## 3 Results
### Spatio-Temporal Analysis of Seismicity  
The temporal evolution of seismicity in the WGoC during 2013-2014 is examined in terms of seismicity rates, spatiotemporal seismicity migration speeds and pore-pressure diffusion. Figure 5 (top) shows the cumulative number of events per spatial group, for selected seismicity above the magnitude of completeness, which is estimated at \(M_{\rm c}\) = 1.8 for the manual dataset (Figure S19). The application of this threshold enhances the occurrence of seismicity bursts, usually triggered by events of larger magnitude, related to specific sequences whose initiation is marked by vertical gray lines in Figure 5. Some spatial groups are characterized by generally constant background seismicity rates, i.e., \(\sim\)0.1 events/day in group #1, 0.2 events/day in group #2 and 0.4-0.5 events/day in group #5. The miscellaneous group #10 (gray) presents a background seismicity rate of 0.4-0.7 events/day, increased to \(\sim\)1.1 events/day in the second half of 2014. In other groups, their low seismicity rates, excluding periods of bursts, range between \(\leq\)0.1 and 0.6 events/day. A general sense of the spatial distribution of background seismicity in the WGoC can be observed during January-August 2013 (Figure S22a). During that period, the more significant cluster was the 2013 Helike swarm in the south, whereas only sparse seismicity and small clusters are distributed in the rest of the study area. Figure 5 (bottom) shows the projection of epicenters along the N100\({}^{\circ}\)E profile line A-B (Figure 4, top) with respect to the origin time, without filtering out events with \(M_{\rm w}<M_{\rm c}\). In early 2013, most seismic activity was concentrated mid-gulf at group #6 (red), following an \(M_{\rm w}=3.8\) event on 28 January 2013, and at group #8 (brown) with a few minor bursts. Groups #2 (magenta), #4 (green), #5 (orange) and #7 (yellow) exhibited relatively constant seismicity rates of 0.2-0.4 events/day. Then, on 21 May 2013, the first phase of the Helike swarm (group #9, blue) was initiated with a series of events reaching \(M_{\rm w}\) 3.6-3.7, mainly activating the eastern half of the cluster. The activity in Helike culminated with a second phase during July, involving an \(M_{\rm w}=3.8\) event on 15 July 2013, which triggered seismicity at the western part of the group. The first two phases of the swarm, until August 2013, are described in detail by [6]. A third phase began on 26 October 2013, lasted for about 20 days and was concentrated at the mid-northern part of the cluster. Group #7, near Marathias, presented a small burst of activity in early September 2013. An increase in the seismicity rate to \(\sim\)1.1 events/day began in October 2013 at the offshore group #4, in the region between Nafpaktos and Psathopyrgos, presenting bursts associated with the occurrence of larger events (\(M_{\rm w}\geq 3.0\)). This first wave of seismic activity in group #4 lasted up to February 2014, with its seismicity rate returning to 0.6 events/day. Seismicity of group #4 was initially concentrated in the Y-range of 10-20 km (Figure 5, bottom), but gradually spread bilaterally towards \(Y=25\) km in January and \(Y=5\) km in February 2014. At that time, the seismic activity was also increased, temporarily, in the neighboring groups #7 (yellow) and #8 (brown). The isolated cluster #3 (cyan) near Itea presented swarm-like activity between 8 March and 14 September 2014, following a series of events, the largest being an \(M_{\rm w}=4.0\) on 10 May 2014. On 8 June 2014, 15:10:51 UTC, an \(M_{\rm w}=4.3\) event initiated an aftershock sequence in group #8, at the offshore region SW of the Trizonia Island, lasting for about one month. Increase in the seismicity rate of group #6 (red), including several \(M_{\rm w}\geq 3.0\) events, began in July 2014 (Figure A1). Part of that group was triggered by the 8 June 2014 event in group #8 (Figure A2), likely due to the partial overlap between the involved structures, as these groups cannot be fully distinguished with spatial margins.