Static displacement correction method of magnetotelluric field based on inversion model

Abstract

A method for correcting static displacement of magnetotelluric field based on an inversion model of the present invention belongs to the technical field of data processing in magnetotelluric sounding methods. The correction method of the present invention includes the following steps: in the initial model of the design inversion, add a high-resistance body or a low-resistance body whose superficial assignment is the generalized static displacement resistivity, and there will be a model grid resistance corresponding to the static displacement measuring point The rate is assigned as generalized static displacement resistivity to participate in the inversion, and then realizes the correction of the static displacement of the measuring point, and obtains the inversion result with the effect of static displacement correction. Wherein, the resistivity of the high-resistance body is greater than the background resistivity, and the resistivity of the low-resistance body is smaller than the background resistivity. The correction method of the present invention performs the static displacement correction of the magnetotelluric field on the basis of the three-dimensional theory, so that the corrected result is closer to the actual underground electrical structure, and the information is more accurate; and the static displacement correction is realized by designing the initial model, reducing the need for static correction complexity, and achieve zero cost of work.

Description

technical field [0001] The invention relates to the technical field of data processing in a magnetotelluric sounding method, in particular to a method for correcting a static displacement of a magnetotelluric field for correcting distortion data generated by a distortion field. Background technique [0002] Magnetotelluric sounding (MT) has become one of the important means of deep crustal exploration and prospecting due to its advantages of large exploration depth, portable equipment, and low data acquisition cost. However, the existence of static displacement seriously affects the accuracy and application effect of magnetotelluric sounding (MT) data. It was thought that the surface The secondary electric field generated by the accumulated charge on the boundary of a two-dimensional or three-dimensional inhomogeneous body leads to a sudden change in the observed electric field component, causing the static displacement phenomenon; because the charge on the boundary area o...

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Problems solved by technology

[0004] There are some defects and deficiencies in the above five static displacement correction methods respectively: Among them, (1) the spatial filtering method obtains the average electric field intensity through multi-channel measurement, and when the electric field measurement dipole moment is greater than It is very effective when there is an inhomogeneous body, but when the electrode arrangement direction is parallel to the inhomogeneous body distribution, this method is invalid, and the method has high cost and low efficiency; (2) The impedance tensor decomposition method calculates the distortion tensor by decomposing the impedance tensor When there is no inductive distortion effect, this method can restore the apparent resistivity curve well, but the calculation of this method is an underdetermined problem, and all the distortion parameters cannot be determined; (3) The independent measurement and correction method mainly It is a distorted apparent resistivity curve corrected by using the results of transient electromagnetic sounding (TEM) at the magnetotelluric sounding (MT) measuring point. The TEM result is not affected by the static displacement effect, but it can only be used when there is an overlapping frequency band between MT and TEM. and this method cannot be used for (4) The comprehensive data interpretation method puts the static displacement correction coefficient into the forward modeling and inversion calculation or uses the prior information to directly give the correction coefficient, but it is easy to cause the inversion to fall into a local minimum and stop (5) The phase correction method uses the phase not affected by the static displacement effect to estimate the subsurface resistivity through the phase transformation of adjacent points, but the actual situation is difficult to meet the requirements of this method

[0005] At the same time, the current understanding of static displacement and existing correction methods are still based on one- and two-dimensional magnetotelluric field theory and assumptions, which do not meet the definition of three-dimensional static displacement effects, so there are large theoretical flaws

Moreover, none of the existing methods has the basis of field experiments (field exploration experiments, including parameter experiments and actual physical model tests) measured data as a basis for technical supplements or method verification.

For the magnetotelluric sounding observation curve, without knowing the influencing factors, it is impossible to judge whether the static displacement exists, the offset direction and the magnitude of the offset, and it is impossible to use the current correction method to perform complete static correction

Therefore, the existing methods are not universal and uncertain about the correction results

[0006] In addition, the existing methods are all correction methods based on the data processing process, the implementation of the method is very complicated, and some methods have high economic costs and are not easy to implement

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