Prominent Postseismic Displacements of the 2003 MW 6.5 Chengkung Earthquake in Eastern Taiwan

The MW 6.5 Chengkung earthquake occurred at 04:38 UTC on 10 December 2003. Thirty continuously recording GPS stations (CORS) have been set up at different geological sites and distributed throughout a 140 km by 140 km area in southern Taiwan beginning in 2000. The GPS data is recorded daily for the CORS in 30 seconds sampling rate. The GPS data is utilized to study the coseismic and postseismic deformation associated with the Chengkung earthquake. The coordinates of the daily solution for each station were extracted from SINEX (Software INdependent EXchange) files to establish time series in the topocentric north-east-up (NEU) coordinate system. The secular crustal deformation of the station during the one year period was removed by applying the 2000-2003 interseismic velocities. The CORS near the Chihshan fault, which are located at the southern segment of the Longitudinal Valley Fault, indicated the largest postseismic displacement in eighteen months approached 86 mm (station SHAN) and 91 mm (station TAPO) in the horizontal and vertical components, respectively. The results of the CORS provide detailed information for the temporal process of postseismic deformation.