Tracking the Movements of Electrodes on an Active Landslide over Time Using Only Time-lapse Resistivity Data

The movements of permanently installed monitoring electrodes on an active landslide will cause artefacts in the resulting resistivity images if their positions are not continuously updated and incorporated in the inversion. In this paper we investigate the effects of electrode movements on time-lapse resistivity tomography using a simple analytical model and real data. The correspondence between this model and the data is sufficiently good to be able to predict the electrode movements with reasonable accuracy. We show that the model can be used to invert the downslope displacements of the electrodes from their original baseline positions using only the time-lapse ratios of the apparent resistivity data. The example datasets are taken from an electrode array on an active lobe of a landslide. We show that the electrode positions can be recovered to an accuracy of 4% of the baseline electrode spacing, which is sufficient to correct the artefacts in the resistivity images. Using a time-lapse sequence of resistivity data, we demonstrate that this technique can be used to track the movement of the landslide over time to the same level of accuracy.