Crustal Structure in Southern Korea from Joint Analysis of Teleseismic Receiver Functions and Surface-Wave Dispersion

摘要

We estimated crustal structures under 18 broadband stations in southern Korea by combining receiver functions and surface-wave dispersion with the genetic algorithm (GA). Estimated crustal structures were analyzed together with previously determined structures under four stations (GKP, INCN, SNU, and TJN) in Chang et al. (2004). The trend of Moho depths estimated from the GA inversion generally coincides with the surface topography, ranging from 26 km to 36 km in the inland. However, the Moho depth distribution does not agree with the topography in the region around the Chugaryeong fault, which extends approximately north-northeast–south-southwest in the central Korean Peninsula. The shallow Moho depth under this region may be related to consequential crustal thinning processes along the fault caused by extensional tectonic movements. Another discrepancy is found in the Gyeongsang basin formed in a retroarc setting by the subduction of the Izanagi Plate in the early Cretaceous. A thick crust observed in the basin may be caused by two factors—maturity of the basin and underplating of magma materials. Average crustal velocities vary from 6.02 km/sec to 6.51 km/sec in southern Korea. This variation indicates that crustal structures in southern Korea involve diverse velocity profiles that change rapidly with distance. Remarkably, a clear velocity discontinuity is observed at the depth range of 8–10 km under several stations.