Applicability of electrical resistivity tomography monitoring to coarse blocky and ice‐rich permafrost landforms

Abstract

The inversion and interpretation of electrical resistivity tomography (ERT) data from coarse blocky and ice-rich permafrost sites are challenging due to strong resistivity contrasts and high contact resistances. To assess temporal changes during ERT monitoring (ERTM), corresponding inversion artefacts have to be separated from true subsurface changes. Appraisal techniques serve to analyse an ERTM data set from a rockglacier, including synthetic modelling, the depth of investigation index technique and the so-called resolution matrix approach. The application of these methods led step by step to the identification of unreliable model regions and thus to the improvement in interpretation of temporal resistivity changes. An important result is that resistivity values of model regions with strong resistivity contrasts and highly resistive features are generally of critical reliability, and resistivity changes within or below the ice core of a rockglacier should therefore not be interpreted as a permafrost signal. Conversely, long-term degradation phenomena in terms of warming of massive ground ice at the permafrost table are detectable by ERTM.

A new model for estimating subsurface ice content based on combined electrical and seismic data sets

“…In comparison to Muragl rock glacier, this rock glacier is still exhibiting a solid supersaturated ice body within most of its morphology -a result which is confirmed by additional electrical resistivity tomography monitoring and crossprofile data sets (Hilbich et al, 2009).…”

“…At both field sites borehole data and additional geophysical data are available for model validation (Musil et al, 2002;Maurer et al, 2003;Arenson and Springman, 2005;Hilbich et al, 2009). The tomographic geoelectric and refraction seismic data sets for the case studies presented here were obtained during several field campaigns and include an almost 300 m cross profile near the tongue of Muragl rock glacier and a shorter 145 m longitudinal profile at Murtèl rock glacier (Fig.…”

“…at the lower boundary of the active layer) can often be plagued by inversion artefacts (Hilbich et al, 2009;. As the inversion algorithm and the choice of inversion parameters determine how well the inverted model will reproduce the real distribution, reliability studies addressing the influence of inversion parameters on the resulting resistivity and velocity distribution have to be usually performed (Rings and Hauck, 2009;Hilbich et al, 2009;Kneisel et al, 2008). Day-Lewis et al (2005) refer to this loss of information caused by the inversion process, lack of sufficient prior information and survey geometry as "correlation loss" and computed it with respect to its effect on inferred petrophysical parameters.…”

“…Resistivity values of massive ground ice and of model regions with strong resistivity contrasts (e.g. at the lower boundary of the active layer) can often be plagued by inversion artefacts (Hilbich et al, 2009;. As the inversion algorithm and the choice of inversion parameters determine how well the inverted model will reproduce the real distribution, reliability studies addressing the influence of inversion parameters on the resulting resistivity and velocity distribution have to be usually performed (Rings and Hauck, 2009;Hilbich et al, 2009;Kneisel et al, 2008).…”

Investigating groundwater flow components in an Alpine relict rock glacier (Austria) using a numerical model

“…Electrical resistivity tomography might be a cost-effective solution, but the coarse blocky material at the surface of relict rock glaciers results in a weak electrode coupling to the ground. Furthermore, the extended, air filled voids, and the lack of mineral soils or ice lead to weak electrical contacts between the individual blocks which makes the application of this method rather challenging (Hilbich et al 2009;Kellerer-Pirklbauer et al 2014); however, capacitively coupled resistivity methods, which use an alternating current across a transmitter-earth capacitor, can be used as an alternative to overcome these (Hauck 2013).…”