Assessment of the relative ratio of correlated and uncorrelated waiting times in the Southern California earthquakes catalogue

In the present study, we investigated the interevent time interval distribution of earthquakes in Southern California. We analyzed and compared datasets of waiting times between consecutive earthquakes and time structure-distorted datasets. The aim of this study was to determine the proportion of waiting time values in the original catalogue that can be regarded as statistically distinguishable or indistinguishable from the baseline time intervals datasets where the original structure of the temporal distribution of earthquakes was disrupted. We compiled two types of time structure-distorted baseline sequences, which comprised mean values of: (a) shuffled original interevent data and (b) interevent times data from time-randomized catalogues. To compare the dynamical characteristics of the original and time structure-distorted baseline sequences, we used several data analysis methods such as power spectrum regression, detrended fluctuation, and multifractal detrended fluctuation analysis. We also tested the nonlinear structure of the original and baseline sequences using the magnitude and sign scaling analysis method. We calculated theZscore in order to assess whether the interevent time values in the original dataset shared statistical similarity or dissimilarity with the time structure-distorted baseline interevent data sequence. We compared the interevent time values in the original dataset with the mean baseline interevent times computed for two types of time structure-distorted sequences. The results showed that about 30% of the original interevent times were statistically indistinguishable from the mean of the shuffled dataset and 10% from the mean of the time structure-distorted baseline interevent dataset. We performed similar analyses for other catalogues obtained from different parts of the world. According to the results of this analysis, the proportion of events in the original catalogues that were indistinguishable from sequences with disturbed time structure did not contradict the results obtained for the Southern California catalogue.