## 3 Methods  
### DInSAR Technology  
The phase of InSAR interferograms is divided into several main components, including surface elevation phase, surface deformation phase, atmospheric effect phase, flat earth phase and noise phase [22]. The DInSAR technique is a further development of the InSAR technique, which obtains the surface deformation information by retaining only the phase caused by surface deformation through differential processing [23]. The phase of InSAR interferograms can be described as  
\[\mathcal{O}=\mathcal{O}_{\text{topography}}+\mathcal{O}_{\text{displacement}}+ \mathcal{O}_{\text{atmosphere}}+\mathcal{O}_{\text{flat}}+\mathcal{O}_{ \text{noise}} \tag{1}\]  
where \(\mathcal{O}_{\text{topography}}\) is the topographic phase; \(\mathcal{O}_{\text{displacement}}\) is the deformation phase; \(\mathcal{O}_{\text{atmosphere}}\) is the atmospheric delay effect; \(\mathcal{O}_{\text{flat}}\) is the flat phase; and \(\mathcal{O}_{\text{noise}}\) is the noise phase.  
\(\mathcal{O}_{\text{topography}}\) is the phase difference due to variations in the height of the terrain. It can be obtained by the existing digital elevation model (DEM) or stereo survey. \(\mathcal{O}_{\text{displacement}}\) is the phase difference due to ground deformation and is the part relevant to our study. \(\mathcal{O}_{\text{atmosphere}}\) is the phase difference due to changes in atmospheric conditions (e.g., humidity, temperature, etc.), which can be simulated and removed by atmospheric models or other methods. \(\mathcal{O}_{\text{flat}}\) is the phase difference due to the curvature of the Earth and the observed geometry. It can be calculated and removed by flooding the reference plane phase model. \(\mathcal{O}_{\text{noise}}\) includes both the system noise and the noise caused by the scatterer variation. It can be partially removed by the filtering method.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Date** & **Path** & **Frame** & **Track Direction** & **Resolution** & **Model** & **Width** \\ \hline
20210430 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20210617 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20210828 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20211027 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20211226 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20220224 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20220413 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20220612 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\
20220811 & 157 & 112 & Ascending & 5 \(\times\) 20 m & IW & 250 km \\ \hline \hline \end{tabular}
\end{table}
Table 1: Cont.  
The equation is organized as follows:  
\[\mathcal{O}=\mathcal{O}_{\text{topography}}+\mathcal{O}_{\text{displacement}}+ \mathcal{O}_{\text{atmosphere}}+\mathcal{O}_{\text{flat}}+\mathcal{O}_{\text{ noise}}=\frac{4\pi}{\lambda}\Delta R \tag{2}\]  
where \(\lambda\) is the wavelength of the SAR system and \(\Delta R\) represents the slant range between the satellite and the target point during satellite imaging.  
Therefore, the phase information of the interference is removed, and the tiny deformation information of the surface can be obtained by using the two-scene SAR data through the imaging principle. The resolution of the obtained deformation effect map is 30 m.