## 4 Results and Discussion  
### Spatiotemporal Evolution Characteristics of Land Subsidence in Kunming  
Due to the influence of natural environmental factors, the Kunming prefecture territory has a relatively lush vegetation cover, especially in the surrounding mountainous areas, where the vegetation density is particularly high. This leads to some areas experiencing decorrelation issues. However, this study focused on the urban areas of Kunming, where the coherence is generally good. The line-of-sight surface deformation velocity distribution in the Kunming study area is shown in Figure 6, where red indicates ground uplift and blue indicates LS. Figure 6: Deformation velocity map of the study area, with indication of five distinct LS regions and points. The minimum deformation rate in the study area was \(-44.23\) mm/year, and the maximum rate was \(17.89\) mm/year. Most of the area had a deformation rate between \(-12.5\) mm/year and \(5\) mm/year, with the highest proportion of the area showing rates between \(-3\) mm/year and \(3\) mm/year, indicating normal ground deformation. The analysis of the LS rates revealed that the western and southern regions of the study area experience relatively mild subsidence, with significant subsidence primarily concentrated along the shores of Dianchi Lake and in the mountainous areas to the east of the urban area. The eastern part of the study area is a newly developed zone, where the LS is attributed to large-scale engineering activities that have taken place in recent years. Within Kunming's urban area, particularly near Dianchi Lake, five distinct LS zones have been identified and labeled as regions A, B, C, D, and E.  
* **Region A** is located along the northern shore of Dianchi Lake, encompassing areas in Xishan District. * **Region B** is in the southwest of Kunming's central urban area and appears to be expanding toward the city center, covering areas in the Guandu District. * **Region C** is situated within the Guandu District. * **Region D** encompasses the Chenggong District. * **Region E**, located in the Jinning District, is the most severely affected area, with a maximum subsidence rate exceeding \(42\) mm/year. From Figure 6, it is evident that the relationship between urbanization and LS phenomena in regions A, B, and C is quite clear. However, in regions D and E, the connection between urbanization and LS is less straightforward. Specifically in region E, investigations have revealed that this area is centered around Xinjie Town, where LS is primarily associated with the construction of industrial zones and fluctuations in groundwater levels in the mines. Key facilities such as the China National Petroleum Corporation and the Baiyu River Water Purification Plant are located here. The extensive extraction during phosphate mining operations has led to a decline in the groundwater levels, ultimately leading to LS [36]. Correlating these findings with geological data also revealed a close relationship between these subsidence areas and the soft, loose sediments near Dianchi Lake. We selected the point of maximum subsidence within each of these typical areas. The results of the present study refer only to those five sites that experienced the maximum rates of subsidence in the considered time interval. In contrast, the central urban area in the northern part of the study area exhibited noticeable ground uplift, with the uplift rates exceeding \(5\) mm/year. This uplift phenomenon extended outward from the central area, although the degree of uplift diminished progressively. This can be attributed to the recent control over groundwater extraction in the city center, leading to a rise in water levels and subsequent ground uplift. According to previous studies [37; 38; 39; 40], significant subsidence areas around Dianchi Lake have been identified, highlighting the effects of soft sediments and groundwater extraction.