Journal of the Korean earth science society (한국지구과학회지)

The Korean Earth Science Society (한국지구과학회)
권호 표지
DOI QR코드

DOI QR Code

A Study of the Seocheon Fireball Explosion on September 23, 2020

2020년 9월 23일 서천 화구 폭발 관측 연구

  • Che, Il-Young (Earthquake Research Center, Korea Institute of Geoscience and Mineral Resources) ;
  • Kim, Inho (Earthquake Research Center, Korea Institute of Geoscience and Mineral Resources)
  • 제일영 (한국지질자원연구원 지진연구센터) ;
  • 김인호 (한국지질자원연구원 지진연구센터)
  • Received : 2021.10.28
  • Accepted : 2021.11.24
  • Published : 2021.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

On September 23, 2020, at 1:39 a.m., a bright fireball above Seocheon was observed across the country. Two fireball explosions were identified in the images of the All-Sky Camera (ASC), and the shock waves were recorded at seismic and infrasound stations in the southwestern Korean Peninsula. The location of the explosion was estimated by a Bayesian-based location method using the arrival times of the fireball-associated seismic and infrasound signals at 17 stations. Realistic azimuth- and rang-dependent propagation speeds of sound waves were incorporated into the location method to increase the reliability of the results. The location of the sound source was found to be 36.050°N, 126.855°E at an altitude of 35 km, which was close to the location of the second fireball explosion. The two explosions were identified as sequential infrasound arrivals at local infrasound stations. Simulations of waveforms for long ranges explain the detection results at distant infrasound stations, up to ~266 km from the sound source. The dominant period of the signals recorded at five infrasound stations is about 0.4 s. A period-energy relation suggests the explosion energy was equivalent to ~0.3 ton of TNT.

2020년 9월 23일 새벽 1시 39분경 전국 여러 곳에서 목격된 서천 화구는 대기권에 진입 후 두 차례 폭발했음이 전천 카메라 영상에 확인되었으며, 충격파는 한반도 서남부 지역 지진 및 인프라사운드 관측소에 기록되었다. 17개 관측소에서 측정된 화구 지진파 및 음파의 도달 시간 정보와 베이지안에 기초한 격자탐색법으로 화구 발생 위치를 추정하였다. 위치결정에는 대기권 바람 분포에 따른 음파 속도 변화를 반영하여 계산 결과의 신뢰도를 높였다. 화구 발생 위치는 36.050°N, 126.855°E, 고도 35 km로 전천 카메라 영상에서 관측된 두번째 화구 위치와 유사하였다. 서해 상공에서 한반도 내륙으로 입사하며 발생한 두 차례의 폭발이 근거리 인프라사운드 관측소에서 확인되었다. 또한 서천 화구 폭발 충격음은 장거리를 전파하여 최대 ~266 km에 위치하는 관측소에서도 기록되었으며 파형 모델링이 관측 결과를 뒷받침하였다. 인프라사운드 5개 관측소에서 측정된 두번째 화구 폭발 신호의 평균 주기는 ~0.4 s이며, 주기-폭발 에너지 관계식을 적용했을 때 서천 화구의 폭발 에너지는 약 0.3 ton TNT 폭발에 상응한다.

Keywords

Acknowledgement

유럽중기예보모델(ECMWF)을 제공한 CTBTO/PTS(Provisional Technical Secretariat)에 감사드립니다. 화구 지진파 분석을 위해 기상청과 한국지질자원연구원 지진관측망 자료를 활용하였습니다. 한국천문연구원의 보도자료 원문을 인용하였으며, 보도자료 이외 관측 시간 정보 등을 제공해 주신 동 연구원의 박장현 박사님께 감사드립니다. 본 연구는 한국지질자원연구원 기본사업인 '지진활동 추적 및 관측자료 통합관리기술 개발(GP2020-017)' 과제의 일환으로 수행되었습니다.

