Method and apparatus for building near-surface velocity model

Abstract

The application discloses a method and device for establishing a near-surface velocity model, and belongs to the technical field of geophysical exploration. The method comprises the following steps: acquiring the positions of a plurality of shot points, the positions of a plurality of geophones, and the actual first arrival time corresponding to each shot-geophone pair; obtaining the isotropic near-surface velocity corresponding to each detection area based on the positions of the shot points, the positions of the geophones, the actual first arrival time corresponding to each shot-geophone pair and an initial near-surface velocity model; determining the predicted first arrival time corresponding to each shot-geophone pair based on the isotropic near-surface velocity; and determining the near-surface velocity corresponding to different directions in each detection area based on the isotropic near-surface velocity corresponding to each detection area, the predicted first arrival time corresponding to each shot-geophone pair and the actual first arrival time. The near-surface velocity determined by the method takes the speed difference of seismic waves propagating in the crust along different directions into account, and can more truly and accurately determine the near-surface velocity of seismic waves.

Description

Technical Field

[0001] This application relates to the field of geophysical exploration technology, and in particular to a method and apparatus for establishing a near-surface velocity model. Background Technology

[0002] In the field of geophysical exploration, the propagation velocity of seismic waves in the Earth's crust is an important parameter reflecting subsurface structures and rock properties. The accuracy of seismic wave propagation velocity directly affects the static correction, velocity analysis, and final imaging results of seismic data in the exploration area.

[0003] Currently, near-surface velocity models are often used to determine the propagation speed of seismic waves near the surface. To establish a near-surface velocity model, the first arrival time of the seismic waves needs to be obtained. Then, the first arrival time is inverted through methods such as first arrival wave refraction analysis and first arrival wave travel time tomography, thereby obtaining the near-surface velocity model.

[0004] The near-surface velocity models determined using current methods typically assume that seismic wave propagation speeds are isotropic, meaning that seismic waves travel at the same speed in all directions within the Earth's crust. However, in reality, due to the uneven geological distribution within the Earth's crust, the propagation speeds of seismic waves vary significantly in different directions. Therefore, the seismic wave propagation speeds determined using current near-surface velocity models are not accurate. Summary of the Invention

[0005] This application provides a method, apparatus, device, and storage medium for establishing a near-surface velocity model, which can solve the problem of inaccurate near-surface velocity models in the prior art. The technical solution is as follows:

[0006] Firstly, a method for establishing a near-surface velocity model is provided, the method comprising:

[0007] The positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair in the target area are obtained. The target area has several detection areas, and the shot-receiver pair consists of one shot point and one receiver point.

[0008] Based on the locations of multiple shot points, multiple receiver points, the actual first arrival time and the initial near-surface velocity model for each shot-receiver pair, the isotropic near-surface velocity corresponding to each detection area is determined.

[0009] Based on the locations of multiple shot points, multiple receiver points, and the isotropic near-surface velocity corresponding to each detection area, the predicted first arrival time for each shot-receiver pair is determined.

[0010] Based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair, an anisotropic near-surface velocity model corresponding to each detection area is determined. The anisotropic near-surface velocity model corresponding to the detection area is used to represent the near-surface velocity corresponding to different azimuths in the detection area, where azimuth is the azimuth relative to the center point of the detection area.

[0011] In one possible implementation, based on the locations of multiple shot points, multiple receiver points, the actual first arrival time of each shot-receiver pair, and the initial near-surface velocity model, the isotropic near-surface velocity corresponding to each detection area is determined, including:

[0012] Based on the positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair, the shot-receiver distance for each shot-receiver pair, the shot point delay time for each detection area, and the receiver point delay time are determined.

[0013] Based on the shot delay time and receiver delay time corresponding to each detection area, the shot-receiver distance and actual first arrival time corresponding to each shot-receiver pair, the isotropic near-surface velocity corresponding to each detection area is determined.

[0014] In one possible implementation, based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair, an anisotropic near-surface velocity model corresponding to each detection area is determined, including:

[0015] Determine the first arrival time difference for each shot-receiver pair. The first arrival time difference is the difference between the actual first arrival time and the predicted first arrival time.

[0016] Based on the locations of multiple shot points, multiple receiver points, and the first arrival time difference of each shot-receiver pair, the near-surface azimuth anisotropy perturbation term corresponding to each detection area is determined;

[0017] The anisotropic near-surface velocity model for each detection area is determined as V. aniso =V iso +ΔV, where V aniso For anisotropic near-surface velocities, V iso Here, ΔV represents the isotropic near-surface velocity, and ΔV represents the near-surface azimuth anisotropic disturbance term.

[0018] In one possible implementation, based on the locations of multiple shot points, multiple receiver points, and the first arrival time difference corresponding to each shot-receiver pair, the near-surface azimuth anisotropy perturbation term corresponding to each detection area is determined, including:

[0019] Determine the midpoint of the shot-receiver line for each shot-receiver pair. The shot-receiver line is the line connecting the shot point and the receiver point in the shot-receiver pair.

[0020] Determine the shot-receiver pair corresponding to each detection area, wherein the shot-receiver pair corresponding to the detection area is the shot-receiver pair whose midpoint is within the detection area;

[0021] In each detection area, the corresponding shot-receiver distance and azimuth of the shot-receiver pair are determined based on the positions of multiple shot points and multiple receiver points;

[0022] For each detection area, among the shot-receiver distance, azimuth, and first arrival time difference for the corresponding shot-receiver pair, the azimuth and first arrival time difference for the same shot-receiver distance are determined. The azimuth and first arrival time difference for each shot-receiver distance are fitted to obtain the relationship between the azimuth and first arrival time difference for each shot-receiver distance. Based on each shot-receiver distance and the corresponding relationship, the expression for the near-surface velocity in terms of azimuth is determined for each shot-receiver distance. Based on the expression for each shot-receiver distance, the near-surface azimuth anisotropy perturbation term for the detection area is determined.

[0023] In one possible implementation, after determining the anisotropic near-surface velocity model for each detection area based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair, the following is also included:

[0024] Based on the anisotropic near-surface velocity model corresponding to each detection area, the near-surface azimuth anisotropy amplitude corresponding to each detection area is determined.

[0025] In one possible implementation, based on the anisotropic near-surface velocity model corresponding to each detection area, the near-surface azimuth anisotropy amplitude corresponding to each detection area is determined, including:

[0026] For each detection area, based on the anisotropic near-surface velocity model corresponding to the detection area, the near-surface velocity corresponding to each orientation of the detection area is determined. The least squares ellipse fitting method is used to fit the near-surface velocity corresponding to each orientation of the detection area to determine the minimum and maximum near-surface velocities corresponding to the detection area.

[0027] For each detection area, determine the velocity difference between the maximum and minimum near-surface velocities corresponding to the detection area. Based on the velocity difference and the maximum near-surface velocity corresponding to the detection area, determine the near-surface azimuth anisotropy amplitude corresponding to the detection area.

