Observation of Expansive Clay Movement with DInSAR

Abstract

The research summarized herein aims at answering the question of how movement caused by swelling clays can be observed with differential SAR (synthetic aperture radar) interferometry (DInSAR). The study area is located in the southwestern Denver metropolitan area, and was selected due to its location in a semi-arid climate, the existence of swelling clay soils and bedrock, and available historic, geological and climatic background information. Twenty-one ERS (European Remote Sensor) SAR images from a time-period between February 1993 and August 1997 were used in the analysis. The analysis included a “conventional” DInSAR and a small baseline subset analysis (SBAS) approach. The influence of noise and atmospheric phase-contributions in the results of the “conventional” method rendered this technique infeasible for the data and area investigated. To overcome the limitations, algorithms of the SBAS DInSAR method were applied to the data. Preliminary results of the SBAS analysis, although still requiring caution in their interpretation, appear promising and indicate small changes (uplift) over time in areas of high swell potential. They also reflect seasonal fluctuations due to swelling and shrinking.