  We study the structural similarity of earthquake networks constructed from
seismic catalogs of different geographical regions. A hierarchical clustering
of underlying undirected earthquake networks is shown using Jensen-Shannon
divergence in graph spectra. The directed nature of links indicates that each
earthquake network is strongly connected, which motivates us to study the
directed version statistically. Our statistical analysis of each earthquake
region identifies the hub regions. We calculate the conditional probability of
the forthcoming occurrences of earthquakes in each region. The conditional
probability of each event has been compared with their stationary distribution.
