On the methods to identify clustering properties in sequences of seismic time-occurrences

In recent years there has been deep development in the use of techniques to analyse the statistical properties of point process time series. Furthermore many efforts have been made to establish robust methods to identify time clustering structures in the temporal distribution of seismic events. In this paper we intend to give a systematic review of some common used techniques to characterise the temporal properties of an earthquake sequence; we also present new methods, commonly used in other scientific fields, to reveal time clustering structures in a seismic sequence and to clearly identify non-poissonian behaviours at different time scales. An application of these methods has been performed on the seismicity of Irpinia-Basilicata area (Southern Italy).