A boundary truncation layer method and device for three-dimensional forward modeling of low-frequency magnetotelluric method

Abstract

The present application discloses a method and device for three-dimensional forward modeling of the low-frequency magnetotelluric method, the method includes: low-frequency electromagnetic waves are incident from the target area into the anisotropic boundary truncation layer without reflection, and the anisotropic boundary truncation layer is determined The modulation parameter expression of the boundary truncation layer; the modulation parameter of the boundary truncation layer is gradually changed to obtain the absorption parameter of the transmitted wave, and the optimal modulation parameter value of the finite thickness boundary truncation layer is determined; the method adopted according to the low-frequency magnetotelluric forward modeling , the modulation parameters of the boundary truncation layer of finite thickness are introduced into the electromagnetic field Maxwell equations, and the forward modeling parameter information of the low-frequency magnetotelluric method is obtained. It can effectively cut off the target area of ​​low-frequency electromagnetic methods such as magnetotelluric method.

Description

technical field [0001] The present application relates to the field of geophysical electromagnetic detection, in particular to a Boundary Truncation Layer (Boundary Truncation Layer, BTL) method and device for three-dimensional forward modeling of low-frequency magnetotelluric method. Background technique [0002] At present, the target area of ​​the electromagnetic wave needs to be truncated artificially. Due to the limited computing power of the current computer, it is impossible to calculate the electromagnetic field in an infinite area. In the field of electromagnetic waves, in the previous simulations, the boundary conditions were used to extend several times the skin depth with grids of increasing size, and the secondary field was attenuated to 0, so that Dirichlet boundary conditions or Neumann boundary conditions were set at the outer boundary of the simulation area. , allowing the outer wave to enter without reflection and rapidly attenuate it. However, this method...

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Problems solved by technology

However, this method needs to be extended far enough, and for a wider frequency range, the extended grid size needs to increase slowly, so the number of grids that need to be extended is large, requiring a large amount of calculation and consumption. calculation time

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