Method for joint inversion of site model based on vertical array seismic record and borehole test data

Abstract

The invention belongs to the field of soil layer shear wave velocity and damping inversion, and provides a method for joint inversion of a site model based on vertical array seismic records and drilling test data, which comprises the following steps: layering a soil layer, determining initial reference values of shear wave velocity and damping ratio after layering, and determining an observation transfer function. Constructing an inversion objective function and performing iterative search on an optimal solution by using a hill-climbing-random search algorithm, wherein the key point is to construct the inversion objective function and perform iterative search on the optimal solution by using the hill-climbing-random search algorithm; according to the method, the field model is inversed by using the actually measured vertical station seismic record and the drilling test data in a combined manner, the problem of multiplicity of solutions of a traditional inversion method is effectively solved, the shear wave velocity and damping ratio structure obtained through inversion can effectively represent the amplification effect of a local field on seismic oscillation, meanwhile, the drilling test result can be reflected, and the method is suitable for the field simulation. Therefore, the method accords with reality.

Description

Technical Field

[0001] The invention belongs to the field of soil layer shear wave velocity and damping inversion, and specifically is a method for jointly inverting a site model based on vertical array seismic records and borehole test data. Background Art

[0002] The amplification effect of local sites on seismic waves is mainly affected by the shear wave velocity structure and damping ratio. Among them, the natural frequency of the site is mainly determined by the shear wave velocity structure, and the corresponding amplification factor is mainly affected by the shear wave velocity structure and damping ratio. Accurate estimation of the shear wave velocity structure and damping ratio is crucial for the simulation and prediction of site seismic response.

[0003] At present, the determination of the shear wave velocity structure of the site in the project mainly relies on the borehole test method and the surface wave test method. Although the borehole test method shows obvious advantages in test accuracy and resolution compared with the surface wave test method, the shear wave velocity obtained by the borehole test is sometimes still difficult to reflect the in-situ mechanical properties of the soil due to reasons such as the difficulty of the sensor and the side wall of the borehole to fit completely. On the other hand, the determination of the damping ratio of the soil at this stage mainly relies on the indoor resonant column test. However, since the indoor test can only represent the material damping and cannot reflect the scattering effect caused by the spatial variability of the soil during the propagation of seismic waves, the damping ratio directly used in the numerical analysis of site response often leads to a significant overestimation of the predicted site amplification effect.

[0004] Inversion using seismic data is another method to estimate site model parameters. However, due to the large number of inversion parameters and the fact that there are usually some differences between the actual site and the ideal model, the multi-solution problem has always been a key technical problem that is difficult to avoid and solve in the inversion process.

[0005] In view of the above problems, the present invention proposes a method for jointly inverting a site model based on seismic records and borehole test data. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for jointly inverting a site model based on vertical array seismic records and borehole test data to solve the problems raised in the background technology.

[0007] A method for jointly inverting a site model based on vertical array seismic records and borehole test data comprises the following steps:

[0008] S1. Layer the soil layers according to the soil properties of the site. If the thickness of each layer does not meet the requirements, further subdivide the soil layers of the studied site according to the thickness of the soil layers;

[0009] S2, determine the initial reference values ​​of shear wave velocity and damping ratio of each layer;

[0010] S3. Determine the observed transfer function;

[0011] S4. Construct an inversion objective function using the correlation coefficient between the theoretical transfer function and the observed transfer function, as well as the normalization error terms of the shear wave velocity and damping ratio, and solve for the optimal shear wave velocity and damping ratio model corresponding to the maximum value of the objective function through the hill-climbing - random search algorithm;

[0012] S5. Save and output the optimal shear wave velocity and damping models.

[0013] Preferably, in step S1, the first stratification is performed according to the soil properties, and the number of layers is denoted as u1. Then, according to the thickness of each layer after the first stratification, the i-th layer is further subdivided into n i layers of equal thickness soil layers, expressed as:

[0014]

[0015] where, T i represents the thickness of the i-th layer after the first stratification according to the soil properties, represents rounding up;

[0016] T max = max{T b * c1, T r}

[0017] where, max represents the symbol for taking the maximum value, T b is the total thickness of the borehole, c1 takes 0.1, and T r takes 20 m;

[0018] Then the soil layer is divided into n layers in total, expressed as:

[0019] Preferably, in step S2, the equivalent shear wave velocity method is applied to the shear wave velocity obtained by the borehole method to find the initial reference value of the equivalent shear wave velocity of each layer after stratification, and the initial reference value of the damping ratio is determined using the equivalent shear wave velocity of each layer, including the following steps:

[0020] For any i-th layer after stratification, the initial shear wave velocity v i is expressed as:

[0021]

[0022] where, i = 1, 2,..., n; H i represents the thickness of the i-th layer after subdivision, and t i is the propagation time of the shear wave in the i-th layer obtained according to the borehole test results;

[0023] For any i-th layer after layering, the initial damping ratio is expressed as:

[0024]

[0025] where d i represents the initial damping ratio, and v i is in the unit of m / s.

