## 4 Results  
### Spatial and Temporal Changes on the Surface of Zhengzhou City  
During the period from July 2019 to June 2022, the main areas of surface uplift in Zhengzhou City were distributed in the central and western parts of the city, while the subsidence areas were mainly concentrated in the northern and eastern parts (Figure 3a). The area of weakly developed areas with deformation rates within 10 mm/yr was 1504 km\({}^{2}\), accounting for 98% of the total area and belonging to the low-risk area. The area of moderately developed areas within the range of 10-30 mm/yr. is 22.47 km\({}^{2}\). These areas with moderate risk of deformation are mainly distributed in the eastern and northeastern parts of Zhengzhou City (Figure 3b). They are distributed in a block-like manner and exhibit subsidence phenomena. In addition, the area of hazardous areas with a settlement rate greater than 30 mm/yr. only accounts for 0.1% of the total area (as shown in Figure 3c,d). According to the risk assessment indicators for surface deformation, the surface situation in Zhengzhou City is characterized by low risk in most areas, but there are still some areas with moderate risk of settlement, and there are almost no high-risk surface deformation areas. Therefore, the following will only discuss the situation of moderate-risk settlement areas in detail. In order to visually analyze the development of deformation in the area of moderately hazardous subsidence, the PS points in the area with larger patches were sampled, and three sampling points (P01, P02, and P03) were selected, the distribution of which is shown in Figure 3b, and as a comparison, P04 was selected in the city center with weakly developed ground uplift.  
P01 is located in the east of Guixing Town (Figure 4a), surrounded by mostly agricultural land and low-rise buildings, which are also intersections of multiple expressways. The cumulative deformation curves and average cumulative deformation curves of all sampling points in this area gradually decrease over time (as shown in Figure 4b), and the annual settlement rate is concentrated at 12 mm/yr. P02 is located to the east of Jialu River Station (as shown in Figure 4c), surrounded by newly developed high-rise residential buildings with low population density. Similarly, the sampling point curve in this area shows a downward trend (Figure 4d), with an annual settlement rate concentrated at 11 mm/yr. P03 is located in Yangqiao Village (Figure 4e), surrounded by newly developed high-rise residential buildings with a concentrated population density. There is a high demand for agricultural water in this area, and the main source of agricultural water comes from groundwater extraction. The sampling point curve in this area shows a downward trend (Figure 4f), and the annual settlement rate is concentrated at 11 mm/yr. P04 is located at Henan University of Education (Figure 4g). Although it is surrounded by high-rise office buildings and has a high population density, the sampling point curve in this area shows an upward trend (Figure 4h), with an annual uplift rate concentrated at 6 mm/yr. It is a typical area of surface uplift after the recovery of groundwater levels in recent years [21]. Therefore, the moderately dangerous subsidence areas in Zhengzhou City are mainly located near agricultural land with high demand for groundwater and the development of new residential areas.  
The precipitation of Zhengzhou City from May 2019 to June 2022 is shown in Figure 3e, where the gray background is the rainy season of that year, and, similarly, in Figure 4b,d,f,h, the gray background is the rainy season of the corresponding year. By observing the surface deformation of each sampling area, even around 20 July 2021, it is difficult to detect anomaly surface deformation fluctuations based on existing indicators.