근거리 지진관측자료의 S파를 이용한 지진규모 평가 연구
A Study on Estimating Earthquake Magnitudes Based on the Observed S-Wave Seismograms at the Near-Source Region
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초록
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.
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.
참고문헌 (13)
- Korea Meteorological Administration, "Documentation for the second half of year 2023 Earthquake", Tsunami and Volcanic activity Council of Observation Agencies, 59~ (2023)
- "NECIS (National Earthquake Comprehensive Information System)of Korea Meteorological Administration"[URL]
- Cho CS, "Personal Communication", ~ (2023)
- Atkinson GM, "A high-frequency magnitude scale", Bull Seismol Soc Am, 85(3), pp.825~833 (1995)
- Hanks TC, "A moment magnitude scale", J Geophys Res, 84(B5), pp.2348~2350 (1979)
- Boore DM, "Simulation of ground motion using the stochastic method", Pure Appl Geophys, 160, pp.635~676 (2003)
- Lior I, "The relation between ground motion, earthquake source parameters and attenuation : Implications for source parameter inversion and ground motion prediction equations", J Geophys Res, 123(7), pp.5886~5901 (2018)
- Lior I, "Generic source parameter determination and ground-Motion prediction for earthquake early warning", Bull Seismol Soc Am, 110(1), pp.345~356 (2020)
- Yun KH, "Method of estimating the Ground-Motion Intensity Measures at a nearby site by using the Time-domain Transformation of Site Response", Korean Society of Earth and Exploration Geophysicists, 13(2), pp.219~226 (2010)
- Yun KH, "Two-dimensional Q tomography inversion for the southern part of the Korean Peninsula", Ph. D, pp.2007
- Yun KH, "Inversion of stochastic earthquake model parameters using the modified Levenberg-Marquardt’s method in Korea", Proceedings of EESK Conference, pp.20~27 (2002)
- Brune JN, "Tectonic stress and the spectra of seismic shear waves from earthquakes", J Geophys Res, 75(26), pp.4997~5009 (1970)
- Brune JN, "Correction", J Geophys Res, 76(20), pp.5002~ (1971)