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Different geophysical investigations, such as electrical resistivitytomography (ERT) and refraction seismic tomography (RST), allow for an improvedcharacterization of subsurface conditions in mountain permafrost areas. Theknowledge of the permafrost internal composition constitutes a majorprerequisite for climate-related modelling studies, for detailed hazard orlocal infrastructure assessments. To detect the small-scale variations ofpermafrost characteristics and its varying sensitivity to climate influencingfactors, two ERT and RST monitoring profiles were installed in 2009 at twodifferent sites called Chastelets and Murtèl forefield located in theMurtèl–Corvatsch area, Upper Engadin, eastern Swiss Alps. The geophysicalprofiles extend over four existing boreholes and are characterized by strongsmall-scale variations of surface as well as subsurface structures such asbedrock, fine material or coarse debris. Here we present ERT measurementscarried out in a bimonthly interval during the years of 2009 to 2012 and RSTmeasurements which were performed once a year, normally in August, during thesame period. Based on these data sets the so-called four-phase model, based onpetrophysical relationships, was applied to determine the volumetricfractions of ice, water and air within the heterogeneous ground, resulting ina relatively precise description of the subsurface material around theexisting boreholes.  The observations revealed a permafrost occurrence at the Chastelets rockglacier with an estimated ice-saturated layer of at least 10 m thickness andthe detection of a thawed layer with increased water content in the lowerfrontal part of the rock glacier within an area of fine material. In the areaof the Murtèl forefield the analysis revealed strongly weathered bedrock,which is in the upper part covered by a pronounced layer of coarse debrisestablishing a thermal regime which is able to sustain permafrost beneath. Inaddition, the high temporal ERT measurements revealed a seasonal formation ofice during wintertime within the coarse- as well as the fine-grained activelayer zones. It can be concluded that the combination of existing boreholetemperature measurements, the ERT/RST measurements and the application of thefour-phase model resulted in an in-depth view of the investigated area, which isa major prerequisite for future modelling studies allowing for a better treatmentof the present small-scale spatial ground variabilities

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A spatial and temporal analysis of different periglacial materials by using geoelectrical, seismic and borehole temperature data at Murtèl–Corvatsch, Upper Engadin, Swiss Alps