Abstract：The dynamical characteristics of ground soil and structure of frequency spectrum of ground microtremor in Fuzhou，Fujian province，are studied in this paper. The ground microtremor signals were observed，and the signals were analyzed by fast Fourier transform method (FFT). The characteristics of structure of frequency spectrum and response of ground soil to frequency of ground microtremor are revealed， and the function of microtremor with frequency-dependence and frequency-selection for different foundation soil strata is also researched. The results are shown as follows. First，ground microtremor is a kind of geophysics information with abundant intension. The frequency characteristics of ground microtremor can be obtained by spectral analyses of its signals，which can be used to probe into dynamical characteristics of rock and soil of studied area. Secondly，there exists a function with frequency-dependence and frequency-selection for the response of site soil. The change of predominant period of ground microtremor is closely related to the formation of site soil layers，and mutually corresponds to the change of engineering geological conditions of the site. Therefore，the structure and feature of different foundation soil strata can be distinguished with different kinds of frequency response of site. Thirdly，the structure of rock and soil layers directly influences the spectral structure characteristics of ground microtremor. The covered layer with the structure of different foundation soil strata is related to the frequency of ground microtremor. The thickness of covered layer is one of important factors to affect the predominant period of ground microtremor. Fourthly，there exist some corresponding relationships between spectral structure characters of ground microtremor and shear wave velocity of site soil layers. The outcomes of these two kinds of tests can be conferred each other. Fifthly，the correlations among predominant period of ground microtremor，thickness，and value of shear wave velocity of covered layer are established. The study results have been applied to selecting the infrastructure and buried depth of high building foundation in the coastal area of Fujian province.
