Fast establishment of initial model for seismic shear wave velocity inversion, inversion method and system

Abstract

The application discloses a kind of inversion initial model fast establishment, inversion method and system of seismic transverse wave velocity, comprising: first, extracting surface wave dispersion curve from original surface wave data, and the phase velocity in surface wave dispersion curve, frequency is converted into apparent transverse wave velocity and depth.Then, based on the converted surface wave dispersion curve, according to the depth corresponding to the layer depth array in initial model, the apparent transverse wave velocity in the converted surface wave dispersion curve is assigned to each layer depth array using interpolation algorithm, and the inversion initial model of seismic transverse wave velocity is established.Because the apparent transverse wave velocity and the actual transverse wave velocity are consistent in variation trend, the inversion initial model thus established can ensure the convergence of algorithm to remain stable when seismic transverse wave velocity is inverted, and avoid inversion into local minimum value or not convergent.

Description

Technical Field

[0001] This invention relates to the field of seismic data processing technology, specifically to a method and system for rapidly establishing and inverting an initial model for seismic shear wave velocity inversion. Background Technology

[0002] Seismic shear wave velocity inversion is a crucial step in surface wave exploration. By inverting the dispersion curve, the distribution of shear wave velocities in the subsurface space can be obtained, and the location of the target can be inferred from this. Conventional inversion algorithms typically rely on an initial model. However, current initial models are generally built by first designing the layer thickness and then assigning wave velocities to each layer based on experience, which can easily lead to significant deviations between the initial model and the actual wave velocities. If the initial model deviates too much from the actual wave velocities, the inversion algorithm will have difficulty converging and will not yield accurate inversion results. Therefore, to quickly and accurately infer the location of the target, it is necessary to rapidly establish an effective initial model for seismic shear wave velocity inversion. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a rapid method and system for establishing and inverting an initial model for seismic shear wave velocity inversion. This method can quickly and effectively establish an initial model for seismic shear wave velocity inversion. The specific technical solution is as follows:

[0004] In a first aspect, a method for rapidly establishing an initial model for seismic shear wave velocity inversion is provided. In a first feasible implementation of this first aspect, the method includes:

[0005] The surface wave dispersion curve is extracted from the original surface wave data, and the phase velocity and frequency in the surface wave dispersion curve are converted into apparent shear wave velocity and depth, respectively.

[0006] The surface wave dispersion curve obtained by conversion is interpolated according to the layer depth array of the initial model to obtain the inversion initial model.

[0007] In conjunction with the first feasible method of the first aspect, in the second feasible method of the first aspect, the phase velocity in the surface wave dispersion curve is converted into the apparent shear wave velocity using the following formula:

[0008] ;

[0009] , The first and second lines in the surface wave dispersion curves are respectively The reciprocal of the frequency and the phase velocity corresponding to each data point.

[0010] In conjunction with the first feasible method of the first aspect, in the third feasible method of the first aspect, the frequency in the surface wave dispersion curve is converted into depth using the following formula:

[0011] ;

[0012] in, , The first and second lines in the surface wave dispersion curves are respectively The frequency and phase velocity corresponding to each data point.

[0013] In conjunction with the first feasible method of the first aspect, in the fourth feasible method of the first aspect, the surface wave dispersion curve obtained by transformation is interpolated according to the layer depth array of the initial model, including:

[0014] Extract the two data points from the surface wave dispersion curve obtained by the transformation that are closest to the depth of the element in the layer depth array, and determine the apparent shear wave velocity of the element based on the apparent shear wave velocity corresponding to the two data points.

[0015] Secondly, a seismic shear wave velocity inversion method is provided, including:

[0016] The inversion initial model is constructed by using any of the first to fourth feasible methods described in the first aspect;

[0017] Seismic shear wave velocity inversion is performed based on the initial inversion model to determine the shear wave velocity distribution in the underground space.

[0018] Thirdly, a rapid initial model establishment system for seismic shear wave velocity inversion is provided. The first feasible method of this third aspect includes:

[0019] The curve conversion module is configured to extract the surface wave dispersion curve from the original surface wave data and convert the phase velocity and frequency in the surface wave dispersion curve into the apparent shear wave velocity and depth, respectively.

[0020] The model building module is configured to interpolate the transformed surface wave dispersion curve according to the layer depth array of the initial model to obtain the inversion initial model.

[0021] In conjunction with the first possible implementation of the third aspect, in the second possible implementation of the third aspect, the curve conversion module includes a velocity conversion unit configured to convert the phase velocity in the surface wave dispersion curve into the apparent shear wave velocity using the following calculation formula:

[0022] ;

[0023] , The first and second lines in the surface wave dispersion curves are respectively The reciprocal of the frequency and the phase velocity corresponding to each data point.

