Journal of the Korean earth science society (한국지구과학회지)

The Korean Earth Science Society (한국지구과학회)
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A Study on Temporal Variations of Geomagnetic Transfer Functions and Polarization Values Obtained at Cheongyang Geomagnetic Observatory

청양 지자기관측소에서 획득된 지자기전달함수와 분극값의 시간변동성에 대한 연구

  • Yang, Jun-Mo (Deep Sea and Marine Resource Research Division, Korea Ocean Research and Development Institute) ;
  • Lee, Heui-Soon (Department of Science Education, Gyeongin National University of Education) ;
  • Oh, Seok-Hoon (Department of Geosystem Engineering, Kangwon National University)
  • 양준모 (한국해양연구원 심해.해저자원연구부) ;
  • 이희순 (경인교육대학교 과학교육과) ;
  • 오석훈 (강원대학교 지구시스템공학부)
  • Published : 2009.12.31
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Abstract

We analyzed a total of six months of geomagnetic data obtained at Cheonyang observatory, which is operated by Korean Meteorological Administration, to monitor earthquake precursors. Geomagnetic transfer functions (GTFs) and polarization values, which reflect the time-variations of the resistivity of subsurface, were estimated from 3-component geomagnetic data. The time-variant fluctuations were compared with the earthquake events occurred in the same period. Now that the daily GTFs show fairly irregular variations, we can not identify any correlation with the already occurred earthquakes and Kp index. On the other hand, we detect clear increases of the Ultra-Low-Frequency (ULF) band polarization values before the earthquakes, but the similar features are also observed even though the earthquake did not occur. This result may indicate that these time-variations are not just due to the earthquake precursor. For further understanding about these results, we need to investigate the relationship between the previous earthquake events and the geomagnetic data of other observatories.

지진전조현상을 모니터링 하기 위해 기상청이 운영하고 있는 청양 지자기관측소에서 총 6개월간 획득된 지자기장 자료를 분석하였다. 지자기 3성분 자료로부터 지하의 전기비저항 변화를 반영하는 전달함수 및 분극값을 계산하였고, 이를 동일기간 발생한 지진이벤트와 비교하였다. 전달함수의 경우 일별 전달함수 값의 변화가 상당히 심하였으며, 발생한 지진 및 Kp 인덱스와의 상관성을 찾기 어려웠다. ULF 대역 자기장은 지진발생 전 뚜렷한 분극값의 증가가 관찰되었으나, 지진이 발생하지 않은 기간에도 이러한 변동 패턴이 나타났다. 따라서 이러한 분극값의 변화는 지진 전조현상으로 단정하기에는 한계가 있고, 향후 타 관측소 자료의 추가적인 확보 및 분석을 통해 과거 발생한 일정규모 이상의 지진과 관련성을 분석할 필요가 있다.

Keywords

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