阅读说明：本技术 一种基于重力不同阶梯度特征值交点的场源位置识别方法 (Method for identifying field source position based on intersection points of characteristic values of different gradients of gravity ) 是由 马国庆 明彦伯 王泰涵 李丽丽 张蕊 李达斌 于 2021-01-08 设计创作，主要内容包括：本发明公开了一种基于重力不同阶梯度特征值交点的场源位置识别方法,包括：通过求取不同阶梯度比值的特征值连线交点获得场源的真实界线结果；采用三维不同阶垂直梯度交点成像方法,通过对数据进行向下延拓处理,并寻找向下延拓数据的不同阶梯度的交点位置,即为构造的位置。本发明的方法,利用重力不同阶垂直梯度特征值在地质体位置位置处相交的特点进行场源位置的识别,有效解决单独二阶导数特征值受埋深影响得不到准确位置的缺陷,具有更高的精度。(The invention discloses a field source position identification method based on intersection points of characteristic values of different gravity gradients, which comprises the following steps of: obtaining a real boundary result of the field source by solving the intersection points of the characteristic values of different step ratio lines; and adopting a three-dimensional intersection point imaging method with different-order vertical gradients, carrying out downward continuation processing on the data, and searching intersection point positions of different-order gradients of the downward continuation data, namely the constructed positions. The method of the invention identifies the field source position by using the characteristic that the characteristic values of the vertical gradients of different orders of gravity intersect at the position of the geologic body, effectively solves the defect that the characteristic value of the single second derivative cannot obtain an accurate position due to the influence of the buried depth, and has higher precision.)

1. A field source position identification method based on gravity different step degree characteristic value intersection points is characterized in that

Is characterized by comprising the following steps:

obtaining a real boundary result of the field source by solving the intersection points of the characteristic values of different step ratio lines;

and adopting a three-dimensional intersection point imaging method with different-order vertical gradients, carrying out downward continuation processing on the data, and searching intersection point positions of different-order gradients of the downward continuation data, namely the constructed positions.

2. The field source location based on gravity differential step eigenvalue intersection of claim 1

The identification method is characterized in that the obtaining of the real boundary line result of the field source by obtaining the intersection point of the characteristic values and the connecting lines of different order gradient ratios comprises obtaining a first-order vertical gradient and a second-order vertical gradient of the three-dimensional gravity anomaly field of the underground anomaly:

the three-dimensional gravity anomaly is expressed as formula (1)

(1)

Wherein V is gravity potential, k is constant related to density and universal gravitation constant, N is construction index of geologic body, (x 0, z 0) is field source center coordinate, and (x, z) is observation point coordinate;

the first-order vertical gradient of the three-dimensional gravity anomaly can be deduced to be formula (2) through formula (1)

(2)

Wherein y is a north-south coordinate, and x is an east-west coordinate;

the corresponding relation between the horizontal position of the vertical gradient zero point and the depth of the field source is formula (3):

(3)

similarly, the second-order vertical gradient of the three-dimensional gravity anomaly is deduced to be formula (4) through formula (1)

(4)

The corresponding relation formula (5) of the horizontal position of the zero point of the second-order vertical gradient and the depth of the field source is as follows:

(5)

by combining equation (3) and equation (5), it can be obtained that when z-z0=0, i.e. the geologic body burial depth is 0, the null points of different order vertical gradients intersect at the true location of the field source (x 0, y 0).

3. The field source location based on gravity differential step eigenvalue intersection of claim 1

The identification method is characterized in that the method for imaging the intersection points of the vertical gradients of different orders in three dimensions is adopted, downward continuation processing is carried out on data, and the position of the intersection point of the gradient of different orders of the downward continuation data is found, and the method comprises the following steps:

adopting a horizontal iteration method of stable downward continuation, and calculating downward continuation data by utilizing upward continuation data and different-order horizontal gradients, wherein the basic formula is as follows:

(6)

whereinFor gravity anomaly on the observation plane h, h is the downward continuation depth,is the gravity anomaly observed at the surface;

the calculation of vertical gradients increases the noise disturbance, for which the laplace equation is used to calculate the abnormal high order vertical gradients:

(7)。

4. the field source location based on gravity differential step eigenvalue intersection of claim 1

The identification method is characterized in that the method for imaging the intersection points of the vertical gradients of different orders by three-dimensional is adopted, downward continuation processing is carried out on data, and the positions of the intersection points of the gradients of different orders of the downward continuation data are searched, and the method further comprises the following steps:

performing iterative computation, wherein the iterative process is as follows:

s1, data to be extended downwardsUpward continuation is obtained；

S2，；

S3，；

S4, mixingThe correction amount of (1);

s5, repeating S1 to S4 untilThe mean square error is less than a given value;

s6, the final downward continuation result is

Is the number of iterations.

