CN105807315A - Elastic vector reverse time migration imaging method - Google Patents

Abstract

The invention belongs to the field of exploration earth physics and specifically relates to an elastic vector reverse time migration imaging method. According to the invention, multi-component seismic data is used as input, an elastic wave propagation operator is utilized to carry out wave field prolongation, an elastic vector seismic wave field is constructed; and a decoupling prolongation equation method is utilized to obtain longitudinal and transverse wave fields of decoupling; vector points of the longitudinal and transverse wave fields with seismic source illumination compensation are utilized to construct elastic wave cross-correlation imaging conditions, and a multi-component seismic data elastic vector reverse time migration imaging result is obtained; and low-frequency noise suppression is carried out on the imaging result, and a final elastic vector reverse time migration imaging result is obtained. The elastic vector reverse time migration imaging method solves the scalar imaging problem of the longitudinal and transverse wave fields, and the imaging precision of elastic reverse time migration under a complex construction is improved.

Description

Elastic vector reverse-time migration formation method

Technical field

The invention belongs to exploration geophysics field, in particular it relates to a kind of elastic vector reverse-time migration formation method.

Background technology

Migration imaging currently for multi-component seismic data can be divided into two individual system: first scalar offset imaging system, and under this system, multi-component seismic data is first broken down into compressional wave data and shear wave data, then carries out PP and PS migration imaging respectively；It two is the multi-components elastic reverse-time migration imaging system of associating, multi-component seismic data is directly combined the boundary value condition as vector elastic wave field by this system, wave field reconstruct is carried out based on Time Migration of Elastic Wave Equation, final acquisition component imaging results or elastic wave field imaging results, be one accurate formation method in theory.Normal conditions, utilized Helmholtz to decompose before application image-forming condition to carry out wave field separation obtaining multi-components elastic reverse time migration imaging method by combining that elastic wave field imaging value is final result, but thus obtained compressional wave and shear wave all there occurs change relative to the amplitude and phase place being originally inputted wave field so that it is not enough that wave field separation result protects width.

In the last few years, decoupling extension equation method was developing progressively a kind of method obtaining longitudinal and transverse wave field into practicality.Decoupling extension equation method can obtain compressional wave and the shear wave of the amplitude decoupling consistent with phase place, but the longitudinal and transverse wave field after decoupling is vector field, utilizes these vector wave fields cannot directly obtain the imaging results of scalar, and this brings difficulty to following explanations work.

Summary of the invention

In order to solve the problem that vector wave field cannot directly obtain scalar imaging results, the present invention provides elastic vector reverse-time migration formation method, elastic vector reverse-time migration imaging based on the long-pending cross-correlation of elastic vector wave site, it is possible to obtain the elastic reverse-time migration imaging results of scalar form.

For achieving the above object, the present invention adopts following technical proposals:

Elastic vector reverse-time migration formation method, step is as follows:

Step 1: according to dielectric model, given source wavelet, it is achieved wave field just pushes out, utilizes decoupling extension equation method to obtain the longitudinal and transverse wave field of decoupling；

Step 2: according to dielectric model, using multi-component seismic data as boundary value condition, it is achieved the inverse time extrapolation of seismic wave field, utilizes decoupling extension equation method to obtain the longitudinal and transverse wave field of decoupling；

Step 3: utilize the long-pending cross-correlation image-forming condition of vector wave site of source wavefield illumination compensation to carry out imaging, it is thus achieved that the imaging results of scalar；

Step 4: the imaging results obtained is carried out low frequency noise compacting, it is thus achieved that final imaging results.

Relative to prior art, beneficial effects of the present invention is as follows: provide a kind of elastic vector reverse-time migration imaging implementation, the elastic wave cross-correlation image-forming condition built based on vector dot product can utilize the vector wave field to obtain scalar imaging results, it is to avoid the imaging section caused by component imaging is too much difficult to the difficulty being explained further.

