국내 중규모 지진에 대한 계측진도 추정식 연구 (Study on the Relations to Estimate Instrumental Seismic Intensities for the Moderate Earthquakes in South Korea)

서지정보

· 발행기관 : 한국지진공학회
· 수록지 정보 : 한국지진공학회논문집 / 22권 / 6호 / 323 ~ 332페이지
· 저자명 : 연관희, 이강렬

초록

Recent two moderate earthquakes (2016 Mw=5.4 Gyeongju and 2017 Mw=5.5 Pohang) in Korea provided the unique chance of developing a set of relations to estimate instrumental seismic intensity in Korea by augmenting the time-history data from MMI seismic intensity regions above Ⅴ to the insufficient data previously accumulated from the MMI regions limited up to Ⅳ. The MMI intensity regions of Ⅴ and Ⅵ was identified by delineating the epicentral distance from the reference intensity statistics in distance derived by using the integrated MMI data obtained by combining the intensity survey results of KMA (Korea Meteorological Administration) and ‘DYFI (Did You Feel It)’ MMIs of USGS. The time-histories of the seismic stations from the MMI intensity regions above Ⅴ were then preprocessed by applying the previously developed site-correction filters to be converted to a site-equivalent condition in a manner consistent with the previous study. The average values of the ground-motion parameters for the three ground motion parameters of PGA, PGV and BSPGA (Bracketed Summation of PGA per second for 30 seconds) were calculated for the MMI=Ⅴ and Ⅵ and used to generate the dataset of the average values of the ground-motion parameters for the individual MMIs fromⅠ to Ⅵ. Based on this dataset, the linear regression analysis resulted in the following relations with proposed valid ranges of MMI.


MMI = 2.36 × log10(PGA(gal)) + 1.44 (Ⅰ≤ MMI < Ⅶ ) MMI = 2.44 × log10(PGV(kine)) + 4.86 (Ⅰ≤ MMI < Ⅹ ) MMI = 2.59 × log10(BSPGA(gal․sec)) - 1.02 (Ⅰ≤ MMI < Ⅶ～Ⅷ )

Comparison with other empirical relations developed for the various seismological environments such as western, central, and eastern U.S. leads to the conclusion that the PGV-MMI relation above can be reasonably extrapolated to the MMI up to Ⅹ beyond the observed MMI limit of Ⅵ, while the PGA-MMI is only valid up to Ⅶ. An explanatory interpretation was also tried for the obvious difference of the MMI attenuation pattern in distance between the two moderate earthquakes by introducing the crustal structure with Conrad discontinuity, depth-varying Q-values and the relevant wave phases.

영어초록

Recent two moderate earthquakes (2016 Mw=5.4 Gyeongju and 2017 Mw=5.5 Pohang) in Korea provided the unique chance of developing a set of relations to estimate instrumental seismic intensity in Korea by augmenting the time-history data from MMI seismic intensity regions above Ⅴ to the insufficient data previously accumulated from the MMI regions limited up to Ⅳ. The MMI intensity regions of Ⅴ and Ⅵ was identified by delineating the epicentral distance from the reference intensity statistics in distance derived by using the integrated MMI data obtained by combining the intensity survey results of KMA (Korea Meteorological Administration) and ‘DYFI (Did You Feel It)’ MMIs of USGS. The time-histories of the seismic stations from the MMI intensity regions above Ⅴ were then preprocessed by applying the previously developed site-correction filters to be converted to a site-equivalent condition in a manner consistent with the previous study. The average values of the ground-motion parameters for the three ground motion parameters of PGA, PGV and BSPGA (Bracketed Summation of PGA per second for 30 seconds) were calculated for the MMI=Ⅴ and Ⅵ and used to generate the dataset of the average values of the ground-motion parameters for the individual MMIs fromⅠ to Ⅵ. Based on this dataset, the linear regression analysis resulted in the following relations with proposed valid ranges of MMI.




MMI = 2.36 × log10(PGA(gal)) + 1.44 (Ⅰ≤ MMI < Ⅶ ) MMI = 2.44 × log10(PGV(kine)) + 4.86 (Ⅰ≤ MMI < Ⅹ ) MMI = 2.59 × log10(BSPGA(gal․sec)) - 1.02 (Ⅰ≤ MMI < Ⅶ～Ⅷ )

Comparison with other empirical relations developed for the various seismological environments such as western, central, and eastern U.S. leads to the conclusion that the PGV-MMI relation above can be reasonably extrapolated to the MMI up to Ⅹ beyond the observed MMI limit of Ⅵ, while the PGA-MMI is only valid up to Ⅶ. An explanatory interpretation was also tried for the obvious difference of the MMI attenuation pattern in distance between the two moderate earthquakes by introducing the crustal structure with Conrad discontinuity, depth-varying Q-values and the relevant wave phases.

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