A seismic radar detection system based on a controllable broadband vibrator

Abstract

The application relates to the technical field of underground detection, and discloses a seismic radar detection system based on a controllable wide-frequency vibration source, which comprises an exciting unit, a body wave data processing unit and a surface wave data processing unit. The exciting unit generates vibration through an eccentric wheel driven by a brushless motor, a magnet is additionally arranged on the rotating shaft of the brushless motor, and an encoder is additionally arranged on the motor head of the brushless motor. The body wave data processing unit is based on a source wavelet and collected body wave data, adopts an inverse convolution algorithm to extract a ground medium response Green function, and is used for realizing underground imaging. The surface wave data processing unit carries out time slice cross-correlation operation on mixed recording and extracts a dispersion curve, and inverts a ground P wave velocity structure and S wave velocity structure. The application not only realizes a plurality of breakthroughs on a traditional source in the technical field, but also exhibits remarkable advantages such as high resolution, flexible deployment, low noise, efficient collection and strong adaptability in practical application.

Description

Technical Field

[0001] This invention relates to the field of underground detection technology, specifically to a seismic radar detection system based on a controllable broadband vibration source. This system is suitable for engineering geological exploration, urban seismic detection, geological hazard assessment, and underground resource exploration, and is particularly suitable for acquiring sub-meter resolution information on underground structures. Background Technology

[0002] Currently, seismic exploration technology is widely used in fields such as oil exploration, urban underground space planning, and environmental monitoring. Its core lies in using a seismic source to generate seismic waves, which are then reflected, refracted, or acted upon by surface waves generated after propagation through the underground medium to detect underground structures. However, traditional seismic sources (such as hammer-driven sources, rammed-earth sources, and explosive sources) have the following shortcomings:

[0003] 1. Frequency and amplitude are limited:

[0004] Traditional seismic sources used in urban exploration mostly rely on low-frequency excitation, which has a low output signal frequency and limited vibration amplitude, making it difficult to meet the requirements for detecting fine underground structures (especially at sub-meter resolution).

[0005] 2. Severe noise pollution:

[0006] During operation, traditional seismic sources typically generate significant mechanical noise and vibration pollution, causing disturbance to the surrounding environment. This is especially problematic in urban or densely populated areas, where it can easily lead to complaints and restrictions on their use.

[0007] 3. The equipment is large in size and requires a large operating space:

[0008] Existing controllable seismic sources are typically large in size and weigh more than 1 ton, requiring a large operating space and being difficult to move, making them unsuitable for deployment in urban and confined environments.

[0009] 4. Low work efficiency:

[0010] Due to limitations in vibration transmission methods and frequency ranges, traditional seismic sources have significant shortcomings in data acquisition and resolution, making it difficult to achieve high-quality, high-efficiency underground imaging.

[0011] 5. Security risks exist:

[0012] Traditional explosive seismic sources are generally unusable in urban environments, while drop hammer seismic sources and impact seismic sources also pose risks during use.

[0013] Furthermore, surface wave exploration can only reflect the wave velocity variations of S-waves. Compared to surface waves, leakage waves are dominated by longitudinal waves and also exhibit dispersion characteristics, thus they can be used to detect the underground P-wave velocity structure. Researchers have developed methods for extracting P-guided wave dispersion, but there is no corresponding means to stably excite P-guided waves in the field.

[0014] In recent years, with the development of precision control technology and high-power brushless motor technology, controllable seismic sources have gradually become a research hotspot. Based on different driving methods, controllable seismic sources can be broadly classified into hydraulic, electromagnetic, and precision controllable seismic sources. Among them, precision controllable seismic sources have attracted widespread attention due to their ability to output high-frequency vibrations and their ease of modular assembly. However, although some small, modular controllable seismic sources have made some progress in reducing equipment weight, their combined weight usually still exceeds 100 kg, and their highest operating frequency is generally below 40 Hz, failing to meet the requirements of high-resolution shallow subsurface detection.

