Calculation method, storage medium and device for seabed reflection coefficient of point source elastic wave

Abstract

The present disclosure relates to a calculation method, a storage medium and a device for a seabed reflection coefficient of point source elastic wave. The method includes initializing a calculation accuracy and a calculation range of the seabed reflection coefficient; discretizing a parameter space and obtaining the seabed reflection coefficient of point source elastic wave; combining an equivalent equation and a traditional calculation equation for the seabed reflection coefficient of point source elastic wave; solving an undetermined coefficient of the equivalent equation; obtaining a concise expression for the seabed reflection coefficient of point source under an accuracy in the first step; calculating the seabed reflection coefficient of point source elastic wave within a given calculation accuracy range using an obtained expression. The method of the present disclosure avoids problems of high complexity and low efficiency in a traditional calculation for the seabed reflection coefficient of point source elastic wave.

Claims

1. A calculation method for a seabed reflection coefficient of point source elastic wave, comprising the following steps: step 1: initializing a calculation accuracy and a calculation range of the seabed reflection coefficient; step 2: discretizing a parameter space and obtaining the seabed reflection coefficient of point source elastic wave; step 3: combining an equivalent equation with a traditional calculation equation for the seabed reflection coefficient of point source elastic wave; wherein the equivalent equation and traditional calculation equation for the seabed reflection coefficient of point source elastic wave are combined by the following equation:
f(W,m)=r?r(1), in equation (1), f (w,m)=r represents the equivalent equation, W is an undetermined coefficient of the equivalent equation, r is the seabed reflection coefficient, ? represents an assignment to a variable, and r is the seabed reflection coefficient obtained by the traditional calculation method for the seabed reflection coefficient of point source elastic wave; the combination is performed within a parameter space range to obtain the following:
f(W,M)=R(2), in equation (2), R is the seabed reflection coefficient of point source elastic wave; step 4: solving the undetermined coefficient of the equivalent equation in step 3 with the following equation:
W=G.sup.?1R(3), in equation (3), G is a symmetric matrix G.sub.ij=?(m.sub.i,m.sub.j) composed of Gaussian kernel function, i,j?{k|k>0&k?N}, R is the seabed reflection coefficient of the point source elastic wave; step 5: obtaining a concise expression for the seabed reflection coefficient of point source under an accuracy in step 1 with the following equation:
r=g(m).Math.W(4), in equation (4), g(m)=[?(m.sub.1,m)?(m.sub.2,m) . . . ?(m.sub.i,m)], W is the undetermined coefficient of the equivalent equation; step 6: calculating the seabed reflection coefficient of point source elastic wave within a given calculation accuracy range using an obtained expression in step 5.

2. The calculation method for a seabed reflection coefficient of point source elastic wave according to claim 1, wherein, in step2, the parameter space is discretized to obtain M=[m.sub.1 m.sub.2 . . . m.sub.n].sup.T, a corresponding seabed reflection coefficient of point source elastic wave is denoted as R=[r.sub.1 r.sub.2 . . . r.sub.n].sup.T, m is discrete points for each parameter that are evenly distributed within an initialized parameter space calculation range at intervals in the accuracy set in step 1; r is the seabed reflection coefficient obtained from the traditional calculation method for the seabed reflection coefficient of point source elastic wave.

3. A computer readable storage medium, wherein a computer program is stored thereon, the computer program implements the calculation method for a seabed reflection coefficient of point source elastic wave according to claim 1 when be loaded and executed by a processor.

4. A computer readable storage medium, wherein a computer program is stored thereon, the computer program implements the calculation method for a seabed reflection coefficient of point source elastic wave according to claim 2 when be loaded and executed by a processor.

5. A computer device, comprising a memory and a processor, wherein a computer program is stored on the memory, the computer program implements the calculation method for a seabed reflection coefficient of point source elastic wave according to claim 1 when executed by the processor.

6. A computer device, comprising a memory and a processor, wherein a computer program is stored on the memory, the computer program implements the calculation method for a seabed reflection coefficient of point source elastic wave according to claim 2 when executed by the processor.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a flowchart of a calculation method of the present disclosure.

