Neotectonic Deformation in SW Taiwan as Deduced from Persistent Scatterers SAR Interferometry and Geodetic Observation

The island of Taiwan, where collision and mountain building occur, provides key examples for analyzing tectonic displacements through Interferometric methods. We apply both the D-InSAR and persistent scatterer SAR intereometry technique to monitor the active growing structure on the Tainan Tableland near the deformation front in SW Taiwan using ERS SAR images in the period of 1996-2000. Interferometric processing of six SAR images reveals the average slant range displacement (SRD) to be ~12.5 mm/yr, and it increases from the west edge of the Tainan Tableland and decreases across the Houchiali fault. The GPS campaign data indicate an average horizontal movement of 12±4 mm/yr in the direction of N44°W for the Tainan Tableland with respect to the western coastline. Five precise leveling surveys across the Tainan Tableland over two years show an uplift rate of ~14 mm/yr for the benchmarks on the Tableland. By combining the horizontal velocity of GPS data and the SRD of D-InSAR we transfer the SRD into vertical deformation and discuss the deformation pattern and seismic hazards in the Tainan area. Furthermore, the new Persistent Scatterers Interferometry method is herein applied in order to better understand deformations through time. We use 19 SAR images for Persistent Scatters Interferometry from 26 April 1995 to 12 October 2000 to detect the neotectonic deformation of Tainan Tableland. This allows to know the deformations of thousands points through recent time and then to better map the deformation field due to the active tectonics. The results show a maximum SRD of 12.4 mm/yr located on the NE Tainan Tableland. Our field knowledge combined with result of PS-InSAR and continuouis GPS stations lead us to precisely know the 3D deformation of the area. The latter give knew insights for its geodynamic understanding and the associated seismic hazards for the 2.4 millions inhabitants of the Tainan County.