Earthquake data acquisition device based on ground 3C-DAS optical cable and acquisition method thereof

Abstract

The invention discloses a seismic data acquisition device based on a ground 3C-DAS optical cable and an acquisition method thereof, is applied to the field of seismic exploration, and aims to solve the problems of high layout cost, too long construction time and low operation efficiency of an existing ground three-component detector. According to the method, a 3C-DAS armored optical cable is buried under a shallow earth surface in a parallel or orthogonal mode, a ground multichannel low-frequency DAS modulation-demodulation instrument collects phase data of Rayleigh scattering light reflected back from the 3C-DAS armored optical cable and carries out modulation-demodulation processing, and high-density distributed three-component seismic data distributed along the 3C-DAS armored optical cable is obtained; according to the system, high-density distributed three-component ground seismic data along the armored optical cable can be rapidly and efficiently acquired at low cost; the invention also provides a processing method for the collected high-density distributed three-component ground seismic data, an analysis method for a shallow surface velocity structure with high spatial resolution, and an inversion imaging method for longitudinal waves, transverse waves and surface waves.

Description

Technical Field

[0001] The present invention belongs to the fields of applied geophysics, geophysical exploration technology and seismic exploration, and particularly relates to a seismic data acquisition device based on a ground 3C-DAS optical cable and an acquisition method thereof. Background Art

[0002] Seismic waves are vibrations that propagate from the earthquake's source, referring to elastic waves that radiate from the source. Based on their propagation mode, they can be divided into three types: longitudinal waves (P waves), transverse waves (S waves) (both longitudinal and transverse waves are body waves), and surface waves (L waves). When an earthquake occurs, the medium in the focal area rapidly ruptures and moves, and this disturbance constitutes a wave source. Due to the continuity of the earth's medium, these fluctuations propagate throughout the earth's interior and surface, forming elastic waves in the continuous medium. The propagation speed of seismic waves varies depending on the propagation medium and is usually related to rock type, confining pressure, rock structure, and other geological factors.

[0003] Seismic exploration involves artificially inducing vibrations in the earth's crust (e.g., detonating detonators or explosives, dropping or striking heavy hammers, or vibrating controlled vibrators). Precision instruments then record the vibrations at various receiving points on the surface using a specific observational method. The resulting data, after a series of processing, is used to infer the characteristics of the underground geological structure. Seismic waves artificially generated at the surface are reflected and refracted as they propagate underground. These waves are then received by detectors on the surface or in wells. The received seismic wave signals are related to the characteristics of the source, the location of the detectors, and the properties and structure of the underground rock formations through which the waves pass. Processing and interpretation of these seismic wave recordings allows inferences about the properties and morphology of the underground rock formations.

[0004] Background noise imaging technology is one of the most significant breakthroughs in seismological research since the 21st century. This method, independent of the occurrence of natural earthquake events, exploits the ubiquitous "background noise" in continuous seismic records. By cross-correlating continuous-time signals between pairs of stations, empirical Green's functions are extracted and used to image the structure of subsurface media. Compared with traditional natural source seismic detection methods, background noise imaging extracts structural information from random field signals, offering advantages such as high imaging resolution, high observation timeliness, and excellent repeatability. In recent years, with the continuous development of this method, background noise imaging has achieved increasing application in shallow surface exploration, such as urban underground spaces and mining areas, exploration of crustal and lithospheric structures, exploration of deep Earth structures, such as the mantle and core, and monitoring of time-lapse changes in subsurface media. Rapid progress has also been made in signal-to-noise ratio enhancement and weak signal extraction, body wave signal extraction and application, and the development of new imaging methods. Background noise imaging methods will play an increasingly important role in studying Earth's spatial structure using surface and body wave signals and monitoring subsurface activity through time-lapse imaging.

