Understanding Seismic Clusters: a Study on the 2018 Molise Earthquake Sequence

Accurate identification of seismic clusters is crucial for seismicity forecasting, but the uncertainty in clustering methods can significantly affect results. In a recent study OGS scientists tested different approaches to analyze the clustering taking as a case study  the increase in seismicity observed in Molise, Southern Italy, from April to November 2018.

Our findings revealed several important insights. First, we observed that different clustering methods often produce inconsistent results, highlighting the need for more refined techniques. Additionally, we identified a period of quiescence between major events (April-August 2018) and noticed that seismicity tended to propagate upwards, suggesting a fluid-driven mechanism. The fluid-driven hypothesis may help explain both the prolonged duration of the sequence and the variations in clustering outcomes. 

Moreover, this study highlights the importance of refined methods to identify clusters and encourages further detailed analyses when different methods supply very different results.

The work was conduct in collaboration with The Institute of Statistical Mathematics, ISM of Tokyo,as part of the activities carried out for the bilateral scientific-technological cooperation program between Italy and Japan, projects of great  importance of the 2021-2023 Executive Protocol.