[0026] Preferably, the determination of the observation transfer function in step S3 is obtained by performing a fast Fourier transform on the acceleration data recorded by the vertical array to obtain the Fourier spectrum, smoothing the Fourier spectrum, and the Fourier spectrum ratio between the ground surface and the bottom of the borehole is the observation transfer function.

[0027] Preferably, in step S4, the objective function includes the correlation coefficient between the observation transfer function and the theoretical transfer function, the normalized error term between the inverted damping ratio and the initial damping ratio, and the normalized error term between the inverted shear wave velocity and the initial shear wave velocity, and is expressed as:

[0028]

[0029] where fit is the objective function, Φ d is the correlation coefficient between the observation transfer function ETF and the theoretical transfer function TTF, Φ m is the representative value of the error between the inverted damping ratio and the initial damping ratio, and Φ n is the representative value of the error between the inverted shear wave velocity and the initial shear wave velocity;

[0030] Φ d The calculation formula is as follows:

[0031]

[0032] where nf is the number of frequency points in the frequency band of interest; TTF(f i ) and ETF(f i ) are the corresponding values of the theoretical transfer function and the observation transfer function at the i-th frequency point, that is, when the frequency is equal to f i ; and are the average values of the magnification factors of the theoretical transfer function and the observation transfer function within the frequency band of interest, respectively; the theoretical transfer function can be determined by solving the seismic response of a horizontally layered site under the vertical incidence of SH waves through the matrix transfer method;

[0033] Φ m The calculation formula is as follows:

[0034]

[0035] where D i and di are the inversion damping ratio and the initial damping ratio corresponding to the i-th layer respectively, and max means taking the maximum value, and H i represents the thickness of the i-th layer.

[0036] Φ n The calculation formula of is as follows:

[0037]

[0038] Among them, V i and v i are the inversion shear wave velocity and the initial shear wave velocity corresponding to the i-th layer respectively.

[0039] Preferably, in the step S4, the hill-climbing - random search algorithm is also used to solve the optimal shear wave velocity and damping ratio model corresponding to the maximum value of the objective function. During the optimization process, the search range of the damping ratio of each layer is [0.001, 0.1], and the search range of the shear wave velocity of each layer is [v i* e -3σ , v i* e 3σ , and σ takes 0.2.

[0040] Preferably, obtaining the optimal solution shear wave velocity V and the optimal damping ratio D in the step S4 includes the following steps:

[0041] In the first stage of the hill-climbing - random search algorithm, the hill-climbing algorithm is used to find the optimal solution. The process is to start from the initial solution. At each step, first randomly generate a set of new solutions near the current solution, and then compare the objective function values corresponding to the current solution and the new solutions. If the objective function value of the new solution is greater than the objective function value of the current solution, then accept the new solution; if the objective function value of the new solution is less than the objective function value of the current solution, then do not accept the new solution, and climb the hill 200 steps each time;

[0042] The method for generating new solutions in the hill-climbing algorithm includes:

[0043] Independently add a random number between [-5, 5] to the shear wave velocity of each layer corresponding to the current solution;

[0044] Independently add the product of a random integer between [-10, 10] and 0.005 to the damping ratio of each layer corresponding to the current solution;

[0045] In the second stage of the hill-climbing random search algorithm, the random search algorithm is adopted as the strategy to jump out of the local optimal solution. The process is to batch generate 2000 groups of new solutions around the current solution, calculate the objective function values corresponding to all new solutions one by one, and then select the solution corresponding to the maximum value of the objective function within the range of the current solution and the new solutions as the current optimal solution. If the iteration times of the hill-climbing random search process reach the specified number of times (recommended to be 10 times), the shear wave velocity and damping ratio corresponding to the current optimal solution are output. If the iteration times do not reach the specified number of times, the current optimal solution is used as the initial solution for the next iteration;