[0005] Seismic background noise imaging utilizes surface wave signals obtained by calculating noise cross-correlation functions. Their frequency band is influenced by numerous factors, including the noise source frequency band, internal scattering structure, and station spacing. Traffic signals contribute significantly to seismic background noise in urban areas, with typical traffic noise frequencies ranging from a few to tens of hertz. Surface wave signals in this frequency band can effectively constrain the shear wave velocity structure at depths ranging from several meters to hundreds of meters. High-frequency surface waves experience strong scattering during propagation, so obtaining high-frequency surface wave signals requires a relatively small station spacing. Deploying a high-density seismic observation array within an urban area requires a large number of seismometers. For example, the Long Beach, California, experiment used over 5,300 short-period seismometers spaced 100 meters apart to achieve coverage of an area 8.5 km x 4.5 km. The high deployment and maintenance costs of a large number of seismometers have limited the widespread use of this method.

[0006] With the development of urbanization, urban geophysics has become an increasingly important area of ​​geophysical research. Seismic imaging is a key tool for constructing three-dimensional and four-dimensional images of urban underground spaces, but it faces the challenge of high observation costs. Distributed acoustic sensing (DAS), a recently developed ultra-dense seismic observation system based on fiber-optic sensing technology, can achieve station spacing of 1–10 meters, far exceeding that of traditional seismic arrays. Its system architecture is relatively simple, maintenance costs are extremely low, and it features real-time data transmission, effectively reducing observation costs while providing high resolution. Internationally, considerable progress has been made in using DAS data to study shallow structures, including imaging of active sources and seismic background noise. Currently, this newly developed distributed fiber-optic acoustic sensing technology, as a high-density seismic observation system, has been applied to seismic tomography, improving imaging resolution while reducing observation costs. Distributed fiber-optic acoustic sensing can continuously and in real time record various background noises in the subsurface over long periods of time. By calculating the noise cross-correlation function, high-frequency Rayleigh surface wave signals can be obtained. Multi-channel surface wave analysis was used to extract phase velocity dispersion curves, and the results were consistent with those from traditional geophone records and active sources. A genetic algorithm inversion method was used to obtain a two-dimensional shear wave velocity profile within the study area, revealing the lateral variation characteristics of shallow subsurface sediments.

[0007] Calculating the propagation velocities of various seismic waves in the strata and the elastic or viscoelastic parameters of the subsurface medium (strata or rock formations) is a necessary and crucial step in processing and interpreting seismic data acquired through seismic exploration. Failure to accurately determine the seismic wave velocities and elastic or viscoelastic parameters of shallow subsurface strata can significantly hinder or even render impossible the subsequent processing and interpretation of seismic data. Therefore, accurately measuring and calculating the seismic wave velocities and elastic or viscoelastic parameters of the subsurface medium (strata or rock formations) is a primary task in processing and interpreting seismic exploration data. Summary of the Invention

[0008] To address the aforementioned technical issues, the present invention proposes a seismic data acquisition device and method based on ground-based 3C-DAS optical cables. Using armored 3C-DAS cables buried in a parallel or orthogonal pattern shallowly beneath the surface, the device replaces the expensive wired or wireless three-component geophones deployed at each geophone point according to geophone line design requirements. A ground-based DAS modem instrument collects phase data of Rayleigh scattered light reflected from the 3C-DAS armored cables, performs modulation and demodulation processing, and obtains three-component seismic data distributed along the 3C-DAS cables.

[0009] One of the technical solutions adopted by the present invention is: a seismic data acquisition device based on a ground 3C-DAS optical cable, comprising: an armored 3C-DAS distributed optical fiber sensing cable fixedly buried in a shallow trench on the ground in an investigation area; a shallow surface structure data processing and interpretation system; and a three-channel, four-channel, or five-channel low-frequency 3C-DAS data modulation and demodulation instrument. The 3C-DAS distributed optical fiber sensing cables are all connected to the low-frequency 3C-DAS data modulation and demodulation instrument, and the low-frequency 3C-DAS data modulation and demodulation instrument is connected to the shallow surface structure data processing and interpretation system (2).

