Monitoring and updating landslide hazards based on InSAR and optical imaging in Lanping County, southwestern mountainous area of China

Lanping County is located in a typical high mountain and canyon region of southwestern China, features a complex geographical environment, significant vertical climate variation, and fragile geological conditions, resulting in frequent geological disasters that seriously threaten local lives, property, and ecological security. In this study, the Layover Shadow Map (LSM) and Range Index (R-Index) methods were first combined to identify geometric distortions in Sentinel-1A ascending and descending images of Lanping County, systematically analyzing their distribution characteristics across different elevations, slopes, and aspects. Subsequently, the SBAS-InSAR technique was employed to extract surface deformation information from January 2021 to December 2023. By integrating InSAR-derived deformation data with optical remote sensing images, potential landslide hazards in Lanping County were identified. An updated landslide hazard distribution map was generated by incorporating existing geological disaster data. The results demonstrate that foreshortening is the dominant geometric distortion in Lanping County, accounting for 34.88% and 43.06% of the total area in ascending and descending images, respectively. A total of 258 potential landslide hazards were identified, including 184 newly detected in this study. These findings lay a scientific foundation for geological disaster prevention and control in Lanping County.