Extensive InSAR observations of the Jettan rockslide in northern Norway, using Radarsat-2, TerraSAR-X, and corner reflectors

The Jettan rockslide, in northern Norway, is quite active, with up to 17 Mm3 of rock being displaced at rates of up to 5 cm/year or more. A large failure at this site would cause a tsunami in the adjacent fjord affecting several municipalities. Due to the high risk this landslide poses to the surrounding region, an extensive in-situ deformation monitoring system has been installed, including extensometers and crack meters, tilt meters, lasers, permanent GPS stations and a weather station. In addition, instrumentation is installed for studying the ground thermal regime. Extensive InSAR studies have been carried out in the area using ERS, Envisat ASAR, Radarsat-2 Fine and Ultrafine and TerraSAR-X stripmap images. InSAR processing has been carried out using the short baselines subset (SBAS) algorithm. Due to the long season of snow cover in Norway, the processing has only used summer/autumn scenes, leaving long gaps in the deformation time series. In order to partially offset this problem, we installed four 1.8 metre trihedral radar corner reflectors on the site in 2009, with one located at a position assumed to be stable. These corner reflectors allow us to measure deformation throughout the year. In this study, we compare the results of three years of continuous InSAR measurements of the corner reflectors with in situ measurements. The combination of results from multiple satellite missions allows us to identify both long term trends and seasonal variations. In addition we present the results of the SBAS processing of both Radarsat-2 and TerraSAR-X datasets. These high resolution datasets give us an improved understanding of the spatial variation of movement in the rockslide. In addition, the 11 day acquisition period for the TerraSAR-X gives a much better understanding of the temporal variation of movements.