Slope deformation prior to Zhouqu, China landslide from InSAR time series analysis

A major landslide in Zhouqu, China occurred on August 8, 2010 and caused widespread damage and over 1700 casualties. We study the deformation of the slopes over a time period of about three years prior to the landslide by an enhanced StaMPS-SB technique with 16 ascending ALOS/PALSAR images. In particular, the orbit error and stratified troposphere that were not well dealt with in the original StaMPS-SB method have been satisfactorily corrected by a novel phase ramp correction method. The deformation in four regions of the study area has been retrieved with a maximum of up to 70 mm/yr. In the Luojiayu-Sanyanyu valley, the slopes where the 2010 giant landslide occurred have been found to be quite unstable before the event. Deformation exceeding 30 mm/yr has been detected in the Suoertou slope, which is a well-known place for an ancient fault zone landslide. Fast movement larger than 40 mm/yr is observed in the Xieliupo slope, which poses threats of landslide dam and dammed lake to the Pai-lung River together with another slope deformation detected in the opposite slope. In the Nanshanqiaotou slope, the detected ~ 30 mm/yr deformation can be viewed as the prelude of the large landslide occurred in October 2010. More important, it is found that the slope deformation time series has strong correlation with the precipitation in the area as well as with the devastating Wenchuan earthquake that occurred in May 2008 whose epicenter is about 300 km away from Zhouqu.