Geophysics and Geophysical Exploration (지구물리와물리탐사)

Korean Society of Earth and Exploration Geophysicists (한국지구물리·물리탐사학회)
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MT Response of a Small Island Model with Deep Sea and Topography

깊은 바다와 지형을 고려한 소규모 섬 모델의 MT 반응 연구

  • Kiyeon Kim (Department of Energy and Resources Engineering, Kangwon National University) ;
  • Seong Kon Lee (Mineral Exploration and Mining Research Center, Mineral Resources Division, Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Seokhoon Oh (Department of Energy and Resources Engineering, Kangwon National University) ;
  • Chang Woo Kwon (Volcano Research Group, Geologic Hazards Division, Korea Institute of Geoscience and Mineral Resources (KIGAM))
  • 김기연 (강원대학교 에너지자원공학과) ;
  • 이성곤 (한국지질자원연구원 광물자원연구본부 자원탐사개발연구센터) ;
  • 오석훈 (강원대학교 에너지자원공학과) ;
  • 권창우 (한국지질자원연구원 지질재해연구본부 화산연구단)
  • Received : 2023.10.19
  • Accepted : 2024.01.17
  • Published : 2024.02.29
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Abstract

The magnetotelluric (MT) survey can be affected by external environmental factors. In particular, when acquiring MT data in islands, it is essential to consider the combined effect of topography and sea to understand the results and make accurate interpretations. To analyze the MT response (apparent resistivity, phase) with consideration of the effect of topography and sea, a small cone-shaped island model surrounded by deep sea was created. Two-dimensional (2-D) and three-dimensional (3-D) forward modeling were performed on the terrain model considering topography and the island model considering both topography and sea. The 2-D MT response did not reflect the topographic and sea effect of the direction orthogonal to the 2-D profile. The 3-D MT response included topographic and sea effects in all directions. The XY and YX components of the apparent resistivity were separated on undulating topography, such as a hill. A conductor at 1 km below sea level could be distinguished from topographic and sea effects in the MT response, and low resistivity anomaly was attenuated at greater depths. This study will facilitate understanding of field data measured on small islands.

MT 탐사는 측점 주변의 지형과 바다와 같은 외부적 환경 요인에 의해서도 자료에 영향을 받는데, 특히 섬에서 수행된 MT 탐사 자료에는 지형효과와 해양효과가 복합적으로 작용하게 되며, 올바른 해석을 위해서는 두 효과에 대한 이해가 필요하다. 본 연구에서는 지형과 해양의 영향이 포함된 MT 반응(겉보기비저항, 위상)을 분석하기 위해 깊은 바다에 둘러싸인 원뿔 형태의 소규모 섬 모델을 생성하였다. 지형만을 고려한 지형모델, 지형과 바다를 동시에 고려한 섬 모델에 대하여 2차원 순산모델링과 3차원 순산모델링을 수행하고 MT 반응을 확인하였다. 3차원 섬 모델에 대해 2차원 모델링을 수행하면, 측선의 직교 방향에 대한 지형 변화와 바다를 고려하지 못하는데, 3차원 모델링을 수행함으로써 모든 방향의 지형 변화와 섬을 둘러싼 바다를 고려한 MT 반응을 얻을 수 있었다. 언덕과 같이 주변의 기복이 심한 지형에서는 겉보기비저항 XY 성분과 YX 성분의 벌어짐 현상이 전형적으로 발생하였다. 저비저항 이상체가 해수면 아래 1 km 심도에 존재할 경우, MT 반응에서 지형과 바다로 인한 변동과 구분할 수 있으며, 심도 증가에 따라 이상체의 영향이 감쇠하였다. 다양한 조건에서 모델링을 수행하고 MT 반응을 분석함으로써, 현장 MT 자료에 대한 이해를 높이고 자료 해석에 도움이 될 수 있을 것으로 기대한다.

Keywords

Acknowledgement

본 연구는 한국지질자원연구원 기본사업인 '한반도 활화산 특성 평가 및 화산 감시 기반기술 개발(GP2021-006)' 과제의 지원으로 수행되었습니다. 또한, 정부(과학기술정보통신부)의 재원으로 한국연구재단의 지원을 받아 수행된 연구(No. 2022R1A2C1092301)이며, 2024년도 정부(원자력안전위원회)의 재원으로 사용 후 핵연료관리핵심기술개발사업단 및 한국원자력안전재단의 지원을 받아 수행된 연구사업(RS-2021-KN066110)입니다.

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