[S-EM14] Electric, magnetic and electromagnetic survey technologies and scientific achievements

[SEM14-P05] 3D finite element inversion of magnetotelluric data at a northern Hakkoda geothermal area

*Toshihiro Uchida¹, Yusuke Yamaya¹ (1.National Institute of Advanced Industrial Science and Technology)

Keywords:magnetotellurics, 3D inversion, finite element modeling, topography, Hakkoda area

Three-dimensional (3D) inversion with the finite element modeling (FEM), including topography variation, was conducted for a magnetotelluric (MT) dataset obtained at a geothermal area near the Hakkoda volcano, northern Japan. The inversion code used was FEMTIC (Usui, 2015). FEMTIC can apply both the tetrahedral elements and distorted hexahedral elements for the forward modeling. The 50 m grid digital elevation model (DEM) by the Geospatial Information Authority of Japan (GSI) and the GEBCO 15 arc-second grid data were used for the topography data on land and the seafloor bathymetry, respectively. Coastline data by GSI was used to define the land-sea boundary. The number of MT stations was 34. Full components of the impedance and tipper at 15 frequencies (from 0.0067 Hz to 115 Hz) were used as the observed data. Uchida (2021) conducted a 3D inversion of the same MT dataset using the finite-difference modeling (FDM) code WSINV3DMT (Siripunvaraporn and Egbert, 2009), including topography. 3D models produced by the FEM and FDM inversions present similar resistivity distribution in general, however, several differences are also recognized. This paper compares those results.