Determining structural boundaries using blocky magnetotelluric data inversion

The magnetotelluric method has large depths of investigation and can provide important structural information in many exploration problems. The one-dimensional magnetotelluric inversion also has been applied to extract boundary information and provide the constraints for the interpretation of complementary datasets. Traditional smooth inversion based on the $L_2$ norm only provides a single smooth model that it is difficult to detect the location of the geological boundary. Trans-dimensional inversion provides an effective means to determine the boundaries with uncertainty quantification but incurs significant computational costs. We present an efficient method to detect distinct interfaces from one-dimensional blocky magnetotelluric inversions using an Ekblom norm. The method leverages the Ekblom norm to assess the change in the recovered resistivity model with the threshold parameter as a means to delineate the significant boundaries in the subsurface. The threshold parameter specific to the Ekblom-norm inversion is then used to probe the variability of the inversion to obtain a more robust interface detection. Once the interfaces are detected, we calculate the average resistivity value between detected interfaces to form a final conductivity model. As a demonstration, we apply this method to a synthetic example and the field data from East Tennant in Australia. The results show that the method is effective in obtaining boundaries.