Abstract. The monitoring of statistical network properties could be useful for the short-term hazard assessment of the occurrence of mainshocks in the presence of foreshocks. Using successive connections between events acquired from the earthquake catalogue of INGV for the case of the L'Aquila (Italy) mainshock (Mw = 6.3) of 6th April 2009, we provide evidence that network measures, both global (e.g. average clustering coefficient, small-world index) and local (betweenness centrality), could potentially be exploited for forecasting purposes both in time and space. Our results reveal statistically significant increases of the topological measures and a nucleation of the betweenness centrality around the location of the epicenter about two months before the mainshock. The results of the analysis are robust even when considering either large or off-centered the main event space-windows.

Supplementary Material Figure S1. Betweeness Centrality () computations in the space-window centered at 42.00°N, 13.30°E (off the center of the epicenter) with radius 1 = 1. The mainshock occurred on April 6 th , 2009 (red star): (a-i) snapshots of the maps for each cell from 20.01.2009 to 01.05.2009; (a-e) maps before the mainshock. (f) Cumulative computed at the mainshock cell (*) from 01.