Determinaion of the Direction of the Ground Noise Source

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It is well known that the micro-tremor is the three dimensional ground vibration induced by the various noise sources and the analysis of orbit of the vib ation in three dimensional space is important for discussing the characteristics and mechanism of the micro-tremor.In this project, a new technique for analyzing the orbit of the three dimensional vibration, namely three dimensional rotary spectrum, is presented and the applicability of it to the micro-tremor is discussed.Firstly, the theory of the three dimensional rotary spectrum is presented and experimental procedures and numerical scheme of it are described.secondly, field measurements of the micro-tremor were carried out at two sites, one is located in Yatsushiro plane and the other is located in the ground thermal region, and the characteristics of the miocro-tremor of each sites are analyzed by the proposed scheme. It is made clear that the micro-tremor can classified into two types of vibration, Rayleigh wave type and Love wave type, and the direction of the source which generate the tremor is determined from the analysis of the vibration plane.It is concluded that the three dimensional rotary spectrum has a promise to analyze the characteristics of the ground vibration of micro-tremor as well as the mechanism of it.