Virtual source record automatic selection method suitable for environmental noise seismic exploration

Abstract

The invention belongs to the field of environmental noise seismic exploration, and particularly relates to a virtual source record automatic selection method suitable for environmental noise seismic exploration, which comprises the following steps: step 1, preprocessing original environmental noise seismic data to obtain preprocessed environmental noise seismic data; step 2, reconstructing virtual source seismic records of different time periods at each receiving point position by using the preprocessed environmental noise seismic data; 3, linear scanning superposition calculation processing is carried out on the positive time half axis and the negative time half axis of each section of virtual source seismic record, and scanning superposition amplitude curves based on different linear speeds are obtained; comparing and analyzing the maximum amplitude value of the scanning and superposition amplitude curve based on the positive and negative time half-axis virtual source seismic record, and automatically selecting the virtual source seismic record; and step 4, repeating the step 3, and realizing automatic selection of the virtual source seismic records at different time periods at each receiving point position. According to the invention, automatic screening of high-quality virtual source seismic records rich in surface wave information can be realized.

Description

Technical Field

[0001] The invention belongs to the field of environmental noise seismic exploration, and in particular relates to an automatic selection method for virtual source records suitable for environmental noise seismic exploration. Background Art

[0002] In traditional seismological research, environmental noise seismic data are often regarded as noise interference and need to be suppressed or deleted. But in fact, environmental noise seismic signals contain a lot of useful information about underground media after multiple scattering, transmission, reflection and refraction of underground elastic media. This information is very useful for studying the velocity structure of the earth from shallow to deep.

[0003] In recent years, with the popularization and promotion of seismic intelligent node instruments, environmental noise seismic exploration methods have been rapidly developed and widely used. Using the cross-correlation seismic interferometry method, the virtual source seismic record of surface virtual source point excitation and multi-detection point reception can be reconstructed from the environmental noise seismic data. The seismic record contains response information such as seismic refraction wave, surface wave, reflection wave and diffraction wave, which can be used to invert the structure and physical property information of the stratum medium. However, the quality of the virtual source seismic record reconstructed based on environmental noise seismic interferometry is closely related to the distribution of the environmental noise source. In theory, the environmental noise source should meet the assumption of uniform distribution in three-dimensional space to achieve symmetrical reconstruction of the effective seismic signal of the full wave field. However, in actual seismic exploration, the distribution of environmental noise sources is often non-uniform in time and space, which results in low quality of the reconstructed virtual source seismic record and the characteristics of asymmetric distribution. Therefore, how to select high-quality seismic records from numerous virtual source records has become a key link in quality control and data processing of environmental noise seismic exploration. Summary of the invention

[0004] The purpose of the present invention is to provide a method for automatically selecting virtual source records suitable for environmental noise seismic exploration. The method can realize automatic screening of high-quality virtual source seismic records rich in surface wave information through comparative analysis based on linear tilt stacking seismic wave field energy, and effectively solves the problem of uneven quality of calculated virtual source seismic records caused by non-uniform distribution of noise sources in environmental noise seismic exploration.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A method for automatically selecting virtual source records suitable for environmental noise seismic exploration, the method comprising:

[0007] Step 1, preprocessing the original environmental noise seismic data to obtain preprocessed environmental noise seismic data;

[0008] Step 2, using the pre-processed environmental noise seismic data, reconstruct the virtual source seismic records of each receiving point at different time periods;

[0009] Step 3, for the virtual source seismic records of the positive and negative time semi-axes, linear scanning stacking calculation processing is performed respectively to obtain scanning stacking curves based on different linear velocities; the maximum amplitude value of the scanning stacking amplitude curve based on the virtual source seismic records of the positive and negative time semi-axes is compared and analyzed, and the virtual source seismic records are automatically selected;

[0010] Step 4, repeat step 3 to realize the automatic selection of virtual source seismic records in different time periods at each receiving point location.

[0011] The preprocessing in step 1 includes: removing instrument response, removing mean, removing trend, data segmentation, suppressing abnormal extreme values ​​and spectrum whitening.

[0012] The different time periods of the virtual source seismic record include a positive time semi-axis and a negative time semi-axis.

[0013] The step 3 comprises:

[0014] Step 3.1, set the linear speed range;

[0015] Step 3.2, calculate the time field at different offsets and different linear velocities;

[0016] Step 3.3, calculate the scanning superposition amplitude at different linear speeds;

[0017] Step 3.4, obtaining the maximum superposition amplitude value in the linear scanning superposition amplitude curve;

[0018] Step 3.5, compare and analyze the maximum stacking amplitude value obtained based on the linear scanning stacking amplitude curve of the virtual source seismic records of the positive and negative time half axes, and realize the automatic selection of the virtual source seismic records rich in surface wave information.

[0019] The calculation formula for the time field at different offsets and different linear velocities in step 3.2 is:

[0020] t i,j =x i / v j

[0021] Among them, x i represents the offset distance of the ith track in the virtual source seismic record; v j represents the jth linear velocity; t i,j represents the jth linear velocity v at the i-th offset. j Calculate the time field.