[0046] The method for generating new solutions in the random search algorithm includes:

[0047] Independently add the product of a random integer between [-1, 1] and a random number between [-100, 100] to each layer of shear wave velocity corresponding to the current solution;

[0048] Independently add the product of a random integer between [-10, 10] and 0.005 to each layer of damping ratio corresponding to the current solution.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention uses the reference values of shear wave velocity and damping ratio determined by borehole testing as the inversion initial solution, and adds the normalized error terms of shear wave velocity and damping ratio to the objective function, realizing the use of borehole testing results to provide soft constraints for the inversion results, effectively solving the multi-solution problem faced by traditional inversion methods. The shear wave velocity and damping ratio structures obtained by inversion can not only effectively characterize the amplification effect of local site on ground motion, but also reflect the borehole testing results, thus being more in line with the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is the flow chart of the method for jointly inverting the site model based on vertical array seismic records and borehole testing data of the present invention;

[0052] Figure 2 It is the flow chart of the adaptive staged hill-climbing algorithm of the present invention;

[0053] Figure 3 It is the frequency response comparison diagram of the model transfer function of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] The following further describes in detail the embodiments of the present invention in conjunction with the drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0055] As shown in Figure 1 to Figure 2 the attached drawings:

[0056] Example 1: The present invention provides a method for jointly inverting a site model based on vertical array seismic records and borehole test data, comprising the following steps:

[0057] S1. Stratify the soil layers according to the soil properties of the site. If the thickness of each divided layer does not meet the requirements, further subdivide the soil layers of the studied site according to the soil layer thickness;

[0058] S2. Determine the initial reference values of the shear wave velocity and damping ratio for each layer;

[0059] S3. Determine the observation transfer function;

[0060] S4. Construct an inversion objective function using the correlation coefficient between the theoretical transfer function and the observation transfer function and the normalized error terms of the shear wave velocity and damping ratio, and solve for the optimal shear wave velocity and damping ratio model corresponding to the maximum value of the objective function through the hill-climbing - random search algorithm;

[0061] S5. Save and output the optimal shear wave velocity and damping model.

[0062] Preferably, in step S1, the first stratification is performed according to the soil properties, and the number of layers is denoted as u1. Then, according to the thickness of each layer after the first stratification, the i-th layer is further subdivided into n i layers of equal thickness soil layers, expressed as:

[0063]

[0064] where T i represents the thickness of the i-th layer after the first stratification according to the soil properties, represents rounding up;

[0065] T max = max{T b * c1, T r}

[0066] where max represents the symbol for taking the maximum value, T b is the total thickness of the borehole, c1 is taken as 0.1, and T r is taken as 20 m;

[0067] Then the soil layer is divided into n layers in total, expressed as:

[0068] Preferably, in step S2, the equivalent shear wave velocity method is applied to the shear wave velocity obtained by the borehole method to find the initial reference value of the equivalent shear wave velocity for each layer after stratification, and the initial reference value of the damping ratio is determined using the equivalent shear wave velocity of each layer, comprising the following steps:

[0069] For any i-th layer after layering, the initial shear wave velocity v i is expressed as:

[0070]

[0071] where i = 1, 2,..., n; H i represents the thickness of the i-th layer after subdivision, and t i is the propagation time of the shear wave in the i-th layer obtained from the borehole test results;

[0072] For any i-th layer after layering, the initial damping ratio is expressed as:

[0073]

[0074] where d i represents the initial damping ratio, and v i is in the unit of m / s.

[0075] Preferably, the determination of the observation transfer function in step S3 is obtained by performing a fast Fourier transform on the acceleration data recorded by the vertical array to obtain the Fourier spectrum, smoothing the Fourier spectrum, and the Fourier spectrum ratio between the ground surface and the bottom of the borehole is the observation transfer function.

[0076] Preferably, in step S4, the objective function includes the correlation coefficient between the observation transfer function and the theoretical transfer function, the normalized error term between the inverted damping ratio and the initial damping ratio, and the normalized error term between the inverted shear wave velocity and the initial shear wave velocity, and is expressed as:

[0077]

[0078] where fit is the objective function, Φ d is the correlation coefficient between the observation transfer function ETF and the theoretical transfer function TTF, Φ m is the error representative value between the inverted damping ratio and the initial damping ratio, and Φ n is the error representative value between the inverted shear wave velocity and the initial shear wave velocity;

[0079] The calculation formula of Φ d is as follows:

[0080]

[0081] where nf is the number of frequency points in the frequency band of interest; TTF(f i ) and ETF(f i ) are the corresponding values of the theoretical transfer function and the observation transfer function at the i-th frequency point, that is, when the frequency is equal to f i ; and are the average magnification factors of the theoretical transfer function and the observed transfer function within the concerned frequency band, respectively. The theoretical transfer function can be determined by solving the seismic response of a horizontally layered site under the vertical incidence of SH waves through the matrix transfer method.

