CN110361788B - Air-ground combined three-dimensional gravity data feature analysis and density inversion method - Google Patents
Air-ground combined three-dimensional gravity data feature analysis and density inversion method Download PDFInfo
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Abstract
The invention discloses a method for analyzing characteristics and inverting density of air-ground combined three-dimensional gravity data, which comprises the following steps: the limit height is found by looking for the height as the height rises when two anomalies cannot be resolved on an anomaly. The flight plan need not be designed to discuss flights above the limit altitude. The invention provides the best three-dimensional data acquisition through the correlation analysis and singular value decomposition method, and the cost loss is effectively reduced. And the three-dimensional data density inversion method is provided, because the three-dimensional data can acquire the characteristic of abnormal vertical variation, the inversion result of the geologic body with deeper buried depth is more convergent, the resolution is higher, meanwhile, a corresponding inversion calculation scheme is provided aiming at the problems of terrain fluctuation, scale, flight height and the like in the air-ground combined measurement, and a more effective scheme is provided for the geophysical method to turn to deep exploration.
Description
Technical Field
The invention relates to three-dimensional data inversion, in particular to a space-ground combined three-dimensional gravity data feature analysis and density inversion method.
Background
At present, along with the increasing perfection of aviation gravity exploration technology, the inversion of gravity and magnetic data develops towards the inversion of three-dimensional data, the three-dimensional gravity exploration can acquire abnormal horizontal and vertical variation characteristics, and compared with the previous single ground gravity or aviation gravity data, the inversion method has more geologic body information and higher resolution.
The three-dimensional gravity data has more information than single ground or aviation gravity data, and a better inversion result can be obtained. The three-dimensional data is obtained by combining aerial gravity measurement data obtained by flying for many times at different heights, and the flying height and the flying layer number have important relation with the information content contained in the three-dimensional data, so that the discussion of a better three-dimensional gravity data measurement scheme by analyzing the information content contained in the three-dimensional data under different conditions is very important.
Disclosure of Invention
The invention mainly aims to provide a space-ground combined three-dimensional gravity data feature analysis and density inversion method.
The technical scheme adopted by the invention is as follows: a method for analyzing characteristics and inverting density of air-ground combined three-dimensional gravity data comprises the following steps:
by looking for the height as the height rises when two anomalies cannot be resolved on an anomaly
Is the limit height. The flight plan need not be designed to discuss flights above the limit altitude. The feature that the anomaly cannot be distinguished is represented by correlation, and a specific formula for calculating a correlation coefficient is as follows:
wherein the content of the first and second substances,
is the covariance of X and Y;
is the variance of X and Y;
by carrying out correlation analysis on the ground gravity data and the data at each height, when the height is limited, because the low value between the two extreme points is changed into the high value, a negative value or a zero value appears in the correlation coefficient of the surface anomaly and the extreme height anomaly, and the extreme height is judged; the extreme heights are found with progressively encrypted discrete height changes without calculating the correlation of all heights to the ground.
Further, the method for analyzing characteristics and inverting density of the air-ground combined three-dimensional gravity data further comprises the following steps:
according to the actual situation of an exploration area, determining the number of flight layers by utilizing the inverted horizontal range and depth, estimating the general depth and range of an inverted target according to the previous exploration result, and determining the flight height by utilizing a theoretical model experiment.
Furthermore, the method for analyzing the characteristics and inverting the density of the air-ground combined three-dimensional gravity data further comprises the following steps:
carrying out continuation and correlation analysis by utilizing gravity data measured on the ground to obtain the limit height; then, carrying out model simulation experiments on the observation surface in the limit height according to the exploration range to obtain a relatively optimized flight altitude difference; and finally, designing a kernel function matrix through the range of the exploration area to perform singular value analysis, and determining the number of flight layers.
Furthermore, the method for analyzing the characteristics and inverting the density of the air-ground combined three-dimensional gravity data further comprises the following steps:
for three-dimensional gravity data joint inversion, combining the gravity data of different height layers for inversion, establishing a kernel function matrix of the height of an observation surface in advance for multilayer gravity data joint inversion, wherein a formula is shown as (2), and then solving an equation set by a conjugate gradient method:
in the formula (2), the reaction mixture is,
respectively representing a kernel function matrix of n heights,
represents the observed values at these n heights,
as a function of the depth weights at the n heights.
