Present-day relative displacements between the Jeju Island and the Korean peninsula as seen from GPS observations

Abstract

We use three years data from six permanent GPS stations, in the Korean peninsula and Jeju Island, to examine the relative displacement between Jeju Island and the Korean peninsula and whether the Jeju Island lies on the Amurian Plate or not. Out of these stations, three sites, considered to be on the stable interior of the Amurian Plate (the Korean peninsula), showed relative velocities less than 1.3 mm/yr. On the other hand, the maximum velocity of the Jeju Island stations was 2.1 mm/yr with respect to DAEJ station, and the average relative velocity between the island stations and those in the main land are less than 1.7 mm/yr. By comparing these results with other velocities within the Amurian Plate, we found that the observed velocities are intra-plate. Our results are supported by geological evidences and seismological records, which claimed that the Korean peninsula and the Jeju Island are on the same plate. Hence, the Amurian Plate boundary line is considered to lie somewhere to the south of Jeju Island.