Accompanying drawing explanation

Fig. 1 is the schematic flow sheet of elastic vector reverse-time migration formation method；

Fig. 2-1 is the velocity of longitudinal wave field according to the Marmosi2 elastic fluid model built；

Fig. 2-2 is the shear wave velocity field according to the Marmosi2 elastic fluid model built；

Fig. 3-1 be in the x direction 5.8 kms to forward in 12.4 km regions be extrapolated to the 1s moment adopt decoupling extension equation method to separate after the vector compressional wave component in the x-direction of source wavefield；

Fig. 3-2 be in the x direction 5.8 kms to forward in 12.4 km regions be extrapolated to the 1s moment adopt decoupling extension equation method to separate after the vector compressional wave component in the z-direction of source wavefield；

Fig. 3-3 be in the x direction 5.8 kms to forward in 12.4 km regions be extrapolated to the 1s moment adopt decoupling extension equation method to separate after the vector shear wave component in the x-direction of source wavefield；

Fig. 3-4 be in the x direction 5.8 kms to forward in 12.4 km regions be extrapolated to the 1s moment adopt decoupling extension equation method to separate after the vector shear wave component in the z-direction of source wavefield；

Fig. 4-1 be in the x direction 5.8 kms to inverse time continuation to the 1s moment in 12.4 km regions adopt decoupling extension equation method to separate after the vector compressional wave component in the x-direction of detection wave field；

Fig. 4-2 be in the x direction 5.8 kms to inverse time continuation to the 1s moment in 12.4 km regions adopt decoupling extension equation method to separate after the vector compressional wave component in the z-direction of detection wave field；

Fig. 4-3 be in the x direction 5.8 kms to inverse time continuation to the 1s moment in 12.4 km regions adopt decoupling extension equation method to separate after the vector shear wave component in the x-direction of detection wave field；

Fig. 4-4 be in the x direction 5.8 kms to inverse time continuation to the 1s moment in 12.4 km regions adopt decoupling extension equation method to separate after the vector shear wave component in the z-direction of detection wave field；

Fig. 5-1 is 5.8 kms in the x direction that obtain of the elastic wave cross-correlation image-forming condition adopting vector dot product to build to the PP imaging section in 12.4 km regions；

Fig. 5-2 is 5.8 kms in the x direction that obtain of the elastic wave cross-correlation image-forming condition adopting vector dot product to build to the PS imaging section in 12.4 km regions；

Fig. 5-3 is 5.8 kms in the x direction that obtain of the elastic wave cross-correlation image-forming condition adopting vector dot product to build to the SP imaging section in 12.4 km regions；

Fig. 5-4 is 5.8 kms in the x direction that obtain of the elastic wave cross-correlation image-forming condition adopting vector dot product to build to the SS imaging section in 12.4 km regions；

Fig. 6-1 is after final superposition and carries out the PP imaging section of Laplce's filtering；

Fig. 6-2 is after final superposition and carries out the PS imaging section of Laplce's filtering；

Fig. 6-3 is after final superposition and carries out the SP imaging section of Laplce's filtering；

Fig. 6-4 is after final superposition and carries out the SS imaging section of Laplce's filtering.

Detailed description of the invention

As it is shown in figure 1, elastic vector reverse-time migration method, step is as follows:

Step 1: according to dielectric model, given source wavelet, it is achieved wave field just pushes out, utilizes decoupling extension equation method to obtain the longitudinal and transverse wave field of decoupling, and concrete grammar is as follows:

(1), according to dielectric model set in advance, load source wavelet, utilize elastic wave propagation operator, it is achieved the forward time continuation of seismic wave field, build source vector wave field:

Utilize following one-order velocity-stress equations for elastic waves

$\begin{array}{cc}\left\{\begin{array}{c}\stackrel{\·}{\mathrm{\τ}}={\mathrm{CL}}^{T}v\\ \mathrm{\ρ}\stackrel{\·}{v}=L\mathrm{\τ}\end{array}\right.,& \backslash *MERGEFORMAT\end{array}---\left(1\right)$