(2) FIG. 2 is a diagram of discretized parameters.

(3) FIG. 3 is modular diagram of a seabed reflection coefficient.

(4) FIG. 4 is a phase diagram of the seabed reflection coefficient.

(5) FIG. 5 is a modular diagram of an undetermined coefficient of an equivalent equation.

(6) FIG. 6 is a phase diagram of the undetermined coefficient of the equivalent equation.

(7) FIG. 7 is a diagram showing reflection coefficients under different longitudinal wave velocities; A is an amplitude plot and B is a phase plot.

(8) FIG. 8 is a diagram showing the reflection coefficients under different transverse wave velocities; A is the amplitude plot and B is the phase plot.

(9) FIG. 9 is a diagram showing the reflection coefficients under different densities, A is the amplitude plot, and B is the phase plot.

(10) FIG. 10 is a diagram showing the reflection coefficients at different frequencies, A is the amplitude plot, and B is the phase plot.

(11) FIG. 11 is a diagram showing the reflection coefficients at different propagation distances, A is the amplitude plot and B is the phase plot.

DESCRIPTION OF EMBODIMENTS

(12) The present disclosure is further described in detail below, and the proposed embodiments are only a part of the present application and not all of them. Based on the embodiments in the present disclosure, all other embodiments obtained by relevant technical personnel without creative work fall within the protection scope of the present disclosure.

(13) An embodiment of the present disclosure provides a calculation method for a seabed reflection coefficient of point source elastic wave, as shown in FIG. 1, which mainly includes the following steps: step 1: initializing a calculation accuracy and a calculation range of the seabed reflection coefficient.

(14) In this embodiment, the calculation accuracy and calculation range of the seabed reflection coefficient are constrained by initializing input parameters (including seabed elastic parameters, frequency, and propagation distance). The calculation range of parameter space is represented by ?, ?={(?,?, ?, f, h)|??[1450 1550],??[100 200], ??[1500 1600], f?[40 60], h?[90 110]} and the calculation accuracy is represented by ?, ?=[?? ?? ?? ?f ?h]=[50 50 50 5 5]. And the seabed longitudinal wave velocity, seabed transverse wave velocity, seabed density, frequency, and propagation distance are represented by ?, ?, ?, f, h, respectively; all variables adopt the International System of Units.

(15) Step 2: discretizing a parameter space and obtaining the seabed reflection coefficient of point source elastic wave.

(16) By discretizing an input parameter according to an initialized parameter in step 1, M=[m.sub.1 m.sub.2 . . . m.sub.n].sup.T is obtained, it is obvious that in this embodiment, the number of discrete samples n=675, and the parameter space includes seabed longitudinal wave velocity, seabed transverse wave velocity, seabed density, frequency, and propagation distance m=[? ? ? f h]. The discretized parameters of this embodiment are shown in FIG. 2. The value in abscissa of 1-675 indicates the number of discrete samples. Thick black solid line corresponding to the numerical range of 1450-1550 in the right coordinate axis represents the seabed longitudinal wave velocity ?, dashed line corresponding to the numerical range of 1500-1600 in the right coordinate axis represents the seabed density ?, dotted line corresponding to the numerical range of 100-200 in the left coordinate axis represents the seabed transverse wave velocity ?, thin solid line corresponding to the numerical range of 90-110 in the left coordinate axis represents the propagation distance h, and dashed line corresponding to the numerical range of 40-60 in the left coordinate axis represents the frequency.

(17) By utilizing the discretized parameters mentioned above, the seabed reflection coefficient can be obtained from the traditional calculation method of the seabed reflection coefficient of point source elastic wave. The traditional calculation method of the seabed reflection coefficient of point source elastic wave includes the reflection spherical wave integration method, wave equation method, and reflectance calculation method, and calculation results obtained from various methods are consistent with each other. The seabed reflection coefficients R=[r.sub.1 r.sub.2 . . . r.sub.n].sup.T corresponding to the discretized parameters obtained in this embodiment are shown in FIG. 3 and FIG. 4 within an incidence angle range of 0? to 70?; FIG. 3 is a modular diagram of the seabed reflection coefficient, and FIG. 4 is a phase diagram of the seabed reflection coefficient.

