CN102012517B - Underground medium imaging method and device - Google Patents

Abstract

The invention provides an underground medium imaging method, comprising the steps of: provoking an artificial earthquake at a shot point to obtain the earthquake data of the shot point and a detection point; resolving a paraxial approximate solution of a scalar wave equation to obtain a lens term and a diffraction term; splitting the diffraction term to obtain a diffraction term in vertical line direction and a diffraction term in survey line direction; respectively carrying out continuation solution on the diffraction term in vertical line direction and the diffraction term in survey line direction by adopting a spectrum differential matrix difference method according to the earthquake data of the shot point and the detection point, so as to respectively obtain the wave fields of the shot point and the detection point at an appointed underground depth layer, and carrying out convolution computation according to the wave fields of the shot point and the detection point at the appointed underground depth layer so as to obtain an image of an underground medium at the appointed underground depth layer. The invention also provides an underground medium imaging device. By adopting the underground medium imaging method and device provided by the invention, the influence of the dispersion is effectively reduced in the imaging process, thereby increasing the continuation step length and improving the imaging speed of the underground medium.

Description

Underground medium formation method and device

Technical field

The embodiment of the invention relates to the artificial earthquake exploration engineering, relates in particular to a kind of underground medium formation method and device.

Background technology

In seismic prospecting, in order to observe underground medium intuitively, confirm oil and gas reservoir information, need take the method for artificial earthquake exploration, the seismic event that produces through manual work is carried out to picture to underground medium.Concrete grammar is: bury explosive or other epicenter excitation underground at shot point, thus the artificial seismic event that produces; Be provided for receiving the geophone station of geological data on the face of land; This geological data is that shot point excites after the stratum reflexes to the seismic event information on the face of land; For example; Shot point excites after the stratum reflexes to the information such as earthquake wave amplitude on the face of land, and this geological data can reflect the information of the underground medium from the shot point to the geophone station, according to the geological data that receives underground medium is carried out to picture.

At present, after obtaining seismic event information, calculate through the finite difference of one way wave method underground medium is carried out to picture.In the finite difference computing method of one way wave method, difference operator is carried out the approximate of limited exponent number, adopt approximate difference operator respectively the geological data of in-line direction and line direction to be carried out difference.The approximate common method of difference operator being carried out limited exponent number is; It is approximate or quadravalence approximate that difference operator is carried out second order; For example, the approximate difference operator of the second order of method of finite difference is: the approximate difference operator of the quadravalence of

method of finite difference is:

wherein Δ x is the spacing of differential direction.

Adopting above-mentioned method of finite difference, is approximate to the limited precision of difference operator, can produce frequency dispersion easily if therefore step size is excessive in imaging computation process.For fear of the harmful effect of frequency dispersion for imaging, then must limit the size of step size, therefore reduced computing velocity for the moving equation of one way wave-wave, reduced the speed of underground medium imaging.

Summary of the invention

The embodiment of the invention provides a kind of underground medium formation method, in order to solve defective of the prior art, improves the speed of underground medium imaging.

The embodiment of the invention also provides a kind of underground medium imaging device, in order to solve defective of the prior art, improves the speed of underground medium imaging.

The embodiment of the invention provides a kind of underground medium formation method, comprising:

Excite artificial earthquake at shot point, obtain the geological data of shot point and geophone station;

The paraxonic approximate solution of decomposing scalar wave equation obtains lens item and diffraction item;

Split said diffraction item, obtain in-line direction diffraction item and line direction diffraction item;

According to the geological data of said shot point and geophone station, adopt spectrum differential matrix method of difference respectively said in-line direction diffraction item and line direction diffraction item to be carried out continuation and find the solution, obtain the wave field of the underground depth layer of appointment of said shot point and geophone station respectively;

Carry out convolution according to the wave field of the underground depth layer of appointment of said shot point and geophone station and calculate, obtain the picture of the underground medium of the underground depth layer of said appointment.

