## 4 Seismicity Temporal and Spatial Characteristics
### Spatial Distribution  
The relocated seismicity allowed a refined and more reliable picture than the disperse epicentral distribution provided from the regional catalog as shown in Figure 1, revealing four distinctive clusters along with the disperse activity (Figure 4a). The northernmost cluster is associated with the main shock epicenter, the location of which is shown with a green star, occupying an area of almost 7 km in length, slightly larger than expected for an M\({}_{\rm W}\)5.4 earthquake, according to well-accepted scaling laws [19; 20; 21]. The epicentral elongation at an NE-SW direction agrees with one of the nodal planes of the focal mechanisms of the main shock and the four aftershocks that belong to this cluster (Figure 4a and Table 3). The activated fault segment with a strike of 220\({}^{\circ}\) dips to NW at an angle of 45\({}^{\circ}\) and is associated with dextral strike slip faulting (rake = 160\({}^{\circ}\)) with a considerable thrust component. This agrees with the dextral strike slip motion of the KTFZ to the south of the study area, and the continental collision to the north. The almost E-W azimuth of the axis of maximum compression also agrees with the regional stress pattern. For a more detailed investigation of the geometry of this fault segment, the relocated epicenters of the specific cluster alone are plotted in Figure 5a, along with two cross-sections, strike parallel and strike normal that are shown in Figure 5b,c, respectively. It is worth to note here that the focal depths are restricted in depths between 14 and 20 km, with the vast majority between 16 and 18 km, an important result for the identification of the seismogenic layer in the study area. The dip of the fault plane as derived from the fault plane solution is again in perfect agreement with geometry of the activated fault segment as this is revealed by the strike normal cross-section in Figure 5c. Figure 3: Spatial distribution of the relocated seismicity. The epicenters are colored according to the period of their occurrence as these periods have been defined and shown in Figure 2.  
The next seismicity concentration is located to the south of the previous cluster and encompasses several earthquakes, the spatial distribution of which shows a barely preferable E-W elongation, in agreement with the strike of the one nodal plane from the 05/02/2019 earthquake of M3.3 (Figure 4a). The depth range is between 10 and 15 km, shallower than and exactly above the activated layer in the main cluster and with a steeper dip angle (Figure 5b,c). The faulting type, in addition to the rotation of its strike more to the north as mentioned before, exhibits a dextral strike slip motion with a slight normal component. Figure 4: (**a**) Epicentral distribution of the relocated seismicity, plotted with different symbols and colors according to their magnitude as shown in the inset, along with the fault plane solutions determined in the current study depicted as equal area lower hemisphere projections, with the compression quadrants shown in black. (**b**) Cross-section across a N–S direction, containing the entire set of the relocated seismicity, with the hypocenters depicted with the same symbols as in (**a**) and the fault plane solutions as frontal projections. (**c**) Same as in (**b**) for a cross-section across a W–E direction. (**d**) Fault plane solutions along with the associated polarities (“+” for compression and “o” for dilatation) for the earthquakes numbered 2, 4, 7 and 8 in Table 3.  
The epicentral distribution delineates a distinctly N-S striking structure, as one proceeds more to the south, where two sub-clusters might be recognized, forming an almost N-S striking-activated structure: the northern one, hosting the M4.0 strong event (yellow circle in Figure 4a) and forming a narrow strip of relocated epicenters, and one to its south where the activity appears sparser. The focal depths are now even more shallow, between 5 and 11 km, than the depth range of the relocated seismicity further south to Lefkada [8; 22].