Details of the Abstract
| Title of paper | A simple method to evaluate the uncertainty of magnetotelluric forward modeling for practical three-dimensional conductivity structure models |
| List of authors | Baba, K. |
| Affiliation(s) | Earthquake Research Institute, The University of Tokyo |
| Summary | I propose a simple method to evaluate the uncertainty of MT forward modeling for practical three-dimensional (3D) conductivity structure models in a Cartesian coordinate system. The method is based on the idea that the horizontal coordinate system can be selected arbitrarily for a general 3D structure. The synthesized MT responses are ideally identical irrespective of the selection but are different because of the difference in discretization angles, boundary values, and numerical errors. By synthesizing MT responses to the model in several different coordinate systems, the mean, standard deviation, and coefficient of variation can be calculated. These statistics provide quantitative information on how stably the forward calculations synthesize MT responses under the given conditions of the structure model, observation array, periods, numerical algorithm for the forward modeling, and mesh design. The proposed method was applied to two practical situations of seafloor MT arrays in the northwestern Pacific and southern Atlantic and a land MT array in Hokkaido, Japan. The results show that the uncertainty is comparable to real observation errors and is significantly dependent on the MT impedance element, period, site, structure model, and horizontal coordinate system. The uncertainty of the forward calculation should be considered for each element, period, and site to quantitatively evaluate how well a given model explains the data. I propose a new root-mean-square in which the residuals are normalized by both the standard errors of the MT responses observed and synthesized. This would help avoid overfitting data in the inversion analysis by ignoring the uncertainty of the forward calculation. This method is also useful for testing the appropriate selection of the coordinate system and mesh design. |
| Session Keyword | 2.0 EM theory, modelling and Inversion |
| File upload |
2.0_a_simple_method_to_evalua_baba.pdf
2P06.pdf |