Preliminary result of land subsidence from radar interferometry in the Yunlin County of Central Taiwan

The Taiwan High Speed Rail (THSR), which is due to start operation in early 2007, is one of the most important infrastructures in Taiwan. In the Yunlin County of central Taiwan, a section of the THSR rail passes through an area with large subsidence rate that has been reported by previous studies (maximum 10 cm/yr). The aforementioned land deformation, under certain circumstances, could lead to failures of the foundations of rail structures and damages of rail tracks. In order to monitor and prevent regional subsidence, our team uses Differential SAR Interferometry (DInSAR) to monitor this area with centimeter accuracy. Because the Yunlin County is covered with varying vegetations over different seasons, the noise of DInSAR results are often too high to extract the real surface deformation. Persistent Scatterers (PSInSAR) may overcome this difficulty and. Persistent Scatterers can provide long-term stability of the scattering characteristics and high radar signal coherence in the multi-image analyses. PS can estimate and then reduce the effect of atmospheric disturbance, spatial and temporal decorrelation. By applying PSInSAR, it is possible to extract deformation signals from the study area in Yunlin County. Compared to, PSInSAR can provide geodetic information with high spatial density and mm-level accuracy. The resulting subsidence information could be compared to the GPS and leveling results and improves our understanding in regional deformation