Transient Reactivation of a Deep‐Seated Landslide by Undrained Loading Captured With Repeat Airborne and Terrestrial Lidar

Abstract

Landslides reactivate due to external environmental forcing or internal mass redistribution, but the process is rarely documented quantitatively. We capture the three‐dimensional, 1‐m resolution surface deformation field of a transiently reactivated landslide with image correlation of repeat airborne lidar. Undrained loading by two debris flows in the landslide's head, rather than external forcing, triggered reactivation. After that loading, the lower 2 km of the landslide advanced by up to 14 m in 2 years before completely stopping. The displacement field over those 2 years implies that the slip surface gained 1 kPa of shear strength, which was likely accomplished by a negative dilatancy‐pore pressure feedback as material deformed around basal roughness elements. Thus, landslide motion can be decoupled from external environmental forcing in cases, motivating the need to better understand internal perturbations to the stress field to predict hazards and sediment fluxes as landscapes evolve.

Self‐Entrainment Motion of a Slow‐Moving Landslide Inferred From Landsat‐8 Time Series

“…This highlights the effect of the headscarp retrogression and subsequent supply of sediment to the landslide mass. Previous studies also noticed an acceleration of landslide movements following a period of sediment supply, based on debris flows on the landslide body (Booth et al, 2018), or the triggering of debris flow after sediment supply (Budetta, 2010). In these different cases, the timing of the onset of acceleration is not clearly resolved, which makes the interpretation of the activation mechanism challenging.…”

“…However, different internal processes may also influence landslide motion; for example, progressive failure is thought to play a key role in the initiation of landslide motion (Amitrano, 2004;Carey & Petley, 2014;Eberhardt et al, 2004;Gischig et al, 2016;Lacroix & Amitrano, 2013). Redistribution of mass within a moving landslide can also continuously modify the stress field, leading to complex variations in landslide motion (Booth et al, 2018); for example, destabilization of the headscarp at the rear of the landslide can occur by removal of the lateral confining pressure, in turn leading to landslide development by retrogression of its headscarp (e.g., Locat et al, 2011). Some studies also highlight that in clay-rich sediments, debris coming from outside the landslide can lead to destabi-lization through the generation of dynamic perturbations of already high pore pressures (in undrained conditions; e.g., Booth et al, 2018;Iverson & LaHusen, 1989)-this effect is well-known for sub-marine landslides (e.g., Mountjoy et al, 2009;Urgeles & Camerlenghi, 2013).…”

Diagnosis of Xinmo (China) Landslide Based on Interferometric Synthetic Aperture Radar Observation and Modeling

“…Hence, we wanted to know how the deformation and strain of landslides changed during the development of the landslide. Multi-dimensional deformations can be used to calculate the strain (and strain rate) of the landslide, which can indicate the landslide body's regions of extension and compression [35,36]. However, only one-dimensional deformation of the landslide was obtained during the monitoring period.…”

“…An unconnected area at the bottom of the source area formed the locked section [5]. The shear strength of the landslide could decrease significantly with the expansion of the slip surface [36]. In addition, the long-term gravitational effect and external factors such as precipitation resulted in the failure of the locked section.…”

Widespread Initiation, Reactivation, and Acceleration of Landslides in the Northern California Coast Ranges due to Extreme Rainfall

“…These landslides can display kinematic changes over timescales ranging from 10 −2 to 10 2 days in response to stress perturbations that act to alter the driving stress or resisting strength. Stress perturbations caused by nearby earthquakes (e.g., Lacroix et al, ), variations in atmospheric pressure (e.g., Schulz, Kean, & Wang, ; Van Genuchten & De Rijke, ), and undrained loading (e.g., Booth et al, ; Hutchinson & Bhandari, ) have all been linked to observable changes in landslide behavior. Most commonly, however, stress changes from infiltrating precipitation and snowmelt drive changes in landslide activity (e.g., Coe et al, ; Iverson & Major, ; Malet et al, ; Rutter & Green, ; Terzaghi, ).…”