[0022] The calculation formula for the scanning superposition amplitude at different linear speeds in step 3.3 is:

[0023]

[0024] Among them, u(t i,j ) represents the time t i,j The wave field of virtual source seismic record under s j Represents speed v j The scans under the superposition amplitude.

[0025] The calculation formula of the maximum superposition amplitude value in step 3.4 is:

[0026] s m =max(s j )

[0027] Among them, max represents the maximum value operator; s m Represents the superimposed amplitudes s of each curve j The maximum amplitude value to be obtained.

[0028] In step 3.5, the automatic selection calculation formula of the virtual source seismic record is:

[0029]

[0030] Among them, s m+ and m- Represents the s obtained by calculating the positive and negative time semi-axis respectively m Value, u + and u - represent the virtual source seismic records of the positive and negative time semi-axes respectively, and p represents the automatically selected virtual source seismic record rich in surface wave information.

[0031] The beneficial technical effects of the present invention are:

[0032] 1. The present invention provides an automatic selection method for virtual source records suitable for environmental noise seismic exploration. By comparing and analyzing the energy of linearly inclined stacked seismic wave fields, the automatic screening of high-quality virtual source seismic records rich in surface wave information can be achieved.

[0033] 2. The present invention provides an automatic selection method for virtual source records suitable for environmental noise seismic exploration. By using linear scanning amplitude superposition based on different speeds, the automatic in-phase superposition of seismic surface wave energy represented in virtual source seismic records can be realized, and the linear scanning superposition curve can be efficiently obtained.

[0034] 3. The present invention provides an automatic selection method for virtual source records suitable for environmental noise seismic exploration. By comparing and analyzing the linear scanning superposition amplitude curves calculated on the positive and negative time axes respectively, the method can automatically realize the screening of ideal environmental noise virtual source seismic records and improve the quality of environmental noise seismic exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1It is a virtual source seismic record diagram of environmental noise cross-correlation in an embodiment of the present invention;

[0036] Figure 2 It is a linear scanning superimposed amplitude curve diagram in an embodiment of the present invention;

[0037] Figure 3 This is a virtual source seismic record diagram automatically optimized by linear scanning and stacking in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0039] The present invention provides a method for automatically selecting virtual source records suitable for environmental noise seismic exploration, which specifically includes the following steps:

[0040] Step 1: preprocess the original environmental noise seismic data to obtain the preprocessed environmental noise seismic data

[0041] The original environmental noise seismic data are preprocessed in sequence by removing instrument response, removing mean, removing trend, data segmentation, suppressing abnormal extreme values ​​and spectrum whitening to obtain the preprocessed environmental noise seismic data.

[0042] Step 2: Use the preprocessed environmental noise seismic data to reconstruct the virtual source seismic records of each receiving point at different time periods.

[0043] The pre-processed environmental noise seismic data is used to carry out cross-correlation processing to reconstruct the virtual source seismic records of each receiving point in different time periods.

[0044] In a specific embodiment, different time periods of the virtual source seismic record include a positive time semi-axis and a negative time semi-axis.

[0045] Figure 1 is a virtual source seismic record reconstructed based on preprocessed ambient noise seismic data. Figure 1 It is clearly visible that no effective seismic information is developed on the positive time semi-axis, while there are strong energy and symmetrically distributed seismic surface waves on the negative time semi-axis.

[0046] Step 3: For the virtual source seismic records of the positive and negative time semi-axes, linear scanning stacking calculation processing is performed respectively to obtain scanning stacking curves based on different linear velocities; the maximum amplitude value of the scanning stacking amplitude curve of the virtual source seismic records based on the positive and negative time semi-axes is compared and analyzed, and the virtual source seismic records are automatically selected.

[0047] Step 3.1, set the linear speed range v j ;

[0048] Step 3.2, calculate the time field at different offsets and different linear velocities. The calculation formula is as follows:

[0049] t i,j =x i / v j

[0050] Among them, x i represents the offset distance of the ith track in the virtual source seismic record; v j represents the jth linear velocity; t i,j represents the jth linear velocity v at the i-th offset. j The time field of calculation;

[0051] Step 3.3, calculate the scanning superposition amplitude at different linear speeds, and the calculation formula is as follows:

[0052]

[0053] Among them, u(t i,j ) represents the time t i,j The wave field of virtual source seismic record under s j Represents speed v j The scans under the superposition amplitude.

[0054] Figure 2 To use Figure 1 The stacked amplitude curves of the positive and negative time semi-axis virtual source seismic records and the different linear velocities calculated in step 3.3 are obtained. Figure 2 It can be seen that different superimposed amplitude characteristics are exhibited under the positive and negative time axes.

[0055] Step 3.4, obtain the maximum superposition amplitude value in the linear scanning superposition amplitude curve, and the calculation formula is as follows:

[0056] s m =max(s j )

[0057] Among them, max represents the maximum value operator; s m Represents the superimposed amplitudes s of each curve j The maximum amplitude value to be obtained.

