LAUSR

In Korea, several problems have been identified in the design standards for earthquake resistance, within a high-frequency range, due to the inappropriate characterisation of local site amplification characteristics. Among the methods that have been suggested for analysis of site amplification characteristics is one that uses the H/V spectral ratio of ground motions, which was used in this study. The method can be applied to S-waves, coda waves, and background noise. Based on a series of 15 aftershocks of the Fukuoka earthquake of 20 March 2005, analyses were conducted for a total of 267 sets of ground motion data observed at seismic stations in Korea. Most of the seismic stations suggested consistent site amplification characteristics among the three types of seismic energies despite a logarithmic difference of three or larger in the Fourier transform value of the observed waves, and also despite long epicentre distances, even greater than 600 km. The stations KHD, GSU, HSB and TJN showed no dominant resonance frequencies because they are located on solid bedrock or have borehole seismic sensors. It is necessary to use care when considering stations GKP1, KRA, and SNU, which have distinct resonance frequencies. The results of this study are essential for the effective design of earthquake-resistant structures and also for reliable seismic source and crustal attenuation studies. This study applied a method that uses the H/V spectral ratio of ground motions to analyse site amplification characteristics. Its application was extended to S-waves, coda waves, and background noise. Analysis of data at seismic stations in Korea suggested consistent site amplification characteristics among the three types of seismic energies despite a logarithmic difference in the Fourier transform values.