| Summary: | Abstract Surface displacements associated with earthquake-cycle deformation of active faults significantly influence the accuracy of geodetic datum and reference frames, especially for the Taiwan area with high plate convergence and deformation rates. Following the current architecture of the semi-kinematic reference frame in Taiwan, which does not particularly consider the non-linear behavior of postseismic deformation, we explored the methods to implement a non-linear postseismic deformation model using the 2003 Chengkung earthquake as an example. Together with linear interseismic function, we utilized a logarithmic function to approximate the non-linear postseismic decays. For the time series without preseismic observations, we removed the interseismic velocities by spatial interpolation and fitted the resultant time series with the logarithmic function. After estimating postseismic decays for all GPS stations, we conducted two grid models of accumulative displacements for only postseismic deformation and total deformation after the earthquake. The first grid model provides a useful prediction for tracking surface movements, and the latter model provides a straightforward view to access the timing and amount of displacements to correct the semi-kinematic reference frame. The implementation of the grid models can well approximate non-linear postseismic trends for the semi-kinematic reference frame.
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