## 4 Data Analysis and Results
### DInSAR Analysis  
In terms of satellite observations, the systematic acquisition strategy of the Copernicus Sentinel-1 mission ensured the availability of SAR data to investigate the earthquake sequence. Interferometric coherence levels for 6- to 12-days pairs are maintained, allowing for the extraction of reliable DInSAR ground motion measurements. Independent results from four different satellite tracks (Figures 4 and S2) are consistent, indicating co-seismic downthrow of the epicentral area, extending over an area of about 38 km\({}^{2}\) to the east of the Lagouta and Kastelli faults. The ground displacement patterns are comparable, retaining an elliptical shape of the co-seismic fringes within the epicentral area. The increased ellipticity of the fringes for pairs covering a larger time span after the mainshock (tracks D036, A029, and D109) implies the contribution of post-seismic motion, compared to the more concentric fringes of the A102 track, containing only 2 days of post-seismic activity. In addition, the direction of the major axis of the elliptical fringe pattern  
Figure 10: Map and cross-sections of the relocated 2021 Arkalochori aftershock sequence (period 27 September–18 October 2021). Colors and numbers correspond to the aftershock spatial groups 2–4 presented in Figure 7b. The cross-section profiles are drawn in an N103\({}^{\circ}\) E direction, roughly perpendicular to the strike of the mapped Kastelli and Lagouta faults, whose downdip extension is presented in the cross-sections with gray-dashed lines. The red dashed line is the section of the least-squares plane fitted to the relocated hypocenters of period B, whereas the green (**a\({}_{\textbf{1}}\)**–**a\({}_{\textbf{2}}\)**, **b\({}_{\textbf{1}}\)**–**b\({}_{\textbf{2}}\)**) and blue (**c\({}_{\textbf{1}}\)**–**c\({}_{\textbf{2}}\)**) dashed lines are the planes fitted to groups #2 and #4 (green), and group #3 (blue), respectively. The possible antithetic structures are marked with black-dashed lines (**a\({}_{\textbf{1}}\)**–**a\({}_{\textbf{2}}\)**). Focal mechanisms of the mainshocks and other major events of the sequence, including foreshocks (red beachballs, on the map only) are from the database of GI-NOA. The location of Arkalochori village is marked with a black square on the map. is following the aftershock distribution, retaining roughly an NE-SW trend. The spatial continuity of the interferometric fringes yields that the rupture did not reach the surface. The higher density of fringes at the eastern part of the epicentral area implies higher ground displacement gradients, and thus, proximity to the upper part of the activated rupture zone (i.e., NNE striking, west-dipping fault). However, examining in more detail the DInSAR displacement fields for the various independent measurements, variability arises both in terms of magnitude and location of ground motion maxima (Figure 4). Specifically, for the pair with the shortest temporal extent (2 days) after the mainshock (A102, 23 September 2021-29 September 2021), LoS ground displacement is located in the vicinity of the relocated mainshock epicenter, with values reaching \(-18\) cm. On the contrary, for the pair with the largest temporal extent (track D036, 5 days), the location maximum has been shifted approx. 2.5 km towards ENE and the observed ground displacement increased to \(-20\) cm (Figure 4). The other two displacement pairs (A029 and D109), spanning 3 days within the post-seismic period, show comparable motion (downlift of about \(-20\) cm) with the 5-days D036 pair (Figure S2). The shift of the displacement maxima can be attributed to the amount of post-seismic motion contained in the DInSAR measurements (see Table 1), and it is consistent with the seismological observations indicating migration of aftershocks towards the northern margins (cluster #3) of the mainshock epicentral area. It can also be assumed that no surface deformation occurred, or at least with a magnitude detectable by DInSAR, after three days of post-seismic activity.