阅读说明：本技术 一种构建多层等效源模型计算化极与数据类型转换的方法 (Method for constructing conversion between multi-layer equivalent source model calculation electrode and data type ) 是由 左博新 于 2020-06-29 设计创作，主要内容包括：本发明公开了一种构建多层等效源模型计算化极与数据类型转换的方法,输入磁测数据,根据观测数据的观测位置和高度数据等因素,对自由空间和地下空间进行非均匀网格剖分；利用基于积分方程的多层等效源反演方法,对磁测数据进行三维反演计算,构建多层等效源模型；利用构建的多层等效源模型,进行垂直磁化地磁场的化极与数据转换计算,其中,基于积分方程的三维正演计算方法计算磁测数据,得到化极与数据类型转换结果。该方法基于积分方程理论重新构建了等效源模型的计算框架,实现了对高磁化率场源所产生的含有强退磁效应的磁异常数据的高精度处理；且,采用深度规整因子,实现了利用反演过程对多层等效源模型深度位置的自适应估计。(The invention discloses a method for constructing conversion between a multi-layer equivalent source model calculation polarization and a data type, which comprises the steps of inputting magnetic measurement data, and carrying out non-uniform mesh subdivision on a free space and an underground space according to factors such as an observation position, height data and the like of observation data; performing three-dimensional inversion calculation on the magnetic measurement data by using a multilayer equivalent source inversion method based on an integral equation to construct a multilayer equivalent source model; and performing polarization and data conversion calculation of the vertical magnetization geomagnetic field by using the constructed multilayer equivalent source model, wherein the magnetic measurement data is calculated by using a three-dimensional forward calculation method based on an integral equation, so as to obtain a polarization and data type conversion result. The method reconstructs a calculation frame of an equivalent source model based on an integral equation theory, and realizes high-precision processing of magnetic anomaly data containing strong demagnetization effect generated by a high-magnetization rate field source; and moreover, the depth regularization factor is adopted, so that the self-adaptive estimation of the depth position of the multilayer equivalent source model by utilizing the inversion process is realized.)

1. A method for constructing a multilayer equivalent source model is characterized by comprising the following steps:

s1, inputting the existing magnetic field data d₀；

S2, constructing an equivalent source model space according to the terrain height information of the observation area and the set inversion maximum depth, and performing structured non-uniform multi-layer mesh subdivision on the equivalent source model space;

s3, constructing an objective function, and applying the structured non-uniform grid constructed in the step S2 to the magnetic field data d₀Carry out the strip depth normalization factor W_rAnd carrying out three-dimensional inversion calculation on the integral equation of the positive value constraint term and the regularization term beta to obtain a multilayer equivalent source model m.

2. The method for constructing a multilayer equivalent source model according to claim 1, wherein in step S2, the inverse mesh model is subdivided in a continuous mesh partitioning manner;

and, the number of layers of the model is greater than 3.

3. The method for constructing a multilayer equivalent source model according to claim 2, wherein in step S2, the equivalent source model space comprises a continuous space between an upper top surface and a lower bottom surface, wherein:

the upper top surface of the equivalent source model space is a topographic relief curved surface; and the lower bottom surface of the equivalent source model space is a horizontal plane where the set inversion maximum depth is located.

4. The method for constructing a multi-layered equivalent source model according to claim 3, wherein in step S2, the performing the structured non-uniform multi-layered mesh generation comprises fine mesh generation and extended mesh generation, wherein, in the equivalent source model space:

determining the highest point and the lowest point of a relief surface based on the upper top surface of the equivalent source model space, further determining a relief depth range space, and performing fine mesh subdivision in the relief depth range space;

taking the lowest point of the relief surface of the terrain as a starting point, and performing expanded mesh subdivision in a depth range space determined from the position below the starting point to the lower bottom surface of the equivalent source model space;

the fine grid and the extended grid are one continuous whole.

