## 3 InSAR Utilizations in the Selected Literature Collection  
### Global Distribution Patterns of Articles Utilizing InSAR  
To understand how different countries adopt InSAR technology in response to their landslide hazards, we analyzed the geographical focus of the selected studies using InSAR and correlated them with the global occurrence of landslide events. Firstly, we examined the spatial distribution of landslide research utilizing InSAR by analyzing study areas, that is, the locations of the landslides being studied, from the included articles using InSAR (Figure 4a). The spatial pattern reveals that China, Pakistan, the United States, and Iran have made substantial contributions, with China alone accounting for 46 articles, over half of the total studies using InSAR (80 cases, as mentioned in Section 2). Countries such as Italy, France, Spain, and India have also shown notable interest in applying InSAR techniques to landslide research. A detailed list of articles utilizing InSAR and their corresponding study areas is provided in Appendix A, Table A1. Moreover, we collected a comprehensive global landslide catalog dataset [40,41], which comprises rainfall-triggered landslide events worldwide with detailed location information. Leveraging the spatial join technique, the occurrence of landslide events across various countries was quantified (Figure 4b). Based solely on this dataset, the United States contributed to a dominant portion of global landslide events, followed by nations including India, China, Indonesia, Brazil, Australia, etc. To enhance the visualization of the spatial distribution patterns of landslide research in relation to global landslide events, the natural breaks classification method (Jenks' optimization) [42] was employed to categorize the number of published landslide articles and landslide events into three levels ranging from low to high, after which a bivariate choropleth map was created (Figure 4c), with the four corners of the legend representing the following different scenarios:  
Bottom-left corner (both low): countries where both the number of recorded landslides and the number of InSAR-related landslide studies are low. Figure 3: Statistics of selected literature collection. Notes: ‘publications’ indicates the number of articles within the selected literature collection (total 131 articles for this review), that is, utilizing spaceborne remote sensing (including InSAR and other spaceborne remote sensing techniques like optical remote sensing) for landslide research; ‘publications using InSAR’ indicates the number of articles within the selected literature collection that wholly or partially utilized spaceborne InSAR technique. (Software: Origin 2022). Top-right corner (both high): countries with a high number of recorded landslides and extensive InSAR-based landslide studies. Top-left corner (low landslide frequency, high research activity): countries with relatively few recorded landslides but a high number of landslide studies using InSAR. Bottom-right corner (high landslide frequency, low research activity): Countries with a high number of recorded landslides but limited InSAR-based landslide studies. These areas are particularly noteworthy for landslide monitoring and risk assessment. In most cases, countries with frequent landslide occurrences, such as China and the United States, tend to receive more attention and are selected as study areas. Conversely, regions with relatively fewer landslide events, like most European and African countries, exhibit lower frequencies in the published landslide articles. However, it is noteworthy that  
Figure 4: (**a**) The number of articles using InSAR accounted by study area, namely locations of the landslides being studied, in different countries. (**b**) The number of landslide events based on the global landslide catalog. (**c**) The bivariate choropleth map of the number of studies using InSAR and landslide events in each country. (Software: ESRI ArcGIS Pro v. 3.3.0).