Journal of the Earthquake Engineering Society of Korea (한국지진공학회논문집)

Earthquake Engineering Society of Korea (한국지진공학회)
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A Study on Estimating Earthquake Magnitudes Based on the Observed S-Wave Seismograms at the Near-Source Region

근거리 지진관측자료의 S파를 이용한 지진규모 평가 연구

  • Yun, Kwan-Hee (Structural & Construction Tech. Group, Korea Electric Power Corporation (KEPCO) Research Institute) ;
  • Choi, Shin-Kyu (Structural & Construction Tech. Group, KEPCO Research Institute) ;
  • Lee, Kang-Ryel (Structural & Construction Tech. Group, KEPCO Research Institute)
  • 연관희 (한전전력연구원 구조건설연구실) ;
  • 최신규 (한전전력연구원 구조건설연구실) ;
  • 이강렬 (한전전력연구원 구조건설연구실)
  • Received : 2023.12.21
  • Accepted : 2024.01.23
  • Published : 2024.05.01
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Abstract

There are growing concerns that the recently implemented Earthquake Early Warning service is overestimating the rapidly provided earthquake magnitudes (M). As a result, the predicted damages unnecessarily activate earthquake protection systems for critical facilities and lifeline infrastructures that are far away. This study is conducted to improve the estimation accuracy of M by incorporating the observed S-wave seismograms in the near source region after removing the site effects of the seismograms in real time by filtering in the time domain. The ensemble of horizontal S-wave spectra from at least five seismograms without site effects is calculated and normalized to a hypocentric target distance (21.54 km) by using the distance attenuation model of Q(f)=348f0.52 and a cross-over distance of 50 km. The natural logarithmic mean of the S-wave ensemble spectra is then fitted to Brune's source spectrum to obtain the best estimates for M and stress drop (SD) with the fitting weight of 1/standard deviation. The proposed methodology was tested on the 18 recent inland earthquakes in South Korea, and the condition of at least five records for the near-source region is sufficiently fulfilled at an epicentral distance of 30 km. The natural logarithmic standard deviation of the observed S-wave spectra of the ensemble was calculated to be 0.53 using records near the source for 1~10 Hz, compared to 0.42 using whole records. The result shows that the root-mean-square error of M and ln(SD) is approximately 0.17 and 0.6, respectively. This accuracy can provide a confidence interval of 0.4~2.3 of Peak Ground Acceleration values in the distant range.

Keywords

Acknowledgement

본 논문은 한전 전력연구원의 『변전소 지진관측정보 자동 품질평가 기술개발(R22SA03)』 연구 일환으로 수행되었음.

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