Building source wavefield and just pushing out staggering mesh finite-difference operator, wherein ρ is density, and C is elastic fluid stiffness matrix, v=(v_x,v_y,v_z)^TRepresenting Particle Vibration Velocity vector field, superscript notation " T " represents transposition, v_xRepresent Particle Vibration Velocity vector field component in the x-direction, v_yRepresent the Particle Vibration Velocity vector field component along y, v_zRepresent the Particle Vibration Velocity vector field component along z, τ=(σ_xx,σ_yy,σ_zz,τ_yz,τ_xz,τ_xy)^TIt is stress tensor, σ_xx、σ_yyAnd σ_zzIt is direct stress, τ_yz、τ_xzAnd τ_xyIt is shearing stress,Represent Particle Vibration Velocity vector field derivative on time orientation,Representing stress tensor derivative on time orientation, L is differential matrix,

$L=\left[\begin{array}{cccccc}{l}_x& 0& 0& 0& l_z& l_y\\ 0& l_y& 0& l_z& 0& l_x\\ 0& 0& l_z& l_y& l_x& 0\end{array}\right],$

Wherein, l_x, l_yAnd l_zRepresenting the derivative along x, y and z direction respectively, in isotropic medium, stiffness matrix C is expressed as

$C=\left[\begin{array}{cccccc}\mathrm{\λ}+2\mathrm{\μ}& \mathrm{\λ}& \mathrm{\λ}& 0& 0& 0\\ \mathrm{\λ}& \mathrm{\λ}+2\mathrm{\μ}& \mathrm{\λ}& 0& 0& 0\\ \mathrm{\λ}& \mathrm{\λ}& \mathrm{\λ}+2\mathrm{\μ}& 0& 0& 0\\ 0& 0& 0& \mathrm{\μ}& 0& 0\\ 0& 0& 0& 0& \mathrm{\μ}& 0\\ 0& 0& 0& 0& 0& \mathrm{\μ}\end{array}\right],$

Wherein λ and μ is Lame Coefficient.Above-mentioned wave equation is carried out discretization and obtains following elastic wave continuation operator:

$\begin{array}{c}\left\{\begin{array}{c}{\left({\mathrm{\τ}}^S\right)}^{(n+1)\mathrm{\Δ}t}=\left(\frac{1}{1+0.5\mathrm{\η}\mathrm{\Δ}t}\right)\left(\right(1-0.5\mathrm{\η}\mathrm{\Δ}t){\left({\mathrm{\τ}}^S\right)}^{n\mathrm{\Δ}t}+{\mathrm{\ΔtCD}}^f{\left(v^S\right)}^{(n+1/2)\mathrm{\Δ}t})\\ {\left(v^S\right)}^{(n+1/2)\mathrm{\Δ}t}=\left(\frac{1}{1+0.5\mathrm{\η}\mathrm{\Δ}t}\right)\left(\right(1-0.5\mathrm{\η}\mathrm{\Δ}t){\left(v^S\right)}^{(n-1/2)\mathrm{\Δ}t}+\frac{1}{\mathrm{\ρ}}{\mathrm{\ΔtD}}^b{\left(v^S\right)}^{n\mathrm{\Δ}t})\end{array}\right.\\ \backslash *MERGEFORMAT---\left(2\right)\end{array},$

Wherein, τ^SRepresent the discrete stress field of source wavefield, v^SRepresenting the discrete Particle Vibration Velocity field of source wavefield, η is border absorptance, absorptance η=0 in target area, absorptance η=200 (0.5-0.5cos (π r/R)), r=1,2 in absorption region, border, ..., R, R is the thickness of absorbed layer, π represents that pi, Δ t are time sampling interval, and n Δ t represents whole time point, (n+1/2) Δ t is half timing node, n=1,2, ..., N, T₀=N Δ t represents that total earthquake record receives duration, D^fAnd D^bRepresenting high-order staggering mesh finite-difference matrix operator respectively, expression is

