Characterizing sudden geo-hazards in mountainous areas by D-InSAR with an enhancement of topographic error correction

Differential interferometric synthetic aperture radar (D-InSAR) has been viewed as a promising technique in monitoring sudden geo-hazards (e.g., earthquake and landslide) in mountainous areas. However, the tough natural settings (e.g., steep slopes and vegetation) pose the D-InSAR technique to face many challenges. Among them, phase residuals induced by inaccurate topographic heights that can result in intolerable error have not been paid adequate attention. We present, in this paper, a new strategy of using D-InSAR measurements to characterize sudden geo-hazards with an emphasis on the correction of topographic errors. In the proposed strategy, a least squares model with an outlier detector is constructed to estimate the topographic errors from multi-baseline wrapped differential interferograms, and the error-prone phase unwrapping procedure is not needed. The new strategy is applied to the ALOS PALSAR images acquired for monitoring a giant mudslide occurred in Zhouqu County, China. After refining the topographic height originally from the inaccurate ASTER GDEM, notable improvements to the D-InSAR measurements can be clearly seen, which is helpful to better interpret the deformation signals associated with the mudslide event. It is observed that the Zhouqu mudslide had caused large ground movements in the Luojiayu and Sanyanyu groove valleys. In addition, we find that the Suoertou landslide has been experiencing moderate ground movements during the geologic event.