[0024] In conjunction with the first possible implementation of the third aspect, in the third possible implementation of the third aspect, the curve conversion module includes a depth conversion unit configured to convert the frequency in the surface wave dispersion curve into depth using the following calculation formula:

[0025] ;

[0026] in, , The first and second lines in the surface wave dispersion curves are respectively The frequency and phase velocity corresponding to each data point.

[0027] In conjunction with the first possible implementation of the third aspect, in the fourth possible implementation of the third aspect, the model building module includes:

[0028] The extraction unit is configured to extract the two data points from the transformed surface wave dispersion curve that are closest in depth to the elements in the layer depth array;

[0029] The interpolation unit is configured to calculate the apparent shear wave velocity corresponding to the element based on the apparent shear wave velocities corresponding to two data points.

[0030] Fourthly, a seismic shear wave velocity inversion system is provided, characterized in that it includes:

[0031] The initial model module is configured to use any of the first to fourth implementable methods of the first aspect to construct the inversion initial model quickly;

[0032] The velocity inversion module is configured to perform seismic shear wave velocity inversion based on the initial inversion model to determine the shear wave velocity distribution in the underground space.

[0033] Beneficial Effects: The rapid establishment and inversion method and system for the initial inversion model of seismic shear wave velocity using the present invention can directly establish the initial inversion model from the surface wave dispersion curve, achieving the goal of rapid modeling. Furthermore, by converting the phase velocity and frequency of the surface wave dispersion curve into apparent shear wave velocity and depth, the corresponding apparent shear wave velocity can be assigned to each layer of the initial model based on the depth in the converted surface wave dispersion curve using an interpolation algorithm, thereby quickly and effectively establishing the initial inversion model. The apparent shear wave velocity and the actual shear wave velocity maintain consistent trends in their variation. The initial inversion model established in this way can ensure stable convergence of the algorithm during seismic shear wave velocity inversion, avoiding the inversion from getting trapped in local minima or failing to converge. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly described below. In all the drawings, the elements or parts are not necessarily drawn to scale.

[0035] Figure 1 A flowchart illustrating a method for rapidly establishing an initial model for seismic shear wave velocity inversion according to an embodiment of the present invention;

[0036] Figure 2 A flowchart of a seismic shear wave velocity inversion method provided in an embodiment of the present invention;

[0037] Figure 3 A system block diagram for rapidly establishing an initial model for seismic shear wave velocity inversion according to an embodiment of the present invention;

[0038] Figure 4 This is a system block diagram of a seismic shear wave velocity inversion system provided in an embodiment of the present invention;

[0039] Figure 5 For the extracted surface wave dispersion curve ;

[0040] Figure 6 The surface wave dispersion curve obtained by conversion ;

[0041] Figure 7 This is a schematic diagram comparing the inversion results obtained using the inversion method provided by this invention with the theoretical model. Detailed Implementation

[0042] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0043] like Figure 1 The flowchart shown illustrates a method for rapidly establishing an initial model for seismic shear wave velocity inversion. This method includes:

[0044] Step 1: Extract the surface wave dispersion curve from the original surface wave data, and convert the phase velocity and frequency in the surface wave dispersion curve into the apparent shear wave velocity and depth, respectively.

[0045] Step 2: Interpolate the surface wave dispersion curve obtained by conversion according to the layer depth array of the initial model to obtain the inversion initial model.

[0046] Specifically, firstly, dispersion curves can be extracted from the acquired raw surface wave data to obtain the corresponding surface wave dispersion curves. ,like Figure 5 As shown. The surface wave dispersion curve... The vertical axis in the figure represents the phase velocity. Converted to apparent transverse wave velocity and the surface wave dispersion curve The horizontal axis in the graph represents frequency. Convert to depth The transformed surface wave dispersion curve is obtained. ,like Figure 6 As shown. Then, the surface wave dispersion curve can be directly obtained. Establishing an initial inversion model eliminates the need for a pre-designed initial model, achieving rapid modeling. When establishing the initial inversion model, the underground space can be divided into several layers of fixed thickness, determining the layer depth array of the initial inversion model, and based on the transformed surface wave dispersion curve... Based on the depths corresponding to each layer's depth array, an interpolation algorithm is used to transform the surface wave dispersion curves. The apparent shear wave velocity is assigned to the depth array of each layer, thus establishing an initial inversion model for seismic shear wave velocity. Since the apparent shear wave velocity and the actual shear wave velocity have the same trend of change, the initial inversion model established in this way can ensure the stable convergence of the algorithm during seismic shear wave velocity inversion, avoiding the inversion from getting trapped in local minima or failing to converge.

[0047] In this embodiment, optionally, the phase velocity in the surface wave dispersion curve can be converted into the apparent shear wave velocity using the following calculation formula:

[0048] ;

[0049] , The first and second lines in the surface wave dispersion curves are respectively The reciprocal of the frequency and the phase velocity corresponding to each data point.

