## 3 Results
### Shear-Wave Splitting Parameters  
The distribution of the fast shear-wave polarization direction (\(\varphi\)) measurements from Cat1 for selected stations, representing sites with different average \(\varphi\) directions, is presented in Figure 8 in the form of rose diagrams. The respective diagrams for the rest of the stations are available in Figure S16. Rose diagrams, widely used in shear-wave splitting studies (e.g., [22]), are circular histogram plots which display directional data (in the current case, fast shear-wave polarization direction data) and the frequency of each class, (i.e., the number of measurements for each \(\varphi\) bin). The SWS parameter statistics for Cat1 are presented in Table 2. The average \(\varphi\) value is calculated with circular statistics [62] to avoid wrapping between 0\({}^{\circ}\) and 180\({}^{\circ}\). In most stations, the mean \(\overline{\varphi}\) value coincides with the direction that corresponds to the larger amount of valid measurements. There are, however, a few exceptions, such as station HELI (Figure S16), which presents two main fast-shear-wave polarization directions, one at \(\sim\)N30\({}^{\circ}\)E and another at \(\sim\)N100\({}^{\circ}\)E. The mean \(\varphi\) in that case was calculated at 77.6\({}^{\circ}\)\(\pm\) 11.6\({}^{\circ}\). However, this value does not correspond to either of the two maxima of the distribution. There are also some stations with significant \(\varphi\) scatter, such as VVK, and certain stations of the Magoula array, i.e., MG03, MG05 and MG07, for which the mean value differs from the azimuth that corresponds to the maximum of measurements. The \(\overline{\varphi}\) value of valid measurements for all stations (Cat1) is 98.8\({}^{\circ}\)\(\pm\) 2.8\({}^{\circ}\). Important deviations from this direction are observed for stations LAKA (\(\overline{\varphi}\) = 134.7\({}^{\circ}\)\(\pm\) 5.9\({}^{\circ}\)) and TEME (\(\overline{\varphi}\) = 145.1\({}^{\circ}\)\(\pm\)16.3\({}^{\circ}\)), in the south, and stations SERG (\(\overline{\varphi}\) = 58.4\({}^{\circ}\)\(\pm\)7.5\({}^{\circ}\)) and MALA (\(\overline{\varphi}\) = 68.1\({}^{\circ}\)\(\pm\) 11.0\({}^{\circ}\)), in the north. Stations with significant \(\varphi\) scattering, indicated by the large uncertainty, include MG03 (\(\overline{\varphi}\) = 67.1\({}^{\circ}\)\(\pm\) 30.8\({}^{\circ}\)), PANR (\(\overline{\varphi}\) = 132.8\({}^{\circ}\)\(\pm\) 36.6\({}^{\circ}\)) and PYRG (\(\overline{\varphi}\) = 142.2\({}^{\circ}\)\(\pm\) 41.6\({}^{\circ}\)). The time-delays, \(t_{\rm d}\), are partially depended on the spatial distribution of the seismic sources relative to the receiver. Since the time-delay is accumulated along the path-length of the seismic ray as it travels through the anisotropic medium, longer ray-paths will result in larger \(t_{\rm d}\) values. The time-delays are normalized (\(t_{\rm n}\)) by dividing \(t_{\rm d}\) with the hypocentral distance to remove the effect of the ray-path length. The mean \(t_{\rm n}\) values are overall (9.2 \(\pm\) 0.1) ms/km, while average \(t_{\rm n}\) per station ranges from 5.0 ms/km (AGRP) to 12.5 ms/km (ALIK). The raw \(t_{\rm d}\) measurements have a mean of (112.3 \(\pm\) 1.4) ms.  
Figure 7: Mean squared distance \(\langle x^{2}(t)\rangle\) of seismicity (squares) with time \(t\) in double-logarithmic axes, for the events enclosed within the parabolic envelope defined by the triggering- and back-fronts of seismicity with \(D\) = 2.2 m\({}^{2}\)/s (Figure 6). The solid line indicates the power-law growth of \(\langle x^{2}(t)\rangle\), according to Equation (3). Figure 8: Rose diagrams of the distribution of the fast shear-wave polarization angle, \(\varphi\), for valid measurements with grade A (best) to C (acceptable) from Cat1 (only manually located/relocated events) per station (station-code shown in the label on top of each diagram), for selected stations representing sites with different average \(\varphi\) directions, as well as for all stations (upper-left panel).