(18) Step 3: combining an equivalent equation with a traditional calculation equation for the seabed reflection coefficient of point source elastic wave.

(19) Traditional calculation equation for the seabed reflection coefficient of point source elastic wave is combined with the equivalent equation through an assignment to a variable:
f(W,m)=r?r(1),
in equation (1), f (w,m)=r represents the equivalent equation, W is an undetermined coefficient of the equivalent equation, r is the seabed reflection coefficient, ? represents an assignment to a variable; the combination is performed within a parameter space range to obtain the following:
f(W,M)=R(2),
this embodiment wrote equation (2) to GW=R, G is a symmetric matrix G.sub.ij=?(m.sub.i,m.sub.j) composed of Gaussian kernel function, i,j?{k|k>0&k?N}.

(20) Step 4: solving the undetermined coefficient of the equivalent equation in step 3 with the following equation to obtain the undetermined coefficient of the equivalent equation.
W=G.sup.?1R(3),

(21) The undetermined coefficients of the equivalent equation calculated in this embodiment are shown in FIGS. 5 and 6, where FIG. 5 is a modular diagram of the undetermined coefficient of the equivalent equation, and FIG. 6 is a phase diagram of the undetermined coefficient of the equivalent equation.

(22) Step 5: obtaining a concise expression for the seabed reflection coefficient of point source under an accuracy in step 1 with the following equation:
r=g(m).Math.W(4),
in equation (4), g(m)=[?(m.sub.1,m)?(m.sub.2,m) . . . ?(m.sub.i,m)], ? is Gaussian function.

(23) Step 6: calculating the seabed reflection coefficient of point source elastic wave within a given calculation accuracy range using the concise expression obtained in step 5.

(24) As shown in Table 1, this embodiment calculates the seabed reflection coefficient of point source elastic wave for a center value (value 1) and a center deviation value (value 2, value 3) in the calculation range. Calculation results are shown in FIGS. 7 to 11, where dashed line represents a plane wave calculation result, solid line represents a calculation result of the traditional calculation method for the seabed reflection coefficient of point source elastic wave, and + represents a calculation result of the calculation method of the present disclosure. FIG. 7 shows the reflection coefficients under different longitudinal wave velocities, where the longitudinal wave velocities are value 1, value 2, and value 3, respectively. The calculation results are obtained when all other parameters are value 1; FIG. 8 shows the reflection coefficients under different transverse wave velocities, where the transverse wave velocities are value 1, value 2, and value 3, respectively. The calculation results are obtained when all other parameters are value 1, similarly situations for FIGS. 9 to 11. Obviously, the calculation results of the present disclosure are consistent with those of traditional calculation methods for the seabed reflection coefficient of point source elastic wave at the same time, the calculation results of plane wave have significant errors, which cannot accurately describe the frequency variation and phase characteristics of the seabed reflection coefficient, and also cannot provide an appropriate amplitude information of the reflection coefficient under large incidence angles. The comparison between equation (4) and the reflection spherical wave integration method shows that the calculation time required by the calculation method of the present disclosure is significantly reduced, which greatly improves the calculation efficiency.

(25) From the above results, it can be seen that the efficient calculation method for the seabed reflection coefficient of point source elastic wave proposed by the present disclosure not only has lower computational complexity and higher computational efficiency, but also can achieve the same accuracy as existing calculation methods, which avoids the limitations caused by plane wave calculation errors, and thereby promoting a practical application of point source reflection coefficient.

(26) TABLE-US-00001 TABLE 1 Parameter Longitudinal Transverse Seabed wave wave density Propagation Frequency values velocity ? velocity ? ? distance h f Value 1 1500 150 1550 100 50 Value 2 1475 125 1525 95 45 Value 3 1525 175 1575 105 55