抄録
Earthquake engineering importance of the observation of long-period microtremors as an effective tool to elucidate deep ground characteristics during an earthquake has been confirmed. For achieving better reliability on their engineering applications, however, understanding of them as wave events has been thought indispensable and been attempted.
The long-period microtremors were interpreted as an ensemble of dispersive surface waves (Rayleigh and Love waves) in the preceding paper. As a continuation of this line of study, a more detailed examination on Rayleigh wave component is carried out and reported in this paper. Phase velocity, particle motion, and deposit/basement spectral amplitude ratio are analysed, by which Rayleigh wave mode structure is studied.
Concluding remarks on this examination are as follows.
1. Rayleigh waves in the long-period microtremors are mainly composed of M11 mode. M21 mode is also detected but is not a predominant mode.
2. Rayleigh wave period-ellipticity relationship, known as a useful means to evaluate underground structures, can be disclosed employing three-component records of the long-period microtremors.
3. A detailed and further examination on Love waves is also desired, since the long-period microtremors are composed of both Rayleigh and Love waves.
