Deep fluids can facilitate rupture of slow‐moving giant landslides as a result of stress transfer and frictional weakening

Abstract

[1] Landslides accommodate slow, aseismic slip and fast, seismic rupture, which are sensitive to fluid pressures and rock frictional properties. The study of strain partitioning in the Séchilienne landslide (France) provides a unique insight into this sensitivity. Here we show with hydromechanical modeling that a significant part of the observed landslide motions and associated seismicity may be caused by poroelastic strain below the landslide, induced by groundwater table variations. In the unstable volume near the surface, calculated strain and rupture may be controlled by stress transfer and friction weakening above the phreatic zone and reproduce well high-motion zone characteristics measured by geodesy and geophysics. The key model parameters are friction weakening and the position of groundwater level, which is sufficiently constrained by field data to support the physical validity of the model. These results are of importance for the understanding of surface strain evolution under weak forcing. Citation: Cappa, F., Y. Guglielmi, S. Viseur, and S. Garambois (2014), Deep fluids can facilitate rupture of slowmoving giant landslides as a result of stress transfer and frictional weakening, Geophys. Res. Lett., 41,[61][62][63][64][65][66]

Contribution of time-related environmental tracing combined with tracer tests for characterization of a groundwater conceptual model: a case study at the Séchilienne landslide, western Alps (France)

“…Seasonal monitoring of natural and artificial tracers enables characterization of the groundwater scheme of unstable slopes and their surrounding stable massif. The results obtained in the case of the Séchilienne landslide show that this method is able to solve various important issues for hydromechanical studies (Cappa et al 2014). Due to the general scarcity of hydrogeological monitoring networks in landslide sites, the proposed method could be suitable to conceive outstanding flow schemes for other landslide types.…”

Functioning and precipitation-displacement modelling of rainfall-induced deep-seated landslides subject to creep deformation

“…and spatial datasets (digital elevation models, aerial photographs and geological maps). The hydro-mechanical study of Cappa et al (2014) showed that the deep aquifer water pressure, beneath the unstable zone, can facilitate the rupture of slow-moving landslides as a result of stress transfer and of frictional weakening. In addition to the perched aquifer, the deep aquifer is assumed to possibly trigger the displacement of the deep-seated landslide.…”

“…The hydro-mechanical study of Cappa et al (2014) shows that the deep aquifer can trigger the Séchilienne landslide destabilisation. The Séchilienne landslide destabilisation can therefore be regarded as triggered by a dual-aquifer layer: the landslide-perched aquifer and the deep aquifer.…”

“…Although black-box models show accurate performance and simplicity to be integrated in a warning system, they do not emphasise physical process and therefore can be limited in the understanding of the landslide-control Landslides Original Paper mechanisms. Conversely, physically based models (Cappa et al 2004(Cappa et al , 2014Corominas et al 2005;Guglielmi et al 2005;Malet et al 2005;Tacher et al 2005;van Asch et al 2007) provide a good understanding of the failure mechanisms and integrate timedependent factors. These models require numerous in situ geophysical, geotechnical or hydrodynamic measurements.…”

An efficient workflow to accurately compute groundwater recharge for the study of rainfall-triggered deep-seated landslides, application to the Séchilienne unstable slope (western Alps)

“…The groundwater flow of the entire massif is mainly controlled by the network of fractures with high flow velocities (up to a few kilometres per day; Mudry and Etievant, 2007). The hydromechanical study of Cappa et al (2014) shows that the deep aquifer can also trigger the Séchilienne landslide destabilisation as a result of stress transfer and frictional weakening. Thus, the Séchili-enne landslide destabilisation is likely triggered by a twolayer hydrosystem: the landslide perched aquifer and the deep aquifer.…”