Fig. 3From: On data reduction methods for volcanic tremor characterization: the 2012 eruption of Copahue volcano, Southern AndesTime evolution of the 52 long-duration events. Time evolution, from June 2012 to January 2013, of the 52 long-duration events: a energy, b dominant frequency, c centroid frequency, d permutation entropy, and e dominant polarization degree. The length of each bar represents the duration of the selected periods, whereas blue horizontal lines in a and b depict the average value throughout the entire period analyzed. Black vertical dashed lines show the beginning of weeks, while the black continuous vertical lines show the beginning of monthsBack to article page