$D^f={\left[\begin{array}{cccccc}{D}_x^{+}& 0& 0& 0& D_z^{-}& D_y^{-}\\ 0& D_y^{+}& 0& D_z^{-}& 0& D_x^{-}\\ 0& 0& D_z^{+}& D_y^{-}& D_y^{-}& 0\end{array}\right]}^T$

With

$D^b=\left[\begin{array}{cccccc}{D}_x^{-}& 0& 0& 0& D_z^{+}& D_y^{+}\\ 0& D_y^{-}& 0& D_z^{+}& 0& D_x^{+}\\ 0& 0& D_z^{-}& D_y^{+}& D_y^{+}& 0\end{array}\right],$

WhereinWithRepresent forwardly and rearwardly Difference Schemes with Staggered in the x-direction,WithRepresent forwardly and rearwardly Difference Schemes with Staggered in the y-direction, whereinWithRepresenting forwardly and rearwardly Difference Schemes with Staggered in the z-direction, concrete form is as follows:

$D_x^{+}f(i,j,k)=\frac{1}{\mathrm{\Δ}x}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i+m,j,k)-f(i-m+1,j,k)\],$

$D_x^{-}f(i,j,k)=\frac{1}{\mathrm{\Δ}x}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i+m-1,j,k)-f(i-m,j,k)\],$

$D_y^{+}f(i,j,k)=\frac{1}{\mathrm{\Δ}y}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j+m,k)-f(i,j-m+1,k)\],$

$D_y^{-}f(i,j,k)=\frac{1}{\mathrm{\Δ}y}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j+m-1,k)-f(i,j-m,k)\],$

$D_Z^{+}f(i,j,k)=\frac{1}{\mathrm{\Δ}z}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j,k+m)-f(i,j,k-m+1)\],$

$D_z^{-}f(i,j,k)=\frac{1}{\mathrm{\Δ}z}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j,k+m-1)-f(i,j,k-m)\].$

Wherein, Δ x, Δ y and the Δ z respectively sampling interval along x, y and z direction,Being 2M rank staggering mesh finite-difference coefficients, (i, j k) are space networks lattice point (i, j, smooth function k) to f.

(2), in source wavefield forward time continuation process, the P-wave And S data of the source wavefield of decoupling extension equation method acquisition decoupling are utilized:

Wave field extrapolation process utilizes decoupling extension equation method obtain the P-wave And S field data of decoupling, first passes through formula (3) and calculate source wavefield compressional wave stress wave field:

$\begin{array}{cc}{\stackrel{\·}{\mathrm{\σ}}}_P^S=(\mathrm{\λ}+2\mathrm{\μ})\▿\·v^S,& \backslash *MERGEFORMAT\end{array}---\left(3\right)$

WhereinSource wavefield compressional wave stress field,Represent compressional wave stress wave field derivative on time orientation,Represent divergence operator, obtain the Particle Vibration Velocity field of focus compressional wave again through compressional wave stress field:

$\begin{array}{cc}{\stackrel{\·}{v}}_P^S=\▿{\mathrm{\σ}}_P^S.& \backslash *MERGEFORMAT\end{array}---\left(4\right)$

WhereinRepresent source wavefield longitudinal-wave particle vibration velocity field,The Particle Vibration Velocity field of expression source wavefield compressional wave derivative on time orientation,Represent gradient operator,The Particle Vibration Velocity vector field of expression source wavefield compressional wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of source wavefield compressional wave,Represent the Particle Vibration Velocity vector field component along z of source wavefield compressional wave, finally from the total wave field v of focus^SIn deduct source wavefield longitudinal wave fieldObtain source wavefield shear wave field, namely

$\begin{array}{cc}{v}_S^S=v^S-v_P^S,& \backslash *MERGEFORMAT\end{array}---\left(5\right)$

