| dc.description.abstract | This study used 5 years of continuous GPS observations of 29 stations in the Taipei region and of 9 GPS constrained sites around Taiwan, along with other 11 IGS sites in the Asian Pacific region, to calculate the coordinates and velocities of each site and to obtain the time series of station positions under the ITRF2005 reference frame. The GAMIT/GLOBK software was employed, and influences of earthquakes and changing instruments were evaluated and removed. Furthermore, we reduced the common-mode errors by using the spatial filtering technique to improve the scattering in the time series. In order to accurately estimate velocities and their uncertainties, noises have to be evaluated using more realistic model. I estimated the power spectral index of time-dependent noises of GPS stations in Taipei Region, and found the spectral index are -0.59, -0.52, and -0.45 for N, E, U components, respectively. This result indicates the noise of GPS time series are best described as a combination of white noise and flicker noise. Amplitudes of these noises were estimated by using the maximum likelihood method. The corrected secular velocities and their uncertainties were used to evaluate crustal kinematic behaviors such as principal strain rates, dilatation rates, shear strain rates, and rotation strain rates. Results show that the horizontal ground motion of the Taipei Basin area is about 2.0~5.1 mm/yr in direction of N5 E to N75 E, relative to the Paisha GPS station (S01R) at Panghu, which was considered as a stable continental margin station. Moreover, a NW-SE extension strain rate of about 0.03±0.05 μstrain/yr is measured in an area of 574 km-wide across the Shanchiao fault. Consistent with previous measurements of Permanent Scatter Interferometric Synthetic Aperture Radar (PSInSAR). our GPS data revealed vertical deformation in the northern Taiwan including: (1) a slight uplift about 1~2 mm/yr in the Western Foothills, the Tatun volcano group and the Linkou Tableland, and (2) the subsidence about 2~5 mm/yr around the Taipei Basin. Local substantial subsidence in the Taipei Basin can be distinguished by combined effects from the compaction of shallow sediments and the activity of Shanchiao fault.
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