Technical Field

The invention relates to the technology of geoscience, in particular to a field source position identification method based on intersection points of characteristic values of different gradients of gravity.

Background

At present, the main mineral exploration problems in China mineral resource replacing bases are as follows: the ore exploration difficulty of deep old mines and various concealed areas is high, and advanced and efficient theoretical and technical methods are urgently needed to guide deep ore exploration. Most metal mines in China are located in areas with relatively good terrain conditions, and exploration and mining depths are within a range of more than 500 meters.

With the comprehensive application of exploration means such as satellites and aviation and the continuous improvement of data precision and exploration precision requirements, the role of gravity exploration in the aspect of deep exploration is obviously enhanced. However, the traditional inversion method has large computation amount and low computation speed, and is difficult to meet the requirement of high-precision deep inversion under the condition of large data volume at present. Compared with the traditional inversion method, the space imaging method has higher calculation efficiency and higher precision.

Today, the feature value of the second-order vertical derivative is mostly used for defining the position of the geologic body, but the identification precision of the position of the field source is low because the feature value position is related to the buried depth of the geologic body. The invention creatively utilizes the relation between the characteristic value positions of different-order vertical gradients of gravity data and the buried depth of the geologic body, provides a method for tracking the structure positions of the different-order vertical gradients, establishes a technical system for tracking the structure positions and directly and accurately gives the position of the geologic body. In the aspect of field source position identification, the method has higher precision and higher calculation efficiency, and is well applied to the identification of the geological structure position of the actual region.

The prior art has the following defects:

today, the feature value of the second-order vertical derivative is mostly used for defining the position of the geologic body, but the identification precision of the position of the field source is low because the feature value position is related to the buried depth of the geologic body.

The gravity exploration researches the geological structure characteristics of the underground space by measuring gravity anomaly on the basis of the physical property of density difference between an exploration target and surrounding rocks. The method has the advantages of economy, large exploration depth, rapid acquisition of information on the area and the like, and is widely applied to the fields of exploration of deep structures of the earth, division of regional geologic structure units, delineation of sedimentary basins, exploration of solid mineral products and oil and gas resources and the like. In recent years, with the upgrade of hardware equipment and the rapid development of computer technology, the accuracy and the efficiency of gravity exploration equipment are greatly improved, and meanwhile, a data processing and interpretation method is gradually developed from traditional qualitative interpretation to quantitative interpretation.

In gravity data interpretation, identification and imaging of the field source position is an essential task in gravity data processing and interpretation. The invention discloses a method for directly providing a field source position by using an intersection point of characteristic values of vertical gradients of different orders of gravity, which is necessary for quickly and accurately identifying the horizontal and depth positions of the field source.

Disclosure of Invention

The invention mainly aims to provide a field source position identification method based on the intersection points of gravity different step degree characteristic values, which utilizes the characteristic that the gravity different step degree vertical gradient characteristic values intersect at the position of a geologic body to identify the position of a field source, effectively solves the defect that the single second derivative characteristic value cannot obtain an accurate position due to the influence of burial depth, and has higher precision.

The technical scheme adopted by the invention is as follows: a field source position identification method based on gravity different step degree characteristic value intersection points comprises the following steps:

obtaining a real boundary result of the field source by solving the intersection points of the characteristic values of different step ratio lines;

and adopting a three-dimensional intersection point imaging method with different-order vertical gradients, carrying out downward continuation processing on the data, and searching intersection point positions of different-order gradients of the downward continuation data, namely the constructed positions.

