Identifying features in time-occurrence sequences of volcanic eruptions

Investigating the presence of 'memory' in time series represents a crucial aspect in the context of studies devoted to the analysis of geophysical phenomena. The Hurst rescaled range (R/S) approach is an adequate method to discriminate among persistent, antipersistent and uncorrelated dynamics, this leading to the characterization of three different types of memory. This method has been performed in the analysis of the activity of 14 volcanoes in the world, in order to detect and quantify the presence of correlations in the sequences of time-occurrences of volcanic eruptions with volcanic explosivity index VEI >= 0. The statistical analysis has revealed that the temporal fluctuations of seven volcanoes are persistent, while the others are characterized by uncorrelated dynamics.