桜島における C 型微動について

抄録

At Sakurazima Volcano, the tremors such as a sinusoidal wave of which amplitude is modulated are frequently observed. This type of tremor is called as “C type”. The relatively simple type of the tremors is as a Gaussian wave packet. In the present paper, the characteristics of oscillation, spectral characteristics, etc. are investigated for relatively simple type tremors. At Stations B and A, the particle motions of the tremors are in both longitudial and transverse directions to the Minamidake Crater. The oscillation characteristic at Station C shows the Rayleigh type wave passing through from the northeast to the southwest. The mean periods of the tremors are relatively longer for waves with small amplitudes, and shorter for larger amplitude waves. It is suggested that relatively complicated or continuous tremors are consisted of the numerous events taking place one after another.