[0050] In this embodiment, optionally, the frequency in the surface wave dispersion curve can be converted to depth using the following formula:

[0051] ;

[0052] in, , The first and second lines in the surface wave dispersion curves are respectively The frequency and phase velocity corresponding to each data point.

[0053] In this embodiment, optionally, the obtained surface wave dispersion curve is interpolated according to the layer depth array of the initial model, including:

[0054] Extract the two data points from the surface wave dispersion curve obtained by the transformation that are closest to the depth of the element in the layer depth array, and determine the apparent shear wave velocity of the element based on the apparent shear wave velocity corresponding to the two data points.

[0055] Specifically, for the layer depth array of the first... element The surface wave dispersion curve can be determined based on the depth corresponding to the element. Search for the closest element Two data points , Based on these two data points , Corresponding apparent transverse wave velocity , Calculate the elements Corresponding apparent transverse wave velocity The specific calculation formula is as follows:

[0056] .

[0057] By repeating this process, the apparent transverse wave velocity corresponding to all elements in the layer depth array can be obtained, and a curve can then be established based on this. That is, the inversion of the initial model.

[0058] like Figure 2 The flowchart shown illustrates the seismic shear wave velocity inversion method, which includes:

[0059] Step S1: Using the above-described method for rapidly establishing the initial inversion model, construct the initial inversion model;

[0060] Step S2: Perform seismic shear wave velocity inversion based on the initial inversion model to determine the shear wave velocity distribution in the underground space.

[0061] Specifically, firstly, the aforementioned method for rapidly establishing an initial inversion model can be used to quickly and effectively establish an initial inversion model for seismic shear wave velocity. Then, based on this initial model, existing inversion algorithms can be used to invert seismic shear wave velocity, thereby determining the distribution of shear wave velocity in the subsurface space and inferring the location of the target. Because the apparent shear wave velocity and the actual shear wave velocity in the established initial inversion model maintain consistent trends in their variation, the initial inversion model ensures stable convergence of the algorithm during seismic shear wave velocity inversion, preventing the inversion from getting trapped in local minima or failing to converge.

[0062] Figure 7 For the seismic shear wave velocity inversion results obtained using the inversion method claimed in this application, from Figure 7 It can be seen that the inversion results obtained by the inversion method protected in this application are basically consistent with the theoretical values, proving that the initial inversion model constructed in this application can ensure the stable convergence of the algorithm during seismic shear wave velocity inversion, and avoid the inversion from getting trapped in local minima or failing to converge.

[0063] like Figure 3The diagram shown is a system block diagram for the rapid establishment of the initial model for seismic shear wave velocity inversion. This system includes:

[0064] The curve conversion module is configured to extract the surface wave dispersion curve from the original surface wave data and convert the phase velocity and frequency in the surface wave dispersion curve into the apparent shear wave velocity and depth, respectively.

[0065] The model building module is configured to interpolate the transformed surface wave dispersion curve according to the layer depth array of the initial model to obtain the inversion initial model.

[0066] Specifically, the system includes a curve conversion module and a model building module. The curve conversion module extracts dispersion curves from the acquired raw surface wave data to obtain the corresponding surface wave dispersion curves. and the surface wave dispersion curve phase velocity in Converted to apparent transverse wave velocity and the surface wave dispersion curve frequency in Convert to depth The transformed surface wave dispersion curve is obtained. The model building module can divide the underground space into several layers with a fixed thickness, determine the layer depth array of the initial inversion model, and base it on the transformed surface wave dispersion curve. Based on the depths corresponding to each layer's depth array, an interpolation algorithm is used to transform the surface wave dispersion curves. The apparent shear wave velocity is assigned to each layer depth array, thereby establishing an initial inversion model for seismic shear wave velocity.

[0067] In this embodiment, optionally, the curve conversion module includes a velocity conversion unit configured to convert the phase velocity in the surface wave dispersion curve into the apparent shear wave velocity using the following calculation formula:

[0068] ;

[0069] , The first and second lines in the surface wave dispersion curves are respectively The reciprocal of the frequency and the phase velocity corresponding to each data point.

[0070] In this embodiment, optionally, the curve conversion module includes a depth conversion unit, configured to convert the frequency in the surface wave dispersion curve into depth using the following calculation formula:

[0071] ;

[0072] in, , The first and second lines in the surface wave dispersion curves are respectively The frequency and phase velocity corresponding to each data point.

[0073] In this embodiment, optionally, the model building module includes:

[0074] The extraction unit is configured to extract the two data points from the transformed surface wave dispersion curve that are closest in depth to the elements in the layer depth array;

[0075] The interpolation unit is configured to calculate the apparent shear wave velocity corresponding to the element based on the apparent shear wave velocities corresponding to two data points.

