Polarization Analysis of Ultra Low Frequency (ULF) Geomagnetic Data for Monitoring Earthquake-precusory Phenomenon in Korea

지진 전조현상 모니터링을 위한 ULF 대역 지자기장의 분극 분석

  • Yang, Jun-Mo (Deep Sea and Marine Resource Research Division, Ocean R&D Inst.) ;
  • Lee, Heui-Soon (Department of Science Education, Gyeongin National University of Education) ;
  • Lee, Young-Gyun (Department of Earth Science Education, Seoul National University)
  • 양준모 (한국해양연구원 심해.해저자원연구부) ;
  • 이희순 (경인교육대학교 과학교육과) ;
  • 이영균 (서울대학교 지구과학교육과)
  • Received : 2010.07.20
  • Accepted : 2010.08.05
  • Published : 2010.08.31

Abstract

Since the 1990's, a number of ULF geomagnetic disturbance associated with earthquake occurrences have actively been reported, and polarization analysis of geomagnetic fields becomes one of potential candidates to be capable of predicting short-term earthquake. This study develops the modified polarization analysis method based on the previous studies, and analyzes three-component geomagnetic fields obtained at Cheongyang geomagnetic observatory using the developed method. A daily polarization value (the ratio of spectral power of horizontal and vertical geomagnetic field) is calculated with a focus on the 0.01 Hz band, which is known to be the most sensitive to seismogenic ULF radiation. We analyze a total of 10 months of geomagnetic data obtained at Cheongyang observatory, and compare the polarization values with the Kp index and the earthquake occurred in the analysis period. The results show that there is little correlation between the temporal variations of polarization values and Kp index, but remarkable increases in polarization values are identified which are associated with two earthquakes. Comparison the polarization values obtained at Cheongyang and Kanoya observatory indicates that the increases of polarization values at Cheongyang might be due to not global geomagnetic induction but the locally occurred earthquakes. Furthermore, these features are clearly shown in normalized polarization values, which take account in the statistical characteristics of each geomagnetic field. On the basis of these results, polarization analysis can be used as promising tool for monitoring the earthquake-precursory phenomenon.

Acknowledgement

Supported by : 기상청

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