## 5 Results
The values of computed ground displacement differ from LOS displacement values by 30% and 50% for vertical and horizontal displacements, respectively, as seen in Table 2. This relation between the LOS and ground displacements corresponds to similar studies [71], where authors have used fixed value for the incident angle and therefore got the enlargement of 20% in favor of vertical displacement regarding the LOS displacement. However, for the purpose of this study conducted on a relatively small area, it was found necessary to use origin pixel values of incident angle to estimate behavior of ground deformation as much as possible with SAR data. Figure 5: Figure shows interferograms over the earthquake area in NW Croatia: from the ascending orbit of Sentinel-1A (**left**) and descending orbit of Sentinel-1B satellite (**right**). During the January 2021, we acquired subsequent time-series of SAR images (see Table 1) and analyzed the behavior of the ground movement in the weeks following the mainshock. We corrected the displacement for the coherence factor of \(<\)0.4, eliminating the noise signal and giving the true insight in the most significantly affected areas. We have analyzed four pairs of subsequent images from both orbits, but the ground movement is visible only on the first pair taken shortly prior and after the earthquake. Despite the fact that more than a thousand aftershocks happened during January (see Figure 3), the images acquired in the month following the mainshock show neglectable ground displacement of only few millimeters, while the first pair of images clearly identifies Petrinja town as the most displaced one, shifted up to 40 cm to the east (see Figure 7), situated on the eastern part of the Pokupsko fault. On the western side of Pokupsko fault and on the side of the epicenter, the displacement toward the West is visible with the greatest shift of 60 cm luckily mainly in the uninhabited area, reaching Glina city at its borders. Majake poljane is the village that has been razed to the ground. The Figure 8 gives an insight: Majake poljane is located over the Petrinja fault where there was also the epicenter is located. This is the area mostly affected by the western displacement of Pokupsko surface rupture. The twofold impact made an immense damage both in Majake Poljane and Petrinja. Dominant impact of the earthquake on horizontal movement is visible from the computed east-west ground displacement shown in Figure 8. Moreover, the enlargement of the horizontal displacement related to LOS displacement implies such a conclusion. Taking into account that SAR images show the movement relative to satellite position and are not referenced to fixed ground point, ground displacements obtained from the SAR can be used for the interpretation and indication, not as an absolute determination of the displacement. The horizontal ground displacement happened related to Pokupsko fault, shifting the area of Petrinja to the east by up to 40 cm, and the area towards Glina by around 30 cm to the West. The extreme values of horizontal displacement are bounding the longitudinal Pokupsko strike-slip fault with the epicenter at transversal Petrinja strike-slip fault. The horizontal west-east ground displacement seen in Figure 8 identifies the intersection of the Pokupsko and Petrinja strike-slip faults as the maximum horizontal shift occurred at the left and right quadrant related to it. The wider affected area shown in Figure 8 is horizontally displaced within 5 cm, seen on Figure 8, which coincides with GNSS analysis discussed at the end of this section. Figure 6: Figure shows LOS displacement over earthquake area in NW Croatia: ascending orbit of Sentinel-1A (**left**) and descending orbit of Sentinel-1B satellite (**right**) [54]. Figure 8: Figure shows east-west ground displacement over affected area.