[0010] The 3C-DAS distributed fiber optic sensor cable contains an elastomer with a square or triangular cross-section. A high-reflection coefficient single-mode optical fiber with a sinusoidal or triangular distribution is fixed on each surface of the elastomer. A straight high-reflection coefficient single-mode optical fiber is embedded in the center of the elastomer along the extension direction of the elastomer. The elastomer and the high-reflection coefficient single-mode optical fiber are covered with a protective sheath made of a waterproof, wear-resistant and corrosion-resistant composite material; the protective sheath is at least one layer, and the outermost protective sheath is a metal or composite armored sheath that is resistant to pressure and tension.

[0011] The 3C-DAS distributed optical fiber sensor cable can be buried in a shallow trench on the ground of the work area in parallel according to the designed two-dimensional detection point measurement line or three-dimensional detection point measurement network, or can be buried in a shallow trench on the ground of the work area according to the orthogonal grid measurement line method.

[0012] The 3C-DAS distributed optical fiber sensing cable is used for real-time monitoring and measurement of distributed deformation data, distributed three-component fluid noise data, distributed three-component strain data, distributed three-component SDAS microseismic data, two-dimensional or three-dimensional distributed three-component SDAS seismic data, and distributed three-component time-lapse SDAS seismic data on the ground surface.

[0013] The ground of the survey area can also be laid out with two-dimensional or three-dimensional artificial seismic source excitation lines according to design requirements. The trigger signal of the artificial seismic source is consistent with the trigger signal of starting the ground low-frequency 3C-DAS data modulation and demodulation instrument.

[0014] The artificial seismic source is one of an explosive seismic source, a controllable seismic source, a heavy hammer seismic source, a gas explosion seismic source, an electric energy seismic source, an electric spark seismic source, an air gun seismic source or a plasma seismic source.

[0015] The seismic data acquisition method based on the ground 3C-DAS optical cable comprises the following steps:

[0016] S1. Dig a shallow trench below the surface along a two-dimensional geophone point measurement line or a three-dimensional geophone point measurement network or an orthogonal grid line, and bury the 3C-DAS distributed optical fiber sensor cable in the shallow trench;

[0017] S2. Stimulate artificial seismic sources in sequence along the pre-designed seismic source points on the source line, and synchronously transmit the trigger signals for stimulating the artificial seismic sources to the trigger ports of a three-channel, four-channel, or five-channel low-frequency 3C-DAS data modem instrument connected to a 3C-DAS distributed optical fiber sensor cable on the ground in a wired or wireless manner;

[0018] S3, triggering the low-frequency 3C-DAS data modulation and demodulation instrument to start synchronously collecting distributed three-component ground seismic data of the artificial source along the 3C-DAS distributed optical fiber sensing cable at the same time as the ground source is excited;

[0019] S4. In the absence of an artificial seismic source trigger, manually start the low-frequency 3C-DAS data modem instrument to continuously collect distributed three-component ground seismic data excited by natural earthquakes, passive earthquakes, background noise, or fluid noise signals along the 3C-DAS distributed optical fiber sensing cable in an automatic continuous data acquisition mode;

[0020] S5, a low-frequency 3C-DAS data modem instrument collects the Rayleigh scattered light signal reflected from the optical fiber in the 3C-DAS distributed optical fiber sensor cable;

[0021] S6. By modulating and demodulating the phase data of the Rayleigh scattered light signal, the distributed three-component ground seismic data excited by the distributed three-component artificial earthquake, natural earthquake, passive earthquake, background noise or fluid noise signal distributed along the 3C-DAS distributed optical fiber sensing cable are obtained.

