## 4 Discussion  
The high seismicity of the study area, both onshore and offshore, is due to the high average extension rate of the tectonic rift [5]. It is expressed through both large earthquakes and seismic swarms [7; 112; 20; 39; 113; 114], which confirm the great importance of seismic hazard assessment as a means to quantify anticipated levels of ground shaking. When performing PSHA, there are two types of uncertainties, i.e., aleatory uncertainty and epistemic uncertainty [115]. The first one accounts for random variations in PGA, PGV and Sa values due to the implementation of a GMPE, whereas the second one accounts for the accuracy of the values [115]. Epistemic uncertainty is usually handled by the incorporation of a logic tree approach to account for the implementa-tion of more than one  
Figure 8: Response spectra of the selected earthquake scenarios for (**a**) Aigion, (**b**) Patras, and (**c**) Nafpaktos corresponding to 5% damping. TF: Trizonia Fault, HF: Helike Fault, PF: Psathopyrgos Fault. GMPE [115; 116; 117]. This is the procedure followed in the present study, given that by taking into account alternative models the uncertainties can be reduced [115]. The PGA results for a return period of 475 years, obtained through the Cornell-McGuire approach, can be directly compared with the reference value proposed by the current Greek Building Code [109]. EAK2003 divides Greece into three zones and defines the maximum expected ground acceleration for a return period of 475 years. The Western Gulf of Corinth is within zone II, with a reference value of 0.24 g (\(\sim\)240 cm/s\({}^{2}\)). However, in the herein proposed model, the entire study area exceeded 240 cm/s\({}^{2}\). The computed PGA results in the northeastern part of the area were close to the EAK provisions, even though they still slightly exceeded them. The highest value was about 325 cm/s\({}^{2}\), surpassing EAK2003 by 74%. The calculated PGA for a return period of 950 years can be utilized for the construction of buildings of greater importance, such as schools and medical centers. The spatial patterns of PGA and PGV for both return periods were similar; i.e., the highest values were found close to the Gulf, where seismicity is higher, whereas the lowest values were onshore, far from the coastline. A comparison of the PGA results obtained to those of [PERSON] et al. [49] and [PERSON] et al. [54] was attempted, both of which are for the whole Greek territory. [PERSON] et al. 's [49] computed PGA values were for certain cities, one of them being Patras, which was assigned a PGA of 0.26 g for a return period of 475 years. In this study, the corresponding PGA was \(\approx\)300 cm/s\({}^{2}\), which is slightly higher. [PERSON] et al. [54] computed PGA and PGV for the same return period for Greece. PGA values varied between 0.40 g and 0.50 g close to Patras and Nafpaktos and between 0.50 g and 0.60 g close to Aigion. Concerning PGV, [PERSON] et al. [54] proposed values in the broad range of [20.0-105.0] cm/s. In the present study, PGA and PGV values were in the range of [0.25-0.33] g and [15.0-18.5] cm/s, respectively. The existing deviations can be attributed to the different seismic and geometry data used in each case. Hazard curves were constructed for the most populated sites of the study area, the city of Patras and the towns of Nafpaktos and Aigion. All three are located close to the coastline and are characterized by high expected ground motion values. The distances between them are relatively small and they belong in the same or neighboring (according to the model) area source zones, parameterized with similar geometry and seismicity data. For this reason, their corresponding hazard curves were quite close to each other, whereas strong ground motions (\(>\)1 g) occurred only at low exceedance probabilities. Uniform hazard spectra were obtained by adopting the GMPE from [PERSON] and [PERSON] [76]. The final results were derived using the same logic tree but without the minor branches, as they were replaced with this GMPE.