Types and characteristics of slow-moving slope geo-hazards recognized by TS-InSAR along Xianshuihe active fault in the eastern Tibet Plateau

Displacement for a long time is an important clue to recognize slow-moving slope geo-hazards (SMSGH). And active fault zones in Tibet Plateau are usually the regions developing serious SMSGHs because of rugged terrain, strong tectonic movement, frequent earthquakes and cracked rock masses, etc. Taking the persistent active Xianshuihe Fault (XSF) zone in the eastern Tibet Plateau as study area, this paper carries out time series InSAR observation using 18 periods of L-band ALOS/PALSAR datasets acquired from December, 2006 to September, 2010, gain millimetric-scale ground velocity. Furthermore, combining InSAR velocity with works of field investigation, optical remote sensing interpretation and geological setting analysis, we recognize 394 SMSGHs and gain some understanding of SMSGHs in types, deformation and spatial distribution. Firstly, creep landslide, debris flow and slow-moving moraine are three main types of SMSGH. Secondly, most paleo-landslides, co-seismic landslides and cracked unstable slopes distribute alone the northern section of XSF, and the majority of landslides intersecting with XSF is obviously movable and others are stable or of smaller movement. Thirdly, in the areas of debris flow source, the slow and disperse deformation commonly develop, which can be taken as the clue to identify debris flow; and two types of debris flow sources, “earth-forest” and “loose deposition,” are found. Finally, moraine in hanging glacier valley above 4200 m a.s.l. exists extensively, with huge body and fast dislocation, which is the majority surface erosion type nowadays in this uplifting plateau. The study results also indicate that the combination of InSAR displacement and geological setting analysis can recognize SMSGHs efficiently and effectively, being suitable for mountainous and inaccessible area as this study.