[0022] S7, low-frequency 3C-DAS data modem instrument and 3C-DAS distributed optical fiber sensing cable buried under the surface can also measure surface deformation data, distributed three-component strain data, temperature data, distributed three-component SDAS microseismic data, two-dimensional or three-dimensional distributed three-component SDAS seismic data, and distributed three-component time-lapse SDAS seismic data in real time, continuously or intermittently;

[0023] Also included is a processing method comprising the steps of:

[0024] S8. Shallow surface structure data processing and interpretation system, based on the distance from any detection point on the 3C-DAS distributed optical fiber sensor cable to each ground artificial source point, as well as the direct P-wave travel time, direct S-wave travel time, surface wave travel time, refracted wave travel time along the underground wave impedance interface to the detection point, and reflected wave travel time from the underground wave impedance interface to the detection point, the system inversely calculates the P-wave velocity, S-wave velocity, surface wave velocity, velocity anisotropy of the P-wave velocity in different directions, velocity anisotropy of the S-wave velocity in different directions, attenuation coefficient of the P-wave propagation in the underground medium, and attenuation coefficient of the S-wave propagation in the underground medium.

[0025] S9. For the low-frequency 3C-DAS data modem instrument continuously collecting distributed three-component ground seismic data excited by natural earthquakes, passive earthquakes, background noise, or fluid noise signals along the 3C-DAS distributed optical fiber sensor cable in the automatic continuous data acquisition mode, or passive source 3C-DAS array seismic data, first perform passive source noise data processing, including using AI-based processing technology to perform rapid scanning processing on the energy and amplitude of each component of the continuously collected 3C-DAS passive source noise data, segmenting each scanned high background noise seismic data, and segmenting the continuously collected 3C-DAS data into independent 3C-DAS high noise source shot gather data;

[0026] S10, subjecting each independent 3C-DAS high-noise source shot gather data generated in step S9 to special processing using the strain field Green's empirical function;

[0027] S11, performing surface wave dispersion extraction on each 3C-DAS high-noise source shot gather data after the strain field Green's empirical function processing in step S10;

[0028] S12, generating a surface wave multi-mode phase velocity dispersion curve using the surface wave dispersion data extracted in step S11;

[0029] S13, performing surface wave dispersion inversion processing on the surface wave multi-mode phase velocity dispersion curve generated in step S12;

[0030] S14, the data after the surface wave dispersion inversion processing in step S13 is subjected to shallow surface shear wave velocity (V S ) imaging processing;

[0031] S15, the shallow surface P-wave velocity (V P ) imaging data and shear wave velocity (V S) imaging data are integrated and interpreted to obtain accurate structural and lithological imaging of shallow surface structures, fluid distribution imaging, and imaging of bedrock surface depth and fluctuation changes.

[0032] The present invention provides the following beneficial effects: 3C-DAS distributed fiber optic sensing cables are buried parallel or orthogonally within shallow trenches in the work area, along a designed two-dimensional geophone point survey line or three-dimensional geophone point survey network. The system enables rapid, efficient, and low-cost acquisition of distributed three-component ground seismic data along armored fiber optic cables. It also provides methods for processing the acquired distributed three-component ground seismic data and for analyzing and imaging shallow surface velocity structures.

[0033] The present invention has the following advantages:

[0034] 1. Greatly reduce the equipment cost for collecting 2D or 3D three-component seismic data;

[0035] 2. Accelerate construction progress and improve work efficiency;

[0036] 3. It can quickly and cost-effectively acquire three-component ground seismic data with ultra-high density (meter or sub-meter level) or extremely high spatial resolution (meter or sub-meter level);

[0037] 4. Using orthogonal grid lines to bury 3C-DAS distributed fiber optic sensor cables in shallow trenches, three-component ground seismic data with the same ultra-high density (meter or sub-meter level) or extremely high spatial resolution (meter or sub-meter level) can be collected simultaneously on the main survey line and the connecting line. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 : Schematic diagram of the square structure elastic body of the 3C-DAS distributed optical fiber sensing cable targeted by the present invention;

[0039] Figure 2 : Schematic diagram of the triangular structure elastic body of the 3C-DAS distributed optical fiber sensing cable targeted by the present invention;

[0040] Figure 3 : Schematic diagram of parallel layout of ground two-dimensional or three-dimensional 3C-DAS distributed optical fiber sensing cables targeted by the present invention;

[0041] Figure 4 : Schematic diagram of the ground three-dimensional 3C-DAS distributed optical fiber sensing cable arranged according to an orthogonal grid;

[0042] Figure numerals: 1-3C-DAS distributed optical fiber sensing cable; 2-shallow surface structure data processing and interpretation system; 3-low-frequency 3C-DAS data modulation and demodulation instrument; 11-elastomer; 12-high reflection coefficient single-mode optical fiber; 13-protective cover. DETAILED DESCRIPTION

[0043] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further explained below with reference to the accompanying drawings.

