Analysis of seismic sequences by using the method of visibility graph

The seismicity of Italy between April 16, 2005 and December 31, 2010 is investigated by means of the visibility graph method. The degree distribution of the magnitude point process is power- law-shaped. The method does not seem to detect time-clustering structures in the magnitude point process. The degree distribution does not change significantly with the increase of the magnitude threshold from 1.9 to 3.5. The exponent of the degree distribution shows a certain stability vs. the threshold magnitude, ranging between 3.00 and 3.25, with mean value 3.11 +/- 0.06.