Seismic reflection image of the crust structure along the KCRT-2002 profile in the southern Korean peninsula

Abstract

In order to reveal the perspective of velocity structure in the southern part of the Korean peninsula, a seismic experiment was carried out along a WNW-ESE profile of 294-km length in December, 2002. In 100-m deep drill-holes, seismic explosives of 1000 and 500 kg were detonated on the west coast and near the center of the profile, respectively. The seismic signals were detected by 198 portable seismometers spaced approximately at an 1.5 km interval and digitally recorded for 115 s at an 120-Hz sampling rate. Normal moveout corrections were applied to yield reflection images for P, S, and PS converted waves followed by time-to-depth conversion through forward modeling of travel times using the fourth-order equation for wide angle reflections. Three distinct reflection events are identified at average two-way travel times of 4.90, 8.02, and 10.99 s on the NMO corrected P-wave sections. Their converted depths are 13.71, 23.37, and 33.67 km, respectively, and the P-wave interval velocities between the depth boundaries including the free surface are 5.60, 6.19, and 6.96 km/s from top to bottom. The reflection Moho is imaged as a sharp boundary in the middle of the profile while multi-layers are featured near both ends of the profile.