1D crustal velocity structure beneath broadband seismic stations in the Okcheon Fold Belt of Korea by receiver function analysis

Abstract

The crustal velocity structure is one of the fundamental and important subjects for seismology. The receiver function analysis technique is applied to the data from six broadband stations (HKU, JSB, MGB, NPR, SND, and TJN) in the Okcheon Fold Belt of Korea. The genetic algorithm that is independent of the initial model is adopted as the inversion method. The surfacewave dispersion data are used as constraints in the receiver function inversion. Among these stations, the receiver function analyses on the velocity structures beneath stations JSB, MGB, and SND have not been carried out before. Since recent large teleseismic earthquake data of magnitudes larger than 6.5 are included in the analyses, the velocity structures found in the present work are expected to be more reliable than those by the previous independent works. The characteristics of crustal velocity structures in the Okcheon Fold Belt are revealed. The crustal thickness in the Okcheon Fold Belt is estimated to be 32−34 km. The Moho depths are 32, 34, 32, 32−34, 32, and 32 km beneath stations HKU, JSB, MGB, NPR, SND, and TJN, respectively. These results are similar to those found in the previous independent works. The low velocity layers around the depth of 10 km are also found. Geological interpretation or correlations are, however, skipped since they are not always distinctive. Midcrustal velocity discontinuities at the 18-km depth are found beneath stations NPR and TJN although the former is only distinctive. Those at the 22-km depth are also found beneath stations HKU and SND. The crustal velocity structures estimated in this study will be able to offer fundamental information to other geologists, and the geological and tectonic interpretation of the velocity structures is expected.