WhereinRepresent the Particle Vibration Velocity field of source wavefield shear wave,The Particle Vibration Velocity vector field of expression source wavefield shear wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of source wavefield shear wave,Represent the Particle Vibration Velocity vector field component along z of source wavefield shear wave.Outside description word describes, can also embodying the present invention in Figure of description intuitively, accompanying drawing 3-1 is the focus longitudinal wave field that obtains after the elastic wave field separation that rate pattern 5.8 kms in the x direction to the 12.4 km regions that 2-1 and Fig. 2 with reference to the accompanying drawings-2 is given are calculated component in the x-direction；Accompanying drawing 3-2 is the focus longitudinal wave field that obtains after the elastic wave field separation that rate pattern 5.8 kms in the x direction to the 12.4 km regions that 2-1 and Fig. 2 with reference to the accompanying drawings-2 is given are calculated component in the z-direction；Accompanying drawing 3-3 is the focus shear wave field that obtains after the elastic wave field that rate pattern 5.8 kms in the x direction to the 12.4 km regions that 2-1 and Fig. 2 with reference to the accompanying drawings-2 is given are calculated separates component in the x-direction, and accompanying drawing 3-4 is the focus shear wave field that obtains after the elastic wave field separation that rate pattern 5.8 kms in the x direction to the 12.4 km regions that 2-1 and Fig. 2-2 with reference to the accompanying drawings is given are calculated component in the z-direction.From accompanying drawing 3-1 to accompanying drawing 3-4 it can clearly be seen that wave field is separated comes.

Step 2: according to dielectric model, using multi-component seismic data as boundary value condition, it is achieved the inverse time extrapolation of seismic wave field, utilizes decoupling extension equation method to obtain the longitudinal and transverse wave field of decoupling, and concrete grammar is as follows:

(1), according to dielectric model set in advance, using the multi-component seismic data of surface seismic records as boundary value condition, utilize elastic wave propagation operator, it is achieved the inverse time continuation of seismic wave field, build detection vector wave field:

Multi-component earthquake data is used as boundary value condition, is loaded in following inverse time extrapolation equation

$\begin{array}{c}\left\{\begin{array}{c}{\left({\mathrm{\τ}}^R\right)}^{(n+1)\mathrm{\Δ}t}=\left(\frac{1}{1+0.5\mathrm{\η}\mathrm{\Δ}t}\right)\left(\right(1-0.5\mathrm{\η}\mathrm{\Δ}t){\left({\mathrm{\τ}}^R\right)}^{n\mathrm{\Δ}t}+{\mathrm{\ΔtCD}}^f{\left(v^R\right)}^{(n+1/2)\mathrm{\Δ}t})\\ {\left(v^R\right)}^{(n+1/2)\mathrm{\Δ}t}=\left(\frac{1}{1+0.5\mathrm{\η}\mathrm{\Δ}t}\right)\left(\right(1-0.5\mathrm{\η}\mathrm{\Δ}t){\left(v^R\right)}^{(n-1/2)\mathrm{\Δ}t}+\frac{1}{\mathrm{\ρ}}{\mathrm{\ΔtD}}^b{\left(v^R\right)}^{n\mathrm{\Δ}t})\end{array}\right.\\ \backslash *MERGEFORMAT---\left(2\right)\end{array},$

Wherein, τ^RRepresent the discrete stress field of detection wave field, v^RRepresenting the discrete Particle Vibration Velocity field of detection wave field, η is border absorptance, absorptance η=0 in target area, absorptance η=200 (0.5-0.5cos (π r/R)), r=1,2 in absorption region, border, ..., R, R is the thickness of absorbed layer, π represents that pi, Δ t are time sampling interval, and n Δ t represents whole time point, (n+1/2) Δ t is half timing node, n=1,2, ..., N, T₀=N Δ t represents that total earthquake record receives duration, D^fAnd D^bRepresenting high-order staggering mesh finite-difference matrix operator respectively, expression is

