Characterizing landslide dynamics from time-lapse time domain induced polarization and ground-based imaging: a case study of the MontGombert landslide (French, Alps)
Electrical resistivity tomography (ERT) is widely used to investigate landslide morphology and dynamics. Landslide behavior is strongly influenced by clay content, pore pressure, and the spatial distribution of permeability. However, conventional direct current (DC) resistivity methods have limited capacity to characterize permeability, as materials with low electrical resistivity may exhibit either high or low permeability depending on their clay content and the relative contributions of surface and electrolytic conduction. Induced polarization (IP) offers a valuable complementary approach for investigating the petrophysical properties of geological materials. Despite its potential, IP has been rarely applied to landslide studies and has not yet been widely used for landslide monitoring. This study investigates the added value of IP measurements alongside conventional DC resistivity for landslide characterization and monitoring. Three time-domain induced polarization (TDIP) surveys were conducted at different time steps on an active landslide in the French Alps. Time-lapse inversions of resistivity and chargeability were performed, and spectral IP parameters were derived using Debye decomposition. The results were then compared with surface displacement estimates obtained from optical image processing. The findings demonstrate that TDIP is particularly valuable for delineating unstable volumes within the landslide. The geophysical results show strong agreement with independent measurements from piezometers and inclinometers. Furthermore, applying an empirical relationship between IP parameters and permeability enables the spatial distribution of permeability within the landslide to be estimated, as well as its seasonal variations. Overall, this study highlights the potential of combining IP and DC resistivity measurements to improve the characterization of landslide properties and support the monitoring of their temporal evolution.