Multichannel Analysis of Surface Waves (MASW) for the internal characterisation of the Flüela rock glacier: overcoming the limitations of seismic refraction tomography

A multi-method geophysical campaign was carried out to characterize the subsurface of the Flüela rock glacier in Grisons, Switzerland, using electrical resistivity tomography (ERT), seismic refraction tomography (SRT), and multichannel analysis of surface waves (MASW). Surface-wave analysis is not commonly applied in mountain permafrost environments, although it can be used on any dataset acquired for conventional SRT when low-frequency geophones are employed. Here, we show that the MASW method can be effectively used to highlight the presence of an ice-bearing layer, thereby overcoming potential limitations of conventional SRT in these environments, such as noisy first arrivals, attenuation effects, and velocity inversions at depth. Our results are corroborated by synthetic ERT and full-wave seismic modelling, which independently support our subsurface interpretation.