Impact of strong earthquake on deformation of large-scale high steep slopes using sentinel-1 SAR images: insights from 2017 milin Ms6.9 earthquake

Earthquake-induced slope deformation poses a significant threat to human life and property safety. Understanding the impact of strong earthquakes on slopes is crucial to improve post-earthquake rescue efforts. However,there is a lack of comprehensive investigation into the impact and driving forces behind large-scale slope deformation caused by earthquakes. Here, we employ remote sensing images to thoroughly examine the deformation change characteristics of high steep slopes and reveal the impact of strong earthquakes on them. Our primary focus is on the Milin earthquake that struck Tibet on November 18, 2017. The results indicate that: (1) The earthquake-induced slope deformation exhibits a maximum line-of-sight settlement of 18cm and uplift of 6cm. The deformation is primarily concentrated in the near-field area within 20km on both sides of the fault. Most landslides occur within approximately 2km on either side of the seismic fault, predominantly distributed along rivers. The steep slope near Gyala Peri Peak experiences the most intense settlement deformation, despite being distant from the epicenter and the river. This area, with a lower density of landslides, may experience slope loosening due to seismic shaking. (2) Seismic faults and rivers exert a strong control over the spatial distribution of landslides. The development of seismic faults along rivers leads to significant erosion and scouring of the high and steep slopes on both sides, greatly impacting slope stability. Factors with a high correlation to slope deformation include the distance from the epicenter, lithology, and distance from the seismic fault, while the distance from the water system and elevation exhibit a moderate correlation. The interplay between these factors enhances the spatial variation of deformation. The findings of this study provide a more comprehensive understanding of the impact by which earthquakes affect slopes.