抄録
We analyze five explosion earthquakes observed at Asama volcano in 2004. The main phase consisting of Rayleigh wave is well explained by a vertical downward single force with peak amplitude of 1010-1011 N and pulse width of 5-6s. These source parameters are in the range expected from a scaling relation presented by Nishimura and Hamaguchi (1993), which suggests that the 2004 explosions of Asama volcano are typical Vulcanian eruptions. The internal pressure built up beneath the crater is estimated to be 0.2-1.5MPa, which tends to become large after the formation of lava dome in the crater.