Aforesaid underground medium formation method; Wherein, Said geological data according to said shot point and geophone station; Adopt spectrum differential matrix method of difference respectively said in-line direction diffraction item and line direction diffraction item to be carried out continuation and find the solution, the wave field that obtains the underground depth layer of appointment of said shot point and geophone station respectively comprises:

The geological data of said shot point of substitution and geophone station in said in-line direction diffraction item and line direction diffraction item;

Adopt spectrum differential matrix method of difference to find the solution said in-line direction diffraction item and line direction diffraction item respectively, obtain to descend medially the in-line direction of depth layer and the wave field of line direction;

Judge whether the said depth layer of descending medially equals to specify underground depth layer;

If finish the calculation process that said continuation is found the solution;

Otherwise; The said in-line direction of depth layer and the wave field of line direction of descending medially of difference substitution in said in-line direction diffraction item and line direction diffraction item returns the said employing spectrum of execution differential matrix method of difference and finds the solution the step of said in-line direction diffraction item and line direction diffraction item respectively.

Aforesaid underground medium formation method, wherein, said employing spectrum differential matrix method of difference finds the solution said in-line direction diffraction item respectively and line direction diffraction item comprises:

Find the solution said in-line direction diffraction item and line direction diffraction item respectively according to difference algorithm, wherein, the difference operator of said difference algorithm is the spectrum differential matrix.

Aforesaid underground medium formation method, wherein, each in the said spectrum differential matrix is:

$d_{p,q}=\left\{\begin{array}{cc}\frac{1}{2}{\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)}^2{(-1)}^{p+q+1}\frac{1}{{\sin }^2(\mathrm{\π}(p-q)/n_x)},& p\≠q\\ -\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)\frac{2{(n_x/2)}^2+1}{6},& p=q\end{array}\right.$

Wherein, n _xFor the population variance of differential direction is counted, Δ x is the spacing of differential direction, and p is the capable sequence number of spectrum differential matrix, and q is the row sequence number of spectrum differential matrix.

The embodiment of the invention also provides a kind of underground medium imaging device, comprising:

Detecting unit is used for after shot point excites artificial earthquake, obtaining the geological data of shot point and geophone station;

First computing unit, the paraxonic approximate solution that is used to decompose scalar wave equation obtains lens item and diffraction item;

Split cells is used to split said diffraction item, obtains in-line direction diffraction item and line direction diffraction item;

Second computing unit; Be used for geological data according to said shot point and geophone station; Adopt spectrum differential matrix method of difference that said in-line direction diffraction item and line direction diffraction item are carried out continuation and find the solution, obtain the wave field of the underground depth layer of appointment of said shot point and geophone station respectively;

Image-generating unit is used for carrying out the convolution imaging according to the wave field of the underground depth layer of appointment of said shot point and geophone station, obtains the picture of the underground medium of the underground depth layer of said appointment.

Aforesaid underground medium imaging device, wherein, said second computing unit comprises:

The substitution module is used under the control of control module, and the geological data of said shot point of substitution and geophone station perhaps descends the in-line direction of depth layer and the wave field of line direction medially in said in-line direction diffraction item and line direction diffraction item;

Computing module is used for adopting spectrum differential matrix method of difference to find the solution said in-line direction diffraction item and line direction diffraction item respectively, obtains to descend medially the in-line direction of depth layer and the wave field of line direction;

Control module is used to judge whether the said depth layer of descending medially equals to specify underground depth layer; If finish the calculation process that said continuation is found the solution; Otherwise, the said in-line direction of depth layer and the wave field of line direction of descending medially of control substitution module substitution in said in-line direction diffraction item and line direction diffraction item.

Aforesaid underground medium imaging device, wherein, said computing module specifically is used for finding the solution said in-line direction diffraction item and line direction diffraction item respectively according to difference algorithm, and wherein, the difference operator of said difference algorithm is the spectrum differential matrix.

Aforesaid underground medium imaging device, wherein, each in the said spectrum differential matrix is:

$d_{p,q}=\left\{\begin{array}{cc}\frac{1}{2}{\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)}^2{(-1)}^{p+q+1}\frac{1}{{\sin }^2(\mathrm{\π}(p-q)/n_x)},& p\≠q\\ -\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)\frac{2{(n_x/2)}^2+1}{6},& p=q\end{array}\right.$

Wherein, n _xFor the population variance of differential direction is counted, Δ x is the spacing of differential direction, and p is the capable sequence number of spectrum differential matrix, and q is the row sequence number of spectrum differential matrix.