[0028] Secondly, an apparatus for establishing a near-surface velocity model is provided, the apparatus comprising:

[0029] The acquisition module is used to acquire the positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair in the target area. The target area has several detection areas, and the shot-receiver pair consists of one shot point and one receiver point.

[0030] The first determining module is used to determine the isotropic near-surface velocity corresponding to each detection area based on the positions of multiple shot points, multiple receiver points, the actual first arrival time and the initial near-surface velocity model corresponding to each shot-receiver pair.

[0031] The prediction module is used to determine the predicted first arrival time for each shot-receiver pair based on the positions of multiple shot points, multiple receiver points, and the isotropic near-surface velocity corresponding to each detection area.

[0032] The second determining module is used to determine the anisotropic near-surface velocity model corresponding to each detection area based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair. The anisotropic near-surface velocity model corresponding to the detection area is used to represent the near-surface velocity corresponding to different azimuths in the detection area, where the azimuth is the azimuth relative to the center point of the detection area.

[0033] In one possible implementation, the first determining module is configured to:

[0034] Based on the positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair, the shot-receiver distance for each shot-receiver pair, the shot point delay time for each detection area, and the receiver point delay time are determined.

[0035] Based on the shot delay time and receiver delay time corresponding to each detection area, the shot-receiver distance and actual first arrival time corresponding to each shot-receiver pair, the isotropic near-surface velocity corresponding to each detection area is determined.

[0036] In one possible implementation, the second determining module is configured to:

[0037] Determine the first arrival time difference for each shot-receiver pair. The first arrival time difference is the difference between the actual first arrival time and the predicted first arrival time.

[0038] Based on the locations of multiple shot points, multiple receiver points, and the first arrival time difference of each shot-receiver pair, the near-surface azimuth anisotropy perturbation term corresponding to each detection area is determined.

[0039] The anisotropic near-surface velocity model for each detection area is determined as V. aniso =V iso +ΔV, where V aniso For anisotropic near-surface velocities, V isoHere, ΔV represents the isotropic near-surface velocity, and ΔV represents the near-surface azimuth anisotropic disturbance term.

[0040] In one possible implementation, the second determining module is configured to:

[0041] Determine the midpoint of the shot-receiver line for each shot-receiver pair. The shot-receiver line is the line connecting the shot point and the receiver point in the shot-receiver pair.

[0042] Determine the shot-receiver pair corresponding to each detection area, wherein the shot-receiver pair corresponding to the detection area is the shot-receiver pair whose midpoint is within the detection area;

[0043] In each detection area, the corresponding shot-receiver distance and azimuth of the shot-receiver pair are determined based on the positions of multiple shot points and multiple receiver points;

[0044] For each detection area, among the shot-receiver distance, azimuth, and first arrival time difference for the corresponding shot-receiver pair, the azimuth and first arrival time difference for the same shot-receiver distance are determined. The azimuth and first arrival time difference for each shot-receiver distance are fitted to obtain the relationship between the azimuth and first arrival time difference for each shot-receiver distance. Based on each shot-receiver distance and the corresponding relationship, the expression for the near-surface velocity in terms of azimuth is determined for each shot-receiver distance. Based on the expression for each shot-receiver distance, the near-surface azimuth anisotropy perturbation term for the detection area is determined.

[0045] In one possible implementation, the second determining module is further configured to:

[0046] Based on the anisotropic near-surface velocity model corresponding to each detection area, the near-surface azimuth anisotropy amplitude corresponding to each detection area is determined.

[0047] In one possible implementation, the second determining module is further configured to:

[0048] For each detection area, based on the anisotropic near-surface velocity model corresponding to the detection area, the near-surface velocity corresponding to each orientation of the detection area is determined. The least squares ellipse fitting method is used to fit the near-surface velocity corresponding to each orientation of the detection area to determine the minimum and maximum near-surface velocities corresponding to the detection area.

[0049] For each detection area, determine the velocity difference between the maximum and minimum near-surface velocities corresponding to the detection area. Based on the velocity difference and the maximum near-surface velocity corresponding to the detection area, determine the near-surface azimuth anisotropy amplitude corresponding to the detection area.

[0050] Thirdly, a computer device is provided, the computer device including a processor and a memory, the memory storing at least one instruction, the instruction being loaded and executed by the processor to implement the operations performed by the method for establishing a near-surface velocity model.

[0051] Fourthly, a computer-readable storage medium is provided, wherein at least one instruction is stored in the storage medium, the instruction being loaded and executed by a processor to implement the operations performed by the method for establishing a near-surface velocity model.

[0052] Fifthly, a computer program product is provided, comprising computer program code, wherein when the computer program code is executed by a computer device, the computer device executes the method described in the first aspect and its possible implementations.

[0053] The beneficial effects of the technical solutions provided in this application are:

[0054] The scheme mentioned in this application firstly obtains the isotropic near-surface velocity for each detection area based on the location of the shot point, the location of the receiver point, the actual first arrival time of the shot-receiver pair, and the initial near-surface velocity model. Then, the predicted first arrival time for each shot-receiver pair is determined based on the isotropic near-surface velocity. Finally, the near-surface velocity corresponding to different azimuths within each detection area is determined based on the isotropic near-surface velocity, the predicted first arrival time, and the actual first arrival time for each shot-receiver pair. The near-surface velocity determined using this method is anisotropic, taking into account the velocity differences of seismic waves propagating in different directions within the Earth's crust. Therefore, using this anisotropic near-surface velocity model to determine the propagation speed of seismic waves can more realistically and accurately determine the near-surface velocity of seismic waves. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 This is a schematic diagram of a target area and coordinate system provided in an embodiment of this application;

[0057] Figure 2 This is a schematic diagram of a target area provided in an embodiment of this application;

[0058] Figure 3 This is a flowchart of a method for establishing a near-surface velocity model provided in an embodiment of this application;

[0059] Figure 4 This is a schematic diagram of a detection area and a shot-detector pair provided in an embodiment of this application;

[0060] Figure 5 This is a schematic diagram of the azimuth angle of a shot-receiver pair provided in an embodiment of this application;

[0061] Figure 6 This is a flowchart of a method for determining the amplitude of near-surface azimuth anisotropy provided in an embodiment of this application;

[0062] Figure 7 This is a schematic diagram of the structure of a model training device provided in an embodiment of this application;

[0063] Figure 8 This is a structural block diagram of a computer device provided in an embodiment of this application. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0065] The method for establishing a near-surface velocity model provided in this application can be applied to seismic exploration. Seismic exploration refers to establishing an artificial earthquake source at a certain point on the Earth's surface to induce crustal vibration (i.e., generate seismic waves). Simultaneously, using pre-placed seismic detectors, raw data (such as arrival time, frequency, and amplitude of seismic waves) are recorded when the seismic waves arrive at the detectors according to a certain observation method. After a series of processing steps on the raw data, corresponding results are obtained, thereby inferring the characteristics of underground geological structures.

[0066] First, several terms used in the embodiments of this application will be explained:

[0067] A blast point is the location of an artificial earthquake source on or near the Earth's surface, i.e., the location where seismic waves are generated artificially. For example, in the case of using explosives, the blast point is the location where the explosives are placed (i.e., the detonation point). In another example, in the case of using a hammer to strike the ground, the blast point is the location where the hammer is installed (i.e., the hammer impact point), and so on.

