# Characterizing Micro-Displacements on Active Faults in the Gobi Desert with Time-Series InSAR
## 4 Results and Discussion
### The Structural Geology of the Jiujing Region  
4.2.1. F\({}_{16-2}\), F\({}_{17}\), F\({}_{18}\), and F\({}_{20-2}\) as Active Faults  
The PSI results in Figures 6 and 7 clearly show that the NE-SW trending normal faults F\({}_{16-2}\), F\({}_{17}\), F\({}_{18}\), and F\({}_{20-2}\) are still vertically active. The direct evidence of this comes from the patterns of D\({}_{\rm U}\) across the fault planes, where there is a clear difference in the relative vertical motion of the blocks on either side of the fault lines.  
F\({}_{20-2}\) controls the eastern boundary of the Jiujing region. The eastern side of the fault (block JJ8) has a maximum elevation difference of 90 m, with Jiujing Basin on the western side of the fault (JJ6), caused by past tectonic activity [43]. The Sentinel-1 data in Figure 6 indicates the western side of F\({}_{20-2}\) in JJ6 is subsiding by 0.20 mm a\({}^{-1}\) on average whilst the eastern side of the fault (JJ8) is uplifting by an average of 0.02 mm a\({}^{-1}\). These differences in vertical displacement rates and the relative subsidence at JJ6 confirm that F\({}_{20-2}\) is a normal fault dipping to the northwest [43; 46], where JJ6 and JJ7 form the hanging wall of that fault and are expected to move downwards relative to JJ8.  
The PSI results also indicate that the average uplift rates on the southern side of F\({}_{18}\) (JJ4, JJ5, JJ9, JJ10, and JJ11) range from \(-\)0.18 to 0.26 mm a\({}^{-1}\), while uplift of the northern side of the fault (JJ2, JJ3, JJ12, and JJ19) ranges from 0 to 0.60 mm a\({}^{-1}\). This shows F\({}_{18}\)  
Figure 8: The distribution of faults in the Jiujing region in a Google Earth image, where faults found in the literature are highlighted by black lines and the newly identified faults are highlighted by blue lines.  
is a vertically active normal fault dipping towards the southwest. This vertical velocity difference along cross section AA' shown in Figure 6 is presented in Figure 10.  
Conversely, the southern side of F17 (JJ2, JJ3, JJ12, JJ19, JJ20, and JJ21) is uplifting faster compared to the northern side (JJ1, JJ13, JJ17, JJ18, and JJ22). The average vertical displacement rates on the southern and northern sides range from \(-\)0.03 to 0.6 mm a\({}^{-1}\) and \(-\)0.41 to 0.33 mm a\({}^{-1}\), respectively, indicating that F17 is a normal fault dipping towards the northwest, consistent with the literature.  
In Figure 7, along fault F16-2 between JJ13 and JJ14, it is shown that the average vertical deformation patterns indicate JJ13 is subsiding (\(-\)0.04 mm a\({}^{-1}\)) at a slower rate than block JJ14 on the northern side of fault F16-2 (JJ14, \(-\)0.14 mm a\({}^{-1}\)). This confirms that F16-2 is a northwest-dipping normal fault, whereas the northern side of the fault (JJ14) is expected to subside relative to the southern side, showing that this part of fault F16-2 is vertically active.  
Figure 9: cont.  
Figure 9: **(a–f)**. (**a**) The average time-series analysis for J6 along F\({}_{\rm a}\). J6 studied by 0.5 mm from October 2017 to February 2020, equivalent to an annual rate around 0.2 mm; (**b**) the average time-series analysis for JJ7 along F\({}_{\rm a}\). JJ7 uplifted by 0.2 mm from October 2017 to February 2020, equivalent to an annual rate of about 0.07 mm; (**c**) the average time-series analysis for JJ3 along F\({}_{\rm g}\). JJ3 uplifted by 1.0 mm from October 2017 to February 2020, equivalent to an annual rate of about 0.40 mm; (**d**) the average time-series analysis for JJ12 along F\({}_{\rm g}\). JJ12 subsided by 0.5 mm from October 2017 to February 2020, equivalent to an annual rate of about 0.2 mm a\({}^{-1}\); (**e**) the average time-series analysis for JJ19 along F\({}_{\rm m}\), F\({}_{\rm n}\), and F\({}_{\rm o}\). JJ19 uplifted by 1 mm from October 2017 to February 2020, equivalent to an annual rate around 0.40 mm; (**f**) The average time-series analysis for JJ21 along F\({}_{\rm m}\), F\({}_{\rm n}\) and F\({}_{\rm o}\) suggests JJ21 subsided slightly by 0.03 mm a\({}^{-1}\) from October 2017 to February 2020.