Can know by technique scheme; The embodiment of the invention through adopting the spectrum differential matrix as difference operator, has been carried out the approximate of infinite order precision to difference operator when finding the solution in-line direction diffraction item and line direction diffraction item; Therefore can not receive the influence of frequency dispersion in the imaging process; Thereby can increase step size, dwindle the computation period of the moving equation of one way wave-wave, so can improve the speed of underground medium imaging.

Description of drawings

In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art; To do one to the accompanying drawing of required use in embodiment or the description of the Prior Art below introduces simply; Obviously, the accompanying drawing in describing below is some embodiments of the present invention, for those of ordinary skills; Under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is the process flow diagram of the embodiment of the invention one underground medium formation method;

Fig. 2 is the structural representation of the embodiment of the invention two underground medium imaging devices.

Embodiment

For the purpose, technical scheme and the advantage that make the embodiment of the invention clearer; To combine the accompanying drawing in the embodiment of the invention below; Technical scheme in the embodiment of the invention is carried out clear, intactly description; Obviously, described embodiment is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills are not making the every other embodiment that is obtained under the creative work prerequisite, all belong to the scope of the present invention's protection.

Fig. 1 is the process flow diagram of the embodiment of the invention one underground medium formation method.As shown in Figure 1, this method may further comprise the steps.

Step 101: excite artificial earthquake at shot point, obtain the geological data of shot point and geophone station.

In this step, the geological data of shot point is according to exciting the preset data of artificial earthquake to obtain, and the geological data of geophone station obtains through detecting at geophone station.Geological data specifically can comprise: the amplitude information of shot point coordinate, geophone station coordinate, geophone station seismic event, seismic event travel-time and the geological data from the shot point to the geophone station is in the SI of geophone station.The detailed process of this step comprises: at first, the shot point and the geophone station of artificial earthquake is set, record or detection obtain the coordinate of shot point and geophone station.Then; Bury explosive underground also according to exciting the preset data of artificial earthquake to excite the generation seismic event at shot point; Receive this seismic event at geophone station and in underground medium, propagate the seismic event that back reflection goes back to the face of land, detect the amplitude information and the travel-time of seismic event from the shot point to the geophone station of the seismic event of geophone station.

Step 102: decompose the paraxonic approximate equation of scalar wave equation, obtain lens item and diffraction item.

The detailed process of this step comprises:

At first, seismic event is at the following scalar wave equation of underground communication satisfaction:

$\frac{{\∂}^{2}P}{{\∂x}^2}+\frac{{\∂}^{2}P}{{\∂y}^2}+\frac{{\∂}^{2}P}{{\∂z}^2}=\frac{1}{\mathrm{\υ}{(x,y,z)}^2}\frac{{\∂}^{2}P}{{\∂t}^2}$

Wherein, P is a pressure field, and (x, y z) are the SVEL of underground medium to υ, and x, y, z represent three number direction of principal axis of three-dimensional cartesian coordinate system, t express time respectively.Above-mentioned scalar wave equation is converted into Helmholtz equation and obtains the paraxonic approximate equation of this scalar wave equation.This paraxonic approximate equation is:

$\frac{\∂P}{\∂z}=\±\frac{\mathrm{i\ω}}{\mathrm{\υ}(x,y,z)}\sqrt{1+\frac{{\mathrm{\υ}}^2(x,y,z)}{{\mathrm{\ω}}^2}(\frac{{\∂}^2}{{\∂x}^2}+\frac{{\∂}^2}{\∂y^2})}P$

Wherein, ω is the earthquake wave frequency, and sign is represented the continuation direction.

