## 4 Results
### Cluster Analysis
#### 4.2.1 Corinth Gulf Area  
The western subarea of the Corinth Gulf is characterized by rich seismic activity, especially in 2013-2014, when 13 out of the 22 clusters with \(N\geq 30\) occurred. One of the major detected sequences is the 2013 Aigion swarm (C6 in Figure 4b) which initiated on 21 May 2013 with a bulk of small events and several bursts associated to earthquakes with magnitudes ranging between 3.3-3.7 (Figure S3) [63,64]. Two distinct excitations followed (C8 and C10 in Figure 4b) in accordance with the ones observed by [PERSON] et al. [65]. The first cluster began on 7 July with some activity prior to the \(M=3.7\) event on 15 July 2013, and lasted until 27 August, 2013 (Figure S3). The second half of 2014 is also a well-studied period with intense seismic activity. Five clusters with \(N\geq 30\) are detected (C15, C16, C18, C19 and C20) in the western subarea, including the offshore \(M4.8\) earthquake on 7 November 2014, associated with C19 (Figure 4b), and the \(M4.6\) event on 21 September 2014, associated with the earthquake swarm located between Nafpaktos and Psathopyrgos [66] (C15 in Figure 4b). Persistent activity since 22 July 2014 is also observed offshore Aigion (C16), close to the earthquake swarm, C15, which began on 7 November 2014 (Figure S5). In 2012, fewer clusters are observed, mostly during the first semester, with three clusters comprising \(N\geq 30\) events, C1, C2 and C3, and a plethora of smaller clusters (Figures 4b and S2). Between November 2013 and July 2014, the activity is sparse with three relatively large clusters, C11, C12 and C14 (Figures 4b and S4). Six more clusters with \(N\geq 30\) are observed until the end of 2017 (C21, C22, C23, C24, C25, C27, Figure 4b).  
The eastern subarea is characterized by more sparse activity. A major seismic sequence, Offshore Perachora (C4 in Figure 5b), is detected, including two sub-sequences, the first initiated on 22 September and the second on 30 September 2012 (Figure S6). Two relatively  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Dataset** & **(_T, dt, e, Npts_)** & **\(N_{clust}\)** & **\(N_{bg}\)** & **\#** & & \\  & & & & & **Clusters** & & \\ \hline D1 & \((0,\ 5,\ 2.5,\ 4)\) & 4662 (36\%) & 8381 (64\%) & 255 & 12.50 & 18.28 \\ D2 & \((5,\ 5,\ 2.5,\ 4)\) & 5221 (75\%) & 1770 (25\%) & 45 & 54.60 & 118.43 \\ D3 & \((5,\ 5,\ 5,\ 4)\) & 3688 (44\%) & 4640 (56\%) & 187 & 15.08 & 19.72 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Cluster statistics and the parameter set of the clustering algorithm for the three datasets. \(N_{clust}\) corresponds to the number of clustered events and \(N_{bg}\) to the background seismicity frequency. \(\tilde{\tau}\) and \(\tilde{n}\) are the mean duration in days and size of the clusters, respectively.  
Figure 4: **(a) Spatial distribution of the centroids of the identified clusters for the western subarea of Corinth Gulf along with major faults (yellow lines). The size of the circles is proportional to the earthquake number in each cluster, whereas the duration is represented by the color scale. (b) Spatial distribution of the clusters with \(N\geq 30\) events. The index of each cluster is provided in the inset box.**large clusters, C13 and C17, are observed near Itea; the former lasted almost two weeks at the end of March, 2014, and the latter--almost three months between August and October 2014 (Figures 5 and S7).