Surface-wave velocity measurements of shear stiffness of moving earthflows

Berti, Matteo; Bertello, Lara; Squarzoni, Gabriela

doi:10.1007/s10346-018-1102-1

Cited by 9 publications

(7 citation statements)

References 40 publications

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“…Reduced shear-wave velocity has been observed multiple times on the Montevecchio earth flow (Bertello et al, 2018) and on six other landslides in the same region (Berti et al, 2019) following fluidization of the soil, using the active MASW and passive ReMI methods (Park et al, 1999;Louie, 2001). These observations emphasize the strong impact the fluidization of the landslide has on shear-wave velocity, with a considerable drop in Rayleigh wave velocity (−30% to −40%).…”

Section: mentioning

confidence: 81%

“…However, these landslides remained relatively stable over the course of their observation, and consequently no precursor signal was detected. A decrease in velocity related to a failure was observed on seven earthflows (Berti et al, 2019), but after the failure, since no data were recorded just before the failures. The potential of relative change in seismic velocity (called dv/v) to serve as a precursory signal was recently confirmed on Montevecchio earthflow (Bertello et al, 2018).…”

Section: Applications To Landslide Monitoringmentioning

confidence: 96%

“…( 1)). Indeed, on fluidization-prone landslides, reduced shear-wave velocity has been observed in faster-moving zones (Jongmans et al, 2009;Renalier et al, 2010b) before dramatic accelerations (Mainsant et al, 2012b), and immediately after such accelerations (Bertello et al, 2018;Berti et al, 2019). To further analyze these observations, laboratory tests were carried out on soil samples from seven landslides known to have undergone fluidization in the past.…”

Section: Rainfall-induced Fluidizationmentioning

confidence: 99%

“…Indeed, after the rapid decrease in shear-wave velocities due to fluidization of the soil, a progressive increase (recovery) of the Rayleigh waves was observed in the landslide's bulk as the earth flows slowed down. The authors linked this phenomenon to the consolidation of the slope material (Bertello et al, 2018;Berti et al, 2019) (see Fig. 20).…”

Section: mentioning

confidence: 99%

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Landslide monitoring using seismic ambient noise correlation: challenges and applications

Breton

Bontemps

Guillemot

et al. 2021

Earth-Science Reviews

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Monitoring landslides is essential to understand their dynamics and to reduce the risk of human losses by raising warnings before a failure. A decade ago, a decrease of apparent seismic velocity was detected several days before the failure of a clayey landslide, that was monitored with the ambient noise correlation method. It revealed its potential to detect precursor signals before a landslide failure, which could improve early warning systems. To date, nine landslides have been monitored with this method, and its ability to reveal precursors before failure seems confirmed on clayey landslides. However three challenges remain for operational early-warning applications: to detect velocity changes both rapidly and with confidence, to account for seasonal and daily environmental influences, and to check for potential instabilities in measurements. The ability to detect a precursory velocity change requires to adapt the processing workflow to each landslide: the key factors are the filtering frequency, the correlation time window, and the choice of temporal resolution. Other optional processing steps are described, to better measure rapid velocity changes, improve signal-to-noise ratio, or estimate the measurement uncertainty. The velocity also fluctuates seasonally, by 1 to 6% on the reviewed landslide studies, due to environmental influences. This review reveals a linear trend between the amplitude of seasonal fluctuations and the filtering frequency over the 0.1-20 Hz range, encompassing both landslide and non-landslide studies. The environmental velocity fluctuations are caused mostly by groundwater levels and soil freezing/thawing, but could also be affected by snow height, air temperature and tide depending on the site. Daily fluctuations should also occur on landslides, and can be an issue when seeking to obtain a sub-daily resolution useful for early-warning systems. Finally, spurious fluctuations of apparent velocity-unrelated to the material dynamics-should be verified for. They can be caused by changes in noise sources (location or spectral content), in site response (change of scatterers, attenuation, or resonance frequency due to geometrical factors), or in inter-sensor distance. As a perspective, the observation of seismic velocity changes could contribute in as-2 sessing a landslide stability across time, both during the different creeping stages occurring before a potential failure, and during its reconsolidation after a failure.

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Section: mentioning

confidence: 81%

Section: Applications To Landslide Monitoringmentioning

confidence: 96%

Section: Rainfall-induced Fluidizationmentioning

confidence: 99%

Section: mentioning

confidence: 99%

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Landslide monitoring using seismic ambient noise correlation: challenges and applications

Breton

Bontemps

Guillemot

et al. 2021

Earth-Science Reviews

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“…The mechanical behavior of early-stage earthflows in clayey formation might be considered as Coulomb plastic solids whose mobility is developed by sliding (as described above). In this manner, the material flows by internal deformation (internal shears) (Berti et al, 2019). So, the sliding can be resolved into several occurrences of propagation of sliding plane or soil failure (Vouillamoz et al, 2018;Hussain et al, 2019b).…”

Section: Sobradinho Landslidementioning

confidence: 99%

Variation in Rayleigh wave ellipticity as a possible indicator of earthflow mobility: a case study of Sobradinho landslide compared with pile load testing

et al. 2020

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Rainfall-induced landslides pose a significant risk to communities and infrastructures. To improve the prediction of such events, it is imperative to adequately investigate the rainfall-dependent dynamics (leading to fluidization) and any associated internal sliding along shear planes within clayey slopes. Therefore, the present study adopted ambient noise analysis based on the Horizontal to Vertical Spectral Ratio (HVSR) method, to measure the seasonal variation of Rayleigh wave ellipticity as an indicator for the internal deformation and transition in the material state. The methodology was applied to an existing landslide, where variations in soil stiffness and internal sliding were expected to occur in response to rainfall. To improve the interpretation of the HVSR results (and hence the prediction of landslide’ reactivation by rainfall), HVSR measurements were also conducted on a field-scale pile load test. The pile test allowed a comparison of the seismic data generated by the soil movement along shear planes. The HVSR curves of this field test showed two frequency peaks with no changes in the resonance. In comparison with the data obtained from the landslide, the resultant HVSR curves showed three frequency patterns: ubiquitous (2Hz), landslide (4-8Hz), and flat (no peak). However, the HVSR curves did not show any response to the expected seasonally induced variations in the landslide mass because of the relatively short data acquisition. Nevertheless, time-lapse HVSR is a promising technique that can complement other geophysical methods for improving landslide monitoring.

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The MHVSR technique as a rapid, cost-effective, and noninvasive method for landslide investigation: case studies of Sand Gap and Ozark, AR, USA

2021

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Surface-wave velocity measurements of shear stiffness of moving earthflows

Cited by 9 publications

References 40 publications

Landslide monitoring using seismic ambient noise correlation: challenges and applications

Landslide monitoring using seismic ambient noise correlation: challenges and applications

Variation in Rayleigh wave ellipticity as a possible indicator of earthflow mobility: a case study of Sobradinho landslide compared with pile load testing

The MHVSR technique as a rapid, cost-effective, and noninvasive method for landslide investigation: case studies of Sand Gap and Ozark, AR, USA

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