峰形态。软土对高频地微动信号有滤波作用 ,对低频信号起放大作用 ,而硬土层则相反.     

黄土自重湿陷变形的脉动液化机理

提出了一种黄土自重湿陷的机理－地球脉动引起饱和黄土液化,简要地介绍了地球脉动的原理,并从土动力学的角度分析了地球脉动引起饱和黄土液化的过程。通过现场浸水试验、地球脉动的定时测量及室内土地试验等,揭示了脉动的幅值、卓越周期与液化程度的关系。最后还分析了影响脉动液化的因素,结果表明,这些因素都有利于液化的产生,从而导致黄土自重湿陷。     

Non-linear filter, using the wavelet transform, applied to seismological records

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.     

Low-Frequency Variations, Chandler and Annual Wobbles of Polar Motion as Observed Over One Century

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.     

微动台阵探测技术及其应用研究

介绍了利用微动台阵技术探测地壳浅层横波速度结构的仪器设备、观测系统、野外采集和数据处理方法，给出了用空间自相关方法测定相速度和浅层速度结构反演的实例。由于该方法不需要专门的震源，对于探测从地表到3km深度范围的地层结构具有经济、快捷、应用范围广泛等优点，因此将成为一种新的具有很好应用前景的地球物理勘探方法。     

Seasonal and secular positional variations at eight co-located GPS and VLBI stations

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.     

苏北盆地部分古生界原油来自第三系源岩的证据

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。     

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

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…     

Seismic Signals Induced by Snow Avalanche Flow

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.     

龙湖地区地面脉动特性分析

本文对龙湖地区地面脉动的测试结果,结合该地区的土层剪切波速度Vs,第四纪复盖层厚度H,进行分析研究。求得了本地区地面脉动卓越周期T的统计计算式:T=1.8H/Vs。应用这个计算式,根据实测的地面脉动卓越周期,剪切波速度的数据,推算第四纪复盖层厚度,得到了比较满意的结果。 本文的统计计算式与日本学者金井清提出的计算公式T=4H/Vs,有相同的比例关系,但有明显差别的比例常数。文中对此及一些有关问题进行了简要的定性讨论。 综合分析结果,我们认为,地面脉动的卓越周期与场地土的动力特性密切相关,而且有可能反应小区域范围场地土层的动力性质。