The invention has the advantages that:
the invention provides the best three-dimensional data acquisition through the correlation analysis and singular value decomposition method, and the cost loss is effectively reduced. And the three-dimensional data density inversion method is provided, because the three-dimensional data can acquire the characteristic of abnormal vertical variation, the inversion result of the geologic body with deeper buried depth is more convergent, the resolution is higher, meanwhile, a corresponding inversion calculation scheme is provided aiming at the problems of terrain fluctuation, scale, flight height and the like in the air-ground combined measurement, and a more effective scheme is provided for the geophysical method to turn to deep exploration.
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 diagram of the results of the air-ground cooperative inversion of the present invention;
FIG. 2 is a flow chart of the air-ground gravity survey flight 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.
A method for analyzing characteristics and inverting density of air-ground combined three-dimensional gravity data comprises the following steps:
by looking for the height as the height rises when two anomalies cannot be resolved on an anomaly
Is the limit height. The flight plan need not be designed to discuss flights above the limit altitude. The feature that the anomaly cannot be distinguished is represented by correlation, and a specific formula for calculating a correlation coefficient is as follows:
wherein the content of the first and second substances,
is the covariance of X and Y;
is the variance of X and Y;
by carrying out correlation analysis on the ground gravity data and the data at each height, when the height is limited, because the low value between the two extreme points is changed into the high value, a negative value or a zero value appears in the correlation coefficient of the surface anomaly and the extreme height anomaly, and the extreme height is judged; and because the process that the attenuation of the correlation becomes negative is monotonous and decreasing, the correlation of all the heights with the ground is not required to be calculated, and the limit height is searched by using gradually encrypted discrete height change.
The air-ground combined three-dimensional gravity data feature analysis and density inversion method further comprises the following steps:
according to the actual situation of an exploration area, determining the number of flight layers by utilizing the inverted horizontal range and depth, estimating the general depth and range of an inverted target according to the previous exploration result, and determining the flight height by utilizing a theoretical model experiment.
The selection of the flight layer number and the flight height is limited by factors in multiple aspects such as the horizontal range and the depth of an inversion area, the buried depth of an inversion target body, measurement errors and the like. Different flight schemes are designed for different regions, the number of flight layers is determined by utilizing the inverted horizontal range and depth according to the actual situation of an exploration region, the general depth and range of an inverted target are estimated according to an early exploration result, and then the flight height is determined by utilizing a theoretical model experiment. By analyzing the general situation, because the gravity anomaly is approximately inversely proportional to the square of the distance, in an ideal situation, when the flying height is three layers, a change characteristic inversely proportional to the square of the distance can be calculated, so that an accurate anomaly on any height can be obtained, and therefore the flying height of the three layers is considered to be the best in the general situation.
The air-ground combined three-dimensional gravity data feature analysis and density inversion method further comprises the following steps:
referring to fig. 2, as shown in fig. 2, firstly, continuation and correlation analysis are performed by using gravity data measured on the ground to obtain a limit height; then, carrying out model simulation experiments on the observation surface in the limit height according to the exploration range to obtain a relatively optimized flight altitude difference; and finally, designing a kernel function matrix through the range of the exploration area to perform singular value analysis, and determining the number of flight layers.
For the resolution of the multi-height inversion result, on one hand, because more effective characteristic values are needed to participate in the inversion, the higher the singular value curve amplitude is, the better the singular value curve amplitude is; on the other hand, because the single-height inversion effect needs to be compared, when the single-layer singular value curve amplitude is too high, the multi-height inversion effect only improves the inversion stability, but not greatly improves the resolution. Generally speaking, the multi-height inversion method is more suitable for a target body with a lower single-layer singular value curve amplitude value but a significantly improved multi-height joint singular value curve amplitude value, namely suitable for deeper geologic body inversion. As can be seen from the model experiments described below, the multi-height combination has a significant improvement in deep geologic inversion resolution.
The aerial measurement also has the problems of inconsistent multi-observation-surface scale and change of flying height at any time, the general actual measurement aerial gravity carries out interpolation and leveling processing on observation data, but part of calculation errors are added in the processing, so that the data for inversion is not accurate enough. It is proposed to perform direct inversion by designing a kernel function matrix that matches the observation points. By directly calculating the kernel function matrixes corresponding to the observation points with different heights, the air-ground cooperative inversion is directly carried out without leveling processing.
The air-ground combined three-dimensional gravity data feature analysis and density inversion method further comprises the following steps:
for three-dimensional gravity data joint inversion, combining the gravity data of different height layers for inversion, establishing a kernel function matrix of the height of an observation surface in advance for multilayer gravity data joint inversion, wherein a formula is shown as (2), and then solving an equation set by a conjugate gradient method:
in the formula (2), the reaction mixture is,
respectively representing a kernel function matrix of n heights,
represents the observed values at these n heights,
as a function of the depth weights at the n heights.
