Moho Depth and Crustal VP/VS Variation in Southern Korea from Teleseismic Receiver Functions: Implication for Tectonic Affinity between the Korean Peninsula and China

Abstract

We estimated Moho depths and V P / V S ratios of the crust under 21 broadband stations in southern Korea by using a grid search in the crustal thickness– V P / V S ratio ( H-κ ) domain. The Moho depth varies from 25.9 km to 32.5 km, and the V P / V S ratio ranges from 1.71 to 1.82 inland. Moho depths in the southernmost area of the Korean Peninsula were estimated shallower than those of the previous results obtained assuming a Poisson solid in the joint analysis of receiver functions and surface-wave dispersion. This southernmost area is roughly in accord with the Yeongnam massif, where relatively high V P / V S ratios of 1.78–1.82 are estimated. On the contrary, comparatively low V P / V S ratio measurements (1.71–1.76) are generally distributed in the Gyeonggi massif, which is located in the central area of the Korean Peninsula. The major factor for the high V P / V S ratios in the Yeongnam massif is thought to be the plagioclase-rich mafic composition of the lower crust rather than partial melting or crustal fluids, because high crustal S -wave velocities are reported in the Yeongnam massif. The mafic composition might have been supplied by the magmatic underplating. From the clearly divided feature of V P / V S ratios in southern Korea and the V P / V S ratio similarities between southern Korea and China, it seems that the Yeongnam massif might be related to the Sino-Korea craton, whereas the Gyeonggi massif is related to the Yangtze craton.