Three-dimensional Surface-wave Group-velocity Tomography of the Southern Korean Peninsula Using Ambient Seismic Noise Cross-correlation

The uppermost crustal velocity structure of the southern Korean peninsula is investigated based on surface-wave group-velocity using the cross-correlation technique of ambient seismic noise. We use seismograms from 91 accelerograph stations in the southern Korean peninsula recorded during August of 2005. From the correlation results of 4095 data pairs, arrival times of Green's functions between pair of stations are measured in discrete bins of frequency band with overlap. The arrival times for each bin of frequency band are inverted in order to obtain two-dimensional tomographic map of Rayleigh wave group-velocity. Then we obtain dispersion curves by extracting group-velocities at each center frequency of the bins for each tomographic cell. Shear-wave velocity to depth inversion of the dispersion curve at each cell produces one-dimensional velocity profile. After aligning each profile at each tomographic cell, we can obtain a three-dimensional uppermost crustal velocity model above about 5 km depth with high resolution in the southern Korean peninsula.