## 2 Seismological Data and Results
### Seismic Hazard  
The intense and large magnitude seismic activity in the broad area of the Ionian Islands makes the assessment of seismic hazard crucial in the urban planning, as well as in the construction of critical infrastructure. Additionally, the tourism industry in the Ionian Islands is a major concern for the local and national economy that requires enhancing its earthquake resilience. The strong earthquakes that occurred in the area have yielded high values of Peak Ground Acceleration (PGA). At Cephalonia, the two events of 2014 induced shakings reaching ~560 cm/s\({}^{2}\) and 735 cm/s\({}^{2}\), respectively [73]. At Lefkada, PGAs of ~412 cm/s\({}^{2}\) were recorded in the 2003 event [74] and 363 cm/s\({}^{2}\) during the 2015 earthquake [67]. Finally, the Mw6.7 earthquake of Zakynthos led to a recorded PGA of ~382 cm/s\({}^{2}\)[75], on the island. On the framework of this study, the seismic hazard of the Ionian Islands was evaluated, aiming to estimate the maximum anticipated ground motion values in this highly active seismogenic area. A probabilistic seismic hazard assessment (PSHA) method has been applied. Based on the regional character of this study, a source-zone approach was selected. Zone boundaries were obtained from the SHARE project [76,77]. However, the b-value, earthquake rate and maximum magnitude for each area were re-estimated, from the catalogue compiled in the context of the current study. To account for time periods of incomplete data, the modified b-value (\(\beta\)) was determined using a maximum likelihood  
Figure 6: Same as Figure 4, but for the temporal evolution of seismicity south of Zakynthos Island (group #4), for events with \(M\geq 2.5\). method [78]. The ground motion prediction equations (GMPEs) of [79], which have been successfully applied in seismic hazard studies in Greece [80; 81; 82], were used to obtain PGA values in the final PSHA model. A reverse/strike-slip focal mechanism type and a rock basement were considered in the GMPE, for all areas. Finally, the seismic hazard was assessed using the R-CRISIS software [83]. The software can calculate the expected hazard value (in this case, PGA and the Peak Ground Velocity; PGV) for estimated earthquake occurrence probabilities at specific timeframes, for the given distribution of sources and the event magnitudes within the limits of each zone. The PGA and PGV values were computed for a 10% exceedance probability level in 50 years (return period of 475 years) (Figure 7). The two hazard quantities follow similar distributions. Highest values are observed at Cephalonia and the nearby Ithaca Island. The high seismic activity on these islands fully complied with the obtained hazard values. Similarly, increased values are observed at the NW edge of Zakynthos. The hazard quantities decrease towards the central part of Zakynthos, in accordance with the lack of strong events in this area. The high hazard zone is terminated at the southern part of Lefkada Island. The lowest hazard values in the area are observed in the north Ionian Islands (Paxoi and Corfu); as expected, since no large-magnitude events (\(M\geq 6.0\)) have occurred in this area during the past 120 years [28]. The Greek Building Code [62] classifies the Ionian islands into two zones: Zone II (with PGA of 235 cm/s\({}^{2}\)) and Zone III (with a value of 353 cm/s\({}^{2}\)). Lefkada, Cephalonia, Ithaca and Zakynthos Islands are in Zone III, with Corfu and Paxoi classified in Zone II. While the code provides wide ranges, the current analysis indicates that there may be a need for a more detailed approach. The expected PGA at Corfu and Paxoi was found to be the lowest in the Ionian Islands, being less than 353 cm/s\({}^{2}\). However, it was observed that for Zone III islands, a much finer distribution could be extracted (Figure 7a). Moreover, Cephalonia and Ithaca seemed to feature PGA values much higher than that of the Seismic Code.