Study On The Component Of Frequency Spectrum Of Microtremor And Response Of Dynamics Of Site Soil

The dynamical characteristics of ground soil and structure of frequency spectrum of ground micro-tremor in Fuzhou and Quanzhou of Fujian Province are studied in this thesis. 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 micro-tremor are revealed, and the function with frequency-dependence and frequency-selection of micro-tremor for different foundation soil strata is also researched.The results are shown as follows: First, ground micro-tremor is a kind of geophysics information with abundant intension. The frequency characteristic of ground micro-tremor can be obtained by spectral analyses of its signals, which can be used to probe into dynamical characteristics of rock and soil of a studying area. Second, there exists a function with frequency-dependence and frequency-selection for the response of site soil on micro-tremor. The change of predominant period of ground micro-tremor 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 for different kinds of frequency response of site. Third, the structure of rock and soil layers directly influences the spectral structure characteristics of ground micro-tremor. The site overburden layer with the structure of different foundation soil strata and different rigidity of soil layer transforms structure of frequency of ground micro-tremor with different degree. The thickness of site overburden layer is one of important reasons that affect the predominant period of ground micro-tremor. Fourth, there exists some corresponding relationships between spectral structure characters of ground micro-tremor and shear wave velocity of site soil layers. The outcomes of these two kinds of tests can be conferred each other. Fifth, the correlations between predominant period of ground micro-tremor and thickness, and value of shear wave velocity of overburden layer are established. The results are of important theoretical and practical significance for deeply understanding the characteristic of ground micro-tremor, and developing the project application of ground micro-tremor, and antiseismic design, shock isolation, and selecting the infrastructure and buried depth of high buildings foundation in coastal area of Fujian.