Econ. Environ. Geol. 2008; 41(2): 225-242

Published online April 30, 2008

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

The Site Effect of the Broadband Seismic Stations in Korea

Soung Hoon Wee1 and Sung Kyun Kim2*

1Earthquake Research Center, KIGAM, Daejeon 305-350, Korea
2School of Earth and Environmental Sciences, Chonnam National University, Gwangju 500-757, Korea

Correspondence to :

Sung Kyun Kim

kimsk@jnu.ac.kr

Received: January 10, 2008; Accepted: April 11, 2008

Abstract

The site effect for 23 broadband seismic stations in the southern Korean Peninsula was estimated by using the spectral ratio of coda waves. In principle, the site effect means the pure amplification below the station excluding effects of seismic source and attenuation in the wave transmission. However, the site effect determined in this study is equivalent with the relative site amplification factor to the mean amplification for all stations. A total of 500 three-component seismograms from 35 earthquakes, of which magnitude ranged from 2.5 to 5.1 occurred from January, 2001 to January, 2007 was used to obtain the site amplification factor. The site amplification factors were estimated for the frequency bands centered at 0.2, 0.5, 1, 2, 5, 10, 15, and 20 Hz. It was found that the factors for two horizontal components of transverse and radial records were concordant with each other in the all frequency bands. However, the factor for the vertical component was found to be systematically lower than those for two horizontal components. The factors obtained in the low frequency band below 2 Hz ranged from 0.5 to 1.5 in all seismic stations except for KMA and KIGAM stations in Bagryeongdo (BRD1 and BRD2) of which factor showed high value above 1.5. Some stations such as SEO, SNU, HKU, NPR, and GKP1 showed high value above 1.5 in the high frequency band from 5 to 20 Hz. Especially, the factors of GKP1 station represented extremely high value ranging from 1.8 to 7.8. Also, the factors for stations of KWJ, SND, and ULJ showed low value below 0.5. The spatial distribution for the relative amplification factor represented a tendency of being approximately lower in north-eastern area than south-western area in the southern Korean Peninsula.

Keywords site effect, seismic station, coda-normalization, Korean Peninsula

Article

Econ. Environ. Geol. 2008; 41(2): 225-242

Published online April 30, 2008

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

The Site Effect of the Broadband Seismic Stations in Korea

Soung Hoon Wee1 and Sung Kyun Kim2*

1Earthquake Research Center, KIGAM, Daejeon 305-350, Korea
2School of Earth and Environmental Sciences, Chonnam National University, Gwangju 500-757, Korea

Correspondence to:

Sung Kyun Kim

kimsk@jnu.ac.kr

Received: January 10, 2008; Accepted: April 11, 2008

Abstract

The site effect for 23 broadband seismic stations in the southern Korean Peninsula was estimated by using the spectral ratio of coda waves. In principle, the site effect means the pure amplification below the station excluding effects of seismic source and attenuation in the wave transmission. However, the site effect determined in this study is equivalent with the relative site amplification factor to the mean amplification for all stations. A total of 500 three-component seismograms from 35 earthquakes, of which magnitude ranged from 2.5 to 5.1 occurred from January, 2001 to January, 2007 was used to obtain the site amplification factor. The site amplification factors were estimated for the frequency bands centered at 0.2, 0.5, 1, 2, 5, 10, 15, and 20 Hz. It was found that the factors for two horizontal components of transverse and radial records were concordant with each other in the all frequency bands. However, the factor for the vertical component was found to be systematically lower than those for two horizontal components. The factors obtained in the low frequency band below 2 Hz ranged from 0.5 to 1.5 in all seismic stations except for KMA and KIGAM stations in Bagryeongdo (BRD1 and BRD2) of which factor showed high value above 1.5. Some stations such as SEO, SNU, HKU, NPR, and GKP1 showed high value above 1.5 in the high frequency band from 5 to 20 Hz. Especially, the factors of GKP1 station represented extremely high value ranging from 1.8 to 7.8. Also, the factors for stations of KWJ, SND, and ULJ showed low value below 0.5. The spatial distribution for the relative amplification factor represented a tendency of being approximately lower in north-eastern area than south-western area in the southern Korean Peninsula.

Keywords site effect, seismic station, coda-normalization, Korean Peninsula

    KSEEG
    Apr 30, 2024 Vol.57 No.2, pp. 107~280

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