Characterization of earthquake clustering in North-Eastern Italy: new insights from local scale OGS data

Abstract:

The space and time properties of earthquakes occurrence in the Friuli Venezia Giulia Region (NE Italy) are explored, taking advantage of information from local bulletins compiled at OGS since 1977, with the aim to detect possible general features of seismic clusters in the area.

Since reliable quantification of how seismicity evolves in space and time requires the use of consistent input data, a preliminary reappraisal of the earthquake bulletins is carried out and the area of sufficient completeness is outlined. For this purpose different techniques are applied, including comparative analysis with global data, which are available in the region for the moderate size earthquakes (i.e. magnitude larger than 3.0).

Using the revised data, a quantitative analysis of seismicity patterns is performed. In particular, a formal method for detection of earthquake clusters, based on nearest-neighbor distances of events in space-time-energy domain, is applied. Different techniques are considered to estimate the main parameters that characterize seismicity in the region, including the b-value and the fractal dimension. Stability tests are carried out with respect to the time span of the input catalog.

Results from clusters identification are discussed and are compared with those from earlier studies, discussing limits and possible improvements.