[0044] When this embodiment is implemented, the seismic data acquisition device based on the ground 3C-DAS optical cable includes: a 3C-DAS distributed optical fiber sensor cable 1 fixedly buried in a shallow trench on the ground in the investigation area; a shallow surface structure data processing and interpretation system 2; a three-channel, four-channel or five-channel low-frequency 3C-DAS data modulation and demodulation instrument 3. The 3C-DAS distributed optical fiber sensor cable 1 is connected to the low-frequency 3C-DAS data modulation and demodulation instrument 3, and the low-frequency 3C-DAS data modulation and demodulation instrument 3 is connected to the shallow surface structure data processing and interpretation system (2).

[0045] The 3C-DAS distributed optical fiber sensing cable 1 includes an elastic body 11 with a square or triangular cross section. Figure 1 It is a schematic diagram of a square structured elastic body; Figure 2 It is a schematic diagram of a triangular structured elastomer.

[0046] A high-reflection coefficient single-mode optical fiber 12 with a sinusoidal or triangular distribution is fixed on each surface of the elastomer 11, and a straight high-reflection coefficient single-mode optical fiber 12 along the extension direction of the elastomer 11 is embedded in the center of the elastomer 11. The elastomer 11 and the high-reflection coefficient single-mode optical fiber 12 are covered with a protective cover 13 made of a waterproof, wear-resistant and corrosion-resistant composite material.

[0047] The protective cover 13 is at least one layer, and the outermost protective cover is a metal or composite material armored cover that is resistant to compression and tension.

[0048] Figure 3 It is a schematic diagram of the parallel layout of the ground two-dimensional or three-dimensional 3C-DAS distributed optical fiber sensor cable 1 targeted by the present invention. Figure 4 This is a schematic diagram of the layout of the ground three-dimensional 3C-DAS distributed optical fiber sensing cable 1 according to the orthogonal grid targeted by the present invention.

[0049] The 3C-DAS distributed optical fiber sensor cable 1 can be buried in a shallow trench on the ground of the work area in parallel according to the designed two-dimensional detection point measurement line or three-dimensional detection point measurement network, or can be buried in a shallow trench on the ground of the work area according to the orthogonal grid measurement line method.

[0050] The 3C-DAS distributed optical fiber sensing cable 1 can also be used for real-time monitoring and measurement of distributed deformation data, distributed three-component fluid noise data, distributed three-component strain data, distributed three-component SDAS microseismic data, two-dimensional or three-dimensional distributed three-component SDAS seismic data, and distributed three-component time-lapse SDAS seismic data of the earth's surface.

[0051] The ground of the investigation area can also be equipped with two-dimensional or three-dimensional artificial seismic source 4 excitation lines according to design requirements. The trigger signal of the artificial seismic source 4 is consistent with the trigger signal of starting the ground low-frequency 3C-DAS data modulation and demodulation instrument 3; the artificial seismic source 4 is one of an explosive seismic source, a controllable seismic source, a heavy hammer seismic source, a gas explosion seismic source, an electric energy seismic source, an electric spark seismic source, an air gun seismic source or a plasma seismic source.