[0015] Therefore, developing a new type of precision controllable seismic source that can achieve high-frequency vibration (up to 1kHz), is lightweight, low-noise, and easy to move, and a high-resolution seismic radar detection system based on this source, has become an urgent need for the development of current seismic exploration technology. Summary of the Invention

[0016] To address the aforementioned technical problems, this invention provides a seismic radar detection system based on a controllable broadband vibration source.

[0017] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0018] A seismic radar detection system based on a controllable broadband vibration source includes:

[0019] Excitation unit: Vibration is generated by an eccentric wheel driven by a brushless motor. By adding a magnet to the shaft of the brushless motor and an encoder to the motor head, a closed-loop control system based on negative feedback is formed to achieve the adjustment of vibration frequency from 0Hz to 1000Hz. The vibration source wavelet is calculated based on GPS time synchronization and the real-time acquisition of the speed of the brushless motor by the encoder.

[0020] Body wave data processing unit: Based on the source wavelet and the acquired body wave data, the Green's function of the subsurface medium response is extracted using the deconvolution algorithm to realize subsurface imaging;

[0021] Surface wave data processing unit: By controlling the initial phase of the eccentric wheel and superimposing observation records excited by positive-phase vibration or excited by negative-phase vibration, a pure P-wave source or a pure S-wave source is obtained; using background noise as a passive source and the pure P-wave source and pure S-wave source as active sources, a hybrid record is excited and received. The hybrid record includes the active source signal excited by the active source and the passive source signal generated by the background noise. By performing time slicing and cross-correlation operations on the hybrid record and extracting the dispersion curve, the underground P-wave velocity structure and S-wave velocity structure are inverted.

[0022] In one embodiment, the calculation of the source wavelet based on the brushless motor's rotational speed, acquired in real-time via GPS timing and encoder data, specifically includes:

[0023] Source wavelet for:

[0024] ;

[0025] Among them, the source frequency With the speed of the brushless motor The following relationship exists:

[0026] ;

[0027] Source output It satisfies the following characteristics:

[0028] ;

[0029] in, It is the equivalent mass of the eccentric wheel. It is the equivalent eccentricity of the eccentric wheel.

[0030] In one embodiment, the extraction of the Green's function of the subsurface medium response using a deconvolution algorithm based on the source wavelet and the acquired body wave data specifically includes:

[0031] Green's function of subsurface medium response in the frequency domain for:

[0032] ;

[0033] in, They are Fourier transform, For the collected body wave data, For the source wavelet, yes The complex conjugate, This value is set to avoid the denominator being zero;

[0034] right Performing an inverse Fourier transform yields the Green's function of the subsurface medium response in the time domain. .

[0035] In one embodiment, the process of obtaining a pure P-wave source and a pure S-wave source by controlling the initial phase of the eccentric wheel and superimposing observation records of positive-phase vibration excitation and anti-phase vibration excitation specifically includes:

[0036] Pure P-wave source: The eccentric wheel first uses the initial phase Start rotating clockwise, vibration is excited and observed. The eccentric wheel starts from the same initial phase for the second time. Initially, the device rotates counterclockwise with the same acceleration, and the vibration is excited and recorded. Then, the observation records induced by the pure P-wave source are obtained by superposition. :

[0037] ;

[0038] Pure S-wave source: The eccentric wheel first uses the initial phase Start rotating clockwise, vibration is excited and observed. The eccentric wheel is in its initial phase for the second time. Starting at 180°, rotating counterclockwise with the same acceleration, the vibration was excited and recorded. Then, the observation records induced by the pure S-wave source are obtained by superposition. :

[0039] .

[0040] In one embodiment, the process of using background noise as a passive source and pure P-wave and pure S-wave sources as active sources to excite and receive a hybrid record, which includes active source signals generated by the active source excitation and passive source signals generated by the background noise, and then inverting the underground P-wave velocity structure and S-wave velocity structure by performing time slicing and cross-correlation operations on the hybrid record and extracting dispersion curves, specifically includes:

[0041] The mixed records are received through multiple stations;

[0042] The mixed records are time-sliced;

[0043] Cross-correlation is performed on the mixed records received by any two different stations within each time slice;

[0044] The cross-correlation results of all time slices are superimposed;

[0045] Dispersion analysis was performed on the superimposed cross-correlation results to generate a dispersion energy map, which was then used to invert the underground P-wave velocity structure and S-wave velocity structure.

