Geophysics and Geophysical Exploration ISSN:1229-1064(Print) 2384-051X(Online) 지구물리와 물리탐사

We estimated near-surface shear-wave velocity (vs) at the Hwacheon seismic station using a geologic log of a well, microtremors recorded during a period of 56 days, and records of three teleseismic events (Mw ≥ 6.0). The vs of the 10-m thick soil layer ( = 296 m/s) was determined from horizontal-to-vertical spectral ratios of microtremors recorded at the surface. The average vs ( = 1,309 m/s) from the surface to the 96-m depth of a borehole sensor, was computed using spectral coherence analyses of data recorded by surface- and borehole-sensors for the three teleseismic events. Using these calculated values of and , the computed bedrock vs is 2,150 m/s and the time-averaged vs to a 30-m depth is 696 m/s. Accordingly the Hwacheon seismic station is regarded as a relatively good site. The deduced near-surface vs can be used for further quantitative evaluation of site amplification and earthquake hazard.