Processes that control permafrost warming in Alpine regions are still not completely understood. Recently, geoelectrical monitoring has emerged as a useful tool to investigate thawing and freezing processes. However, high resistive environments and harsh environmental conditions pose very unfavourable conditions for automated resistivity measurements. Based on the results of several test studies, an improved data acquisition system for geoelectrical monitoring of frozen soils was developed. Furthermore, the implementation of algorithms for statistical analysis of raw data time series led to a significant improvement in the reliability of inversion results. At two Alpine sites, namely Mölltaler Glacier and Magnetköpfl/Kitzsteinhorn, the adapted system was tested at soil temperature conditions between 0°C and -12°C. Data was continuously collected at both locations over nearly a full seasonal cycle. The results showed an almost linear dependency of resistivity and temperature at values above -0.5°C. At lower temperatures, the relation was non-linear, indicating that the reduction of porosity due to the shrinking of connected brine channels was the dominating process that determined the value of resistivity. Based on the derived results, further improvements were suggested, especially for measurements at soil temperatures below -4.5°C as low injection currents make it extremely challenging to gather these. permafrost regions is high priority. The advancement of innovative methods, such as geoelectrical monitoring, allowing all-seasonal, permanent monitoring of remote areas is in demand.The geoelectrical method determines the distribution of the specific electrical resistivity within the subsurface. The specific electrical resistivity mainly depends on porosity, water saturation, conductivity of pore fluid and clay content, and to a minor extent on particle shape and pore geometry. During the process of permafrost thawing and freezing, the volume fraction of the fluid phase (equivalent to a change in porosity), the connectivity of fluid areas and the salinity of the pore fluid is expected to vary. Therefore, geoelectrical monitoring could be an appropriate tool to investigate such processes.

Permanent geoelectrical monitoring, using the GEOMON 4D instrumentation in combination with high resolution displacement monitoring by means of the D.M.S. system, was performed at two active landslide areas: Ampflwang/Hausruck in Austria, and Bagnaschino in Italy. These sites are part of the Austrian geoelectrical monitoring network, which currently comprises six permanently monitored landslides in Europe. Within the observation intervals, several displacement events, triggered by intense precipitation, were monitored and analysed. All of these events were preceded by a decrease of electric resistivity. The application of an innovative 4D inversion algorithm made it possible to investigate the potential processes which led to the triggering of these events. We conclude that resistivity monitoring can significantly help in the investigation of the causes of landslide reactivation. Since the results also contribute to the extrapolation of local displacement monitoring data to a larger scale, resistivity monitoring can definitely support decision-finding in emergencies.techniques, long-term continuous monitoring of deformation and triggering factors and by establishing early-warning systems/centres. The most commonly used early-warning parameters are pore pressure and displacement. However, recent research has shown that other parameters exist, which might give indications of impending triggering before an actual displacement is measurable.The geoelectrical method (direct current DC) has recently been established as a routine geophysical method to investigate subsurface geometry and structural pattern of landslides in Europe (Mauritsch et al.

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Abstract.After a large landslide event in Sibratsgfäll/Austria several exploration methods were evaluated on their applicability to investigate and monitor landslide areas. The resulting optimised strategy consists of the combined application of airborne electromagnetics, ground geoelectrical measurements and geoelectrical monitoring combined with hydrological and geological mapping and geotechnical modelling. Interdisciplinary communication and discussion was the primary key to assess this complicated hazard situation.

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