[0046] Compared with the prior art, the beneficial technical effects of the present invention are:

[0047] (1) High-resolution detection capability: The system utilizes the high-frequency vibration (frequency range 0~1kHz) generated by the brushless motor driving the eccentric wheel, enabling it to image sub-meter or even smaller underground fine structures, effectively breaking through the resolution bottleneck of traditional seismic sources in shallow exploration.

[0048] (2) Lightweight and easy to deploy: The equipment adopts a lightweight modular design, which is easy to move and deploy in cities or small areas. It is suitable for complex or space-constrained environments. Compared with traditional large-tonnage controllable seismic source vehicles, it greatly reduces the difficulty and cost of on-site operations.

[0049] (3) Low noise environment adaptability: Through brushless motor and precision vibration control technology, while achieving efficient vibration excitation, the mechanical noise and vibration interference during operation are effectively reduced, meeting the operation requirements of urban environment and environmentally sensitive areas, and reducing the negative impact on the surrounding environment.

[0050] (4) Excellent data processing effect: The system adopts advanced deconvolution processing method, which improves the signal-to-noise ratio and imaging quality of the data by accurately extracting the Green's function of the underground medium, ensuring that clear and accurate images of underground structures can be obtained even under complex geological conditions.

[0051] (5) High-efficiency data acquisition: The integrated high-speed data acquisition module provides a foundation for the subsequent rapid scanning and real-time imaging of the target area.

[0052] (6) Strong adaptability and penetration capability: Compared with ground-penetrating radar that relies on electromagnetic waves, this system uses seismic waves for detection, which has better penetration and stability. It can maintain relatively stable signal transmission in complex media such as aquifers and loose layers, thus broadening the exploration depth and application range.

[0053] (7) Cost and safety advantages: The equipment’s portability (less than 100kg) and modular design significantly reduce transportation, installation and maintenance costs. At the same time, the reduced equipment weight and operating noise further reduce on-site safety hazards.

[0054] In summary, this invention not only achieves several technological breakthroughs over traditional seismic sources, but also demonstrates significant advantages in practical applications, such as high resolution, flexible deployment, low noise, efficient acquisition, and strong adaptability, and has broad prospects for engineering applications and market promotion value. Attached Figure Description

[0055] Figure 1 This is a system design diagram of the precision controllable vibration source of the present invention.

[0056] Figure 2 This is a schematic diagram of the motor and encoder of the present invention. In the diagram, (a) is the modified motor, (b) is the motor body, (c) is the modified motor head, (d) is the redesigned encoder with a flight plug, and (e) is the encoder circuit diagram.

[0057] Figure 3 This is an arrangement of earthquake records observed using the controlled source of the present invention.

[0058] Figure 4 To Figure 3 The results of earthquake records observed in the study are compared using different processing methods. Among them, (a) shows the result of wavelet compression using the traditional cross-correlation method; (b) shows the result obtained using the method of this invention.

[0059] Figure 5 (a) is a schematic diagram of seismic image acquisition; Figure 5 (b) is the data processing flowchart.

[0060] Figure 6 The diagram shows the field observation system for seismic surface wave exploration; (a) represents acquisition method one, (b) represents acquisition method two, and (c) represents the data processing flowchart.

[0061] Figure 7 The following figures show the results of using transient surface wave processing on seismic data acquired by a linear array with a 2-meter channel spacing: (a) is the seismic signal, (b) is the dispersion energy distribution map, (c) is the station cross-correlation curve obtained using the process of this invention, and (d) is the dispersion energy map.

[0062] Figure 8 Comparison of surface wave dispersion energy maps of primary and passive sources. Among them, (a) is the dispersion curve obtained by observing the background noise signal for 1 hour using the same arrangement (containing 20 seismographs) with a trace spacing of 5 meters; (b) is the dispersion curve extracted from 20 vibration data collected using a sweep frequency source.

