## 3 Experiments and Results
### Datasets  
Three sets of high-resolution RS images after earthquakes were used in the experiment. All the images contain different secondary disasters caused by severe earthquakes. The first image is the QuickBird multispectral image (2.4 m) of the Wenchuan area that suffered from the Wenchuan earthquake (magnitude 8.2) on 12 May 2018. The image, with a size of \(2427\times 2569\) pixels, was acquired on 26 December 2008. The elevation of the image ranges from 1346 to 2960 m, as shown in Figure 8a. A large number of landslides can be seen in the image, as well as the reference image employed (Figure 8b). The second post-earthquake image is a GaoFen-1 (GF-1) multispectral image (8 m) covering Baoxing Town, which experienced the Yaan earthquake (magnitude 7.0) on 20 April 2013. The GF-1 image, recorded on 23 July 2013, has a size of \(1218\times 1363\) pixels. Both landslides and river expansion caused by the earthquake can be observed in the image, as shown in Figure 9a. Its elevation ranges from 711 to 2406 m. The third image is a GaoFen-2 (GF-2) image of the Juzhaigou area after the 7.0-magnitude Juzhaigou earthquake on 8 August 2017. The image was acquired on 9 August 2017, and has a size of \(2096\times 1789\) pixels. Its elevation, from 1892 to 3760 m, has a larger span. Landslides caused by the earthquake can be seen in the image, as shown in Figure 10a.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**No.** & **Satellite** & **Resolution (m)** & **Size (pixel)** & **Date** & **Earthquake** & **Disaster** \\ \hline \multirow{2}{*}{1} & QuickBird & 2.4 & \(2427\times 2569\) & 2008/12/26 & 2008 Wenchuan & \multirow{2}{*}{Landslides} \\  & GE & 2 & \(2932\times 3108\) & 2008/05/23 & earthquake & \\ \hline \multirow{2}{*}{2} & GF-1 & 8 & \(1218\times 1363\) & 2013/07/23 & 2013 Yaan & Landslides, river \\  & GE & 2 & \(6568\times 8644\) & 2010/02/08 & earthquake. & expansion \\ \hline \multirow{2}{*}{3} & GF-2 & 4 & \(2096\times 1789\) & 2017/08/09 & 2017 Jüzhaigou & \multirow{2}{*}{Landslides} \\  & GE & 2 & \(4632\times 4002\) & 2014/02/05 & earthquake. & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Details of the three image datasets used in the experiment.  
Figure 8: The Wenchuan earthquake dataset. The left (**a**) is the post-earthquake image (the input image), whereas the right (**b**) is the reference image in the pre-earthquake database. The points in red are the verification points used for calculating the accuracy of the rectified image.  
The details of the three post-disaster images and the corresponding reference images obtained from the pre-earthquake image database are presented in Table 2. The reference images are also shown on the right of Figures 8-10.  
According to the characteristics of the three datasets, the parameter settings of the proposed method are presented in Table 3.  
Figure 10: The Jiuzhaigou earthquake dataset. The left (**a**) is the post-earthquake image (the input image), and the right (**b**) is the reference image in the pre-earthquake database. The points in red are the verification points used for calculating the accuracy of the rectified image.  
Figure 9: The Yaan earthquake dataset. The left (**a**) is the post-earthquake image (the input image), and the right (**b**) is the reference image in the pre-earthquake database. The points in red are the verification points used for calculating the accuracy of the rectified image.