[0068] Detector point: The location where a seismic detector is placed on or near the ground surface.

[0069] Shot-receiver pair: Typically, in seismic exploration of a certain area, multiple shot points and multiple receiver points can be set up, and any shot point and any receiver point form a shot-receiver pair.

[0070] Shot-receiver line: The line connecting the shot point and the receiver point in any shot-receiver alignment.

[0071] Shot-receiver distance: The distance between the shot point and the receiver point in any shot-receiver alignment.

[0072] Azimuth: In the horizontal plane, the horizontal angle obtained by rotating clockwise around the reference point from the true north direction line to the target direction line.

[0073] Near-surface velocity: the speed at which seismic waves propagate through the Earth's crust near the Earth's surface.

[0074] Isotropic: Seismic waves travel at the same speed in the Earth's crust along different directions (i.e., in different azimuth angles).

[0075] Anisotropy: Seismic waves travel at different or different speeds in the Earth's crust along different directions (i.e., in different azimuth angles).

[0076] First arrival wave: The seismic wave that arrives at the geophone location first among the various types of seismic waves generated at the shot point.

[0077] First arrival time: The time it takes for a seismic wave generated at the shot point to reach the location of the first receiver point in any shot-receiver pair.

[0078] When the shot point is delayed: In refraction analysis, the difference between the propagation time of the seismic wave in the low velocity zone and the propagation time of the ray path over the horizontal projection distance of the refraction layer at the shot point is calculated. This difference is equal to the thickness of the low velocity zone at the shot point divided by the velocity of the low velocity zone and then multiplied by the cosine of the critical refraction angle.

[0079] When the receiver point is delayed: In refraction analysis, the difference between the propagation time of the seismic wave in the low velocity zone and the propagation time of the ray path over the horizontal projection distance of the refraction layer is calculated at the receiver point. This difference is equal to the thickness of the low velocity zone at the receiver point divided by the velocity of the low velocity zone and then multiplied by the cosine of the critical refraction angle.

[0080] The method for establishing a near-surface velocity model provided in this application embodiment can be executed by a server. The server may include a processor, memory, and communication components, etc.

[0081] The processor can be a CPU (Central Processing Unit) or a SoC (System on Chip), etc. The processor can be used to acquire initial data for the target area, determine the isotropic near-surface velocity corresponding to each detection area, determine the predicted first arrival time for each shot-receiver pair, determine the anisotropic near-surface velocity model for each detection area, and so on.

[0082] The memory can be various types of volatile or non-volatile memory, such as SSD (Solid State Disk) and DRAM (Dynamic Random Access Memory). The memory can be used to store pre-stored data, intermediate data, and result data during the process of building the near-surface velocity model. For example, initial data for the target area, isotropic near-surface velocities corresponding to each detection area, predicted first arrival times for each shot-receiver pair, anisotropic near-surface velocity models for each detection area, and so on.

[0083] Communication components can be wired network connectors, WiFi (Wireless Fidelity) modules, Bluetooth modules, cellular network communication modules, etc. These components can be used for data transmission with other devices, such as detectors, servers, or operating terminals. They can also be used to receive the actual first arrival times transmitted by each detector, and to send anisotropic near-surface velocity models corresponding to each detection area to other servers, etc.

[0084] After the exploration personnel determine the target area to be explored, they can establish a coordinate system corresponding to the target area on the server, and determine the coordinate information of each boundary point of the target area in the coordinate system. Any point in the target area can be used as the origin of this coordinate system. For example, the target area and its corresponding coordinate system are as follows: Figure 1 As shown, the target area is a rectangle. The lower left vertex of the rectangle is the origin of the coordinate system. The north direction of this vertex is the positive direction of the Y-axis of the coordinate system, and the east direction of this vertex is the positive direction of the X-axis of the coordinate system.

[0085] Exploration personnel can divide the target area into several detection zones (also called surface elements). Each detection zone can be the same size or different sizes. For example, a rectangular target area can be divided into several sub-rectangles of the same size; each sub-rectangle is called a detection zone. The server can determine the position of each detection zone in the aforementioned coordinate system, that is, the coordinate information of each vertex of each detection zone in the coordinate system, and determine the corresponding identification information for each detection zone. Within each detection zone, a maximum of one shot point (i.e., an artificial seismic source) or one receiver point (i.e., a seismic detector) can be set. For example, a shot point or a receiver point can be set at the center point of each detection zone in the target area. Figure 2 As shown.

[0086] For each shot point set up in the target area, the exploration personnel can send its identification information and location within the target area to the server. The server can then determine the coordinates of the shot point in the corresponding coordinate system of the target area, thus establishing a correspondence between the shot point's identification information and its coordinates. Similarly, for each geophone point set up in the target area, the exploration personnel can send its identification information and location within the target area to the server. The server can then determine the coordinates of the geophone point in the corresponding coordinate system of the target area, thus establishing a correspondence between the geophone point's identification information and its coordinates.

[0087] In seismic exploration, a shot point can be fired once to generate one seismic wave, or it can be fired multiple times to generate multiple seismic waves. The period from when a shot point generates a seismic wave to when the seismic wave ends its propagation in the Earth's crust can be called a detection cycle. After a detection cycle for a shot point ends, the same location is fired again or the shot point is moved to enter the next detection cycle.

[0088] In seismic exploration, a shot point can generate a seismic wave once, and multiple shot points can generate seismic waves in sequence at intervals. The period from the start of seismic wave generation at each shot point to the end of the seismic wave propagation in the Earth's crust can be called a detection cycle. After the detection cycle corresponding to one shot point ends, the detection cycle corresponding to the next shot point begins.

[0089] In seismic exploration, multiple shot points can simultaneously generate seismic waves. The period from when multiple shot points generate seismic waves until all seismic waves have propagated to the target area can be called a detection cycle. In this case, the server can perform synchronous source data classification on all raw data received by each detector to determine the raw data corresponding to each shot point.

[0090] Next, we will take the example of multiple shot points generating only one seismic wave and working in sequence at intervals as an example. Other cases are similar and will not be described in detail.

[0091] This application provides embodiments such as Figure 3 The processing flow of the method for establishing a near-surface velocity model, as shown, includes the following steps:

[0092] S101. Obtain the positions of multiple shot points, multiple receiver points, and the actual first arrival time for each shot-receiver pair in the target area.

[0093] After the exploration personnel have set up the shot points and receiver points, they can carry out seismic exploration. The seismic waves generated by any shot point can be received by multiple receiver points (i.e., receiver points). For example, the seismic waves generated by shot point S1 can be received by receiver points R1, R2, and R3.

[0094] At the same time that the seismic wave is generated at the shot point, the geophone point begins to detect the seismic wave and starts timing. When the preset recording duration threshold is reached, the timing can be stopped, and the seismic record data corresponding to that geophone point can be obtained.