[0063] Figure 9 According to Figure 8 The P-wave and S-wave dispersion curves extracted were used to invert the P-wave velocity and S-wave velocity variation curves with depth, respectively.

[0064] Figure 10 This image shows the results of detecting goaf areas using the Distributed Fiber Optic Sensing Vertical Seismic Profile (DAS-VSP) scheme. The red lines indicate the locations of the fiber optic cables buried in the wells, and the yellow circles indicate the detected locations of the goaf areas. Detailed Implementation

[0065] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0066] The main objective of this invention is to provide a precise and controllable broadband vibration source and its corresponding seismic radar detection system. This system utilizes a brushless motor to drive an eccentric wheel, generating vibration signals of variable frequency. Furthermore, by combining advanced data processing and seismic imaging technologies, it enables efficient and high-resolution detection of fine underground structures.

[0067] To achieve the above objectives, the present invention includes the following technical solutions:

[0068] 1. Novel precision controllable seismic source design.

[0069] The structure of the earthquake source of the present invention is as follows Figure 1 As shown, the device consists of a trolley, a control box, a vibration motor, and a counterweight plate. Inside the control box, a Raspberry Pi, a brushless motor driver with closed-loop feedback, and a lithium battery are housed. The control box is connected to the brushless motor via a power cable supplying power and a signal cable controlling and monitoring its operation. The brushless motor is bolted to the counterweight plate, which is fixed to the underside of the trolley. The device is compact, lightweight, and incorporates a noise control module to reduce noise impact on the surrounding environment, making it suitable for detection tasks in urban and environmentally sensitive areas.

[0070] The control module in this invention is presented in the form of a control box; however, it may also be implemented in other ways in some other embodiments. The vibration module in this invention is presented in the form of a vibration motor; however, it may also be implemented in other ways in some other embodiments.

[0071] This invention uses a high-speed brushless motor as the drive source to drive an eccentric wheel to generate vibration. Currently available brushless motors either only rotate at a constant high speed but lack precise control, or they can be precisely controlled but only operate at low speeds (less than 3000 rpm) with low torque, unable to drive a large-mass eccentric wheel to generate vibration. However, for the detection of intricate underground structures, the higher the motor speed, the better. Furthermore, existing encoders are not waterproofed, and their wiring methods are unsuitable for this invention. Therefore, this invention, based on a closed-loop brushless motor, develops a precision control system for high-speed motors. To use negative feedback for precise control of the brushless motor, the existing high-speed motor needs to be modified. First, a magnet is added to the motor shaft, and a modified encoder is added to the motor head (see...). Figure 2Secondly, to ensure a certain degree of waterproofing after the encoder is installed on the motor head, this invention redesigns the encoder with an aviation plug. After modification, the motor speed is precisely controlled, thereby driving the eccentric wheel to generate periodic vibrations. The shaft, magnet, and encoder are located on the same central axis. The shaft rotates, while the encoder remains stationary. In a preferred embodiment, the distance between the top of the motor shaft and the encoder is the magnet thickness plus 1-2 mm.

[0072] Figure 2 In (e), AS5047P (U1) is a magnetic rotary encoder chip. Its function is to detect the rotation angle of a magnet using a Hall sensor array and output the angle information via an SPI interface. The SPI signal lines include MOSI (master transmit), MISO (master receive), CLK (clock), and CS (chip select). Small resistors R1, R2, R3, and R4 are connected in series with parallel capacitors C3 and C4 to provide impedance matching and filtering, reducing high-speed signal reflection and interference. The SPI signal lines are connected to port J2 for testing and to the J1 aviation connector, which connects to the control box via an external shielded cable for communication. Pins A, B, I, U, V, and W of the U1 chip are for other communication modes, commonly used for intra-circuit communication, but unsuitable for the current scenario and therefore not used. Power is supplied from VCC, and noise is filtered out by decoupling capacitors C1, C2, and C6 to ensure stable power supply to the chip. The metal pads SCREW1, SCREW2, SCREW3, and SCREW4 serve as mounting screw holes. After the circuit board is mounted to the metal casing using metal screws, the circuit ground can be connected to the casing through R5 (1MΩ) and capacitor C5 (100nF) for circuit grounding and electrostatic protection.

