Correction of the Sea Effect in the Magnetotelluric (MT) Data Using an Iterative Tensor Stripping During Inversion

MT 자료 역산과정에서 반복적인 Tensor Stripping을 통한 해양효과 보정

  • Yang, Jun-Mo (Deep. Sea & Marine Resource Research Division, Korea Ocean Research & Development Institute) ;
  • Lee, Chun-Ki (Groundwater & Geothermal Resource Division, Korea Institute Geoscience & Mineral Resources) ;
  • Yoo, Hai-Soo (Deep. Sea & Marine Resource Research Division, Korea Ocean Research & Development Institute)
  • 양준모 (한국해양연구원 심해해저자원연구부) ;
  • 이춘기 (한국지질자원연구원 지하수지열연구부) ;
  • 유해수 (한국해양연구원 심해해저자원연구부)
  • Published : 2008.11.30

Abstract

When magnetotelluric (MT) data are obtained in vicinity of the coast, the sea can distort observed MT responses, especially those of deep part of subsurface. We introduce an iterative method to correct the sea effect, based on the previous topographic correction method which removes the distortions due to topographic changes in seafloor MT data. The method first corrects the sea effect in observed MT impedance, and then inverts corrected responses in a model space without the sea. Due to mutual coupling between sea and subsurface structure, the correction and inversion steps are iterated until changes in each result become negligible. The method is validated for 1-D and 2-D structure using synthetic MT data produced by 3-D forward modeling including surrounding seas. In all cases, the method closely recovers the given structure after a few iterations. To test the applicability of the proposed method to field data, we generate synthetic MT data for the Jeju Island whose 1-D conductivity structure is well known, using 3-D forward modeling. The distortions due to the surrounding sea start to appear below the frequency about 1 Hz, and are relatively severe in the electrical field perpendicular to the coastline because of the location of the observation sites. The proposed method successfully eliminates the sea effect after three iterations, and both 1-D and 2-D inversion of corrected responses closely recover the given subsurface structure of the Jeju Island model.

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