Comparative analyses of seismic site conditions and microzonation of the major cities in Gangwon Province, Korea

초록

To determine the seismic site conditions and microzonation of Chuncheon, Wonju and Gangneung cities in the Gangwon Province, Korea, the dispersion curves of Rayleigh waves were derived at 313 sites by the extended spatial autocorrelation (ESPAC) method. Using the shear-wave velocities (Vs) determined from dispersion curves, average depth to the bedrock (D-b) and Vs at the top of the bedrock (Vs(b)), the overburden layer (Vs(o)) and the top 30 m depth layer (Vs(30)) were determined. The resonance frequencies (f(r)) were then computed using both Db and Vs(o). The estimated averages of the three cities were 13 +/- 7m for Db, 472 +/- 109 m/s for Vsb, 248 +/- 44 m/s for Vs(o), 411 +/- 157m/s for Vs(30) and 5.8 +/- 2.8Hz for f(r). Microzonation maps based on the proxy-based Vs30 indicated that the three cities were mainly categorised into National Earthquake Hazards Reduction Program (NEHRP) classes B, C and D, with a minor proportion of A. Although no area was estimated to be in class E using the proxy-based Vs(30), the Vs(30) values derived from the recorded Rayleigh waves at 13 sites in Gangneung were less than 180m/s. This indicates a greater vulnerability to seismic amplification during large earthquakes in this city, which had the smallest Vs(o), Vs(30) and f(r), and the greatest D-b of the three cities. Microzonation maps, together with information for f(r), can be effectively used for seismic risk assessments, urban planning, and disaster management.

키워드