A Study on Geoelectrical Structure of Jeju Island Using 3D MT Inversion of 2D Profile Data

2차원 MT 자료의 3차원 역산을 통한 제주도 지전기구조 연구

  • Choi, Ji-Hyang (Dept. of Civil, Urban and Geosystem Eng., Seoul National University) ;
  • Kim, Hee-Joon (Dept. of Environmental Exploration Eng., Pukyong National University) ;
  • Nam, Myung-Jin (Dept. of Petroleum and Geosystems Eng., The University of Texas at Austin) ;
  • Lee, Tae-Jong (Groundwater and Geothermal Resources Div., KIGAM) ;
  • Han, Nu-Ree (Dept. of Civil, Urban and Geosystem Eng., Seoul National University) ;
  • Lee, Seong-Kon (Groundwater and Geothermal Resources Div., KIGAM) ;
  • Song, Yoon-Ho (Groundwater and Geothermal Resources Div., KIGAM) ;
  • Suh, Jung-Hee (Dept. of Civil, Urban and Geosystem Eng., Seoul National University)
  • 최지향 (서울대학교 지구환경시스템공학부) ;
  • 김희준 (부경대학교 환경탐사공학과) ;
  • 남명진 ;
  • 이태종 (한국지질자원연구원 지하수지열연구부) ;
  • 한누리 (서울대학교 지구환경시스템공학부) ;
  • 이성곤 (한국지질자원연구원 지하수지열연구부) ;
  • 송윤호 (한국지질자원연구원 지하수지열연구부) ;
  • 서정희 (서울대학교 지구환경시스템공학부)
  • Published : 2007.11.30

Abstract

Traditional two-dimensional (2D) interpretation of magnetotelluric (MT) data utilizes only transverse magnetic (TM)-mode data, because 2D inversion of transverse electric (TE)-mode data results in spurious features when 3D structures exist in the subsurface. The application of a 3D inversion algorithm to a single MT profile can reduce contamination due to off-profile anomalies and help us to incorporate TE-mode data in the interpretation. In this study, we conduct 2D and 3D inversions of MT data observed along two lines in Jeju Island. First, we invert apparent resistivities and phases in the TM and TE modes separately. Then, we perform 2D joint inversion of both TM- and TE-mode data and 3D inversion of both Zxy- and Zyx-mode data corresponding to TE- and TM-mode data in 2D. The resistivity images derived from all four data show that the geoelectrical structure in Jeju Island is a three-layered earth with the resistive-conductive-resistive stratigraphy within a depth of 5 km. The 3D inversion does not produce clear anomalies in the reconstructed profile image, while all of 2D do. This attributed to the possibility that 2D inversion results are distorted by exiting off-profile 3D anomalies in Jeju. With 3D inversion of 2D profile MT data, we can deduce more reliable results that are not seriously distorted by off-profile 3D anomalies.

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