Magnetotelluric three-dimensional forward modeling method based on spherical coordinate system

Abstract

The invention discloses a magnetotelluric three-dimensional forward modeling method based on a spherical coordinate system, and belongs to the technical field of geophysical exploration. The method comprises the following steps: a, establishing a magnetotelluric control equation; b, dividing the spherical coordinate system into a plurality of small inverted quadrangular prism grid units; c, setting spherical coordinate model parameters, and constructing a spherical coordinate staggered grid unit with a discrete magnetic field; d, cycling a single frequency, and performing numerical dispersionon the magnetotelluric control equation in the spherical coordinate staggered grid unit; e, solving a system of linear equations; and f, calculating impedance via a spherical coordinate tensor impedance formula, and then substituting the impedance into a Kania apparent resistivity calculation formula to figure out the apparent resistivity and phase at a measuring point. By adoption of the magnetotelluric three-dimensional forward modeling method disclosed by the invention, the interference of the earth curvature on the magnetotelluric three-dimensional deep detection can be effectively overcome, calculation errors caused by the earth curvature are avoided, the magnetotelluric three-dimensional forward modeling method is suitable for the numerical simulation of magnetotelluric three-dimensional forward modeling, and can be better matched with an earth model, and the accuracy is high.

Description

technical field [0001] The invention relates to the technical field of geophysical exploration, in particular to a three-dimensional magnetotelluric forward modeling method based on a spherical coordinate system. Background technique [0002] Magnetotelluric sounding is the main method to detect the deep electrical structure of the earth. By synchronously observing the electric field and magnetic field components on the surface, and qualitative or quantitative analysis, the electrical structure model of the earth within a certain depth range can be obtained. , Deep geological structure detection, geothermal and groundwater resource investigation, earthquake prediction and geological disaster prevention and other fields are widely used. [0003] Forward modeling is the core of geophysical methods. The essence of 3D forward modeling of magnetotellurics is to find the numerical solution of the 3D electromagnetic diffusion equation in complex media. The main calculation methods...

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Problems solved by technology

[0007] The 3D forward modeling of geomagnetic sounding based on finite difference in the spherical coordinate system disclosed in this journal literature, in which geomagnetic sounding only observes and analyzes magnetic field signals to detect the deep electrical structure of the earth, and its effective signal frequency range is generally between 10 5 ~10 7 Seconds, the detection depth is mainly from the upper mantle to the middle and lower mantle of the earth about 200 kilometers; therefore, it is not suitable for 3D forward numerical simulation of magnetotellurics, cannot better match the earth model, and has low accuracy

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