Monitoring of Recent Land Subsidence and Ground Fissures in Xian with Sar Interferometry

The City of Xian, China, has been experiencing significant land subsidence and ground fissure activities since 1960s that have brought various severe geohazards including damages to buildings, bridges and other facilities. Monitoring of land subsidence and ground fissure activities can provide useful information for assessing the extent of, and mitigating such geohazards. We study the land subsidence and ground fissure activities during 1992 2006 using ERS and Envisat SAR data. Three main land subsidence stages in 1992, 1996 and post 2004 are identified. The maximum land subsidence rates increased from 16cm/a in 1992 to 22 cm/a in 1996 and then decreased to 7.5cm/a by 2004, while the area affected by the subsidence expanded from the first stage to the second and then decreased from the second to the third. Some of the ground fissures that were active during 1990s became inactive after 2004 while some new fissures appeared in the new subsidence areas. It is also found that the land subsidence and ground fissure activities were related to ground water withdrawal and city development.