The Study Of Theory And Application On Ground Microtremor In Anisotropy Media

The study of ground microtremor can be applied to analysis on the response of ground seismic, characterization of some speciality of ground seismic. It's one of the most important and convenient methods for determining the dynamic properties of the soil , predicting the characteristics of ground seismic, and studying of the shock resistance of the architecture.At present, the study of theory and the engineering application on ground microtremor are based on the hypothesis of isotropy basically. In fact, the characteristic of the soil is usually anisotropy. It is important and useful to study the theory and the application of ground microtremor in the anisotropy soil, influence of the anisotropy to the ground microtremor, the dynamic properties of the ground based on the theory of elastic wave. This is one of the leading topic in the area of the seismology .Based on the theory of elastic wave in anisotropy medium, the characteristic of the seismic wave is analyzed in this paper. Wave field in anisotropy medium is quite different from that of in isotropy medium. As the influence of the characteristic of anisotropy, the wave modes and the surveying method have important effect on the results of the velocity, then the velocity will affect the calculation of the fundamental period. Therefore, considering the anisotropy in study and analysis of the ground velocity testing is necessary.In this paper, the characteristics of the ground microtremor in anisotropy soil, the influence of the frequency of the incident wave to the characteristics of the ground microtremor, and the variation of the ground characteristics with depth have been studied. The mechanism of the ground microtremor has been studied based on the analysis of theory and numerical modeling. The conception of the principal axis has been put forward. The method for determining of the principal axis has been studied systematically in this article. This study make up the foundation of the analysis of the ground response.The effect of the anisotropy to the soil dynamics has been studied in this article. The effects of ground microtremor to the stability of the soil, and the relationship to the stability of the soil and principal axis have also been studied. Taking account of the effect of the fundamentally period to the ground response, the design of seismic structures considering structural vibration period restraint should respect the influence of the anisotropy of the fundamental period. A method considering fundamentalperiod of the principal axis for the structural vibration period restraint has been put forward. The observation measurement and processing technique with wavelet have been studied.The method of the soil category is analyzed in this paper. Method for the classification of soil considering the characteristics of anisotropy of the ground microtremor , and method for the selection of the earthquake time history considering anisotropy are put forward respecting to the ground microtremor.In this paper, only the effect of the anisotropy of the earth covering was considered. In fact characteristics of the soil including the heterogeneity of the earth covering, the heterogeneity and the anisotropy of the base rock are also important factors that affect the characteristics of the ground microtremor. All of these will be studied further in the future.