5. The method for constructing a multilayer equivalent source model according to claim 4, wherein in step S3, when performing three-dimensional inversion calculation based on an integral equation on the subdivided equivalent source grid model, the objective function constructed is:

wherein phi is an error value, namely an optimization target;for the numerical constraint term of the objective function, F ═ is positive to "+"Performing calculation operation;a model constraint term that is an objective function; d₀For the input observation data, β is a predefined first regularization factor, W_rIs a depth normalization factor; m is_refAnd m are respectively the magnetic susceptibility matrixes represented by the reference equivalent source model and the target output equivalent source model in the current objective function optimization process.

6. The method for constructing a multi-layered equivalent source model according to claim 4, wherein in constructing the fine and extended meshes:

the side length of the fine grid is set to be 1;

the side length of the expanded grid will be a of the side length of the fine grid₁The speed is increased by a multiple, and the maximum speed increase is set to alpha₂(ii) a Wherein alpha is₂＞α₁＞1。

7. The method of constructing a multi-layered equivalent source model according to claim 5, wherein the depth normalization factor W_rThe mathematical expression of (a) is:

wherein z is the distance from the multilayer equivalent source model to an observation surface, and z₀R is the depth coefficient for the height of the observation plane.

8. A method of computing polarization data according to any one of claims 1 to 7, wherein the method comprises:

s4, obtaining polarization data through three-dimensional forward calculation of an integral equation magnetic field by utilizing the multilayer equivalent source model m obtained through the solution in the step S3; wherein the polarization data B_SThe calculation formula of (2) is as follows:

B_S＝Gm；

wherein, B_s＝[B_sx,B_sy,B_sz]，B_sx、B_sy、B_szThree-component magnetic anomalous fields obtained based on forward calculation are respectively obtained, and G is a sensitivity matrix.

9. A method for performing data type conversion according to the method for constructing a multilayer equivalent source model claimed in claims 1-7, comprising:

s4, obtaining the multilayer equivalent source model m by utilizing the step S3 to solve, and obtaining the polarization data B by calculating based on the multilayer equivalent source model_SThen, the converted magnetic field data is calculated by a data type conversion formula.

10. The method of data type conversion according to claim 9, wherein calculating the converted magnetic field data comprises the steps of:

s41, calculating fitted magnetic anomaly data d by the following formula by using three-component field data of the background field_s：

Wherein, B₀＝[B_0x,B_0y,B_0z]Three-component field data of a background field; b is_0x、B_0yAnd B_0zRespectively field data under corresponding components;

s42, based on the magnetic anomaly data d_sThe magnetic field data is converted using the following magnetic field tensor conversion formula:

where ∑ is the gradient operator, each factor in the matrix [ ] is a different tensor of the magnetic field.

Technical Field

The invention relates to the technical field of geophysics, in particular to a method for realizing conversion between a heterogeneous grid multilayer equivalent source magnetic measurement data polarization and a data type based on an integration method.

Background

In geomagnetic detection, people usually detect the total field of a magnetic field, but in actual data interpretation, data types required by data conversion, such as polarization data, magnetic field components, tensor data, and the like, are often required, and magnetic field data type conversion is to convert the observed magnetic field data type into different types of magnetic field data required. The main challenge of this task is that the magnetic topography has certain limit to the traditional data type conversion and polarization calculation, and the data conversion method of the traditional equivalent source has certain loss to the precision of the data.

In the prior art document 1, "damper, c.n.g. the EQUIVALENT SOURCE of low-latitude magnetic anomaly", the method of polarization of low-latitude magnetic anomaly is considered, wherein "damper is used to regulate the magnetic anomaly [ J ]. in 1969,34(1): 39.", "Li y.reduction to the pole using EQUIVALENT SOURCEs [ J ]. SEG Technical Program Expanded abstract extracts, 1999,19(1): 2484".

Prior documents 2 "Li d., q.liang, j.du, s.sun, y.zhang, c.chen,2019, transformational-biological and interactive within a three-way component using dual-layerequivalent sources, geographic Research Letter,47(3), and e 2019gl084607" disclose the separation of underground equivalent sources into two layers.