Actual data processing:
according to the method, the space-ground cooperative three-dimensional data density inversion method is applied to the abnormal actual measurement in the mine area of Shandong, and in the actual space-ground cooperative inversion, because the regional field responses contained in the actual data on different observation surfaces are different, the influence of a regional field is removed by carrying out position field separation on the cooperative inversion data on each observation surface. The invention utilizes the potential field to separate and remove the regional field and carries out continuation on the ground abnormity after denoising, and obtains the gravity abnormity on continuation heights of 100m and 200m respectively, as shown in figure 1.
As can be seen from fig. 1, the attenuation of the high value anomaly is larger with the increase of the extension height, so that the suppression of the high value anomaly on the weak anomaly can be weakened to a certain extent, and the resolution of the inversion result is improved. In the space-ground cooperative inversion, the underground is divided into 31 × 31 × 20 prisms with the length, width and height of 880, 1440 and 200m respectively, and the inversion result is shown in fig. 1. As can be seen from figure 1, five high-density areas mainly exist in the region, I and III are main large-scale high-density bodies, and the burial depth is about 1000 meters basically. The range and density of II density body are relatively small, and the II density body is supposed to be an ore body with deeper burial depth, because the inversion result is low due to the pressing of strong anomaly. The analysis results are consistent with the actual inversion results in chapter two, and compared with the actual inversion results in chapter two, the ranges of the ore bodies in positions I, II and V are all converged, and the range of the ore body in position IV is enlarged, which shows that the air-ground cooperative inversion result well improves the problem that weak anomaly in position IV is suppressed by strong anomaly, so that the resolution of the inversion result is low. In conclusion, the space-ground collaborative inversion method is also suitable for the actual region, and the obtained result has better resolution.
The invention provides the optimal design of three-dimensional data acquisition by a correlation analysis and singular value decomposition method, thereby effectively reducing the cost loss. And the three-dimensional data density inversion method is provided, because the three-dimensional data can acquire the characteristic of abnormal vertical variation, the inversion result of the geologic body with deeper buried depth is more convergent, the resolution is higher, meanwhile, a corresponding inversion calculation scheme is provided aiming at the problems of terrain fluctuation, scale, flight height and the like in the air-ground combined measurement, and a more effective scheme is provided for the geophysical method to turn to deep exploration.
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.
Claims (4)
1. A method for analyzing characteristics and inverting density of air-ground combined three-dimensional gravity data is characterized in that
The method comprises the following steps:
by looking for the height as the height rises when two anomalies cannot be resolved on an anomaly
For the limit height, the flight above the limit height does not need to be discussed when a flight scheme is designed, the characteristic that the abnormity cannot be distinguished is represented by correlation, and a formula for specifically calculating a correlation coefficient is as follows:
wherein the content of the first and second substances,
is the covariance of X and Y;
is the variance of X and Y;
by carrying out correlation analysis on the ground gravity data and the data at each height, when the height is limited, because the low value between the two extreme points is changed into the high value, a negative value or a zero value appears in the correlation coefficient of the surface anomaly and the extreme height anomaly, and the extreme height is judged; the extreme heights are found with progressively encrypted discrete height changes without calculating the correlation of all heights to the ground.
2. Air-ground combined three-dimensional gravity data feature analysis and density inversion of claim 1
The method is characterized by further comprising the following steps:
according to the actual situation of an exploration area, determining the number of flight layers by utilizing the inverted horizontal range and depth, estimating the general depth and range of an inverted target according to the previous exploration result, and determining the flight height by utilizing a theoretical model experiment.
3. Air-ground combined three-dimensional gravity data feature analysis and density inversion of claim 1
The method is characterized by further comprising the following steps:
carrying out continuation and correlation analysis by utilizing gravity data measured on the ground to obtain the limit height; then, carrying out model simulation experiments on the observation surface in the limit height according to the exploration range to obtain a relatively optimized flight altitude difference; and finally, designing a kernel function matrix through the range of the exploration area to perform singular value analysis, and determining the number of flight layers.
4. Air-ground combined three-dimensional gravity data feature analysis and density inversion of claim 1
The method is characterized by further comprising the following steps:
for three-dimensional gravity data joint inversion, combining the gravity data of different height layers for inversion, establishing a kernel function matrix of the height of an observation surface in advance for multilayer gravity data joint inversion, wherein a formula is shown as (2), and then solving an equation set by a conjugate gradient method:
in the formula (2), the reaction mixture is,
respectively representing a kernel function matrix of n heights,
represents the observed values at these n heights,
as a function of the depth weights at the n heights.
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