## 2 Data and Methods
### Extraction of the Module Samples  
The data were processed to obtain the sample; the entire extraction process is shown in Figure 1.  
(1) The attributes of the earthquake event, such as depth, magnitude, location, and occurrence time from earthquake events, as well as the number of human residential points and population within the earthquake-affected zone, were obtained and used as sample attributes.  
(2) The NTL image was processed to obtain the NTL value. Data noise reduction was necessary due to the influence of stray light, lightning, moonlight, and cloud cover. Firstly, cloud cover was removed using the cloud mask band of NPP-VIIRS. Next, a threshold method was used to eliminate background noise caused by factors such as fire, moonlight, and aurora. Any negative values were set to 0 to address noise-induced minima issues, followed by reassigning the maximum value to match the maximum value among the surrounding nine pixels.  
(3) The distance from the earthquake epicenter to the urban area and roads were, respectively, calculated. The urban area here refers to a prefecture-level city within the earthquake's impact zone (100 km buffer zone was made according to the coordinates of the earthquake epicenter), and the roads refer to all roads above the third level.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Name** & **Format** & **Time** & **Resolution** & **Source** \\ \hline NPP-VIIRS & Image & 2013/01/01— & 500 m & NOAA \\  & & 2023/10/31 & & \\ Earthquake catalogue & csv & 2013/01/01— & None & USGS \\  & & 2023/10/31 & & \\ Administrative division & shapefile & 2022 & 1:4,000,000 & National Basic Geographic \\  & & & & Information Center \\ road & grid & 2022 & 1000 m & Provincial official website \\ Human residential data & shp & 2023 & 1 m & OpenStreetMap \\ LandScan dataset & TIFImage.Document & 2013–2022 & 1000 m & Oak Ridge National \\ Statistical yearbook of & & & & Laboratory \\ urban area & & 2013–2022 & None & Local government official \\  & & & & website \\ \hline \hline \end{tabular}
\end{table}
Table 1: Basic information of multisourced data.  
(4) We iteratively extracted the urban built-up area from the night light data and compared it with the urban built-up area documented in the statistical yearbook. The threshold was selected based on minimizing the disparity between the extracted area and the corresponding value from the statistical yearbook. This method was applied to analyze data from 2013 to 2022, selecting the minimum threshold from those identified. As shown in Figure 1, this is an example for the year 2021, where real-time images were used to ensure data validity during calculations.  
(5) The reference comparison method was used to determine a threshold for each seismic event, through which the corresponding urban area was identified. The final urban NTL was determined using multi-temporal images. Specifically, the images from 3 days before and 3 days after each earthquake were selected based on the earthquake's timing and the light image threshold. Then, the difference value was calculated with the average value.  
At this stage, the difference results were further screened. If the result was negative (indicating an increase in light value due to the occurrence of disasters), the region was misidentified.  
(6) The final sample was determined by finding the intersection between the region meeting the conditions in (4) and the buffer zone. These samples already included the properties of the light attenuation values calculated in (5).