Fig. 6

Frequency of events of each VEI and eruption magnitude category. As an example, the case of moving average calculation with window size of 8 is shown. Error bar shows the range of 95 percentile confidence interval estimated by the bootstrap method (Efron 1979) with 10,000 replicates. a Result for VEI datasets; open squares show results of the Japanese data (this study); black squares show the results of global data (De la Cruz-Reina 1991). b Result for eruption magnitude datasets; open squares show results of the Japanese data (this study). The dashed line shows the linear relationship of logarithmic frequency and eruption magnitude compiled from Pyle (1995)