[0073] The vibration frequency range of the earthquake source can cover 0 to 1 kHz, where the source wavelet... It can be represented as:

[0074] (1)

[0075] Among them, the source frequency With motor speed The following relationship exists:

[0076] ;

[0077] At the same time, the source of the earthquake output The following characteristics are satisfied:

[0078] ;

[0079] in, It is the equivalent mass of the eccentric wheel. It is the equivalent eccentricity of the eccentric wheel.

[0080] Traditional controllable seismic sources use two eccentric wheels rotating simultaneously to generate pure P-wave or S-wave sources through vibration combinations. However, when the seismic source is precisely controllable (e.g., the initial position and rotational acceleration of the eccentric wheels), only one eccentric wheel can be used to excite the source twice and superimpose the corresponding observation records to obtain pure P-wave or S-wave source records, thus simplifying the seismic source design.

[0081] To obtain a pure P-wave source (vertical vibration), the eccentric wheel first uses the initial phase. Initially, the rotation is clockwise, and the vibration is excited and recorded. The eccentric wheel starts from the same initial phase for the second time. Initially, the device rotates counterclockwise with the same acceleration, and the vibration is excited and recorded. Then, the observation records induced by the pure P-wave source are obtained by superposition. :

[0082] (2)

[0083] To obtain a pure S-wave source (horizontal vibration), the eccentric wheel first uses an initial phase. Initially, rotate clockwise to generate an observation record. The second eccentric wheel Starting with an initial phase of 180°, and then rotating counterclockwise with the same acceleration, the excitation is used to obtain the observation record. Then, the observation records induced by the pure S-wave source are obtained by superposition. :

[0084] (3)

[0085] If only a hybrid source is needed, and a pure P-wave source or a pure S-wave source is not required, then a single excitation is sufficient.

[0086] 2. Data processing technology.

[0087] (1) Body wave data processing:

[0088] Traditional seismic sources such as hammer strikes, falling hammers, or explosives use source wavelet approximation pulse (delta) functions to record seismic signals that can be directly used for reflection or refraction imaging of underground structures. However, the source of this system is a swept-frequency signal, requiring processing of the acquired seismic signals before imaging can be performed.

[0089] The seismic signals acquired by this invention It is the source wavelet Green's function with underground medium Convolution, i.e. The actual observation records are as follows: Figure 3 As shown. From Figure 3 It is not possible to directly read the time of each seismic phase. Figure 3 There were a total of 20 seismographs in the middle, and the epicenter was located near the first seismograph.

[0090] To extract the Green's function reflecting the response of the subsurface medium. The signal needs to be processed by wavelet compression or deconvolution (or wavelet compression). In the past, when observing a precise controllable seismic source, a seismograph or accelerometer was set up near the source. Then, during wavelet compression, the waveform recorded by the seismograph or accelerometer was used as the source wavelet. This method is equivalent to treating the near-source station as a virtual source, and then using the signal received by the near-source station to re-align and calibrate the waveforms of all stations. However, when relying on a precise seismic source to conduct reflection or refraction imaging of underground structures, the propagation time of seismic waves from the precise source to the near-source station, which is not considered or is difficult to consider, will be an important source of error. This invention uses GPS timing to accurately record the start time of the source and reads the real-time rotational speed curve from the encoder, and substitutes it into formula (1) to obtain the source wavelet.

[0091] This invention employs the following deconvolution formula to obtain the Green's function of the medium response in the frequency domain. :

[0092] (4)

[0093] in, , , They are , , Fourier transform, yes The complex conjugate, It is a value that is very small relative to the first term in the denominator, mainly to avoid the denominator being zero.