[0095] The server can pre-store the coordinate information of each shot point and each receiver point. The server can determine the coordinate information of the shot point and the receiver point based on the identification information of the shot point and the receiver point. At the same time, the first arrival picking algorithm can be used to pick the first arrival time (in milliseconds) of each seismic trace (i.e., shot-receiver pair) from the seismic record data corresponding to the receiver point. For example, if the shot point identifier is "S1", the receiver identifier is "R1" and its corresponding seismic record data is "I1", the receiver identifier is "R2" and its corresponding seismic record data is "I2", and the receiver identifier is "R3" and its corresponding seismic record data is "I3", the server can determine the coordinate information of the shot point S1, receiver R1, receiver R2, and receiver R3 respectively based on the identifier information. At the same time, the server can use the first arrival picking algorithm to determine the corresponding actual first arrival times of 63 milliseconds, 88 milliseconds, and 108 milliseconds from the seismic record data I1, I2, and I3, respectively. Thus, the three shot-receiver pairs and their corresponding actual first arrival times are determined as "S1-R1-63", "S1-R2-88", and "S1-R3-108", respectively.

[0096] Simultaneously, the shot-receiver distance (i.e., the distance from the shot point to the receiver point) corresponding to each shot-receiver pair can be calculated based on the coordinate information of the shot-receiver points. Anomalies can be identified in the actual first arrival time (ART) for each shot-receiver pair based on preset thresholds for different ARTs. If anomalies are found, the data set can be deleted. For example, the ART threshold for a shot-receiver distance of 90-110 meters is [60, 80]. If the ART between shot point S1 and receiver point R1 is 100 meters, the corresponding ART is 90 milliseconds. This ART is then identified as abnormal and deleted. Conversely, if the ART threshold for a shot-receiver distance of 1000 meters is [640, 780], and the ART between shot point S1 and receiver point R2 is 1000 meters, the corresponding ART is 700 milliseconds. This ART is then identified as normal and retained, and so on.

[0097] S102. Based on the positions of multiple shot points, multiple receiver points, the actual first arrival time and the initial near-surface velocity model corresponding to each shot-receiver pair, determine the isotropic near-surface velocity corresponding to each detection area.

[0098] After the server determines the coordinates of each shot point, each receiver point, and the corresponding shot-receiver distance and actual first arrival time for each shot-receiver pair according to step S101, it can use the refraction layering method to determine the isotropic near-surface velocity corresponding to each detection area. When using the refraction layering method, the initial near-surface velocity model can be the basic refraction equation:

[0099]

[0100] Among them, T sr τ is the initial arrival time. s When the shot point is delayed, τ r When the receiver delay is denoted by X, the shot-receiver distance is denoted by V. iso The initial near-surface velocity is isotropic. Using the basic refraction equations, a functional relationship can be derived expressing the near-surface velocity in terms of shot-receiver distance and first arrival time. For each detection area, the initial near-surface velocity model can also be a set of velocity values. This set of velocity values ​​can represent the near-surface velocity corresponding to different shot-receiver distances within the detection area, or it can represent the near-surface velocity corresponding to different azimuths within the detection area. Whether the initial velocity model is a functional relationship or a set of velocity values, both can be considered equivalent.

[0101] First, the server can determine the midpoint of the shot-detector line corresponding to each shot-detector pair in the aforementioned coordinate system based on the coordinates of the shot point and the receiver point in each shot-detector pair. Thus, the server can determine the shot-detector pair corresponding to each detection area, where the shot-detector pair corresponding to the detection area is the one whose midpoint of the shot-detector line is located within that detection area.

[0102] If the midpoint of the shot-receiver line falls on the common boundary line of multiple detection zones, then the shot-receiver pair corresponding to that line can be considered to correspond to all of these detection zones. For example, if the midpoint of the shot-receiver line of the shot-receiver pair "P1-J1" falls on the common boundary line of detection zones t5 and t6, then... Figure 4 As shown, the shot detection pair “P1-J1” corresponds to both detection area t5 and detection area t6, and so on.

[0103] Optionally, if the midpoint of the shot-receiver line falls on the common boundary line of multiple detection areas, then it can be considered that the shot-receiver pair corresponding to that shot-receiver line does not correspond to any of these multiple detection areas. This case will not be elaborated further.

[0104] Secondly, for each detection area, the server can determine the shot-receiver distance and actual first arrival time of the shot-receiver pair with the same shot-receiver distance from the shot-receiver distance and actual first arrival time of the shot-receiver pair corresponding to that detection area.

[0105] Optionally, the server can pre-store shot-receiver distance intervals. Multiple shot-receiver distances belonging to the same interval can be considered as the same shot-receiver distance. For example, if the server pre-stores a shot-receiver distance interval [100, 120), and the server obtains shot-receiver distances of 100 meters, 120 meters, 102 meters, and 113 meters for shot-receiver pairs P1-J6, P1-J7, P2-J5, and P4-J3 within a certain detection area, then it can be determined that shot-receiver pairs P1-J6, P2-J5, and P4-J3 are shot-receiver pairs with the same distance.

[0106] Then, for shot-receiver pairs with the same shot-receiver offset (i.e., belonging to the range of shot-receiver offset), the server can use least squares fitting and the Gauss-Seidel method to fit multiple shot-receiver offsets and the corresponding actual first arrival times, and determine the shot point delay time, receiver point delay time and isotropic near-surface velocity in the above basic refraction equation corresponding to the current shot-receiver offset.

[0107] Finally, for each detection area, the server can use an arithmetic mean (or weighted average) method to process the isotropic near-surface velocities corresponding to multiple shot-receiver distances, and use the calculated average (or weighted average) as the isotropic near-surface velocity corresponding to that detection area. Similarly, the same processing can be performed for shot-point delay and receiver-point delay, which will not be elaborated here.

[0108] Optionally, for each detection area, after the server determines the shot-receiver pair corresponding to each detection area, it can use least squares fitting and Gauss-Seidel method to fit the shot-receiver distance and actual first arrival time corresponding to each shot-receiver pair, and determine the shot delay time, receiver delay time and isotropic near-surface velocity in the above basic refraction equation corresponding to the current detection area.

[0109] Optionally, for the target area, the server can use least squares fitting and the Gauss-Seidel method to fit the corresponding shot-receiver distance and actual first arrival time for each shot-receiver pair, determining the shot delay time, receiver delay time, and isotropic near-surface velocity in the aforementioned basic refraction equation for the target area. The server can then use the shot delay time, receiver delay time, and isotropic near-surface velocity corresponding to the target area as the isotropic near-surface velocity for each detection area.

[0110] Alternatively, in addition to using the refraction layering method to determine the isotropic near-surface velocity corresponding to each detection area as mentioned above, the first-arrival travel-time tomography method can also be used for determination. This method will not be elaborated here.

[0111] Alternatively, in addition to the least squares fitting and Gauss-Seidel method mentioned above, the server can also use simple velocity analysis, refraction velocity analysis, interchangeable velocity analysis, extended normalized interchange algorithm, etc., to fit multiple shot-receiver distances and corresponding actual first arrival times to determine isotropic near-surface velocities. Other determination methods will not be elaborated here.

