Mechanism of Co‐Seismic Deformation of the Slow‐Moving La Sorbella Landslide in Italy Revealed by MPM Analysis

Abstract

AbstractPredicting the seismic behavior of slow‐moving landslides presents a significant challenge. Their yearly displacements of a few millimeters to several meters indicate that even before any earthquake they are balancing at the verge of instability. It is therefore not surprising that conventional analysis predicts large co‐seismic displacements even for light‐to‐moderate ground motions. In reality, however, negligibly small displacements have often been observed for such earthquakes, while strong ground motions can still lead to catastrophic failure. This discrepancy challenges both our understanding of the underlying mechanisms and the reliability of conventional analysis, resulting in significant uncertainties for risk assessment. Progress in this field has been further hindered by incompleteness of the available monitoring data and a lack of reliable numerical models capable of dealing simultaneously with small and large deformations under seismic loading. In this article, recently published monitoring data on La Sorbella landslide in Italy and the latest developments in seismic material point method analysis are used to gain insights into the mechanisms controlling the co‐seismic behavior of slow‐moving landslides. This forms the basis for a subsequent investigation of the potential landslide behavior during strong motions, using various material models. The study demonstrates that the co‐seismic behavior of La Sorbella slide is strongly influenced by the interplay between geometrical and viscous effects, as well as potential softening in the shear zone and the surrounding soil mass. The proposed approach paves a way toward quantification of these effects in risk assessment for slow‐moving landslides.