[0052] The method for collecting distributed three-component ground seismic data based on the seismic data acquisition device of the ground 3C-DAS distributed optical fiber sensing cable 1 comprises the following steps:

[0053] S1. Dig a shallow trench below the surface along a two-dimensional geophone point measurement line or a three-dimensional geophone point measurement network or an orthogonal grid line, and bury a 3C-DAS distributed optical fiber sensor cable 1 in the shallow trench;

[0054] S2, sequentially stimulating the artificial seismic sources 4 at the pre-designed seismic source points along the source line, and synchronously transmitting the trigger signal for stimulating the artificial seismic source 4 to the trigger port of the three-channel, four-channel, or five-channel low-frequency 3C-DAS data modem 3 connected to the 3C-DAS distributed optical fiber sensing cable 1 on the ground in a wired or wireless manner;

[0055] S3, triggering the low-frequency 3C-DAS data modem instrument 3 to start synchronously collecting distributed three-component ground seismic data excited by the artificial seismic source 4 along the 3C-DAS distributed optical fiber sensing cable 1 at the same time as the ground seismic source is excited;

[0056] S4. In the absence of triggering by the artificial seismic source 4, manually starting the low-frequency 3C-DAS data modem instrument 3 in the automatic continuous data acquisition mode to continuously acquire distributed three-component ground seismic data excited by natural earthquakes, passive earthquakes, background noise, or fluid noise signals along the 3C-DAS distributed optical fiber sensing cable 1;

[0057] S5, the low-frequency 3C-DAS data modem instrument 3 collects the Rayleigh scattered light signal reflected from the optical fiber in the 3C-DAS distributed optical fiber sensor cable 1;

[0058] S6. Modulating and demodulating the phase data of the Rayleigh scattered light signal to obtain distributed three-component ground seismic data excited by the distributed three-component artificial earthquake, natural earthquake, passive earthquake, background noise or fluid noise signal distributed along the 3C-DAS distributed optical fiber sensing cable 1;

[0059] S7, the low-frequency 3C-DAS data modem instrument 3 and the 3C-DAS distributed optical fiber sensing cable 1 buried under the surface can also measure surface deformation data, distributed three-component strain data, distributed three-component SDAS microseismic data, two-dimensional or three-dimensional distributed three-component SDAS seismic data, and distributed three-component time-lapse SDAS seismic data in real time, continuously or intermittently;

[0060] The method for processing distributed three-component ground seismic data based on the seismic data acquisition device of the ground 3C-DAS distributed optical fiber sensing cable 1 comprises the following steps:

[0061] S8. Using the shallow surface structure data processing and interpretation system 2, based on the distance from any detection point on the 3C-DAS distributed optical fiber sensor cable 1 to each of the four ground artificial seismic sources, and data such as the direct P-wave travel time, direct S-wave travel time, surface wave travel time, refracted wave travel time along the underground wave impedance interface to the detection point, and reflected wave travel time reflected from the underground wave impedance interface to the detection point, inversely calculate the P-wave velocity, S-wave velocity, surface wave velocity, velocity anisotropy of the P-wave velocity in different directions, velocity anisotropy of the S-wave velocity in different directions, attenuation coefficient of the P-wave propagation in the underground medium, and attenuation coefficient of the S-wave propagation in the underground medium of the underground medium;

[0062] S9. For the low-frequency 3C-DAS data modem instrument 3 continuously collecting distributed three-component ground seismic data excited by natural earthquakes, passive earthquakes, background noise, or fluid noise signals along the 3C-DAS distributed optical fiber sensor cable 1 in the automatic continuous data acquisition mode, or passive source 3C-DAS array seismic data, firstly performing passive source noise data processing, including using AI-based processing technology to perform rapid scanning processing on the energy and amplitude of each component of the continuously collected 3C-DAS passive source noise data, performing segmentation processing on each scanned high background noise seismic data, and segmenting the continuously collected 3C-DAS data into independent 3C-DAS high noise source shot gather data;

[0063] S10, subjecting each independent 3C-DAS high-noise source shot gather data generated in step S9 to special processing using the strain field Green's empirical function;

[0064] S11, performing surface wave dispersion extraction on each 3C-DAS high-noise source shot gather data after the strain field Green's empirical function processing in step S10;

[0065] S12, generating a surface wave multi-mode phase velocity dispersion curve using the surface wave dispersion data extracted in step S11;

[0066] S13, performing surface wave dispersion inversion processing on the surface wave multi-mode phase velocity dispersion curve generated in step S12;

[0067] S14, the data after the surface wave dispersion inversion processing in step S13 is subjected to shallow surface shear wave velocity (V S ) imaging processing;

[0068] S15, the shallow surface P-wave velocity (V P ) imaging data and shear wave velocity (V S ) imaging data are integrated and interpreted to obtain accurate structural and lithological imaging of shallow surface structures, fluid distribution imaging, and imaging of bedrock surface depth and fluctuation changes.