$D^f={\left[\begin{array}{cccccc}{D}_x^{+}& 0& 0& 0& D_z^{-}& D_y^{-}\\ 0& D_y^{+}& 0& D_z^{-}& 0& D_x^{-}\\ 0& 0& D_z^{+}& D_y^{-}& D_y^{-}& 0\end{array}\right]}^T$

With

$D^b=\left[\begin{array}{cccccc}{D}_x^{-}& 0& 0& 0& D_z^{+}& D_y^{+}\\ 0& D_y^{-}& 0& D_z^{+}& 0& D_x^{+}\\ 0& 0& D_z^{-}& D_y^{+}& D_y^{+}& 0\end{array}\right],$

WhereinWithRepresent forwardly and rearwardly Difference Schemes with Staggered in the x-direction,WithRepresent forwardly and rearwardly Difference Schemes with Staggered in the y-direction, whereinWithRepresenting forwardly and rearwardly Difference Schemes with Staggered in the z-direction, concrete form is as follows:

$D_x^{+}f(i,j,k)=\frac{1}{\mathrm{\Δ}x}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i+m,j,k)-f(i-m+1,j,k)\],$

$D_x^{-}f(i,j,k)=\frac{1}{\mathrm{\Δ}x}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i+m-1,j,k)-f(i-m,j,k)\],$

$D_y^{+}f(i,j,k)=\frac{1}{\mathrm{\Δ}y}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j+m,k)-f(i,j-m+1,k)\],$

$D_y^{-}f(i,j,k)=\frac{1}{\mathrm{\Δ}y}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j+m-1,k)-f(i,j-m,k)\],$

$D_Z^{+}f(i,j,k)=\frac{1}{\mathrm{\Δ}z}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j,k+m)-f(i,j,k-m+1)\],$

$D_z^{-}f(i,j,k)=\frac{1}{\mathrm{\Δ}z}\underset{m=1}{\overset{M}{\Σ}}{c}_m^{\left(M\right)}\[f(i,j,k+m-1)-f(i,j,k-m)\].$

Wherein, Δ x, Δ y and the Δ z respectively sampling interval along x, y and z direction,Being 2M rank staggering mesh finite-difference coefficients, (i, j k) are space networks lattice point (i, j, smooth function k) to f.

(2), in detection wave field inverse time continuation process, the P-wave And S data of the detection wave field of decoupling extension equation method acquisition decoupling are utilized:

Wave field extrapolation process utilizes decoupling extension equation method obtain the P-wave And S field data of decoupling, first passes through formula (7) and calculate detection wave field compressional wave stress field:

$\begin{array}{cc}{\stackrel{\·}{\mathrm{\σ}}}_P^R=(\mathrm{\λ}+2\mathrm{\μ})\▿\·v^R,& \backslash *MERGEFORMAT\end{array}---\left(7\right)$

WhereinDetection wave field compressional wave stress field,Represent detection wave field compressional wave stress field derivative on time orientation,Represent divergence operator, obtain the Particle Vibration Velocity field of detection wave field compressional wave again through detection wave field compressional wave stress field:

$\begin{array}{cc}{\stackrel{\·}{v}}_P^R=\▿{\mathrm{\σ}}_P^R.& \backslash *MERGEFORMAT\end{array}---\left(8\right)$

WhereinRepresent detection wave field longitudinal-wave particle vibration velocity field,The Particle Vibration Velocity field of expression detection wave field compressional wave derivative on time orientation,Represent gradient operator,The Particle Vibration Velocity vector field of expression detection wave field compressional wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of detection wave field compressional wave,Represent the Particle Vibration Velocity vector field component along z of detection wave field compressional wave, finally from the total wave field v of detection wave field^RIn deduct detection wave field longitudinal wave fieldObtain detection wave field shear wave field, namely

$\begin{array}{cc}{v}_S^R=v^R-v_P^R,& \backslash *MERGEFORMAT\end{array}---\left(9\right)$