Further, the obtaining of the real boundary result of the field source by obtaining the intersection point of the characteristic values of different step ratio values includes obtaining a first-order vertical gradient and a second-order vertical gradient of the three-dimensional gravity anomaly field of the underground anomaly:

the three-dimensional gravity anomaly is expressed as formula (1)

(1)

Wherein V is gravity potential, k is constant related to density and universal gravitation constant, N is construction index of geologic body, (x 0, z 0) is field source center coordinate, and (x, z) is observation point coordinate;

the first-order vertical gradient of the three-dimensional gravity anomaly can be deduced to be formula (2) through formula (1)

(2)

Wherein y is a north-south coordinate, and x is an east-west coordinate;

the corresponding relation between the horizontal position of the vertical gradient zero point and the depth of the field source is formula (3):

(3)

similarly, the second-order vertical gradient of the three-dimensional gravity anomaly is deduced to be formula (4) through formula (1)

(4)

The corresponding relation formula (5) of the horizontal position of the zero point of the second-order vertical gradient and the depth of the field source is as follows:

(5)

by combining equation (3) and equation (5), it can be obtained that when z-z0=0, i.e. the geologic body burial depth is 0, the null points of different order vertical gradients intersect at the true location of the field source (x 0, y 0).

Furthermore, the method for imaging intersection points of vertical gradients of different three-dimensional orders by performing downward continuation processing on data and finding intersection point positions of gradients of different orders of downward continuation data includes:

adopting a horizontal iteration method of stable downward continuation, and calculating downward continuation data by utilizing upward continuation data and different-order horizontal gradients, wherein the basic formula is as follows:

(6)

whereinFor gravity anomaly on the observation plane h, h is the downward continuation depth,is the gravity anomaly observed at the surface;

the calculation of vertical gradients increases the noise disturbance, for which the laplace equation is used to calculate the abnormal high order vertical gradients:

(7)。

furthermore, the method for imaging intersection points of vertical gradients of different three-dimensional orders by performing downward continuation processing on data and finding the positions of intersection points of gradients of different orders of downward continuation data further includes:

performing iterative computation, wherein the iterative process is as follows:

s1, data to be extended downwardsUpward continuation is obtained；

S2，；

S3，；

S4, mixingThe correction amount of (1);

s5, repeating S1 to S4 untilThe mean square error is less than a given value;

s6, the final downward continuation result is

Is the number of iterations.

The invention has the advantages that:

the method of the invention identifies the field source position by using the characteristic that the characteristic values of the vertical gradients of different orders of gravity intersect at the position of the geologic body, effectively solves the defect that the characteristic value of the single second derivative cannot obtain an accurate position due to the influence of the buried depth, and has higher precision.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention.

FIG. 1 is a flow chart of a method of the present invention;

FIG. 2 is a graph of the free air gravity anomaly of a depression in West lake, east Hai of the present invention;

FIG. 3 is a spatial gravity anomaly data volume diagram of the present invention;

FIG. 4 is a diagram of a TDX and FSTE boundary-identifying three-dimensional data volume of the present invention;

FIG. 5 is a graph showing the result of the cross-sectional structure tracking method of the present invention;

FIG. 6 is a diagram illustrating a distribution of the sunken structure of West lake of the east sea according to the structure tracking result of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1, a method for identifying a field source position based on intersections of feature values of different gravity gradients includes:

obtaining a real boundary result of the field source by solving the intersection points of the characteristic values of different step ratio lines;

and adopting a three-dimensional intersection point imaging method with different-order vertical gradients, carrying out downward continuation processing on the data, and searching intersection point positions of different-order gradients of the downward continuation data, namely the constructed positions.

The method of the invention identifies the field source position by using the characteristic that the characteristic values of the vertical gradients of different orders of gravity intersect at the position of the geologic body, effectively solves the defect that the characteristic value of the single second derivative cannot obtain an accurate position due to the influence of the buried depth, and has higher precision.

The principle of the invention is as follows:

the boundary identification method based on the gradient cannot obtain the real boundary of the field source, the error is larger along with the increase of the burial depth, and an accurate result can be obtained by solving the intersection point of the characteristic value connecting lines with different step ratio values.