[0082] Φ m The calculation formula of

[0083]

[0084] where D i and d i are the inversion damping ratio and the initial damping ratio corresponding to the i-th layer, respectively. max represents taking the maximum value, and H i represents the thickness of the i-th layer.

[0085] Φ n The calculation formula of

[0086]

[0087] where V i and v i are the inversion shear wave velocity and the initial shear wave velocity corresponding to the i-th layer, respectively.

[0088] Preferably, in step S4, the hill-climbing - random search algorithm is further used to solve the optimal shear wave velocity and damping ratio model corresponding to the maximum value of the objective function. During the optimization process, the search range of the damping ratio of each layer is [0.001, 0.1], and the search range of the shear wave velocity of each layer is [v i* e -3σ , v i* e 3σ , and σ is taken as 0.2.

[0089] Preferably, obtaining the optimal shear wave velocity V and the optimal damping ratio D in step S4 includes the following steps:

[0090] In the first stage of the hill-climbing - random search algorithm, the hill-climbing algorithm is used to find the optimal solution. The process is to start from the initial solution. In each step, a group of new solutions is randomly generated near the current solution first, and then the objective function values corresponding to the current solution and the new solutions are compared. If the objective function value of the new solution is greater than that of the current solution, the new solution is accepted; if the objective function value of the new solution is less than that of the current solution, the new solution is not accepted, and 200 steps of hill-climbing are performed in each iteration.

[0091] The method for generating new solutions in the hill-climbing algorithm includes:

[0092] Independently add a random number between [-5, 5] to the shear wave velocity of each layer corresponding to the current solution.

[0093] Independently add the product of a random integer between [-10, 10] and 0.005 to the damping ratio of each layer corresponding to the current solution;

[0094] In the second stage of the hill-climbing random search algorithm, the random search algorithm is adopted as the strategy to jump out of the local optimal solution. The process is to batch generate 2000 groups of new solutions around the current solution, calculate the objective function values corresponding to all new solutions one by one, and then select the solution corresponding to the maximum objective function value within the range of the current solution and the new solutions as the current optimal solution. If the iteration times of the hill-climbing random search process reach the specified number of times (recommended to be 10 times), then output the shear wave velocity and damping ratio corresponding to the current optimal solution. If the iteration times do not reach the specified number of times, then use the current optimal solution as the initial solution for the next iteration;

[0095] The method for generating new solutions in the random search algorithm includes:

[0096] Independently add the product of a random integer between [-1, 1] and a random number between [-100, 100] to the shear wave velocity of each layer corresponding to the current solution;

[0097] Independently add the product of a random integer between [-10, 10] and 0.005 to the damping ratio of each layer corresponding to the current solution

[0098] As shown in the appendix Figure 3 shown:

[0099] Example 2: Taking the vertical array in Delaney Park, USA as an example, this array is equipped with a total of seven observation points, and the positions are: the ground surface, 4.6 m underground, 10.7 m underground, 18.3 m underground, 30.5 m underground, 45.4 m underground, and 61 m underground (bottom of the borehole). There are certain differences in the soil properties between different adjacent observation points;

[0100] According to step S1, the soil layer is stratified. Stratify according to soil properties and soil layer thickness. The site can be divided into 6 layers, and the thicknesses of each layer from top to bottom are 4.6 m, 6.1 m, 7.6 m, 12.2 m, 14.9 m, and 15.6 m respectively;

[0101] According to step S2, determine the initial reference values of the shear wave velocity and damping ratio of each layer. First, calculate the initial shear wave velocity of each layer according to the shear wave velocity obtained from borehole tests. The shear wave velocities of each layer from top to bottom are 334.81 m / s, 426.39 m / s, 241.62 m / s, 251.75 m / s, 286.16 m / s, and 775.11 m / s respectively. From this, the initial damping ratios of each layer can be further determined, which are 0.0500, 0.0409, 0.0500, 0.0500, 0.0500, and 0.0184 in sequence from top to bottom;

