Non-linear conjugate gradient three-dimensional inversion method of magnetotelluric field

Abstract

The invention discloses a non-linear conjugate gradient three-dimensional inversion method of a magnetotelluric field, which comprises the following steps of: a, establishing a three-dimensional model, and determining model parameters; b, acquiring impedance response through the model resistivity by using the staggered-grid finite difference of the magnetotelluric field as a forward modeling method; c, comparing the impedance which is acquired by forward modeling with an actually measured impedance to acquire an impedance data deviation; d, judging whether a target function value is enough small or not, finishing iteration when the target function value is small enough, otherwise entering the next step; e, calculating the gradient of a target function, and acquiring a search step-length and a search direction by using a non-linear conjugate gradient method as an inversion method so as to calculate a model modifier, wherein the resistivity calculated by using the impedance data error and current iteration is used as a preprocessing factor in the inversion method; and f, modifying the model, and returning to the step b. The non-linear conjugate gradient three-dimensional inversion method of the magnetotelluric field has the characteristics of high efficiency and high accuracy.

Description

technical field [0001] The invention relates to the processing technical field of the magnetotelluric sounding method, in particular to a three-dimensional inversion method of the magnetotelluric field nonlinear conjugate gradient. Background technique [0002] The magnetotelluric sounding method is widely used in deep geological exploration and exploration of minerals, water, oil, geothermal and other resources. At present, two-dimensional inversion is the mainstream method of data processing, and there are few studies on three-dimensional inversion methods. Foreign scientists have proposed methods such as fast relaxation method, conjugate gradient method, nonlinear conjugate gradient method, etc., which have been realized in China. Fast relaxation and conjugate gradient methods. [0003] At present, the 3D inversion technology of the magnetotelluric field is still a frontier research issue in the industry. The key issues to be solved are to reduce the amount of inversion ...

AI Technical Summary

Problems solved by technology

In the existing nonlinear conjugate gradient method, the selection of preprocessing factors is either very complicated and the calculation efficiency is low; or it is relatively simple and related to the initial model resistivity, which reduces the effectiveness of the algorithm

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