Site Amplification Characteristics of the Seismic Stations at Jeju Island, Korea, using Background Noise, S-wave Energy, and Coda waves from Kumamoto Earthquakes Series

In Korea, a number of problems the design standards for earthquake resistance, within a high frequency range, due to the inappropriate of local site amplification characteristics. Among the methods that have been suggested for analysis of site amplification characteristics, this study applied the method of H/V spectral ratio of ground motions. Its application has been extended to S-waves, coda waves, and background noise. Based on a series of aftershocks of the Kumamoto earthquake, April 16th (2016), analysis was conducted for more than 250 sets of horizontal and vertical ground motions observed at seismic stations in Jeju Island(Korea). Most of the seismic stations showed consistent site amplification characteristics among three types of seismic energies despite a logarithmic difference of three or larger in the Fourier transform values of the observed waves and also despite long epicenter distances, even greater than 500 km. The stations JJU, SGP, HALB, SSP, GOS1 and JJB (Fig. 1) showed characteristics of resonance frequencies, respectively. It is necessary to study more precisely on characteristics of resonance frequencies of the sites, concerning kappa.