## 4 Discussion  
Using InSAR time series and ground truth observations, we investigated the occurrence and recent development of local fractures within the Al-Yutamah Valley, western Arabia. These hazards are associated with land deformation/subsidence as mapped using InSAR and identify potential areas at risk. We report three main observations: continuous subsidence since 2014 (Figure 3 right panel), development of large surface fracture events (Figure 5A-D), and long period oscillations in surface displacements (Figure 5D). The long-term linear subsidence pattern (Figure 3, right panel) within the Al-Yutamah Valley suggests a long-lived subsurface process. The observed subsidence distribution prompts many questions about the nature of its causes. The most obvious of which is the role of groundwater exploitation that may also drive compaction processes within a subsurface aquifer [(8)] (Figure 3, right panel). Multiple studies of different examples around the world [(50; 51; 16; 52)] show a strong relationship between groundwater exploitation and surface subsidence. Although the subsidence area appeared in the alluvial sediments and basalt flow, the fractures are observed only in the alluvial sediments (Figure 7). The observed pattern (Figure 5D) displays a sinkhole-like shape within the basalt area linked with a long meandering region of subsidence. Prior studies have attributed this subsidence to withdrawal of groundwater [(7; 8)] based on an analysis collected of soil samples from the Al-Yutamah Valley. In the Najran Valley [(12)] geophysical surveys were conducted across observed surface fissures and they were attributed to water pumping and consequent continuous decline in groundwater, which led to the development of subsurface topography characterized with steep slopes (buried cliff) that are correlated with the observed surface fissures. Figure 6: (Upper left panel) Map of the spatial gradient amplitude of the observed LOS InSAR velocity (cm/(y*pixel)). The fuchsia line demonstrates the boundary between basalt and alluvium deposits. (Upper right panel) Cross-section through the gradient of the LOS velocity (cm/(y*pixel)) cross-section along the Haramain High Speed Railway. (Lower left panel) A similar cross-section along the national east-west pipeline. (Lower right panel) cross-section within the Al-Yutamah Valley. Cross-sections (**A**-**A**’,**B**-**B**’) are not correlated with surface fractures, while the cross-section **C**-**C**’ is highly correlated with field fractures as reported in Figure 5.  
Reference [8] suggested another possible process based on their soil analysis for surface fractures in the Al-Yutamah Valley as developed due to the hydrocompaction of soil after severe rainy seasons. Though the local accuracy of rainfall accumulations could be missing due to the lack of weather stations in our region as the rainfall data are extracted from gridded dataset. We find that severe rainfall events are correlated with the observed offsets in our displacement time series. One of these events occurred in November of 2018 (Figure 4, left panel). During that event, the displacement field shows uplift along the regions that results in long term subsidence and subsidence along its boundaries. Furthermore, all the  
Figure 7: Surface geology, regional structures, sediment types, reported fractures, subsidence area, gradient of the LOS velocity field, and main infrastructure of the Al-Yutamah Valley. The region is characterized by basalt flow, quaternary sedimentary deposits, and Precambrian rocks. The approximate outline of the principal zone of subsidence is indicated by the sinuous white line, observed fractures are indicated by the thick black lines, and regional faults are shown as dashed black lines. The observed subsidence is associated with fractures in the alluvial sediments, while in the region of basalt flows, no fractures were reported.