[0112] S103. Based on the positions of multiple shot points, multiple receiver points, and the isotropic near-surface velocity corresponding to each detection area, determine the predicted first arrival time for each shot-receiver pair.

[0113] First, for each shot-detector pair, the server can determine the shot-detector distance, the coordinate information of the shot point and the coordinate information of the receiver point corresponding to the shot-detector pair according to the method in step S101, thereby determining the detection area where the midpoint of the shot-detector line is located, that is, the detection area corresponding to the shot-detector pair.

[0114] Secondly, within each detection area, the server can determine the range of shot-receiver distances corresponding to the shot-receiver pair, thereby determining the shot point delay, receiver point delay, and isotropic near-surface velocity corresponding to the shot-receiver pair.

[0115] Optionally, for a shot-receiver pair whose midpoint lies on the common boundary of multiple detection areas, the shot-receiver distance interval to which the pair belongs in the multiple detection areas can be determined. This allows for the determination of the shot delay time, receiver delay time, and isotropic near-surface velocity in each detection area. Finally, the average values ​​of the multiple shot delay times, receiver delay times, and isotropic near-surface velocities are calculated and used as the shot delay time, receiver delay time, and isotropic near-surface velocity corresponding to the shot-receiver pair.

[0116] Then, the server can substitute the shot delay time, receiver delay time, and isotropic near-surface velocity corresponding to the shot-receiver distance interval into the above basic refraction equation to determine the expression between the first arrival time and the shot-receiver distance.

[0117] Finally, the server can substitute the shot-receiver distance corresponding to the shot-receiver pair into the expression between the first arrival time and the shot-receiver distance mentioned above to calculate the predicted first arrival time corresponding to the shot-receiver pair.

[0118] Optionally, for the other cases mentioned in step S102 regarding the shot point delay, receiver delay, and isotropic near-surface velocity corresponding to the detection area, the processing procedure is similar when determining the predicted first arrival time of the shot-receiver pair, and will not be repeated here.

[0119] S104. Determine the first arrival time difference for each shot-receiver pair. The first arrival time difference is the difference between the actual first arrival time and the predicted first arrival time.

[0120] After the server determines the predicted first arrival time for each shot-receiver pair according to step S103, it can calculate the difference between the actual first arrival time and the predicted first arrival time for each shot-receiver pair. This difference is the first arrival time difference for each shot-receiver pair. The calculation formula is as follows:

[0121] Δt=t obs -t cal (2)

[0122] Where Δt is the initial arrival time difference, t obs t represents the actual arrival time. cal To predict the arrival time.

[0123] S105. Based on the positions of multiple shot points, multiple receiver points, and the first arrival time difference corresponding to each shot-receiver pair, determine the near-surface azimuth anisotropy perturbation term corresponding to each detection area.

[0124] First, the server can determine the coordinates of each shot point (i.e., the position of the shot point) and each receiver point (i.e., the position of the receiver point) according to step S101, and calculate the shot-receiver distance corresponding to each shot-receiver pair. Simultaneously, the server can also determine the coordinates of the midpoint of the shot-receiver line corresponding to each shot-receiver pair, thereby determining the shot-receiver pair corresponding to each detection area. The process of determining the shot-receiver pair corresponding to each detection area is similar to the process in step S102, and will not be repeated here.

[0125] For each detection area, after the server determines the corresponding shot-receiver pair, it can use the geometric center of the detection area as a reference point. Based on the coordinate information of any receiver point and the reference point, it can determine the azimuth angle of the line connecting any receiver point and the reference point. This azimuth angle is the azimuth angle corresponding to the shot-receiver pair to which the receiver point belongs. For example, the azimuth angle corresponding to a certain shot-receiver pair is as follows: Figure 5 As shown, the center point of the rectangular detection area is the reference point, the line connecting the reference point and the receiver point is the target direction line, and the angle between the reference point and the target direction line is the azimuth of the receiver point, which is the azimuth of the shot-receiver pair to which the receiver point belongs.

[0126] Then, for each detection area, the server can determine the azimuth and first arrival time difference (FOT) of the shot-receiver pair with the same shot-receiver distance from the shot-receiver distance, azimuth, and first arrival time difference (FOT) of the corresponding shot-receiver pair in that detection area. For shot-receiver pairs with the same shot-receiver distance, the server can perform fitting processing on the azimuth and FOT corresponding to each shot-receiver distance to obtain the relationship between the azimuth and FOT corresponding to each shot-receiver distance. This expression can be denoted as Δt(θ), where Δt is the FOT and θ is the azimuth.

[0127] Optionally, the server can pre-store shot-receiver distance intervals. Multiple shot-receiver distances belonging to the same interval can be considered as the same shot-receiver distance. For example, if the server pre-stores a shot-receiver distance interval [100, 120), and the server obtains shot-receiver distances of 100 meters, 120 meters, 102 meters, and 113 meters for shot-receiver pairs P1-J6, P1-J7, P2-J5, and P4-J3 within a certain detection area, then it can be determined that shot-receiver pairs P1-J6, P2-J5, and P4-J3 are shot-receiver pairs with the same distance.

[0128] For a gun-receiver pair belonging to the same gun-receiver distance interval, the server can determine the median of the gun-receiver distance interval as the gun-receiver distance corresponding to the gun-receiver pair belonging to that distance interval. For example, if the server has a pre-stored gun-receiver distance interval of [100, 120), and the median of this gun-receiver distance interval is 110 meters, and the server obtains that the gun-receiver pairs belonging to this distance interval in a certain detection area are P1-J6, P2-J5, and P4-J3, then it can be determined that the gun-receiver distances corresponding to gun-receiver pairs P1-J6, P2-J5, and P4-J3 are all 110 meters.

[0129] For a gun-receiver pair belonging to the same gun-receiver distance interval, the server can determine the average of the gun-receiver distance intervals as the gun-receiver distance corresponding to the gun-receiver pair belonging to that distance interval. For example, if the server obtains that the gun-receiver pairs belonging to the same gun-receiver distance interval in a certain detection area are P1-J6, P2-J5, and P4-J3, and the gun-receiver distances corresponding to these three gun-receiver pairs are 100 meters, 102 meters, and 113 meters respectively, then it can be determined that the gun-receiver distances corresponding to gun-receiver pairs P1-J6, P2-J5, and P4-J3 are all 105 meters.

[0130] For each shot-receiver distance (or each shot-receiver distance interval), the server can determine the quotient of the shot-receiver distance and the above expression Δt(θ), which serves as the expression for the near-surface azimuth anisotropy disturbance term in terms of azimuth angles corresponding to the shot-receiver distance. This expression can be as follows:

[0131]

[0132] Wherein, ΔV is the near-surface azimuth anisotropic disturbance term, X is the shot-receiver distance, and for a shot-receiver distance, X in formula (3) is a constant term, and Δt(θ) is the relationship between the azimuth angle and the first arrival time difference.

