Estimation of Deformation Parameters to Separate Postseismic Effect after the 2006 Yogyakarta Earthquake Based on Geodetic Observation

The 2006 Yogyakarta earthquake with a magnitude of 6.3 happened with presumption due to activity from the Opak fault. After the earthquake, the activity of the Opak fault continued to be monitored by using Global Positioning System (GPS) technology. GPS data can be used to see the characteristics of deformation, which happened until present after the Yogyakarta earthquake in 2006. The characteristics of the deformation caused by the earthquake can be either afterslip or viscoelastic relaxation, where each of them can be approached by using a logarithmic and exponential function. The results show the data from continuous stations shows better results compilation approached with an exponential function, which means the deformation of the Opak Fault depends on the interseismic phase with still potential as viscoelastic relaxation of material which lies on the lower crust. Then, the results of the exponential parameters are used to correct the velocity for all GPS stations. The statistical result shows that only the velocity of the continuous stations is significantly different from the velocity before being corrected.