Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

Electromagnetic tomography algorithm using multiple frequencies data was developed and tomographic images for synthetic data are analyzed for various models and frequencies. The algorithm used the extended Born approximations for forward modeling and reconstructed a conductivity image by a smoothness-constraint least-squares inversion method. Observed data, the vertical components of secondary magnetic fields for multiple frequencies in a homogeneous whole space, were simulated with the 3-D integral equation code. Image resolution increased with increasing frequency in single frequency EM. Generally, multiple frequencies EM is known to improve the image resolution compared to single frequency EM because additional information supplied by the multiple frequencies data should better constrain the solution in EM tomographic imaging scheme. To examine this, the images simultaneously using two, three, and five frequencies in the inversion scheme were compared with a single frequency image. The results showed that the location of anomalous body could be imaged very well, but conductivity of the body was lower than real one in both multiple frequencies and single frequency EM. But, image resolution was enhanced in multiple frequencies compared to single frequency. The vertical resolution was much higher than the horizontal resolution in both mutiple frequencies and a single frequency EM.