[0102] According to step S3, firstly, the acceleration records at the surface and the bottom of the borehole of the Delaney Park vertical array are subjected to fast Fourier transform to obtain a Fourier spectrum, then the spectrum is smoothed using a Pazen window with a bandwidth of 0.4 Hz, and finally the Fourier spectrum ratio of the acceleration records at the surface and the bottom of the borehole is obtained as the observation transfer function;

[0103] According to step S4, the inversion objective function is constructed and the hill climbing-random search algorithm is used to iteratively search for the optimal solution, wherein the search range of the shear wave velocity of each layer is shown in the following table:

[0104] Lower limit of shear wave velocity (m / s) Upper limit of shear wave velocity (m / s) <![CDATA[V1]]> 183.75 610.06 <![CDATA[V2]]> 234.01 776.93 <![CDATA[V3]]> 132.60 440.26 <![CDATA[V4]]> 138.16 458.72 <![CDATA[V5]]> 157.05 521.42 <![CDATA[V6]]> 425.39 1412.34

[0105] The search range of the damping ratio of each layer is [0.001, 0.1].

[0106] The objective function is optimized using the algorithm mentioned above, and the mean and standard deviation of the shear wave velocity, damping ratio and spectral ratio curves obtained by inversion are calculated. The results are as follows: Figure 3 As shown. It can be found that the shear wave velocity structure obtained by joint inversion of borehole test data and surface and borehole bottom seismic records is basically consistent with the results obtained by seismic interferometry, which effectively verifies the effectiveness of the method proposed in this invention. Secondly, compared with the theoretical transfer function obtained by the initial model, the theoretical transfer function obtained by the final inversion model is more consistent with the empirical transfer function, which fully reflects the advanced nature of the method proposed in this invention.

[0107] According to step S5, the shear wave velocity and damping model corresponding to the optimal solution are saved and output.

[0108] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in the application. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the present invention is not limited to specific embodiments, but extends to a variety of modifications still falling within the scope of the appended claims.

[0109] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0110] It should be understood that, during the development of any actual implementation, in any engineering or design project, a large number of specific implementation decisions can be made. Such development efforts may be complex and time-consuming, but for those of ordinary skill in the art who benefit from this disclosure, without undue experimentation, such development efforts will be routine work of design, manufacturing, and production.

[0111] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for jointly inverting a site model based on vertical array seismic records and borehole test data, characterized in that, It includes the following steps: S1. Layer the soil according to the soil property of the site. If the thickness of each divided layer does not meet the requirements, further subdivide the soil layer of the studied site according to the soil layer thickness; S2. Determine the initial reference values of the shear wave velocity and damping ratio for each layer; S3. Determine the observation transfer function; S4. Construct an inversion objective function by using the correlation coefficient between the theoretical transfer function and the observation transfer function and the normalized error terms of the shear wave velocity and damping ratio, and solve the optimal shear wave velocity and damping ratio model corresponding to the maximum value of the objective function through the hill-climbing - random search algorithm; S5. Save and output the optimal shear wave velocity and damping models.

2. The method for jointly inverting a site model based on vertical array seismic records and borehole test data according to claim 1, wherein: The step S1 performs the first layering according to the soil property, and the number of layers is denoted as u1. Then, according to the thickness of each layer after the first layering, the i-th layer is further subdivided into n i layers of soil with equal thickness, which is expressed as: Among them, T i represents the thickness of the i-th layer after the first stratification according to the soil property, represents rounding up; T max = max{T b * c1, T r} where max represents the symbol for taking the maximum value, and T b is the total drilling thickness, c1 is taken as 0.1, and T r is taken as 20 m; The soil layer is divided into n layers in total, expressed as:

3. The method for jointly inverting a site model based on vertical array seismic records and borehole test data according to claim 1, wherein: In step S2, by applying the equivalent shear wave velocity method to the shear wave velocity obtained by the borehole method, the initial reference value of the equivalent shear wave velocity of each divided layer is obtained, and the initial reference value of the damping ratio is determined by using the equivalent shear wave velocity of each layer, which includes the following steps: For any i-th layer after layering, the initial shear wave velocity v i is expressed as: where \(i = 1, 2, \cdots, n\); \(H\) i represents the thickness of the \(i\)-th layer after subdivision, and \(t\) i is the propagation time of the shear wave in the \(i\)-th layer obtained from the borehole test results; For any i-th layer after layering, the initial damping ratio is expressed as: Among them, d i represents the initial damping ratio, and v i is in the unit of m / s.

