Recent deformation in and around the eastern taiwan longitudinal valley revealed by PSI technique

On the eastern side of the Taiwan mountain belt, the Longitudinal Valley between the Central Range and the Coastal Range marks one of the most active plate boundaries between the Eurasian plate and the Philippine Sea plate. Across it a present-day relative shortening of about 3 cm yr-1 has been detected by geodetic means. In this study we use Persistent Scatterer InSAR technique (PSI) to extract the phase signal of the chosen PS points of the Eastern Taiwan to investigate the recent surface deformation in and around the Longitudinal Valley. As revealed by many existing deformation measurement, our result shows sharp range change offsets along the eastern side of the Longitudinal Valley, but no shallow slip was observed on the western edge of the valley. Along strike, many previous measurements suggest highest creep rates near Chihshang and decreasing rates toward the northern and southern tips. However, our result reveals a much more complex pattern of surface deformation. The slant range displacements appear to be variable spatially. In the valley, the highest uplift (shortening) rate of about 1.6 cm yr-1 occurred in the Luyeh area, but north to 23o15'N the subsidence took place. In general, the uplift rates along the Longitudinal Valley decrease from south to north. This result can helps us to define locations and activities of some uncertain active faults in this area.