Characterizing clusters with strong subsequent events in Central Italy using RAMONES

Italy is a country affected by strong seismic activity due to the collision between the African and Euro-Asian plates. In such an area, it often happens that a first strong earthquake (FSE) is followed by a subsequent strong event (SSE) of similar magnitude. In recent years, several studies have attempted to analyze the correlation between the occurrence of a possible SSE in an area and the spatio-temporal distribution of the stress drop on the same area. In this work, we have investigated this relationship in Central Italy by using the Rapid Assessment of MOmeNt and Energy Service (RAMONES), which provides source parameters for events that have occurred in the area since 2007. Using 12900 M_L≥2 events available in the RAMONES catalog and a window-based clustering method, we obtained 25 clusters between 2009 and 2017 with magnitude of the FSE greater or equal to 4. Among them are also the clusters corresponding to the L'Aquila earthquake (2009) and the Amatrice earthquake (2016). Looking at the magnitude difference between the FSE and the strongest SSE (DM), it is less than or equal to 1 in 64% of the cases and greater than 1 in 36%. In the first case, we labelled the cluster as type A, in the second case as type B. By analyzing the ratio between seismic energy and seismic moment provided by RAMONES over the entire duration of the cluster, we found that almost all A clusters correspond to a maximum change in apparent stress over time larger than the one of B clusters. To a first approximation, this observation also proves to be true when analyzing the seismicity before the strongest SSE or at the first SSE. These preliminary results are therefore encouraging for future use in forecasting SSEs in Central Italy.

Funded by the NEar real-tiME results of Physical and StatIstical Seismology for earthquakes observations, modeling and forecasting (NEMESIS) Project (INGV).