Surface waves analysis for rock glaciers characterization

Rock glaciers are important landforms of mountain permafrost, often found in high mountain areas. This degradation can trigger events like rock falls, landslides, debris flows, and floods, especially in densely populated Alpine regions heavily visited by tourists. Understanding and characterising rock glaciers is crucial for managing natural hazards and addressing on time their socio-economic impact. We propose to use the multichannel analysis of surface waves to further constrain the internal structure of the rock glacier. For this purpose, the same data collected for SRT can be used if they are collected with low-frequency geophones (i.e., 4.5 Hz natural frequency). Rock glaciers ERT and SRT surveys from two different areas, both located on the Eastern Swiss Alps, were acquired. It was performed a MASW analyses using a moving-window approach and picking the fundamental mode in the f-k domain. A window comprising 24 geophones was chosen to strike a balance between spatial and spectral resolution. In addition, analysis of moving windows to retrieve pseudo-2D sections of Vs, were directly compared with the resistivity and Vp sections that were obtained from the ERT and SRT techniques, allowing a thorough characterization of the investigated sites. Finally, each dispersion curve was inverted using Dinver, a stochastic method based on the neighborhood algorithm. Despite the challenging environment, with a rough topography and scattering, the f-k spectra show coherent energy, and at least one mode of propagation is clearly recognizable. The results of surface wave analysis in rock glacier environments show its potential for mountain permafrost characterisation. The use of low-frequency geophones is recommended for seismic surveys, allowing the joint analysis of Rayleigh waves and P-wave first arrivals.