## 3 Results  
### Spatial Distribution of PGA and PGV  
The spatial distribution of PGA values calculated for each sub-area separately using the logic tree approach (Figure 2) for rock conditions is presented in Figure 3. Beginning with the non-island part of the administrative region of Attica (Figure 3a), the highest values were identified in the western part of the region, whereas the lower ones were computed in the southeastern part. The highest PGA value of the first sub-area for a return period of 475 years was \(\sim\)290 cm/s\({}^{2}\), and the lowest was \(\sim\)60 cm/s\({}^{2}\) (Figure 3a). Moreover, the value calculated in the city of Athens was \(\sim\)150 cm/s\({}^{2}\). Continuing with the second sub-area (Salamina and Aegina, Figure 3b), the largest PGA values were identified to the west and northwest part of the group's shoreline, and the minimum ones at the eastern region. More precisely, the highest PGA value was \(\sim\)250 cm/s\({}^{2}\), and the lowest one was 170 cm/s\({}^{2}\)  
Figure 2: The logic tree decision diagram, implemented in the final step of the computational scheme. The term ASj denotes the area source j (j = 1, 2,..., N), with all area sources presented in Figure S1 in the Supplementary Material. The weights in the last column indicate the percentage of normal and non-normal focal mechanisms; these weights for all area sources are provided in Table S1. In order to ensure clarity, the minor logic trees of the GMPE and the predominant type of focal mechanism sections are displayed only for the first area source. For the capitals of Salamina and Aegina, the corresponding values were \(\sim\)220 cm/s\({}^{2}\) and 225 cm/s\({}^{2}\), respectively. A similar PGA distribution was observed in the Methana and Poros sub-area (Figure 3c). However, the overall values were lower, with a local maximum of 175 cm/s\({}^{2}\) NW of Methana and a minimum of \(\sim\)120 cm/s\({}^{2}\) at the southeastern edge of the shoreline. The estimated PGA at Methana was \(\sim\)165 cm/s\({}^{2}\) and at the capital of Poros 155 cm/s\({}^{2}\). The fourth sub-area (Hydra, Spetses) featured the lowest PGA values in the whole region. PGA ranged between \(\sim\)140 cm/s\({}^{2}\) at the eastern part of this area and \(\sim\)170 cm/s\({}^{2}\) at the northern edge (Figure 3d). Specifically, the value at the capital of Hydra was \(\sim\)160 cm/s\({}^{2}\) and \(\sim\)150 cm/s\({}^{2}\) at Spetses. In the last sub-area (Kythira and Antikythira; Figure 3e), the highest PGA was 220 cm/s\({}^{2}\) in Antikythira, and the lowest one (\(\sim\)200 cm/s\({}^{2}\)) was observed at the northern part of Kythira (with 215 cm/s\({}^{2}\) estimated within the capital of the island). The spatial distribution of the PGA values for a return period of 950 years was similar to the previous return period for all groups (Figure 4). In sub-area 1, the highest PGA value was \(\sim\)370 cm/s\({}^{2}\) and the lowest was \(\sim\)80 cm/s\({}^{2}\) (Figure 4a). The estimated value in Athens was \(\sim\)165 cm/s\({}^{2}\), indicating that there was no significant increase for a longer return period. Around Salamina and Aegina (Figure 4b), PGA ranged between \(\sim\)270 cm/s  
Figure 3: The spatial distribution of PGA values for a return period of 475 years for each of the five sub-areas, i.e., (**a**) Attica peninsula, (**b**) Salamina and Aegina, (**c**) Methana and Poros, (**d**) Hydra and Spetses, and (**e**) Kythira and Antikythira. Triangles indicate the main urban site at each sub-area. and \(\sim\)320 cm/s\({}^{2}\). For the capitals of Salamina and Aegina, the PGA levels were \(\sim\)270 cm/s\({}^{2}\) and 290 cm/s\({}^{2}\), respectively. The Methana and Poros sub-area (Figure 4c) featured lower values in the range of \(\sim\)160 cm/s\({}^{2}\) and \(\sim\)230 cm/s\({}^{2}\). This decrease followed a similar pattern to the comparatively low accelerations observed for the 475-year return period. PGA at Methana was \(\sim\)220 cm/s\({}^{2}\), and at the capital of Poros it was \(\sim\)205 cm/s\({}^{2}\).