Then, above-mentioned paraxonic approximate equation is approximately second-order equation, this second-order equation is expressed as:

$\frac{\∂P}{\∂z}=\frac{\mathrm{i\ω}}{\mathrm{\υ}(x,y,z)}[1+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{{\mathrm{\α}}_{i}S}{{\mathrm{\β}}_{i}S}]P$

Wherein, α _iWith β _iFor being optimized to the equation coefficient of image angle degree, n is that the number and the n of second-order equation is integer, S=S _x+ S _y, and

Next; Find the solution above-mentioned second-order equation, obtain lens items

and following diffraction item:

$\frac{\∂P_1}{\∂z}=\frac{\mathrm{i\ω}}{\mathrm{\υ}(x,y,z)}\frac{{\mathrm{\α}}_{1}S}{1+{\mathrm{\β}}_{1}S}{P}_1$

$\frac{\∂P_2}{\∂z}=\frac{\mathrm{i\ω}}{\mathrm{\υ}(x,y,z)}\frac{{\mathrm{\α}}_{2}S}{1+{\mathrm{\β}}_{2}S}{P}_2$

$......$

$\frac{\∂P_n}{\∂z}=\frac{\mathrm{i\ω}}{\mathrm{\υ}(x,y,z)}\frac{{\mathrm{\α}}_{n}S}{1+{\mathrm{\β}}_{n}S}{P}_n$

Step 103: split above-mentioned diffraction item, obtain in-line direction diffraction item and line direction diffraction item.

If the diffraction item that directly step 102 is obtained is found the solution, need relate to large-scale sparse matrix in the solution procedure and calculate, needing to cause the labor time; The restriction image taking speed; So, in step 103, above-mentioned diffraction item is split along in-line direction and line direction.The in-line direction diffraction item and the line direction diffraction item that split the back acquisition are respectively:

$\frac{\∂P_m}{\∂z}=\frac{\mathrm{i\ω}}{\mathrm{\υ}(x,y,z)}\frac{{\mathrm{\α}}_m{S}_x}{1+{\mathrm{\β}}_m{S}_x}{P}_m$

$\frac{\∂P_m}{\∂z}=\frac{\mathrm{i\ω}}{\mathrm{\υ}(x,y,z)}\frac{{\mathrm{\α}}_m{S}_y}{1+{\mathrm{\β}}_m{S}_y}{P}_m$

Wherein, x and y represent in-line direction and line direction respectively, and m is the second-order equation sequence number, and m=1,2 ..., n.

Step 104: according to the geological data of shot point and geophone station, adopt spectrum differential matrix method of difference respectively above-mentioned in-line direction diffraction item and line direction diffraction item to be carried out continuation and find the solution, obtain the wave field of the underground depth layer of appointment of shot point and geophone station respectively.

In this step, comprise shot point and geophone station are calculated respectively, particularly, to wherein one including following process.

At first, substitution geological data in in-line direction diffraction item and line direction diffraction item.

Then, adopt spectrum differential matrix method of difference to find the solution in-line direction diffraction item and line direction diffraction item respectively, obtain to descend medially the in-line direction of depth layer and the wave field of line direction.

At last, judge to descend depth layer whether to equal to specify underground depth layer medially; If, finishing the calculation process that continuation is found the solution, the in-line direction of descending depth layer medially of acquisition and the wave field of line direction are exactly the wave field of specifying underground depth layer; Otherwise; The in-line direction of depth layer and the wave field of line direction are descended in substitution medially respectively in in-line direction diffraction item and line direction diffraction item, return to carry out and adopt spectrum differential matrix method of difference to find the solution the step of in-line direction diffraction item and line direction diffraction item respectively.Adopt said method; In the wave field substitution in-line direction diffraction item and line direction diffraction item with the in-line direction of descending depth layer medially of calculating acquisition and line direction at every turn; Find the solution through circulation; Up to descending depth layer to equal to specify underground depth layer medially, finish the calculation process that continuation is found the solution.

To the geological data of shot point and geophone station,, calculate the wave field of the underground depth layer of appointment of shot point and geophone station respectively according to said process.

In said process,, all adopt difference algorithm to find the solution for in-line direction diffraction item and line direction diffraction item.The expression formula of the difference scheme of diffraction item is:

u _j，k+1+(α ₁-iβ ₁)(D ₂u _j，k+1)＝u _j，k+(α ₁+iβ ₁)(D ₂u _j，k)

Wherein, u is an item to be found the solution, and j representes the sequence number of the point of current Difference Calculation, D ₂Be difference operator, k is the sequence number of underground depth layer.

