Analysis of Time Sequences of Explosive Volcanic Eruptions of Sakurajima

Explosive volcanic eruptions of Sakurajima, which were observed in 1981–1999, are analyzed where the time interval τ between two successive explosions is considered as a dynamical variable. Correlation dimensions of the time series {τ i } shows that it can not be regarded as a genuine low-dimensional chaotic time series. The Hurst exponent H of the time series is also calculated, and the result H =0.72 shows that the eruption is not a Poisson process but has persistent behavior.