In the prior document 3, "processing and conversion of three-dimensional random point-field data by a Huangfeika, Wangymsan in Changchun. equivalent source method [ J ] geophysical progress, 2009(01): 101-.

In the prior document 4, "li tou, chen chao sons, and the like," multilayer equivalent source curved surface magnetic anomaly conversion method [ J ]. geophysical reports, 2018,061(007):3055-3073, "conversion of magnetic field data is realized by dividing an underground equivalent source into three layers.

Based on the above prior documents 1 to 4, the differences of the present application from the previous research mainly include the following points:

1) the multilayer equivalent source proposed herein is based on the forward and backward evolution theoretical framework of the integral equation;

2) the proposed multilayer equivalent source grid is based on continuous grids, the number of the continuous source grids is usually larger than 3, and the multilayer equivalent source grid is greatly different from the maximum three-layer discontinuous grid researched in the past;

3) previous methods required a separate estimation of the depth position of each layer and then a separate placement.

In general, the method provided by the application utilizes the depth normalization factor, the depth and the range of the equivalent layer do not need to be estimated separately, and the depth and the distribution of the equivalent layer can be directly determined by an algorithm in the inversion process.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for constructing a multilayer equivalent source model to calculate conversion between a polarization and a data type aiming at the defect that the precision and the speed of conversion operation between the polarization and the data type are not accurately controlled in the prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method for constructing a multilayer equivalent source model comprises the following steps:

s1, inputting the existing magnetic field data d₀；

S2, constructing an equivalent source model space according to the terrain height information of the observation area and the set inversion maximum depth, and performing structured non-uniform multi-layer mesh subdivision on the equivalent source model space;

s3, constructing an objective function, and applying the structured non-uniform grid constructed in the step S2 to the magnetic field data d₀Carry out the strip depth normalization factor W_rAnd carrying out three-dimensional inversion calculation on the integral equation of the positive value constraint term and the regularization term beta to obtain a multilayer equivalent source model m.

The invention discloses a method for calculating polarization data according to the method for constructing the multilayer equivalent source model, which comprises the following steps:

s4, obtaining polarization data through three-dimensional forward calculation of an integral equation magnetic field by utilizing the multilayer equivalent source model m obtained through the solution in the step S3; wherein the polarization data B_SThe calculation formula of (2) is as follows:

B_S＝Gm；

wherein, B_s＝[B_sx,B_sy,B_sz]，B_sx、B_syAnd B_szThree-component magnetic anomalous fields obtained based on forward calculation are respectively obtained, and G is a sensitivity matrix.

The invention discloses a method for converting data types according to the method for constructing the multilayer equivalent source model, which comprises the following steps:

s4, obtaining the multilayer equivalent source model m by utilizing the step S3 to solve, and obtaining the polarization data B by calculating based on the multilayer equivalent source model_SThen, the converted magnetic field data is calculated by a data type conversion formula.

The method for constructing the conversion between the calculation polarization and the data type of the multilayer equivalent source model has the following beneficial effects:

1) the invention provides a forward and inverse theoretical framework of a multilayer equivalent source based on an integral equation;

2) the multilayer equivalent source grid provided by the invention is based on a continuous grid, the layering number of the multilayer equivalent source grid is more than 3 layers, and the multilayer equivalent source grid is greatly different from the maximum three-layer discontinuous grid in the previous research;

3) the existing method needs to estimate the depth position of each equivalent layer separately and then place the depth position separately. The method provided by the invention does not need to estimate the depth and the range of the equivalent layer independently, wherein the depth and the distribution of the equivalent layer can be directly determined by an algorithm in the inversion process by utilizing a depth normalization factor without independent estimation and placement.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a flow chart of an implementation method for constructing a multi-layer equivalent source model according to the present disclosure;

FIG. 2 is a flowchart of a method for implementing polarization data calculation based on a multi-layer equivalent source model constructed in embodiment 1;

FIG. 3 is a flowchart of a method for implementing data type conversion based on a multi-layer equivalent source model constructed in embodiment 1;

fig. 4 is a schematic diagram of a non-uniform mesh generation constructed according to embodiment 1.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.