Soilstab and Evorisk: a web-service and web-platform for landslide and rock-fall hazards monitoring using ambient seismic noise methods

Abstract

Landslide monitoring is essential to a better understanding of their dynamics and to the reduction of human casualties by detecting precursors before failures. In general, observations on the surface must be supplemented by sub-surface observations, in investigating the material in depth. Ten years ago, seismic ambient noise interferometry method has been applied to monitor the relative variations in surface seismic wave velocity (dV/V). As seismic wave velocities are directly related to material stiffness, any reduction in seismic velocity can be associated with a loss of stiffness with high probability (i.e. ground liquefaction or strong fracturation). This technique has led to the detection of a decrease in wave velocity several days before the rupture of a clay landslide [1], opening the way to a new precursor signal that could be used for alerts or early warning systems. Since then, several landslides have been monitored to this end [2].In addition, by analysing the spectral content of seismic data, the natural resonance frequencies of rock instabilities (rocks columns, rock glaciers) can be monitored [3]. Their relative variation (dF/F) over time depends on the elastic properties and the geometry of the vibrating structure, which makes it possible to monitor its mechanical state, and to deduce precursor signals to significant failure.In order to make these technologies operational, we have built a web-service, Soilstab, which allows for the processing of an existing dataset with the seismological methods described previously. This service is associated with Evorisk, a web-platform that displays the temporal evolution (updated daily or over a fixed period) of the results (dV/V and/or dF/F). This platform also integrates other available observations, such as environmental parameters (temperature, rainfall, snow, …) or surface observations (photogrammetry, GNSS/GPS-based displacement measurements, extensometers, etc..). Correlating all these observations is thus made easier to better understand and quantify the effect of environmental forcings (temperature, rain, freezing, etc.) on the dynamics of landslides and rock instabilities.[1] G. Mainsant, E. Larose, C. Brönnimann, D. Jongmans, C. Michoud, M. Jaboyedoff, Ambient seismic noise monitoring of a clay landslide : toward failure prediction, J. Geophys. Res. 117, F01030 (2012).[2] M. Le Breton, N. Bontemps, A. Guillemot, L. Baillet, E. Larose, Landslide Monitoring Using Seismic Ambient Noise Interferometry:: Challenges and Applications, Earth Science Review (2020)[3] Colombero, C., Jongmans, D., Fiolleau, S., Valentin, J., Baillet, L., & Bièvre, G. (2021). Seismic noise parameters as indicators of reversible modifications in slope stability: a review. Surveys in Geophysics, 42(2), 339-375.