[0133] Finally, for each detection area, the server can use an arithmetic average or weighted average method to process the near-surface azimuth anisotropic disturbance term corresponding to each shot-receiver distance, thus obtaining the near-surface azimuth anisotropic disturbance term for the detection area. For example, for detection area t8, the near-surface azimuth anisotropic disturbance terms corresponding to shot-receiver distances of 10 meters, 70 meters, and 100 meters are ΔV, respectively. 10 =10 / Δt 10(θ), ΔV 70 =70 / Δt 70 (θ), ΔV 100 =100 / Δt 100 (θ), the near-surface azimuth anisotropy disturbance term for the detection area t8 obtained by the arithmetic mean method is ΔV=10 / 3×Δt. 10 (θ)+70 / 3×Δt 70 (θ)+100 / 3×Δt 100 (θ), etc.

[0134] S106. Determine the anisotropic near-surface velocity model for each detection area as V. aniso =V iso +ΔV, where V aniso For anisotropic near-surface velocities, V iso Here, ΔV represents the isotropic near-surface velocity, and ΔV represents the near-surface azimuth anisotropic disturbance term.

[0135] After the server determines the near-surface azimuth anisotropic perturbation term for each detection area, it can combine the isotropic near-surface velocity and the near-surface azimuth anisotropic perturbation term for that area to determine the anisotropic near-surface velocity model for that area. The combination method can be as follows:

[0136] V aniso =V iso +ΔV(4)

[0137] Among them, V aniso For anisotropic near-surface velocities, V iso Here, ΔV represents the isotropic near-surface velocity, and ΔV represents the near-surface azimuth anisotropic disturbance term.

[0138] For example, the server determines the isotropic near-surface velocity corresponding to the detection area t8 as V. iso8 The corresponding near-surface azimuth anisotropy disturbance term is ΔV = 10 / 3 × Δt 10 (θ)+70 / 3×Δt 70 (θ)+100 / 3×Δt 100 (θ), after combination, the anisotropic near-surface velocity model is V aniso8 =V iso8 +10 / 3×Δt 10 (θ)+70 / 3×Δt 70 (θ)+100 / 3×Δt 100 (θ).

[0139] This application provides embodiments such as Figure 6 The processing flow for determining the amplitude of near-surface azimuth anisotropy, as shown, includes the following steps:

[0140] S201. Obtain the positions of multiple shot points, multiple receiver points, and the actual first arrival time for each shot-receiver pair in the target area.

[0141] During seismic exploration, the server can obtain the identification information of the shot point, the identification information of the receiver point, and the actual first arrival time of the first arrival wave detected by the receiver point. This allows the server to determine the coordinates of the shot point, the coordinates of the receiver point, the shot-receiver distance for each shot-receiver pair, and the actual first arrival time. The specific process is similar to step S101 and will not be repeated here.

[0142] S202. Based on the positions of multiple shot points, multiple receiver points, the actual first arrival time and the initial near-surface velocity model corresponding to each shot-receiver pair, determine the isotropic near-surface velocity corresponding to each detection area.

[0143] After the server determines the coordinates of each shot point, each receiver point, and the corresponding shot-receiver distance and actual first arrival time for each shot-receiver pair according to step S201, it can use methods such as refraction layering to determine the isotropic near-surface velocity corresponding to each detection area. The specific process is similar to step S102 and will not be described in detail here.

[0144] S203. Based on the positions of multiple shot points, multiple receiver points, and the isotropic near-surface velocity corresponding to each detection area, determine the predicted first arrival time for each shot-receiver pair.

[0145] The server can determine the detection area corresponding to the shot-detector pair based on the coordinates of the shot point and the receiver point. Then, based on the shot-detector distance and the isotropic near-surface velocity corresponding to the detection area, it can calculate the predicted first arrival time of the shot-detector pair. The specific process is similar to step S103 and will not be repeated here.

[0146] S204. Determine the first arrival time difference for each shot-receiver pair. The first arrival time difference is the difference between the actual first arrival time and the predicted first arrival time.

[0147] The server can calculate the first arrival time difference for each shot-receiver pair based on the actual first arrival time and the predicted first arrival time. The specific process is similar to step S104 and will not be repeated here.

[0148] S205. Based on the positions of multiple shot points, multiple receiver points, and the first arrival time difference corresponding to each shot-receiver pair, determine the near-surface azimuth anisotropy perturbation term corresponding to each detection area.

[0149] The server can determine the detection area, corresponding shot-receiver distance, and azimuth of the shot-receiver pair based on the coordinates of the shot point and the receiver point. For each detection area, the server can determine the near-surface azimuth anisotropy disturbance term corresponding to the shot-receiver pair based on the corresponding shot-receiver distance, azimuth, and first arrival time difference. The specific process is similar to step S105 and will not be repeated here.

[0150] S206. Determine the anisotropic near-surface velocity model for each detection area as V. aniso =V iso +ΔV, where V aniso For anisotropic near-surface velocities, V iso Here, ΔV represents the isotropic near-surface velocity, and ΔV represents the near-surface azimuth anisotropic disturbance term.

[0151] For each detection area, the server can determine the anisotropic near-surface velocity model corresponding to the detection area based on the near-surface azimuth anisotropic disturbance term and isotropic near-surface velocity corresponding to the detection area. The specific process is similar to step S106 and will not be repeated here.

[0152] S207. Based on the anisotropic near-surface velocity model corresponding to each detection area, determine the minimum and maximum near-surface velocities corresponding to each detection area.

[0153] For each detection area, after the server determines the anisotropic near-surface velocity model, the azimuth angle (0-360°) can be substituted into the anisotropic near-surface velocity model to calculate the near-surface velocity corresponding to each azimuth within the detection area. Then, the server can use the least squares ellipse fitting method, with the geometric center of the detection area as the center of the ellipse, to fit the near-surface velocity corresponding to each azimuth within the detection area, determining the near-surface velocity ellipse corresponding to the detection area. This determines the minimum near-surface velocity, maximum near-surface velocity, and the direction of the maximum near-surface velocity for the detection area. The direction of the maximum near-surface velocity can represent the direction of subsurface stress anomalies or the direction perpendicular to fracture-like strata. The calculation formula can be as follows:

[0154]

[0155] Where a is the length of the major semi-axis of the ellipse, b is the length of the minor semi-axis of the ellipse, and V fast For the maximum near-surface velocity, V slow The minimum near-surface velocity is given by θ, where θ is the azimuth angle. This represents the direction of the maximum near-surface velocity.

[0156] S208. Based on the maximum and minimum near-surface velocities corresponding to the detection area, determine the amplitude of near-surface azimuth anisotropy corresponding to the detection area.

[0157] For each detection area, after determining the minimum and maximum near-surface velocities, the server can determine the near-surface azimuth anisotropy amplitude corresponding to that area. The formula for calculating the near-surface azimuth anisotropy amplitude is as follows:

[0158]

[0159] Where M is the amplitude of near-surface azimuth anisotropy, and V fast For the maximum near-surface velocity, V slow The minimum near-surface velocity is denoted by m, where m is the amplitude coefficient (e.g., 100, 100%, etc.).

