Assessment of ground surface displacement in Taihape landslide, New Zealand, with C- and X-band SAR interferometry

In this study, we assess the capability of C-band advanced synthetic aperture radar (ASAR) data from Envisat and X-band Stripmap SAR from TerraSAR-X to analyse the extremely slow displacement rate of Taihape landslide in the central North Island of New Zealand. The small-baseline subset (SBAS) technique is applied to obtain displacement time series from SAR images between 2003 and 2011. Time-series results suggest that the landslide is active near its toe with maximum line-of-sight (LOS) surface velocity of 6 mm a–1 between 2003 and 2010, derived from Envisat, and 8 mm a–1 in the year 2010 to 2011, derived from TerraSAR-X. Comparing TerraSAR-X and Envisat results, the former detects approximately 15 times more coherent pixels for deformation analysis. Interferometric SAR (InSAR) displacement time series show a good agreement with field measurement from prisms installed on the surface of the landslide (maximum root-mean-square error or RMSE