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

Abstract. A multi-method geophysical campaign was carried out to characterize the subsurface of the Flüela rock glacier, Grisons, Switzerland, using electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW). Surface wave analysis is not commonly used in mountain permafrost environments, although it could be applied to any dataset acquired for conventional SRT analysis if collected with low-frequency geophones. Here, we show that the use of the MASW method can be efficiently applied to highlight the presence of an ice-bearing layer, thus overcoming potential limitations of the common SRT analysis in these environments, such as tackling velocity inversions at depth or identifying layers which are invisible due to the lack of head wave arrivals. Our results are corroborated by synthetic models that simulate the propagation of seismic waves in a mountain permafrost environment with changing ice and water contents.