We investigate the post-seismic deformation of Korean Peninsula after the 2011 M 9.0 Tohoku-Oki earthquake. Although the peninsula is more than 1000 km away from the epicenter, the co-seismic deformation by this earthquake was the average of about 3 cm. This amount of deformation is similar to the annual movement. And it occurred a difference in the amount of co-seismic deformation between eastern and western region. In this study, we describe the stability of the crust after the megathrust earthquake. To do this, we performed function fitting regression analysis to investigate post-seismic deformation for 32 GPS sites from 2010 to 2018. The post-seismic time-series are fit with an exponential decay function. We obtain deformation parameters, especially amplitude, for each site associated to the post-seismic deformation. The amplitudes of the relaxation based on the exponential model are used to evaluate the stability of the crust. We suggest that the average relaxation rate is about 86 %. The GPS stations in the southern region of the South Korea show high rate values and central stations had relatively low rate value. The result of the relaxation rate suggests that the crustal stabilization is still in progress in some regions.

Keywords: GPS, 2011 Tohoku-Oki earthquake, post-seismic deformation, Korean Peninsula