[0094] After the above processing, the result is After inverse Fourier transform, it can be recovered to the Green's function in the time domain. This provides fundamental data for subsequent underground reflection and refraction imaging. Figure 4 (a) shows the results of wavelet compression using the traditional cross-correlation method. It can be seen that, regardless of whether it is based on the measured speed curve of the encoder... As the source wavelet function (Blue line) The seismic signal recorded by the near-source station (seismograph) is still used as the source wavelet function. (Red line) The results of wavelet compression all show obvious high-frequency leakage, which significantly reduces the signal-to-noise ratio of the Green's function. However, when wavelet compression is performed using the method shown in formula (4), the effect is significantly improved, and based on the actual measured speed curve of the encoder... As the source wavelet function (Blue line) Wavelet compression is even more effective than using seismic signals recorded by near-source stations (seismographs) as source wavelet functions. (Red line) The result of compression. Figure 4 In the diagram, seis represents the result of processing the near-source station as the source wavelet.

[0095] Therefore, based on the precise controllable seismic source and wavelet compression algorithm of this invention, using Figure 5 The process shown in (b) enables rapid acquisition of shallow seismic exploration data. Figure 5 In (a), the cross represents the earthquake source, the triangle represents the seismograph or detector, and the horizontal dashed line represents the direction of the seismic image scan.

[0096] (2) Surface wave data processing:

[0097] In traditional active-source surface wave observations, sources such as sledgehammers, tampers, and explosives are typically used, generating high frequencies generally not exceeding 20Hz, resulting in limited imaging resolution. Noise reduction and surface wave preservation are required before extracting the dispersion curves. Furthermore, active-source surface wave methods generally only detect relatively shallow depths (approximately 30m), and even increasing the source energy only slightly increases the exploration depth. Moreover, increasing the source energy in modern urban exploration generates significant noise, making it impractical. Passive-source methods (receiving surface wave signals from natural sources, not actively excited) can detect deeper strata due to the lower signal frequency, but the lack of high-frequency signals leads to poor resolution in imaging shallow structures. Previous studies have attempted to combine active and passive source signals for subsurface structure imaging. However, this approach involves deploying a passive-source observation system at the same site after active-source exploration to record passive-source seismic signals, then extracting the dispersion curves of both active and passive source signals separately, and finally stitching the two dispersion curves together to obtain the dispersion curve used for inversion. Currently, some related experiments have shown that the depth range of joint surface wave exploration imaging using active and passive sources is significantly better than that of single data (using only active or passive sources). However, previous joint imaging methods using active and passive sources also have drawbacks. First, passive source acquisition requires a long time and is easily affected by the non-uniformity of noise sources. Second, in many cases, due to the influence of noise directionality on passive sources, the dispersion curves extracted by active and passive sources have poor consistency, making it difficult to stitch the dispersion curves together. Finally, current joint methods only use the fundamental dispersion for inversion, and traditional surface wave inversion methods can only obtain the subsurface S-wave velocity structure, while the P-wave velocity structure is generally obtained by conversion based on empirical formulas.

[0098] Based on this invention, during the frequency-sweeping source excitation process, the seismograph records not only the active source signal generated by the seismic source but also the passive source signal generated by surrounding noise sources. Therefore, using such... Figure 6 The processing flow shown in (c) can directly slice the mixed record composed of active and passive source signals into time slices without denoising. Then, the waveform data recorded by different stations in the same time slice are directly cross-correlated. The cross-correlation of multiple time slices is superimposed to enhance the signal-to-noise ratio. Subsequently, time-frequency variation is performed to obtain a dispersion energy map, and then the dispersion curve is extracted. The resulting dispersion curve contains both active and passive source signals. Figure 7The paper presents a comparison of dispersion energy obtained using the same seismic data acquisition system but different processing methods. The comparison shows that using the processing flow of this invention to process data generated by frequency-sweep sources not only extracts high signal-to-noise ratio (SNR) high-frequency dispersion curves, but also yields low-frequency dispersion curves with better SNR and bandwidth than traditional surface wave processing methods. In addition to a wider bandwidth for the fundamental dispersion, the dispersion curves obtained by this invention also contain a large number of high-quality high-order dispersion curves, which can better constrain the underground S-wave velocity structure.