[0058] Step 3.5: Compare and analyze the maximum stacking amplitude value obtained by linear scanning stacking amplitude curve of virtual source seismic records based on positive and negative time semi-axis, and realize automatic selection of virtual source seismic records rich in surface wave information.

[0059] In one embodiment, the s obtained by comparing and analyzing the positive and negative time semi-axes m The value is used to realize the automatic selection of virtual source seismic records rich in surface wave information. The specific calculation formula is as follows:

[0060]

[0061] Among them, s m+ and m- Represents the s obtained by calculating the positive and negative time semi-axis respectively m Value, u + and u - represent the virtual source seismic records of the positive and negative time semi-axes respectively, and p represents the automatically selected virtual source seismic record rich in surface wave information.

[0062] Step 4, repeat step 3 to realize the automatic selection of virtual source seismic records in different time periods at each receiving point location.

[0063] based on Figure 2 From the linear scanning stacking amplitude curve shown in the figure, it can be seen that the maximum stacking amplitude value of the negative time semi-axis is greater than the maximum stacking amplitude value of the positive time semi-axis. Therefore, based on step 3.5, the virtual source seismic record of the negative time semi-axis is automatically selected as the final preferred virtual source seismic record. Figure 3 It can be seen that the seismic surface waves with linear characteristics in the automatically selected virtual source seismic records are very developed, which can lay a reliable data foundation for the extraction of dispersion curves and surface wave inversion.

[0064] The present invention is described in detail above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. The contents not described in detail in the present invention can adopt the existing technology.

Claims

1. A method for automatically selecting virtual source records for environmental noise seismic exploration, characterized in that: The method comprises: Step 1, preprocessing the original environmental noise seismic data to obtain preprocessed environmental noise seismic data; Step 2, using the pre-processed environmental noise seismic data, reconstruct the virtual source seismic records of each receiving point at different time periods; Step 3, for the virtual source seismic records of the positive and negative time semi-axes, linear scanning stacking calculation processing is performed respectively to obtain scanning stacking curves based on different linear velocities; the maximum amplitude value of the scanning stacking amplitude curve based on the virtual source seismic records of the positive and negative time semi-axes is compared and analyzed, and the virtual source seismic records are automatically selected; Step 4, repeat step 3 to realize the automatic selection of virtual source seismic records in different time periods at each receiving point location.

2. The method for automatically selecting virtual source records for environmental noise seismic exploration according to claim 1, characterized in that: The preprocessing in step 1 includes: removing instrument response, removing mean, removing trend, data segmentation, suppressing abnormal extreme values ​​and spectrum whitening.

3. The method for automatically selecting virtual source records for environmental noise seismic exploration according to claim 1, characterized in that: The different time periods of the virtual source seismic record include a positive time semi-axis and a negative time semi-axis.

4. The method for automatically selecting virtual source records for environmental noise seismic exploration according to claim 1, characterized in that: The step 3 comprises: Step 3.1, set the linear speed range; Step 3.2, calculate the time field at different offsets and different linear velocities; Step 3.3, calculate the scanning superposition amplitude at different linear speeds; Step 3.4, obtaining the maximum superposition amplitude value in the linear scanning superposition amplitude curve; Step 3.5, compare and analyze the maximum stacking amplitude value obtained based on the linear scanning stacking amplitude curve of the virtual source seismic records of the positive and negative time half axes, and realize the automatic selection of the virtual source seismic records rich in surface wave information.

5. The method for automatically selecting virtual source records for environmental noise seismic exploration according to claim 4, characterized in that: The calculation formula for the time field at different offsets and different linear velocities in step 3.2 is: t i,j =x i / v j Among them, x i represents the offset distance of the ith track in the virtual source seismic record; v j represents the jth linear velocity; t i,j represents the jth linear velocity v at the i-th offset. j Calculate the time field.

6. The method for automatically selecting virtual source records for environmental noise seismic exploration according to claim 5, characterized in that: The calculation formula for the scanning superposition amplitude at different linear speeds in step 3.3 is: Among them, u(t i,j ) represents the time t i,j The wave field of virtual source seismic record under s j Represents speed v j The scans under the superposition amplitude.

7. The method for automatically selecting virtual source records for environmental noise seismic exploration according to claim 6, characterized in that: The calculation formula of the maximum superposition amplitude value in step 3.4 is: s m =max(s j ) Among them, max represents the maximum value operator; s m Represents the superimposed amplitudes s of each curve j The maximum amplitude value to be obtained.

8. The method for automatically selecting virtual source records for environmental noise seismic exploration according to claim 7, characterized in that: In step 3.5, the automatic selection calculation formula of the virtual source seismic record is: Among them, s m+ and m- Represents the s obtained by calculating the positive and negative time semi-axis respectively m Value, u + and u - represent the virtual source seismic records of the positive and negative time semi-axes respectively, and p represents the automatically selected virtual source seismic record rich in surface wave information.

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