[0160] For any given detection area, the magnitude of near-surface azimuth anisotropy indicates the strength of anisotropy in that area. A smaller M value indicates weaker anisotropy during seismic wave propagation and a more uniform geological distribution. A larger M value indicates severe anisotropy during seismic wave propagation, potentially representing abnormal underground stress or the presence of fracture-like strata.

[0161] All of the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments of this application, and will not be described in detail here.

[0162] The scheme mentioned in this application firstly obtains the isotropic near-surface velocity for each detection area based on the location of the shot point, the location of the receiver point, the actual first arrival time of the shot-receiver pair, and the initial near-surface velocity model. Then, the predicted first arrival time for each shot-receiver pair is determined based on the isotropic near-surface velocity. Finally, the near-surface velocity corresponding to different azimuths within each detection area is determined based on the isotropic near-surface velocity, the predicted first arrival time, and the actual first arrival time for each shot-receiver pair. The near-surface velocity determined using this method is anisotropic, taking into account the velocity differences of seismic waves propagating in different directions within the Earth's crust. Therefore, using this anisotropic near-surface velocity model to determine the propagation speed of seismic waves can more realistically and accurately determine the near-surface velocity of seismic waves.

[0163] This application provides an apparatus for training a model, which can be the server described in the above embodiments, such as... Figure 7 As shown, the device includes:

[0164] The acquisition module 710 is used to acquire the positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair in the target area. The target area has several detection areas, and the shot-receiver pair consists of one shot point and one receiver point.

[0165] The first determining module 720 is used to determine the isotropic near-surface velocity corresponding to each detection area based on the positions of multiple shot points, multiple receiver points, the actual first arrival time and the initial near-surface velocity model corresponding to each shot-receiver pair.

[0166] The prediction module 730 is used to determine the predicted first arrival time for each shot-receiver pair based on the positions of multiple shot points, multiple receiver points, and the isotropic near-surface velocity corresponding to each detection area.

[0167] The second determining module 740 is used to determine the anisotropic near-surface velocity model corresponding to each detection area based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair. The anisotropic near-surface velocity model corresponding to the detection area is used to represent the near-surface velocity corresponding to different azimuths in the detection area, where the azimuth is the azimuth relative to the center point of the detection area.

[0168] In one possible implementation, the first determining module 720 is configured to:

[0169] Based on the positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair, the shot-receiver distance for each shot-receiver pair, the shot point delay time for each detection area, and the receiver point delay time are determined.

[0170] Based on the shot delay time and receiver delay time corresponding to each detection area, the shot-receiver distance and actual first arrival time corresponding to each shot-receiver pair, the isotropic near-surface velocity corresponding to each detection area is determined.

[0171] In one possible implementation, the second determining module 740 is configured to:

[0172] Determine the first arrival time difference for each shot-receiver pair. The first arrival time difference is the difference between the actual first arrival time and the predicted first arrival time.

[0173] Based on the locations of multiple shot points, multiple receiver points, and the first arrival time difference of each shot-receiver pair, the near-surface azimuth anisotropy perturbation term corresponding to each detection area is determined;

[0174] The anisotropic near-surface velocity model for each detection area is determined as V. aniso =V iso +ΔV, where V aniso For anisotropic near-surface velocities, V iso Here, ΔV represents the isotropic near-surface velocity, and ΔV represents the near-surface azimuth anisotropic disturbance term.

[0175] In one possible implementation, the second determining module 740 is configured to:

[0176] Determine the midpoint of the shot-receiver line for each shot-receiver pair. The shot-receiver line is the line connecting the shot point and the receiver point in the shot-receiver pair.

[0177] Determine the shot-receiver pair corresponding to each detection area, wherein the shot-receiver pair corresponding to the detection area is the shot-receiver pair whose midpoint is within the detection area;

[0178] In each detection area, the corresponding shot-receiver distance and azimuth of the shot-receiver pair are determined based on the positions of multiple shot points and multiple receiver points;

[0179] For each detection area, among the shot-receiver distance, azimuth, and first arrival time difference for the corresponding shot-receiver pair, the azimuth and first arrival time difference for the same shot-receiver distance are determined. The azimuth and first arrival time difference for each shot-receiver distance are fitted to obtain the relationship between the azimuth and first arrival time difference for each shot-receiver distance. Based on each shot-receiver distance and the corresponding relationship, the expression for the near-surface velocity in terms of azimuth is determined for each shot-receiver distance. Based on the expression for each shot-receiver distance, the near-surface azimuth anisotropy perturbation term for the detection area is determined.

[0180] In one possible implementation, the second determining module 740 is further configured to:

[0181] Based on the anisotropic near-surface velocity model corresponding to each detection area, the near-surface azimuth anisotropy amplitude corresponding to each detection area is determined.

[0182] In one possible implementation, the second determining module 740 is further configured to:

[0183] For each detection area, based on the anisotropic near-surface velocity model corresponding to the detection area, the near-surface velocity corresponding to each orientation of the detection area is determined. The least squares ellipse fitting method is used to fit the near-surface velocity corresponding to each orientation of the detection area to determine the minimum and maximum near-surface velocities corresponding to the detection area.

[0184] For each detection area, determine the velocity difference between the maximum and minimum near-surface velocities corresponding to the detection area. Based on the velocity difference and the maximum near-surface velocity corresponding to the detection area, determine the near-surface azimuth anisotropy amplitude corresponding to the detection area.

[0185] The scheme mentioned in this application firstly obtains the isotropic near-surface velocity for each detection area based on the location of the shot point, the location of the receiver point, the actual first arrival time of the shot-receiver pair, and the initial near-surface velocity model. Then, the predicted first arrival time for each shot-receiver pair is determined based on the isotropic near-surface velocity. Finally, the near-surface velocity corresponding to different azimuths within each detection area is determined based on the isotropic near-surface velocity, the predicted first arrival time, and the actual first arrival time for each shot-receiver pair. The near-surface velocity determined using this method is anisotropic, taking into account the velocity differences of seismic waves propagating in different directions within the Earth's crust. Therefore, using this anisotropic near-surface velocity model to determine the propagation speed of seismic waves can more realistically and accurately determine the near-surface velocity of seismic waves.

[0186] It should be noted that the apparatus for establishing a near-surface velocity model provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the apparatus can be divided into different functional modules to complete all or part of the functions described above. Furthermore, the apparatus for establishing a near-surface velocity model and the method embodiment for establishing a near-surface velocity model provided in the above embodiments belong to the same concept, and their specific implementation process is detailed in the method embodiment, which will not be repeated here.

[0187] This application provides a computer device, which may be the server described in the above embodiments. Figure 8 This is a schematic diagram of the computer device 800. The computer device 800 can vary significantly due to differences in configuration or performance. It may include one or more CPUs (Central Processing Units) 810 and one or more memories 820. The memories 810 store at least one instruction, which is loaded and executed by the processor 810 to implement the methods provided in the various method embodiments described above. Of course, the computer device may also have wired or wireless network interfaces, a keyboard, and input / output interfaces for input and output. The computer device may also include other components for implementing device functions, which will not be elaborated upon here.

