Understanding mudslides through micro-seismic monitoring: The Super-Sauze (South French Alps) case study.
Résumé
The macroscopic deformation of rocks, at scales ranging from laboratory samples (cm) to rock hillslopes and earth crust (hm to km), is associated with local irreversible processes (cracks/faults propagation and shearing). These movements involve propagation of acoustic wave's which can be observed by remote sensing. Seismic monitoring during strain progression can help our understanding of rock behaviour and lead to the recognition of failure precursors. Although of significant potential, this observational tool has had only limited application in the study of gravitational instabilities such as landslides. This paper presents seismic monitoring data acquired on a mudslide located in the South French Alps. Results show that recordable seismicity exists in the frequency range of 0.01 Hz to 10 Hz associated with landslide deformation. Acceleration of landslide movement is controlled by rainfall and appears to be well correlated with seismic activity. The origin of the seismicity is attributed to shearing of the moving mass at the interface with the in-situ stable bedrock. Spectral analysis of the seismic wave reveals that the range 0.1-1 Hz is the most sensitive to the variations in landslide velocity. The results emphasize the strong potential of seismic monitoring for improving our understanding of mechanisms controlling rock mass deformation and gravitational instability. The determination of operational failure precursors based on seismic monitoring has yet to be achieved but remains a major target of future research.
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