Taking the first-order vertical gradient and the second-order vertical gradient of the three-dimensional gravity anomaly field of the underground anomaly as examples:

the three-dimensional gravity anomaly is expressed as formula (1)

(1)

Wherein V is gravity potential, k is constant related to density and universal gravitation constant, N is construction index of geologic body, (x 0, z 0) is field source center coordinate, and (x, z) is observation point coordinate;

the first-order vertical gradient of the three-dimensional gravity anomaly can be deduced to be formula (2) through formula (1)

(2)

Wherein y is a north-south coordinate, and x is an east-west coordinate;

the corresponding relation between the horizontal position of the vertical gradient zero point and the depth of the field source is formula (3):

(3)

similarly, the second-order vertical gradient of the three-dimensional gravity anomaly is deduced to be formula (4) through formula (1)

(4)

The corresponding relation formula (5) of the horizontal position of the zero point of the second-order vertical gradient and the depth of the field source is as follows:

(5)

by combining equation (3) and equation (5), it can be obtained that when z-z0=0, i.e. the geologic body burial depth is 0, the null points of different order vertical gradients intersect at the true location of the field source (x 0, y 0).

Therefore, a three-dimensional intersection point imaging method of vertical gradients of different orders is provided, namely, data is subjected to downward continuation processing, and intersection point positions of gradients of different orders of the downward continuation data are searched, namely the intersection point positions are constructed positions.

In order to obtain accurate results for intersection imaging, a steady downward continuation of the horizontal iteration method will be used.

The method calculates downwardly extended data using upwardly extended data and different order horizontal gradients. The basic formula is as follows:

(6)

whereinFor gravity anomaly on the observation plane h, h is the downward continuation depth,is the gravity anomaly observed at the surface;

the calculation of vertical gradients increases the noise disturbance, for which the laplace equation is used to calculate the abnormal high order vertical gradients:

(7)。

this downward continuation method has a high accuracy, but still produces a certain error. To minimize errors as much as possible, iterative calculations will be performed. The iterative process is as follows:

s1, data to be extended downwardsUpward continuation is obtained；

S2，；

S3，；

S4, mixingThe correction amount of (1);

s5, repeating S1 to S4 untilThe mean square error is less than a given value;

s6, the final downward continuation result is

Is the number of iterations.

The invention relates to a quick and high-precision construction position tracking method based on different-order vertical gradients of gravity.

The invention combines two boundary identification methods which utilize different-order vertical gradient characteristic values of gravity data to form a brand-new space imaging method;

detailed embodiments of methods for finding intersections of spatially distinct order vertical gradient eigenvalues.

The method of the invention provides reliable basis for subsequent exploration and geological interpretation.

The implementation case is as follows:

concrete implementation example of division of sunken structure of east-sea west lake

1) Collecting free air gravity anomaly from a depression in the west lake of the east sea (fig. 2);

2) a three-dimensional space gravity anomaly data volume is obtained by downward continuation or spatial data interpolation (fig. 3).

3) Calculating a three-dimensional space data volume of two boundary recognition results, namely a step boundary recognition method (FSTE) and a regularized inclination angle method (TDX), of the three-dimensional space gravity anomaly data volume (fig. 4).

4) Identifying the location of coincident extrema in the two boundary-identified three-dimensional volume of space by a deep learning algorithm, this location being considered as the identified location of the structural boundary (FIG. 5)

5) Division of the internal structure of the recess of West lake is accomplished according to the structure tracing method (FIG. 6)

Detailed description of the drawings:

FIG. 1 is a flow chart of a technical implementation of a method for constructing a position tracking method based on vertical gradients of different orders of gravity;

FIG. 2 shows free air gravity anomaly data for sago regions of the east-sea shelf basin with grid resolution of 1 'x 1';

FIG. 3, a downward continuation processing is performed on the free air gravity anomaly (FIG. 2) to obtain a lower half-space three-dimensional gravity anomaly data volume;

FIG. 4, TDX and FSTE conversion of (FIG. 3) to obtain two boundary-identifying three-dimensional data volumes;

FIG. 5, identifying the coincident extremum positions in two boundary identified three-dimensional data volumes (FIG. 4) by a deep learning algorithm, this position being considered as the identified structural boundary position, and intercepting a cross-section to display the results;

FIG. 6 shows the structural distribution of the sunken regions of the West lake region of the east-sea land-frame basin according to the results of FIG. 5.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.