Research on recent characteristics of spatio-temporal evolution and mechanism of Xi'an land subsidence and ground fissure by using GPS and InSAR techniques

Xi'an city, one of the famous historical cities in China, has been suffering serious land subsidence and ground fissure historically and even recently, which greatly restrict the modernization of this city. This study focuses on the monitoring and analysis of Xi an land subsidence and ground fissure by applying the GPS and InSAR techniques. On the one hand, we achieved precious information of the overall deformation caused by both land subsidence and ground fissure. Based on the information, on the other hand, we studied the characteristics of spatio-temporal evolution and mechanism of the land subsidence and ground fissure, and obtained the following main conclusions. Firstly, owing to the effective controlling of underground water withdrawal, the maximum annual subsidence rate has decreased greatly from 20-30 cm/a in the mid-1990 s to less than 10 cm/a recently. Meanwhile the mean land subsidence rate of approximately 60% subsidence areas has decreased from 5-8 cm/a to 2 cm/a. Secondly, most of the original subsidence cones have disappeared or greatly reduced. Thirdly, we discovered obvious spatio-temporal correlations between ground fissure and land subsidence. Lastly, the land subsidence and ground fissure have gradually extended to south, southwest, and southeast suburbs of the city along with the expanding of the Xi an Hi-tech zones construction.