[0076] Specifically, the model building module includes an extraction unit and an interpolation unit. The extraction unit can, for each element in the layer depth array, interpolate the surface wave dispersion curve based on the depth corresponding to that element. The two data points closest to the element are searched. The interpolation unit can calculate the apparent shear wave velocity corresponding to each element based on the apparent shear wave velocity corresponding to the two corresponding data points, thereby obtaining the apparent shear wave velocity corresponding to all elements in the layer depth array and establishing the initial inversion model.

[0077] like Figure 4 The diagram shown is a system block diagram of a seismic shear wave velocity inversion system. This inversion system includes:

[0078] The initial model module is configured to use the above-mentioned method for quickly establishing an inversion initial model to construct an inversion initial model;

[0079] The velocity inversion module is configured to perform seismic shear wave velocity inversion based on the initial inversion model to determine the shear wave velocity distribution in the underground space.

[0080] Specifically, the inversion system includes an initial model module and a velocity inversion module. The initial model module can quickly and effectively establish an initial inversion model using the aforementioned rapid initial model establishment method. The velocity inversion module, based on the initial inversion model established by the initial model module, can use existing inversion algorithms to perform seismic shear wave velocity inversion, thereby determining the distribution of shear wave velocities in the subsurface space and inferring the location of the target.

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for rapidly establishing an initial model for seismic shear wave velocity inversion, characterized in that, include: The surface wave dispersion curve is extracted from the original surface wave data, and the phase velocity and frequency in the surface wave dispersion curve are converted into apparent shear wave velocity and depth, respectively. The surface wave dispersion curve obtained by conversion is interpolated according to the layer depth array of the initial model to obtain the inversion initial model.

2. The method for rapidly establishing an inversion initial model according to claim 1, characterized in that, The phase velocity in the surface wave dispersion curve is converted into the apparent shear wave velocity using the following formula: ； , The first and second lines in the surface wave dispersion curves are respectively The reciprocal of the frequency and the phase velocity corresponding to each data point.

3. The method for rapidly establishing an inversion initial model according to claim 1, characterized in that, The following formula is used to convert the frequency in the surface wave dispersion curve to the depth: ； in, , The first and second lines in the surface wave dispersion curves are respectively The frequency and phase velocity corresponding to each data point.

4. The method for rapidly establishing an inversion initial model according to claim 1, characterized in that, The surface wave dispersion curves obtained from the transformation are interpolated according to the layer depth array of the initial model, including: Extract the two data points from the surface wave dispersion curve obtained by the transformation that are closest to the depth of the element in the layer depth array, and determine the apparent shear wave velocity of the element based on the apparent shear wave velocity corresponding to the two data points.

5. A method for seismic shear wave velocity inversion, characterized in that, include: An inversion initial model is constructed using the rapid inversion initial model establishment method as described in any one of claims 1-4; Seismic shear wave velocity inversion is performed based on the initial inversion model to determine the shear wave velocity distribution in the underground space.

6. A system for rapidly establishing an initial model for seismic shear wave velocity inversion, characterized in that, include: The curve conversion module is configured to extract the surface wave dispersion curve from the original surface wave data and convert the phase velocity and frequency in the surface wave dispersion curve into the apparent shear wave velocity and depth, respectively. The model building module is configured to interpolate the transformed surface wave dispersion curve according to the layer depth array of the initial model to obtain the inversion initial model.

7. The rapid inversion initial model establishment system according to claim 6, characterized in that, The curve conversion module includes a velocity conversion unit configured to convert the phase velocity in the surface wave dispersion curve into the apparent shear wave velocity using the following calculation formula: ； , The first and second lines in the surface wave dispersion curves are respectively The reciprocal of the frequency and the phase velocity corresponding to each data point.

8. The rapid inversion initial model establishment system according to claim 6, characterized in that, The curve conversion module includes a depth conversion unit, configured to convert the frequency in the surface wave dispersion curve into depth using the following calculation formula: ； in, , The first and second lines in the surface wave dispersion curves are respectively The frequency and phase velocity corresponding to each data point.

9. The rapid establishment system for the inversion initial model according to claim 6, characterized in that, The model building module includes: The extraction unit is configured to extract the two data points from the transformed surface wave dispersion curve that are closest in depth to the elements in the layer depth array; The interpolation unit is configured to calculate the apparent shear wave velocity corresponding to the element based on the apparent shear wave velocities corresponding to two data points.

10. A seismic shear wave velocity inversion system, characterized in that, include: The initial model module is configured to construct the inversion initial model using the rapid inversion initial model establishment method as described in any one of claims 1-4; The velocity inversion module is configured to perform seismic shear wave velocity inversion based on the initial inversion model to determine the shear wave velocity distribution in the underground space.

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