Coupling InSAR and numerical modeling for characterizing landslide movements under complex loads in urbanized hillslopes

Landslides, as a representative geohazard in fault zones, threaten the safety of buildings and infrastructure. Landslide movements are often subject to multiple loads in urbanized hillslopes from both natural and human activity. Synthetic aperture radar interferometry (InSAR) has been used to measure landslide movements. Used independently, InSAR can measure only surface deformation, and the points are sparse. Numerical modeling can simulate the full-scale movements, but it requires a prior knowledge of soil properties that are often not available in practice. To address these limitations, we proposed to couple InSAR and numerical modeling for characterizing landslide movements under multiple loads. We used 60 ascending and 56 descending Sentinel-1 images to measure surface movements in urbanized Daguan County Town. Of 31 landslides in the inventory map, 24 were successfully identified. The InSAR results assisted in determining the optimal soil properties through back-analysis. We used geological, geotechnical, and meteorological data to set three boundary conditions, that is, body loads, precipitation-induced hydraulic conditions, and construction-induced forces. Landslide mobility was demonstrated more distinctly using the coupled analysis. The numerical results revealed that body loads dominated the cumulative downslope movements by squeezing water and air from voids, and precipitation caused seasonal movements with the direction perpendicular to the slope surface. Construction works caused permanent changes (accelerating and decelerating) in time-series trends. Coupling InSAR and numerical modeling can facilitate analysis of the effects of complex loads and potentially predict future deformation. The method developed can be extended to study other urbanized landslide areas for early warning and risk mitigation.