Moho depth and crustal VP/VS variation in southern Korea from teleseismic receiver functions:: Implication for tectonic affinity between the Korean Peninsula and China

We estimated Moho depths and V-P/V-S ratios of the crust under 21 broad-band stations in southern Korea by using a grid search in the crustal thickness-V-P/V-S ratio (H-K) 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.