References

  1. Blom, P., 2014, GeoAc: Numerical Tools to Model Acoustic Propagation in the Geometric Limit. Software. Los Alamos National Laboratory.
  2. Brown, P.G., Spalding, R.E., ReVelle, D.O., Tagliaferri, E., and Worden, S.P., 2002, The flux of small near-Earth objects colliding with the Earth. Nature 420, 294-296. https://doi.org/10.1038/nature01238
  3. Brown, P.G., Kalenda, P., ReVelle, D.O., and Borovicka, J., 2003, The Moravka meteorite fall: 2. Interpretation of infrasonic and seismic data. Meteoritics & Planetary Science, 38, 989-1003. https://doi.org/10.1111/j.1945-5100.2003.tb00294.x
  4. Cansi, Y., 1995, An automatic seismic event processing for detection and location: The PMCC method. Geophysical Research Letters, 22, 1021-1024. https://doi.org/10.1029/95GL00468
  5. Ceplecha, Z., Borovicka, J., Elford, W.G., ReVelle, D.O., Hawkes, R.L., Porubcan, V., and Simek, M., 1998, Meteor phenomena and bodies. Space Science Reviews, 84, 327-471. https://doi.org/10.1023/A:1005069928850
  6. Che, I.-Y., Kim, G.Y., and Lee, H.-I., 2016, Seismic and infrasonic analysis of the 9 March 2014 fireball in South Korea. Geosciences Journal, 20(2), 209-220. https://doi.org/10.1007/s12303-015-0034-1
  7. Edwards, W.N., Brown, P.G., Weryk, R.J., and ReVelle, D.O., 2008, Infrasonic observations of meteoroids: Preliminary results from a coordinated optical-radar-infrasound observing campaign. Earth Moon Planets, 102(1-4), 221-229. https://doi.org/10.1007/s11038-007-9154-6
  8. Edwards, W.N., 2009, Meteor generated infrasound: theory and observation. In Le Pichon, A., Blanc, E., and Hauchecorne, A., Infrasound monitoring for atmospheric studies. Springer, 361-414.
  9. Ens, T.A., Brown, P.G., Edwards, W.N., and Silber, E.A., 2012, Infrasound production by bolides: A global statistical study. Journal of Atmospheric and Solar-Terrestrial Physics, 80, 208-229. https://doi.org/10.1016/j.jastp.2012.01.018
  10. Evatt, G.W., Smedley, A.R.D., Joy, K.H., Hunter, L., Tey, W.H., Abrahams, I.D., and Gerrish, L., 2020, The spatial flux of Earth's meteorite falls found via Antarctic data. Geology, 48, 683-687. https://doi.org/10.1130/g46733.1
  11. Gibson, R.G. and Norris, D.E., 2004, Integration of InfraMAP software with near-real-time atmospheric characterizations. BBN Technologies Final Report for Air Force Research Laboratory (AFRL/VSBYE) under Contract DTRA01-01-C-0084.
  12. Ishihara, Y., Tsukada, S., Sakai, S., Hiramatsu, Y., and Furumoto, M., 2003, The 1998 Miyako fireball's trajectory determined from shock wave records of a dense seismic array. Earth Planets Space, 55, e9-e12. https://doi.org/10.1186/BF03351752
  13. Jensen, F.B., Kuperman, W.A., Porter, M.B., and Schmidt, H., 1994, Computational Ocean Acoustics. AIP Press, New York.
  14. Modrak, R.T., Arrowsmith, S.J., and Anderson, D.N., 2010, A Bayesian framework for infrasound location. Geophysical Journal International, 181(1), 399-405. https://doi.org/10.1111/j.1365-246X.2010.04499.x
  15. Pierce, A.D., Moo, C.A., and Posey, J.W., 1973, Generation and Propagation of Infrasonic Waves. Technical Report AFCRL-TR-73-0135, Air Force Cambridge Research Laboratories, Bedford, Mass.
  16. ReVelle, D.O., Brown, P.G., and Spurny, P., 2004, Entry dynamics and acoustics/infrasonic/seismic analysis for the Neuschwanstein meteorite fall. Meteoritics & Planetary Science, 39, 1605-1626. https://doi.org/10.1111/j.1945-5100.2004.tb00061.x
  17. Walker, K.T., Hedlin, M.A.H., de Groot-Hedlin, C., Vergoz, J., Le Pichon, A., and Drob, D.P., 2010, Source location of the 19 February 2008 Oregon bolide using seismic networks and infrasound arrays. Journal of Geophysical Research, 115, B12329. https://doi.org/10.1029/2010jb007863