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.

ON THE SPECTRAL CHARACTERISTICS OF GROUND MICROTREMOR IN COASTAL AREA OF FUJIAN

The ground micro-tremor signals were observed in Fuzhou, Quanzhou and Putian of Fujian Province, and the signals are analyzed by fast Fourier transform method. The result shows that at the sites with greater thickness of overburden layers intercalating a thick weak layer, the rigidity of the ground is low, the frequency band is wider, the frequency energy is rather disperse, the peak frequency is lower with predominate frequency of 1～5Hz commonly; However, the sites with thinner of overburden layers, and greater rigidity of the ground, the frequency band is narrower, and the peak frequency is higher with predominate frequency of 8～11Hz. Soft soil can filter high frequency signals, but can amplify low frequency signals.