PSInSAR displacements related to soil creep and rainfall intensities in the Alpine foreland of western Slovenia

An assessment of the relationship between displacement rates of objects located in areas of active soil creep and rainfall intensities was performed using a permanent-scatterer technique of synthetic aperture radar interferometry. The study focussed on two areas in central Slovenia during the period between April 1992 and December 2000. Based on field assessments, six permanent scatterers for one area and 11 scatterers for the other were selected for analysis from > 4300 available permanent scatterers. Displacement rates related to creeping processes were compared with the different durations and intensities of rain in order to assess the threshold values that initiate the creeping process and to assess the relationship between the speed of the movement and the precipitation events. Although the permanent scatterer displacement data contain much noise, our results indicate that soil creep is induced by 20 mm of rain in 1 day or 50 mm of rain in 3 days, causing an average elevation decrease of 0.5 and 1 mm, respectively. The elevation decreases due to soil creep were observed as instantaneous events, since no increased correlations were observed when a time lag between precipitation and displacement was taken into account. Models developed in this research indicated very similar rates of tectonic uplift for the two research areas in the event of no rain, and these rates were found to be faster than the regional tectonic uplift. This suggests that areas with high rates of tectonic uplift and areas of active soil creep may be related.