Long-term seismic monitoring of slow-moving, fine-grained landslides. The cases of Avignonet & Harmalière (Trièves, Isère, France), Maca (Peru), and Utiku (NZ)

5 months internship, starting February 2025

Landslides are widespread in mountainous regions and pose major environmental problems, particularly for land-use planning. Among these phenomena, clay slides are a very complex type of ground movement, as they can undergo sudden and unpredictable acceleration phases as they evolve into flows. Among the methods used to monitor these objects over time, seismic background noise interferometry has shown that it is possible to track the elastic seasonal variations in the relative velocity of surface waves (dv/v) that affect these massifs (Colombero et al., 2021 ; Le Breton et al., 2021), as well as precursory signals several days before a rupture (Bièvre et al., in prep. ; Mainsant et al., 2012 ; Fiolleau et al., 2020).

However, few studies have looked into the possibility of characterizing the progressive evolution of damage within a landslide using seismic interferometry. This approach requires long time series, available from observatories. In addition, environmental time series (hydro-meteorology), surface displacements and possibly seismicity are required to calibrate the dv/v time series and to evaluate the environmental parameter(s) controlling the dv/v. This work aims to study the long-term evolution of the mechanical characteristics of clay slides using the dv/v parameter : do these clay masses suffer damage ? If so, is it progressive/regular or does it occur at particular times ? Can it be tracked over time using seismic background noise interferometry ?
To carry out this work, seismic time series will be analysed at several sites with different states of damaging, different controlling factors, and different triggering mechanisms (hydro-meteorology, earthquakes, fluvial incision). dv/v time series are available for most of the sites, but will have to be computed for Maca and Utiku.
This project consists in data processing and analysis. However, geophysical, geotechnical and geological prospecting campaigns will take place during the internship, as part of parallel projects on the Harmalière and Avignonet sites. The intern will be able to participate in these campaigns, and possibly to process the data.

References

• Bièvre G, Fiolleau S & Helmstetter A (in prep.) Seismic ambient noise precursors to snowmelt-triggered, clayey landslide failures, Harmalière, French Western Alps. To be submitted to Landslides.
• Colombero C, Fiolleau S, Jongmans D et al. (2021) Seismic noise parameters as indicators of reversible modifications in slope stability : a review. Surveys in Geophysics 42 : 339-375. doi:10.1007/s10712-021-09632-w
• Fiolleau S, Jongmans D, Bièvre G et al. (2020) Seismic characterization of a clay-block rupture in Harmalière landslide, French Western Alps. Geophysical Journal International 221 : 1777-1788. doi:10.1093/gji/ggaa050
• Le Breton M, Bontemps N, Guillemot A et al. (2021) Landslide monitoring using seismic ambient noise correlation : challenges and applications. Earth-Science Reviews 216 : 103518. doi:10.1016/j.earscirev.2021.103518
• Mainsant G, Larose E, Brönnimann C et al. (2012) Ambient seismic noise monitoring of a clay landslide : Toward failure prediction. Journal of geophysical research 117 : F01030. doi:10.1029/2011JF002159