Joint Use of Seismological and Topological Statistical Methods for the Analysis of 2010–2016 Azerbaijan Seismicity

Abstract

The time variation of several statistical parameters describing the complex time dynamics of the seismicity of Azerbaijan from 2010 to 2016 is investigated. Besides the well-known Gutenberg–Richter b value and the coefficients of variation, two quantities, derived by the recent method of horizontal visibility graph are analysed, namely the mean connectivity degree, which depicts an innovative way to link seismic events, and the Kullback–Leibler divergence (KLD) that informs about the irreversibility of the seismic process. Our findings indicate the emergence of pre- and co-seismic patterns in the time variation of all the analysed parameters in relationship with the strongest events of the Azerbaijan seismic catalog. In particular, the typical increase–decrease behavior has been found in b before the occurrence of large shocks. Similarly, the coefficients of variation signals are statistically significant high value in the period when the largest events occur and in most cases even before they struck the area. The mean connectivity degree and the KLD show several anomalous values in association with the occurrence of large events, in agreement with the view of earthquakes as irreversible ruptures of the crust.