Monitoring land subsidence in the southern part of the lower Liaohe plain, China with a multi-track PS-InSAR technique

The lower Liaohe plain is one of the most important industrial zones in Liaoning Province, China, and activities here include oil and gas exploration, aquaculture and salt production. Heavy land use may have contributed to the different magnitudes of land deformation in this region, and this has been detrimental to the environment and economic construction projects in this zone. In this paper, we employ the permanent scatterer interferometry (PSI) technique with L-band ALOS/PALSAR imagery data to monitor the annual land subsidence and produce accumulative time-series maps for the years of 2007 to 2011. The unwrapped grid size was tested in order to recover the maximum deformation. InSAR results from two adjacent tracks were merged by considering the offset over the overlapped area. A PS standard deviation of 0.91 cm/year was achieved in the vertical direction, according to calculation from two independent PS results. Three kinds of land subsidence were analyzed quantitatively over the oil fields, coastal zones, and salt production areas. Some severe land subsidence regions were verified by field investigations.