WhereinRepresent the Particle Vibration Velocity field of detection wave field shear wave,The Particle Vibration Velocity vector field of expression detection wave field shear wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of detection wave field shear wave,Represent the Particle Vibration Velocity vector field component along z of detection wave field shear wave.Accompanying drawing 4-1 is detection wave field by solving vector longitudinal wave field that decoupling extension equation method obtains component in the x-direction；The vector longitudinal wave field that accompanying drawing 4-2 is detection wave field to be obtained by decoupling extension equation method component in the z-direction；The vector shear wave field that accompanying drawing 4-3 is detection wave field to be obtained by decoupling extension equation method component in the x-direction, the vector shear wave field that accompanying drawing 4-4 is detection wave field to be obtained by decoupling extension equation method component in the z-direction.From accompanying drawing 4-1 to accompanying drawing 4-4 it can clearly be seen that wave field is separated comes.

Step 3: utilizing the long-pending cross-correlation image-forming condition of vector wave site of source wavefield illumination compensation to carry out imaging, it is thus achieved that the imaging results of scalar, concrete grammar is as follows:

The detection wave field decoupling P-wave And S that source wavefield decoupling P-wave And S that step 1 obtains and step 2 obtain is utilized to carry out following

$\begin{array}{cc}\begin{array}{c}{I}_{PP}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_P^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_P^S}\\ I_{PS}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_S^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_P^S}\\ I_{SP}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_P^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_S^S}\\ I_{SS}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_S^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_S^S}\end{array},& \backslash *MERGEFORMAT\end{array}---\left(10\right)$

Vector dot product cross-correlation imaging, and carry out focus illumination compensation, obtain multi-component seismic data elasticity vector reverse-time migration scalar imaging results.Wherein I_PPRepresent PP imaging results, I_PSIt is PS imaging results, I_SPIt is SP imaging results, I_SSIt is SS imaging results, t express time, T₀Represent that earthquake record receives duration,Represent source wavefield longitudinal-wave particle vibration velocity field,The Particle Vibration Velocity vector field of expression source wavefield compressional wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of source wavefield compressional wave,Represent the Particle Vibration Velocity vector field component along z of source wavefield compressional wave,Represent detection wave field longitudinal-wave particle vibration velocity field,The Particle Vibration Velocity vector field of expression detection wave field compressional wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of detection wave field compressional wave,Represent the Particle Vibration Velocity vector field component along z of detection wave field compressional wave,Represent the Particle Vibration Velocity field of source wavefield shear wave,The Particle Vibration Velocity vector field of expression source wavefield shear wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of source wavefield shear wave,Represent the Particle Vibration Velocity vector field component along z of source wavefield shear wave,Represent the Particle Vibration Velocity field of detection wave field shear wave,The Particle Vibration Velocity vector field of expression detection wave field shear wave component in the x-direction,Represent the Particle Vibration Velocity vector field component along y of detection wave field shear wave,Representing the Particle Vibration Velocity vector field component along z of detection wave field shear wave, symbol represents vector dot product.Outside description word describes, it is also possible to embody the present invention in Figure of description intuitively, Fig. 5-1 is the PP imaging section that the elastic wave cross-correlation image-forming condition utilizing the vector dot product based on illumination compensation to build obtains；Fig. 5-2 is the PS imaging section that the elastic wave cross-correlation image-forming condition utilizing the vector dot product based on illumination compensation to build obtains；Fig. 5-3 is the SP imaging section that the elastic wave cross-correlation image-forming condition utilizing the vector dot product based on illumination compensation to build obtains；Fig. 5-4 is the SS imaging section that the elastic wave cross-correlation image-forming condition utilizing the vector dot product based on illumination compensation to build obtains.