[0099] Furthermore, due to the characteristics of the seismic source of this invention, its output in the high-frequency band is much higher than that in the low-frequency band. Therefore, when observations are conducted with an appropriate array length, clear P-guided wave dispersion curves that effectively constrain the P-wave velocity of the underground structure can be extracted. Thus, based on the seismic data generated and acquired by this invention, the P-wave velocity structure and S-wave velocity structure can be simultaneously inverted, and the Poisson's ratio variation of the underground structure can be further inverted, thereby identifying characteristics such as the water content and porosity of the strata.

[0100] 3. Construction of earthquake radar detection system.

[0101] Using the aforementioned high-frequency, precision-controlled seismic source as the excitation unit, a seismic radar detection system can be constructed by deploying a receiving array within the target area. It can collect seismic reflection, refraction, and surface wave signals from the subsurface medium.

[0102] The system includes a data acquisition module and a data processing module. The latter processes the acquired data in real time using a deconvolution algorithm to restore the response of the underground structure and achieve real-time imaging.

[0103] Compared to traditional ground-penetrating radars that rely on electromagnetic waves, this system utilizes the propagation characteristics of seismic waves to achieve deeper detection in complex media, thereby improving overall imaging accuracy and efficiency.

[0104] In summary, this invention combines a high-frequency vibration source driven by a brushless motor with advanced data processing technology, which not only breaks through the limitations of traditional vibration sources in terms of low frequency and low resolution, but also achieves the advantages of lightweight, low noise, and flexible operation, providing a brand-new solution for urban, engineering, and geological exploration fields.

[0105] Implementation Example 1:

[0106] This embodiment deploys a linearly arranged seismic line containing 42 three-component nodal seismographs; the trace spacing is 5 meters, and the N-direction of each seismograph points towards the hypocenter; the total length of the line is 205 meters; the hypocenter (the prototype of the precision controllable seismograph of this invention is shown in the image) Figure 7As shown, excitation is performed at the first stage, with the source being a trapezoidal curve. The frequency rises from 0 Hz to 160 Hz within 20 seconds, is maintained for 5 seconds, and finally drops back to 0 Hz within 20 seconds.

[0107] Figure 8 (b) is the dispersion energy map obtained by the present invention. The fundamental and higher-order curves of the S-wave are clearly visible, as are the clear dispersion curves of the P-guided wave. Comparing the dispersion energy map obtained from the active source observation at 1 hour with the dispersion energy map obtained using the source of the present invention, it can be seen that the present invention can obtain more S-wave dispersion information, and also obtain the dispersion information of the P-guided wave. Figure 8 Finally, by extracting the corresponding dispersion curves, the underground S-wave and P-wave structures can be inverted ( Figure 9 This allows us to further obtain information about the Poisson's ratio underground. Figure 9 The solid black lines and dashed black lines represent the initial velocity models of the P-wave and S-wave, respectively, while the solid red lines and dashed red lines represent the inverted P-wave and S-wave curves, respectively.

[0108] Implementation Example 2:

[0109] By combining optical fibers embedded in the well with the present invention for excitation on the ground, volume wave signals excited at different locations are obtained and analyzed to determine the accurate location of the goaf. This invention can quickly and efficiently detect goaf areas in coal mines and other similar areas, contributing to safe production. Figure 10 These are the results of actual exploration in the mining area. A total of 45 shots were fired, with a shot spacing of 4 meters. Three firings were performed at the same shot point. The seismic record traces demodulated by the distributed fiber optic sensing (DAS) cable had a spacing of 1 meter. The DAS cable was placed at a depth of 1-30 meters using boreholes. Figure 9 As shown by the red line, the track spacing is 1m. The effective imaging depth is 150m. The yellow circle in the image indicates an anomaly in the coal seam goaf, and the in-phase axis shows an amplitude "collapse zone," consistent with the goaf location provided by the mine. The self-developed portable controllable seismic source combined with the 3D DAS-VSP (Distributed Fiber Optic Sensing Vertical Seismic Profile) seismic exploration scheme can quickly and efficiently detect coal mine goafs, providing assistance for safe production.

