Estimating the impact process of the Jeokjung-Chogye Basin in Korea from gravity field interpretation

Abstract

SUMMARY The Jeokjung-Chogye Basin (JCB) is the first impact crater discovered in the Korean peninsula. The geometric centre of the exterior crater rim is demarcated by an elevation high surrounding the JCB, exceeding 200 m. The diameter of the exterior ring is approximately 6500 m, and its centre is located about 1000 m southwest of the basin centre. Using terrestrial measured gravity field interpretations such as dip curvature and Z-derivative analysis of the residual anomaly field, we calculated the diameters of the peak ring and uplift ring to be about 4000 and 1500 m, respectively. The centre of the peak ring is located approximately 350 m to the west of the centre of the exterior ring; meanwhile, the centre of the uplift ring is located about 300 m to the east from the exterior ring's centre. Application of the Euler deconvolution method indicates that the depth discrepancy between the peak and uplift rings is approximately 200 m. This discrepancy indicates that the bedrock under the uplift ring has risen about 200 m following the meteorite impact. The offsets of the peak and the uplift ring's centres, relative to the diameter of the crater centre, allow us to conclude that the JCB was formed by steeply inclined impact (∼50–60° to the horizontal) from the eastern direction.