Step 4: the imaging results obtained is carried out low frequency noise compacting, and specific implementation method is as follows:

Utilize following Laplce's filtering algorithm

$\begin{array}{cc}\begin{array}{c}{I}_{PP}^{Lap}={\▿}^2{I}_{PP}\\ I_{PS}^{Lap}={\▿}^2{I}_{PS}\\ I_{PS}^{Lap}={\▿}^2{I}_{SP}\\ I_{SS}^{Lap}={\▿}^2{I}_{SS}\end{array},& \backslash *MERGEFORMAT\end{array}---\left(11\right)$

It is filtered imaging section processing, obtains final imaging results.WhereinRepresent Laplace operator,WithIt is by the filtered PP of Laplce, PS, SP and SS imaging section respectively.Fig. 6-1 is final superposition the PP imaging section carrying out Laplce's filtering.Fig. 6-2 is final superposition the PS imaging section carrying out Laplce's filtering, and Fig. 6-3 is final superposition the SP imaging section carrying out Laplce's filtering, and Fig. 6-4 is final superposition the SS imaging section carrying out Laplce's filtering.

Claims (5)

1. an elastic vector reverse-time migration formation method, it is characterised in that step is as follows:

Step 1: according to dielectric model, given source wavelet, it is achieved wave field just pushes out, utilizes decoupling extension equation method to obtain the longitudinal and transverse wave field of decoupling；

Step 2: according to dielectric model, using multi-component seismic data as boundary value condition, it is achieved the inverse time extrapolation of seismic wave field, utilizes decoupling extension equation method to obtain the longitudinal and transverse wave field of decoupling；

Step 3: utilize the long-pending cross-correlation image-forming condition of vector wave site of source wavefield illumination compensation to carry out imaging, it is thus achieved that the imaging results of scalar；

Step 4: the imaging results obtained is carried out low frequency noise compacting, it is thus achieved that final imaging results.

2. elastic vector reverse-time migration formation method according to claim 1, it is characterised in that the concrete methods of realizing of step 1 is as follows:

(1), according to dielectric model set in advance, load source wavelet, utilize elastic wave propagation operator, it is achieved the forward time continuation of seismic wave field, build source vector wave field；

(2), in source wavefield forward time continuation process, the P-wave And S data of the source wavefield of decoupling extension equation method acquisition decoupling are utilized.

3. elastic vector reverse-time migration formation method according to claim 1, it is characterised in that the concrete methods of realizing of step 2 is as follows:

(1), according to dielectric model set in advance, using the multi-component seismic data of surface seismic records as boundary value condition, utilize elastic wave propagation operator, it is achieved the inverse time continuation of seismic wave field, build detection vector wave field；

(2), in detection wave field inverse time continuation process, the P-wave And S data of the detection wave field of decoupling extension equation method acquisition decoupling are utilized.

4. elastic vector reverse-time migration formation method according to claim 1, it is characterized in that, the concrete methods of realizing of step 3 is as follows: utilize the detection wave field decoupling P-wave And S that source wavefield decoupling P-wave And S that step 1 obtains and step 2 obtain to carry out following

$I_{PP}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_P^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_P^S}$

$I_{PS}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_S^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_P^S\·v_P^S}$

$I_{SP}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_P^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_S^S}$

$I_{SS}=\frac{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_S^R}{\underset{t=0}{\overset{T_0}{\Σ}}{v}_S^S\·v_S^S}$

Vector dot product cross-correlation imaging, and carry out focus illumination compensation, obtain multi-component seismic data elasticity vector reverse-time migration scalar imaging results.Wherein I_PPRepresent PP imaging results, I_PSIt is PS imaging results, I_SPIt is SP imaging results, I_SSIt is SS imaging results, t express time, T₀Represent that earthquake record receives duration,Represent source wavefield longitudinal-wave particle vibration velocity field,Represent detection wave field longitudinal-wave particle vibration velocity field,Represent source wavefield shear wave Particle Vibration Velocity field,Representing detection wave field shear wave Particle Vibration Velocity field, symbol represents vector dot product.

5. elastic vector reverse-time migration formation method described according to claim 1, it is characterized in that, the concrete methods of realizing of step 4 is as follows: utilize Laplace operator that imaging section is filtered, and carries out lower wave number Noise Elimination, the final stacked section obtained.