## 3 Results  
The Sentinel-1 images obtained from ascending and descending acquisition geometries between May 2018 and October 2022 and the mean deformation velocity maps and standard deviation values in the LOS direction produced as a result of linear phase-based atmospheric correction are shown in Figure 4. The red-colored areas on the average deformation rate map show that they are moving away from the satellite, whereas the blue-colored areas are approaching the satellite. This situation indicates the subsidence of a region centered on the summit caldera with a maximum of \(-10\) mm/yr in the LOS direction, in both the ascending and descending acquisition geometries. In addition, the standard deviation values of the mean deformation maps obtained from descending and ascending acquisition geometries are 0.762 and 1.185 mm/yr, respectively (Figure 4c,d). The mean deformation velocity maps and standard deviation values in the LOS direction produced as a result of atmospheric correction based on GACOS are shown in Figure 5. Although the GACOS and linear phase-based atmospheric correction results show a similar deformation pattern, the GACOS-based results detect greater subsidence rates. In addition, the GACOS-based standard deviation values of the mean deformation maps from descending and ascending acquisition geometries are 0.873 and 1.139 mm/yr, respectively. Results in the LOS direction from both atmospheric correction approaches show a similar deformation pattern with a caldera-centered \(-10\) mm/yr subsidence. However, the linear phase-based atmospheric correction approach exhibits lower standard deviation values in the areas with maximum subsidence. Therefore, we use the linear phase-based atmospheric correction results in the subsequent analyses. To examine the deformations in the Tendurek volcano, transverse and longitudinal sections perpendicular to the volcano were selected, and profile analyses were conducted (Figure 6a,b). Profile analyses show that the deformation rate, which shows maximum subsidence at the summit of the volcano, decreases linearly with distance from the summit of the volcano (Figure 6c-f). In addition, the profiles in both the descending and ascending acquisition geometries show a bowl-shaped pattern that continues with a smaller slope from the summit of the volcano to the eastern flanks. Although the E-W directional profiles of the ascending acquisition geometries show a stronger inclination than the E-W directional profiles of the descending acquisition geometries, the results from both the descending and ascending datasets show the subsidence of a similar region centered on the summit caldera. Time series show the same findings in more detail than the mean deformation velocity maps. Figure 7 shows the deformation time series of four certain PS pixels in ascending and descending orbits at Tendurek volcano. The results show that the Tendurek volcano subsidence gradually evolves between 2018 and 2022, and the temporal evolution of the displacement is linear. Deformation measurements made in areas where the topography changes suddenly, such as Tendurek volcano, may be adversely affected by atmospheric effects, slope, and satellite LOS directions, and the pixel distributions in the resulting datasets may not be homogeneous. Although two different atmospheric correction approaches were applied in this study, atmospheric artifacts were completely removed, and therefore, sufficient point density could not be established in some regions, especially in the center of the  
Figure 4: Linear phase-based mean deformation velocity maps in the LOS direction from descending (**a**) and ascending (**b**) acquisition geometries. Standard deviation map of linear phase-based LOS direction velocities from descending (**c**) and ascending (**d**) acquisition geometries. caldera. For this reason, loss velocity values were created using the biharmonic spline interpolation (MATLAB(r) 4 grid data method) method.