Examples of cumulative events, waiting time distributions, and correlation integral plots. For the temporal distribution of tremors for subsets in Shikoku. Each example corresponds to the episodic (i, left), moderately episodic (ii, center), and continuous (iii, right) cases (corresponding bin locations are shown by circles with crosses in Figure 3). (a) Cumulative event distributions for the three cases. The total number of events is shown in the upper left corner of each diagram. (b) Distributions of waiting time (t
− ti − 1) corresponding to each of the tremor subsets. The points along the red line denote the point-wise frequency distribution of the waiting times for each subset. The light blue lines show the frequency distribution for a Poisson distribution. The vertical dashed line is the average period of the recurrence interval (1/λ). (c) Correlation integral plots for the three cases. The points in red show the correlation integral plot of tremors for each example. The light blue lines show the frequency distribution for a Poisson distribution. The pink lines show the frequency distribution for a periodic distribution. The light blue dashed lines denote the 0.01 level of significance (χ2 test) for a Poisson distribution. The labeled, dashed lines show the value of τ
determined by our analysis. The gray lines show the time periods of the maximum non-Poissonian clustering determined for the different time frames by random sampling.