Journal of the Korean earth science society (한국지구과학회지)

The Korean Earth Science Society (한국지구과학회)
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Electrical Anisotropy of the Okchon Belt Inferred from Magnetotelluric Data

자기지전류 탐사 자료에 나타나는 옥천대의 전기적 이방성 구조

  • Lee, Choon-Ki (Department Earth Science Education, Seoul National University) ;
  • Lee, Heui-Soon (Department Science Education, Gyeongin National University of Education) ;
  • Kwon, Byung-Doo (Department Earth Science Education, Seoul National University) ;
  • Cho, In-Ky (Department Geophysics, Kangwon National University) ;
  • Oh, Seok-Hoon (Department Geosystem Engineering, Kangwon National University) ;
  • Song, Yoon-Ho (Geothermal Resources Group, Korea Institute of Geoscience and Mineral Resources) ;
  • Lee, Tae-Jong (Geothermal Resources Group, Korea Institute of Geoscience and Mineral Resources)
  • 이춘기 (서울대학교 지구과학교육과) ;
  • 이희순 (경인교육대학교 과학교육과) ;
  • 권병두 (서울대학교 지구과학교육과) ;
  • 조인기 (강원대학교 지구물리학과) ;
  • 오석훈 (강원대학교 지구시스템공학과) ;
  • 송윤호 (한국지질자원연구원 지열자원연구실) ;
  • 이태종 (한국지질자원연구원 지열자원연구실)
  • Published : 2007.04.30
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Abstract

The MT data at the Okchon Belt show peculiar phase responses exceeding $90^{\circ}$. A reasonable explanation is that those responses are due to an electrical anisotropy structure which is composed of a narrow anisotropic block and an anisotropic layer. Considering the dominant anisotropic strikes of the block (NE-trend) and the layer (NW-trend) inferred from the MT data, if existing, the electrical anisotropy in the Okchon Belt was probably produced by the deformations in the pre-Jurassic period, since the NE-trending shearing or thrusting should create alternating bands of metamorphic rocks and fractures with NE-trending. Correlation of the structural strike of 2-D block with the latest EW-trending deformation events demonstrates that the geometrical structure of the anisotropic block was formed by the latest Daebo and Bulgugsa orogeny.

옥천대에서의 자기지전류 탐사자료는 위상이 $90^{\circ}$를 초과하는 매우 특이한 반응을 보이고 있으며 이러한 특이성은 매우 강한 이방성 매질의 영향에 기인하는 것으로 추정된다. 자료를 설명할 수 있는 타당한 모델은 좁은 이방성 블록과 이방성 층으로 이루어진 모델이다. 상부의 이방성 블록은 북동 방향의 주향을, 하부의 이방성 층은 북서 방향의 이방성 주향을 가지고 있으며 이방성 매질은 쥬라기 이전 지각변형에 의해 형성된 것으로 추정된다. 이는 옥천대가 백악기 이전에 북동 방향성을 가지는 전단 변형과 트러스트 습곡 변형을 경험하였기 때문에 그 방향으로의 교대구조와 파쇄대가 발달했을 가능성이 높기 때문이다. 반면 이방성 블록의 구조적 주향은 동서 방향이 우세하며 이것은 이방성 블록의 기하학적 구조가 백악기 지각변동인 불국사 조산운동에 의해 형성되었을 가능성을 시사한다.

Keywords

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