In embodiments of the present invention, adopt pseudo-differential operator and Lie algebra theoretical, to D ₂Adopt the approximate of infinite precision.Particularly, with D ₂Be approximately the spectrum differential matrix, each in this matrix is:

$d_{p,q}=\left\{\begin{array}{cc}\frac{1}{2}{\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)}^2{(-1)}^{p+q+1}\frac{1}{{\sin }^2(\mathrm{\π}(p-q)/n_x)},& p\≠q\\ -\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)\frac{2{(n_x/2)}^2+1}{6},& p=q\end{array}\right.$

Wherein, n _xFor the population variance of differential direction is counted, Δ x is the spacing of differential direction, and p is the capable sequence number of spectrum differential matrix, and q is the row sequence number of spectrum differential matrix.

In-line direction diffraction item respectively that the difference operator substitution is to be found the solution and line direction diffraction item solve the wave field of in-line direction and line direction.

Step 105: carry out convolution according to the wave field of the underground depth layer of appointment of above-mentioned shot point and geophone station and calculate, obtain to specify the picture of the underground medium of underground depth layer.

In this step, the concrete grammar of convolution imaging is: the wave field of shot point and geophone station is multiplied each other in the frequency field correspondence.

More than introduce through a pair of underground medium formation method of embodiment, below adopt the underground medium imaging device of this method to briefly introduce through two couples of embodiment.

Fig. 2 is the structural representation of the embodiment of the invention two underground medium imaging devices.As shown in Figure 2, this device specifically comprises: detecting unit 21, first computing unit 22, split cells 23, second computing unit 24 and image-generating unit 25.

Wherein, detecting unit 21 obtains the geological data of shot point and geophone station and sends this geological data to second computing unit 24 after shot point excites artificial earthquake.Wherein, geological data specifically comprises: the amplitude information of shot point coordinate, geophone station coordinate, geophone station seismic event, seismic event travel-time and the SI from the shot point to the geophone station.

The paraxonic approximate solution that first computing unit 22 decomposes scalar wave equation obtains lens item and diffraction item and sends split cells 23 to.Particularly, first computing unit 22 is converted into Helmholtz equation with scalar wave equation and obtains the paraxonic approximate equation of this scalar wave equation, and the paraxonic approximate equation is approximately second-order equation, finds the solution above-mentioned second-order equation, obtains lens item and diffraction item.

Lens item and diffraction item that split cells 23 receives from first computing unit 22 split this lens item, obtain in-line direction lens item and line direction lens item and send second computing unit 24 to.

In-line direction lens item and line direction lens item that second computing unit 24 receives from split cells 23; Reception is from the shot point of detecting unit 21 and the geological data of geophone station; Adopt spectrum differential matrix method of difference that above-mentioned in-line direction lens item and line direction lens item are carried out continuation and find the solution, obtain respectively shot point and geophone station the underground depth layer of appointment wave field and send image-generating unit 25 to.

Particularly, second computing unit 24 comprises: substitution module, computing module and control module.The substitution module is under the control of control module, and the geological data of substitution shot point and geophone station perhaps descends the in-line direction of depth layer and the wave field of line direction medially in in-line direction diffraction item and line direction diffraction item.Computing module adopts spectrum differential matrix method of difference to find the solution said in-line direction diffraction item and line direction diffraction item respectively, obtains to descend medially the in-line direction of depth layer and the wave field of line direction.Control module judges to descend depth layer whether to equal to specify underground depth layer medially; If finish the calculation process that continuation is found the solution; Otherwise the in-line direction of depth layer and the wave field of line direction are descended in the substitution in in-line direction diffraction item and line direction diffraction item of control substitution module medially.Wherein, any in shot point and the geophone station, computing module carries out one way ripple difference algorithm to said in-line direction lens item and line direction lens item respectively finds the solution, and wherein, the difference operator of one way ripple difference algorithm is the spectrum differential matrix.A kind of preferred implementation is that each in this spectrum differential matrix is:

$d_{p,q}=\left\{\begin{array}{cc}\frac{1}{2}{\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)}^2{(-1)}^{p+q+1}\frac{1}{{\sin }^2(\mathrm{\π}(p-q)/n_x)},& p\≠q\\ -\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)\frac{2{(n_x/2)}^2+1}{6},& p=q\end{array}\right.$

Wherein, n _xFor the population variance of differential direction is counted, Δ x is the spacing of differential direction, and p is the capable sequence number of spectrum differential matrix, and q is the row sequence number of spectrum differential matrix.

