The Coherence Analysis for Detecting the Subsidence at Permanent Frozen Area in Qinghai-tibetan Plateau

The surface displacement by seasonally freezing bulge and thawing subsidence are main hazards for engineering construction in permafrost regions, especially for the Qinghai-Tibet railway. For detecting the distortion at permafrost area, we try to study the interferometric method of monitoring the deformation at permafrost area with time-series EnviSat ASAR data. In this paper, the coherence characteristics are analyzed for different baseline, time interval with or without season change and different classes (rock, bare soil, vegetation, water), used 13 time-series ASAR data from Jan. 2004 to June 2006 at the Beiluhe test area in the Qinghai-Tibetan Plateau. The results showed that the coherence coefficients is lower in summer and fall than in other two seasons as the freezing and thawing phenomenon. For pairs of crossed different season, such as from spring to summer or from summer to fall, the coherence coefficient decrease for bare soil and vegetation cover, little decrease for rock cover.