Detection and characterization of earthquake accelerated landslides (EALs) using InSAR observations

Earthquake-induced landslides often pose a great threat to the safety of human life and property, especially in seismic active regions. This has motivated plentiful studies with a focus on coseismic landslides that collapsed during or shortly after an earthquake. However, long-term seismic effects that activated unstable landslides but without causing failures/collapse even after a long period since the earthquake (months to years) are typically ignored due to the minor ground changes caused compared to collapsed slopes. These landslides respond to seismic stress disturbances differently from failed coseismic/post-seismic landslides and their movements are typically accelerated with increased sliding velocity after earthquakes. The acceleration phenomenon of these earthquake accelerated landslides (EALs) could be maintained for a long time and they may generate continuous damage to the ground and develop into catastrophic failures in the future.

 

As a new type of landslides associated with earthquakes, EALs have been largely neglected by the emerging research. In our study, we used satellite radar (Sentinel-1) observations from October 2014 to August 2020 to detect and investigate EALs in Central Italy. Distinguished from previous studies based on single or discrete landslides, we established a large EAL inventory and statistically quantified as a whole their spatial clustering features against a set of landslide conditioning factors. Results show that EALs did not rely on strong seismic shaking or hanging wall effects to occur and larger landslides were more likely to accelerate after earthquakes than smaller ones. We also discovered their accelerating-to-recovering sliding dynamics, and how they differed from the collapsed coseismic landslides. These investigations serve as an important supplement to the complete picture of the landslide inducing mechanism by earthquakes and contribute to a more comprehensive long-term assessment of landslide risk.