Image-generating unit 25 receives the wave field from the underground depth layer of appointment of the shot point of second computing unit 24 and geophone station, carries out the convolution imaging, the picture of the underground medium of the underground depth layer of acquisition appointment according to the wave field of the underground depth layer of appointment of shot point and geophone station.Particularly, image-generating unit 25 multiplies each other the wave field of shot point and geophone station in the frequency field correspondence, obtains the picture of the underground medium of the underground depth layer of appointment.

Visible by above embodiment; In the underground medium imaging process, adopt spectrum differential matrix method to find the solution in-line direction diffraction item and line direction diffraction item, adopt the spectrum differential matrix as difference operator; Because the spectrum differential matrix has carried out the approximate of infinite order precision to difference operator; Therefore solution procedure can not receive the influence of frequency dispersion, needn't worry that the increase of step size causes adverse effect to frequency dispersion, thereby can increase step size.Because in the computation process of the moving equation of one way wave-wave; With the corresponding computation period of each step size; Therefore the underground medium formation method of the embodiment of the invention has dwindled the computation period of the moving equation of one way wave-wave, improves computing velocity, so improved the speed of underground medium imaging.Practice shows; Reaching under the prerequisite of identical imaging effect, adopting the underground medium formation method and the device of the embodiment of the invention, step size can reach 2 times of step size of existing formation method; Therefore, the underground medium image taking speed can be brought up to 2 times that have formation method now.

Need to prove: for aforesaid each method embodiment; For simple description; So it all is expressed as a series of combination of actions, but those skilled in the art should know that the present invention does not receive the restriction of described sequence of movement; Because according to the present invention, some step can adopt other orders or carry out simultaneously.Secondly, those skilled in the art also should know, the embodiment described in the instructions all belongs to preferred embodiment, and related action and module might not be that the present invention is necessary.

In the above-described embodiments, the description of each embodiment is all emphasized particularly on different fields, do not have the part that details among certain embodiment, can be referring to the associated description of other embodiment.

One of ordinary skill in the art will appreciate that: all or part of step that realizes said method embodiment can be accomplished through the relevant hardware of programmed instruction; Aforesaid program can be stored in the computer read/write memory medium; This program the step that comprises said method embodiment when carrying out; And aforesaid storage medium comprises: various media that can be program code stored such as ROM, RAM, magnetic disc or CD.

What should explain at last is: above embodiment is only in order to explaining technical scheme of the present invention, but not to its restriction; Although with reference to previous embodiment the present invention has been carried out detailed explanation, those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that aforementioned each embodiment put down in writing, and perhaps part technical characterictic wherein is equal to replacement; And these are revised or replacement, do not make the spirit and the scope of the essence disengaging various embodiments of the present invention technical scheme of relevant art scheme.

Claims (2)

1. a underground medium formation method is characterized in that, comprising:

Excite artificial earthquake at shot point, obtain the geological data of shot point and geophone station;

The paraxonic approximate solution of decomposing scalar wave equation obtains lens item and diffraction item;

Split said diffraction item, obtain in-line direction diffraction item and line direction diffraction item;

According to the geological data of said shot point and geophone station, adopt spectrum differential matrix method of difference respectively said in-line direction diffraction item and line direction diffraction item to be carried out continuation and find the solution, obtain the wave field of the underground depth layer of appointment of said shot point and geophone station respectively;

Carry out convolution according to the wave field of the underground depth layer of appointment of said shot point and geophone station and calculate, obtain the picture of the underground medium of the underground depth layer of said appointment;

Said geological data according to said shot point and geophone station; Adopt spectrum differential matrix method of difference respectively said in-line direction diffraction item and line direction diffraction item to be carried out continuation and find the solution, the wave field that obtains the underground depth layer of appointment of said shot point and geophone station respectively comprises:

