## 2 Seismological Data and Results
### Seismicity Results  
After visual inspection, the seismicity of the study area during the last decade was divided into 12 spatial groups (Figure 2), to enable the description of its spatiotemporal evolution. Seismicity marginal to the area of interest was placed in the miscellaneous group #13 (white). The magnitude of completeness is estimated at \(M_{\rm c}\) = 2.0 \(\pm\) 0.2, with variations depending on the method used for its determination or the time period of a selected subset. At times, it reaches lower values, e.g., 1.5, whereas during the occurrence of significant earthquakes that produce series of large aftershocks, the magnitude of completeness may temporarily surpass 2.5. The cumulative number of events per spatial group (Figure 3a) and the spatiotemporal projection (Figure 3b) along the A-B profile of Figure 2a are drawn after the application of the magnitude threshold (\(M\geq M_{c}=2.0\)). The herein referred magnitudes are \(M_{\rm L}\), unless otherwise stated. Starting in early 2011, scattered seismicity was observed throughout the Ionian Islands region. An M4.5 earthquake occurred near the northern tip of Cephalonia Island on 16 March 2011, an M4.1 event occurred just offshore south of the island on 5 December 2011 and an M4.2 event near the northwestern part of the Paliki peninsula (Atheras area) on 23 April 2013. The background seismicity rate with \(M\geq 2.0\) was \(\sim\)0.4 events/day, occurring mainly onshore of the island (group #1, red) and in Myrtos Gulf (group #2, orange). Overall, very few events are located near to or onshore of Ithaca Island during the study period. Background seismicity was also recorded along the SW extension of the CLTFZ, at a rate of \(\sim\)0.4 events/day, occurring mainly onshore of the island (group #1, red) and in Myrtos Gulf (group #2, orange). The background seismicity rate was \(\sim\)0.4 events/day, occurring mainly onshore of the island (group #1, red) and in Myrtos Gulf (group #2, orange). Overall, very few events are located near to or onshore of Ith  
of 0.1-0.2 events/day. Further south, near Zakynthos Island, clustered seismicity was recorded following events of magnitude around 4 at group #4 (indigo; -0.3 events/day) and group #8 (yellow; -0.5 events/day), which extended from the area between Zakynthos and Cephalonia to the NW Peloponnese. An M5.0 event occurred at the westernmost end of group #4 on 19 July 2011, triggering seismicity along SW-NE-trending streaks. It should be noted that such delineations of epicenters in that area have been argued to be affected by the large azimuthal gap, causing location biases along this direction [29], so they should not be overinterpreted. The southernmost group #6 (cyan) near the Strofades Islets has a background rate of -0.2 events/day. On Lefkada Island (group #3, green; with a background rate of 0.1-0.2 events/day), seismicity often occurs in spatiotemporal clusters, whereas the background seismicity on Cephalonia Island tends to be more randomly scattered. Significant earthquakes that took place during the study period also include an M4.5 event on 23 October 2012 offshore north of Lefkada and west of Preveza, and an M4.7 event on 23 May 2013 at the southern tip of the island. Figure 3: (**a**) Cumulative number of events per spatial group of Figure 2 (different colors), for events with \(M\geq M_{\rm c}=2.0\). The larger events (\(M\geq 4.0\)) are marked by circles. (**b**) Spatiotemporal projection along the north–south-oriented profile A–B of Figure 2a, for events within a range of \(\pm 50\) km from the profile and \(M\geq M_{\rm c}=2.0\). Symbol size is proportional to magnitude. Events with \(M\geq 5.0\) are marked with stars. Close-ups for the periods January 2014 to September 2017 and August 2016 to November 2021 are presented in Figures A1 and A2 of Appendix A, respectively. Group #9 (black), near the eastern shore of Amvrakikos Gulf, with a background rate of \(\sim\)0.1 events/day, contains an M5.2 event that occurred on 24 October 2014, producing a small cluster.