Investigating small-world and scale-free structure of earthquake networks in Greece

Abstract

Abstract The non-trivial properties of the small-world and scale-free structure are investigated in earthquake networks that are formed from the seismicity taking place in Greece and adjacent area. The nodes of these networks are either well-defined seismic zones or square cells comprised in a normal grid superimposed onto the study area. The network connections are either drawn whenever earthquake succession is observed between the nodes or given by the significant correlation of the seismic activity in two areas. The networks are formed for varying magnitude thresholds and for selected time spans during 1845–2017 to establish that the data are complete for each study period. Rigorous statistical analysis is performed using also appropriate resampling methods to assess the presence of the small-world and scale-free property. The scale-free property was not identified in any network and only for one of the network construction methods the small-world property could be established, disputing the universality of these non-trivial properties because are not verified for the Greek seismicity and for the specific network constructions.