The geological data of said shot point of substitution and geophone station in said in-line direction diffraction item and line direction diffraction item;

Adopt spectrum differential matrix method of difference to find the solution said in-line direction diffraction item and line direction diffraction item respectively, obtain to descend medially the in-line direction of depth layer and the wave field of line direction;

Judge whether the said depth layer of descending medially equals to specify underground depth layer;

If finish the calculation process that said continuation is found the solution;

Otherwise; The said in-line direction of depth layer and the wave field of line direction of descending medially of difference substitution in said in-line direction diffraction item and line direction diffraction item returns the said employing spectrum of execution differential matrix method of difference and finds the solution the step of said in-line direction diffraction item and line direction diffraction item respectively;

Said employing spectrum differential matrix method of difference finds the solution said in-line direction diffraction item respectively and line direction diffraction item comprises:

Find the solution said in-line direction diffraction item and line direction diffraction item respectively according to difference algorithm, wherein, the difference operator of said difference algorithm is the spectrum differential matrix;

In the said spectrum differential matrix each is:

$d_{p,q}=\left\{\begin{array}{cc}\frac{1}{2}{\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)}^2{(-1)}^{p+q+1}\frac{1}{{\sin }^2(\mathrm{\π}(p-q)/n_x)},& p\≠q\\ -\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)\frac{2{(n_x/2)}^2+1}{6},& p=q\end{array}\right.$

Wherein, n _xFor the population variance of differential direction is counted, Δ x is the spacing of differential direction, and p is the capable sequence number of spectrum differential matrix, and q is the row sequence number of spectrum differential matrix.

2. a underground medium imaging device is characterized in that, comprising:

Detecting unit is used for after shot point excites artificial earthquake, obtaining the geological data of shot point and geophone station;

First computing unit, the paraxonic approximate solution that is used to decompose scalar wave equation obtains lens item and diffraction item;

Split cells is used to split said diffraction item, obtains in-line direction diffraction item and line direction diffraction item;

Second computing unit; Be used for geological data according to said shot point and geophone station; Adopt spectrum differential matrix method of difference that said in-line direction diffraction item and line direction diffraction item are carried out continuation and find the solution, obtain the wave field of the underground depth layer of appointment of said shot point and geophone station respectively;

Image-generating unit is used for carrying out the convolution imaging according to the wave field of the underground depth layer of appointment of said shot point and geophone station, obtains the picture of the underground medium of the underground depth layer of said appointment;

Said second computing unit comprises:

The substitution module is used under the control of control module, and the geological data of said shot point of substitution and geophone station perhaps descends the in-line direction of depth layer and the wave field of line direction medially in said in-line direction diffraction item and line direction diffraction item;

Computing module is used for adopting spectrum differential matrix method of difference to find the solution said in-line direction diffraction item and line direction diffraction item respectively, obtains to descend medially the in-line direction of depth layer and the wave field of line direction;

Control module is used to judge whether the said depth layer of descending medially equals to specify underground depth layer; If finish the calculation process that said continuation is found the solution; Otherwise, the said in-line direction of depth layer and the wave field of line direction of descending medially of control substitution module substitution in said in-line direction diffraction item and line direction diffraction item;

Said computing module specifically is used for finding the solution said in-line direction diffraction item and line direction diffraction item respectively according to difference algorithm, and wherein, the difference operator of said difference algorithm is the spectrum differential matrix;

In the said spectrum differential matrix each is:

$d_{p,q}=\left\{\begin{array}{cc}\frac{1}{2}{\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)}^2{(-1)}^{p+q+1}\frac{1}{{\sin }^2(\mathrm{\π}(p-q)/n_x)},& p\≠q\\ -\left(\frac{2\mathrm{\π}}{n_x\mathrm{\Δx}}\right)\frac{2{(n_x/2)}^2+1}{6},& p=q\end{array}\right.$

Wherein, n _xFor the population variance of differential direction is counted, Δ x is the spacing of differential direction, and p is the capable sequence number of spectrum differential matrix, and q is the row sequence number of spectrum differential matrix.

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