INSAR BASED EVALUATION OF LAND SUBSIDENCE AND GROUND FISSURE EVOLUTION AT XIAN

Xian city has been experiencing serious land subsidence and ground fissure activities for a long time. SAR interferometry (InSAR) has been applied to monitor the spatio-temperal characteristics of land subsidence and ground fissure in this area since 1992, where adaptive interferogram filtering and phase unwrapping algorithms with gross elimination are considered in each interferometric pair. The InSAR results are calibrated with leveling and GPS results in the similar monitoring time, respectively. One centimeter precision is achieved. In conclusion, the main subsidence regions are the eastern and southern suburbs. The second subsidence stage was the maximum stage with nearly 21cm subsidence in 1996. The subsidence rate has decreased to 8 cm while the subsidence cone has shifted to southwestern suburb. It is also detected that the non-linear deformation is in active ground fissure areas and the subsidence rate in the south is larger than the north. This research results can give a great data support for further inversion and hazard mitigation.