[0110] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0111] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the flowcharts of the accompanying drawings may include multiple steps or stages, which are not necessarily completed at the same time, but may be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but may be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0112] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0114] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A seismic radar probing system based on a controllable broadband vibratory source, characterized in that, Comprise: The excitation unit: the eccentric wheel is driven by a brushless motor to generate vibration, a magnet is installed on the rotating shaft of the brushless motor, and an encoder is installed on the motor head of the brushless motor, a closed-loop control system based on negative feedback is formed, and the vibration frequency is adjusted from 0Hz to 1000Hz; based on the GPS timing and the real-time acquisition of the rotating speed of the brushless motor, the source wave is calculated, specifically including: the source wave is: The source frequency and the rotating speed of the brushless motor exist the following relationship: The source output satisfies the following characteristics: is the equivalent mass of the eccentric wheel,is the equivalent eccentricity of the eccentric wheel;​​ Body wave data processing unit: based on the source wavelet and the collected body wave data, the response Green function of the underground medium is extracted by using the deconvolution algorithm, which is used to realize the underground imaging; Surface wave data processing unit: by controlling the initial phase of the eccentric wheel, and superimposing the observation records of positive phase vibration excitation or the observation records of reverse phase vibration excitation, pure P wave source or pure S wave source is obtained; background noise is used as passive source, and pure P wave source and pure S wave source are used as active source, mixed records are excited and received, the mixed records include active source signals generated by active source excitation and passive source signals generated by background noise, by time slicing and cross-correlation operation on the mixed records and extracting dispersion curve, the underground P wave velocity structure and S wave velocity structure are inverted.

2. A seismic radar detection system based on a controllable broadband vibration source according to claim 1, characterized in that, The response Green function of the underground medium is extracted by using the deconvolution algorithm based on the source wavelet and the collected body wave data, specifically comprising: Frequency domain subsurface medium response Green's function is: ； wherein are respectively the Fourier transform of is the acquired body wave data, is a source wavelet, is the complex conjugate of is a value set to avoid zero denominator, is a value set to avoid zero denominator; To perform an inverse Fourier transform to obtain the time-domain subsurface medium response Green's function .

3. A seismic radar detection system based on a controllable broadband vibration source according to claim 1, characterized in that, The pure P wave source and the pure S wave source are obtained by controlling the initial phase of the eccentric wheel and superimposing the observation records of positive phase vibration excitation and the observation records of reverse phase vibration excitation, specifically comprising: Pure P-wave source: eccentric first time with initial phase Start clockwise rotation, vibration excitation to get observation records , eccentric second time from the same initial phase Start counterclockwise rotation with the same acceleration, vibration excitation to get observation records Then superimposed to get the observation records triggered by pure P-wave source : ； Pure S-wave source: eccentric wheel first at initial phase Start clockwise rotation, vibration excitation to get observation record , eccentric wheel second at initial phase 180° start, counterclockwise rotation at the same acceleration, vibration excitation to get observation record , then superimposed to get the observation record of pure S-wave source excitation : 。 4. The seismic radar detection system based on a controllable broadband vibration source according to claim 1, characterized in that, The background noise is used as passive source, and the pure P wave source and the pure S wave source are used as active source, mixed records are excited and received, the mixed records include active source signals generated by active source excitation and passive source signals generated by background noise, by time slicing and cross-correlation operation on the mixed records and extracting dispersion curve, the underground P wave velocity structure and S wave velocity structure are inverted, specifically comprising: The mixed records are received by multiple stations; The mixed records are time sliced; For each time slice, the mixed records received by any two different stations are cross-correlated; The cross-correlation results of all time slices are superimposed; The superimposed cross-correlation results are subjected to dispersion analysis to generate dispersion energy map, and then the underground P wave velocity structure and S wave velocity structure are inverted.

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