An Efficient 3D Inversion of MT Data Using Approximate Sensitivities

효율적인 3차원 MT 역산을 위한 다양한 감도의 이용

  • Han, Nu-Ree (Dept. of Civil, Urban and Geosystem Eng., Seoul National University) ;
  • Nam, Myung-Jin (Dept. of Petroleum and Geosystems Eng., The University of Texas at Austin) ;
  • Kim, Hee-Joon (Dept. of Environmental Exploration Eng., Pukyong National University) ;
  • Lee, Tae-Jong (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)
  • 한누리 (서울대학교 지구환경시스템공학부) ;
  • 남명진 ;
  • 김희준 (부경대학교 환경탐사공학과) ;
  • 이태종 (한국지질자원연구원 지하수지열연구부) ;
  • 송윤호 (한국지질자원연구원 지하수지열연구부) ;
  • 서정희 (서울대학교 지구환경시스템공학부)
  • Published : 2007.11.30

Abstract

An efficient algorithm for inverting static-shifted magnetotelluric (MT) data has been proposed to produce a three-dimensional (3D) resistivity model. In the Gauss-Newton approach, computational costs associated with construction of a full sensitivity matrix usually make 3D MT inversion impractical. This computational difficulty may be overcome by using approximate sensitivities. We use four kinds of sensitivities in particular orders in the inversion process. These sensitivities are computed 1) analytically for an initial, homogeneous earth, 2) exactly for a current model, 3) approximately by the Broyden method, and 4) approximately using the previous adjoint fields. Inversion experiments with static-shifted synthetic and field MT data indicate that inversion results are highly dependent on characteristics of data and thus applying various combinations of sensitivities is helpful in obtaining a good image of the subsurface structure with reasonable computation time.

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