[0188] In an exemplary embodiment, a computer-readable storage medium is also provided, such as a memory including instructions that can be executed by a processor in a terminal to complete the method for establishing a near-surface velocity model in the above embodiments. This computer-readable storage medium can be non-transitory. For example, the computer-readable storage medium can be ROM (Read-Only Memory), RAM (Random Access Memory), CD-ROM, magnetic tape, floppy disk, and optical data storage devices, etc.

[0189] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0190] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for establishing a near-surface velocity model, characterized in that, The method includes: The positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair in the target area are obtained. The target area has several detection areas, and the shot-receiver pair consists of one shot point and one receiver point. Based on the locations of the multiple shot points, the locations of the multiple receiver points, the actual first arrival time and the initial near-surface velocity model corresponding to each shot-receiver pair, the isotropic near-surface velocity corresponding to each detection area is determined. Based on the positions of the multiple shot points, the positions of the multiple receiver points, and the isotropic near-surface velocity corresponding to each detection area, the predicted first arrival time of each shot-receiver pair is determined. Based on the isotropic near-surface velocity corresponding to each detection area, the actual first arrival time and the predicted first arrival time corresponding to each shot-receiver pair, an anisotropic near-surface velocity model corresponding to each detection area is determined. The anisotropic near-surface velocity model corresponding to the detection area is used to represent the near-surface velocity corresponding to different azimuths in the detection area, where the azimuth is the azimuth relative to the center point of the detection area.

2. The method according to claim 1, characterized in that, The determination of the isotropic near-surface velocity for each detection area based on the locations of the multiple shot points, the multiple receiver points, the actual first arrival time and the initial near-surface velocity model corresponding to each shot-receiver pair includes: Based on the positions of the multiple shot points, the positions of the multiple receiver points, and the actual first arrival time of each shot-receiver pair, the shot-receiver distance corresponding to each shot-receiver pair, the shot point delay time and the receiver point delay time corresponding to each detection area are determined. Based on the shot delay time and receiver delay time corresponding to each detection area, the shot-receiver distance and actual first arrival time corresponding to each shot-receiver pair, the isotropic near-surface velocity corresponding to each detection area is determined.

3. The method according to claim 1, characterized in that, The determination of the anisotropic near-surface velocity model for each detection area, based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair, includes: Determine the first arrival time difference for each shot-receiver pair, wherein the first arrival time difference is the difference between the actual first arrival time and the predicted first arrival time; Based on the location of the shot point, the location of the receiver point, and the first arrival time difference corresponding to each shot-receiver pair, the near-surface azimuth anisotropy perturbation term corresponding to each detection area is determined; The anisotropic near-surface velocity model corresponding to each detection area is determined as V. aniso =V iso +ΔV, where V aniso For anisotropic near-surface velocities, V iso Here, ΔV represents the isotropic near-surface velocity, and ΔV represents the near-surface azimuth anisotropic disturbance term.

4. The method according to claim 3, characterized in that, The determination of the near-surface azimuth anisotropy perturbation term for each detection area based on the positions of the multiple shot points, the positions of the multiple receiver points, and the first arrival time difference corresponding to each shot-receiver pair includes: Determine the midpoint of the shot-detector line corresponding to each shot-detector pair, where the shot-detector line is the line connecting the shot point and the receiver point in the shot-detector pair. Determine the shot-receiver pair corresponding to each detection area, wherein the shot-receiver pair corresponding to the detection area is the shot-receiver pair whose midpoint is located within the detection area; In each detection area, the shot-receiver distance and azimuth of the shot-receiver pair are determined based on the positions of the plurality of shot points and the plurality of receiver points. For each detection area, among the shot-receiver distance, azimuth, and first arrival time difference corresponding to the shot-receiver pair corresponding to the detection area, the azimuth and first arrival time difference corresponding to the same shot-receiver distance are determined. The azimuth and first arrival time difference corresponding to each shot-receiver distance are fitted to obtain the relationship between the azimuth and first arrival time difference corresponding to each shot-receiver distance. Based on each shot-receiver distance and the corresponding relationship, the expression for the near-surface velocity in terms of azimuth is determined for each shot-receiver distance. Based on the expression for each shot-receiver distance, the near-surface azimuth anisotropy perturbation term corresponding to the detection area is determined.

5. The method according to claim 1, characterized in that, After determining the anisotropic near-surface velocity model for each detection area based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair, the method further includes: Based on the anisotropic near-surface velocity model corresponding to each detection area, the near-surface azimuth anisotropy amplitude corresponding to each detection area is determined.

6. The method according to claim 5, characterized in that, The determination of the near-surface azimuth anisotropy amplitude for each detection area based on the anisotropic near-surface velocity model corresponding to each detection area includes: For each detection area, based on the anisotropic near-surface velocity model corresponding to the detection area, the near-surface velocity corresponding to each orientation of the detection area is determined. The least squares ellipse fitting method is used to fit the near-surface velocity corresponding to each orientation of the detection area to determine the minimum and maximum near-surface velocities corresponding to the detection area. For each detection area, the velocity difference between the maximum and minimum near-surface velocities corresponding to the detection area is determined. Based on the velocity difference and the maximum near-surface velocity corresponding to the detection area, the near-surface azimuth anisotropy amplitude corresponding to the detection area is determined.

7. An apparatus for establishing a near-surface velocity model, characterized in that, The device includes: The acquisition module is used to acquire the positions of multiple shot points, multiple receiver points, and the actual first arrival time of each shot-receiver pair in the target area. The target area has several detection areas, and the shot-receiver pair consists of one shot point and one receiver point. The first determining module is used to determine the isotropic near-surface velocity corresponding to each detection area based on the positions of the plurality of shot points, the positions of the plurality of receiver points, the actual first arrival time and the initial near-surface velocity model corresponding to each shot-receiver pair; The prediction module is used to determine the predicted first arrival time of each shot-receiver pair based on the positions of the multiple shot points, the positions of the multiple receiver points, and the isotropic near-surface velocity corresponding to each detection area. The second determining module is used to determine the anisotropic near-surface velocity model corresponding to each detection area based on the isotropic near-surface velocity corresponding to each detection area and the actual first arrival time and predicted first arrival time corresponding to each shot-receiver pair. The anisotropic near-surface velocity model corresponding to the detection area is used to represent the near-surface velocity corresponding to different azimuths in the detection area, where the azimuth is the azimuth relative to the center point of the detection area.

8. A computer device, characterized in that, The computer device includes a processor and a memory, the memory storing at least one instruction, which is loaded and executed by the processor to perform the operations performed by the method for establishing a near-surface velocity model as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The storage medium stores at least one instruction, which is loaded and executed by a processor to perform the operations performed by the method for establishing a near-surface velocity model as described in any one of claims 1 to 6.

10. A computer program product, characterized in that, The computer program product includes computer program code, which, when executed by a computer device, performs the method for establishing a near-surface velocity model as described in any one of claims 1 to 6.

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