4. The method for jointly inverting a site model based on vertical array seismic records and borehole test data as claimed in claim 1, wherein: In step S3, the determination of the observation transfer function is obtained by performing a fast Fourier transform on the acceleration data recorded by the vertical array to obtain the Fourier spectrum, smoothing the Fourier spectrum, and the Fourier spectrum ratio between the ground surface and the bottom of the borehole is the observation transfer function.

5. The method for jointly inverting a site model based on vertical array seismic records and borehole test data as claimed in claim 1, wherein: In step S4, the objective function includes the correlation coefficient between the observation transfer function and the theoretical transfer function, the normalized error term between the inverted damping ratio and the initial damping ratio, and the normalized error term between the inverted shear wave velocity and the initial shear wave velocity, which is expressed as: where fit is the objective function, Φ d is the correlation coefficient between the observed transfer function ETF and the theoretical transfer function TTF, Φ m is the representative value of the error between the inverted damping ratio and the initial damping ratio, Φ n is the representative value of the error between the inverted shear wave velocity and the initial shear wave velocity; Φ d The calculation formula is as follows: where, nf is the number of frequency points within the frequency band of interest; TTF(f i ) and ETF(f i ) are the corresponding values of the theoretical transfer function and the observed transfer function at the i-th frequency point, i.e., when the frequency is equal to f i ; and are the average values of the magnification factors of the theoretical transfer function and the observed transfer function within the frequency band of interest, respectively; the theoretical transfer function can be determined by solving the seismic response of a horizontally layered site under the vertical incidence of SH waves using the matrix transfer method; Φ m The calculation formula is as follows: Among them, D i and d i are respectively the inversion damping ratio and the initial damping ratio corresponding to the i-th layer, max represents taking the maximum value, and H i represents the thickness of the i-th layer. Φ n The calculation formula is as follows: Among them, V i and v i are respectively the inverted shear wave velocity and the initial shear wave velocity corresponding to the i-th layer.

6. The method for jointly inverting a site model based on vertical array seismic records and borehole test data according to claim 5, wherein: In the step S4, the hill-climbing random search algorithm is also used to solve the optimal shear wave velocity and damping ratio model corresponding to the maximum value of the objective function. During the optimization process, the search range of the damping ratio of each layer is [0.001, 0.1], and the search range of the shear wave velocity of each layer is [v i* e -3σ , v i* e 3σ , and σ is taken as 0.

2.

7. The method for jointly inverting a site model based on vertical array seismic records and borehole test data according to claim 6, wherein: In step S4, to obtain the optimal solution of the shear wave velocity V and the optimal damping ratio D, it includes the following steps: In the first stage of the hill-climbing - random search algorithm, the hill-climbing algorithm is used to find the optimal solution. The process is to start from the initial solution, and in each step, first randomly generate a group of new solutions near the current solution, and then compare the objective function values corresponding to the current solution and the new solutions. If the objective function value of the new solution is greater than that of the current solution, accept the new solution; if the objective function value of the new solution is less than that of the current solution, do not accept the new solution, and climb the hill 200 steps in each iteration; The method for generating new solutions in the hill-climbing algorithm includes: Independently add a random number between [-5, 5] to the shear wave velocity of each layer corresponding to the current solution; Independently add the product of a random integer between [-10, 10] and 0.005 to the damping ratio of each layer corresponding to the current solution; In the second stage of the hill-climbing - random search algorithm, the random search algorithm is used as a strategy to jump out of the local optimal solution. The process is to batch generate 2000 groups of new solutions around the current solution, and calculate the objective function values corresponding to all new solutions one by one, and then select the solution corresponding to the maximum value of the objective function within the range of the current solution and the new solutions as the current optimal solution. If the iteration times of the hill-climbing - random search process reach the specified number of times (recommended to take 10 times), then output the shear wave velocity and damping ratio corresponding to the current optimal solution. If the iteration times do not reach the specified number of times, then use the current optimal solution as the initial solution for the next iteration; The method for generating new solutions in the random search algorithm includes: Independently add the product of a random integer between [-1, 1] and a random number between [-100, 100] to the shear wave velocity of each layer corresponding to the current solution; Independently add the product of a random integer between [-10, 10] and 0.005 to the damping ratio of each layer corresponding to the current solution.

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