Non-linear inversion with the quadratic function approaching method for magnetotelluric data

We present a new technique for inverting magnetotelluric sounding (MT) data by introducing the quadratic function approaching scheme, which is originally used in non-linear optimization. The quadratic function approaching method (QFAM) takes the advantage of that quadratic function has single extreme value. It avoids leading to an inversion solution for local minimum and ensures the solution for global minimization of objective function. The method does not need calculation of the sensitivity matrix and not require a strict initial earth model. In this study, the coefficients of the quadratic function used for the inversion are calculated dexterously by using affine transformation and by adopting an effective method for selecting control points. Examples for synthetic data and field measurement data, indicate that the proposed inversion method is effective.