[0069] Those skilled in the art will appreciate that the embodiments described herein are intended to aid the reader in understanding the principles of the present invention, and it should be understood that the scope of the present invention is not limited to such specific descriptions and embodiments. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims.

Claims

1. A seismic data acquisition device based on a ground 3C-DAS optical cable, characterized in that: include: An armored 3C-DAS distributed optical fiber sensor cable (1) fixedly buried in a shallow trench on the ground in the survey area; a shallow surface structure data processing and interpretation system (2); a three-channel, four-channel, or five-channel low-frequency 3C-DAS data modulation and demodulation instrument (3); The 3C-DAS distributed optical fiber sensor cables (1) are all connected to the low-frequency 3C-DAS data modulation and demodulation instrument (3), and the low-frequency 3C-DAS data modulation and demodulation instrument (3) is connected to the shallow surface structure data processing and interpretation system (2); A two-dimensional or three-dimensional artificial seismic source (4) is also arranged on the ground of the investigation area according to design requirements. The trigger signal of the artificial seismic source (4) is consistent with the trigger signal of starting the ground low-frequency 3C-DAS data modulation and demodulation instrument (3).

2. The seismic data acquisition device based on the ground 3C-DAS optical cable according to claim 1, characterized in that: The 3C-DAS distributed optical fiber sensor cable (1) includes an elastic body (11) with a square or equilateral triangle cross section, and also includes a plurality of high-reflection coefficient single-mode optical fibers (12), wherein one high-reflection coefficient single-mode optical fiber (12) is straight and embedded in the center of the elastic body (11) and extends along the direction of extension of the elastic body (11); the other high-reflection coefficient single-mode optical fibers (12) are fixed on each surface of the elastic body (11) in a sinusoidal or triangular distribution, and a protective sheath (13) made of a waterproof, wear-resistant, and corrosion-resistant composite material is provided outside the elastic body (11) and the high-reflection coefficient single-mode optical fibers (12).

3. The seismic data acquisition device based on the ground 3C-DAS optical cable according to claim 2, characterized in that: The protective sheath (13) of the 3C-DAS distributed optical fiber sensor cable (1) is at least one layer, and the outermost layer is a metal or composite material armored sheath that is resistant to compression and tension.

4. The seismic data acquisition device based on the ground 3C-DAS optical cable according to claim 3, characterized in that: The 3C-DAS distributed optical fiber sensor cable (1) is buried in a shallow trench on the ground of a work area in parallel with a pre-designed two-dimensional detection point measurement line or a three-dimensional detection point measurement network, or is buried in a shallow trench on the ground of a work area in an orthogonal grid measurement line manner.

5. The seismic data acquisition device based on the ground 3C-DAS optical cable according to claim 1, characterized in that: The 3C-DAS distributed optical fiber sensing cable (1) is used for real-time monitoring and measurement of distributed deformation data, distributed three-component fluid noise data, distributed three-component strain data, distributed three-component SDAS microseismic data, two-dimensional or three-dimensional distributed three-component SDAS seismic data, and distributed three-component time-lapse SDAS seismic data on the ground surface along the sensing cable.

6. The seismic data acquisition device based on the ground 3C-DAS optical cable according to claim 1, characterized in that: The artificial seismic source (4) is one of an explosive seismic source, a controllable seismic source, a heavy hammer seismic source, a gas explosion seismic source, an electric energy seismic source, an electric spark seismic source, an air gun seismic source or a plasma seismic source.

7. A seismic data acquisition method based on ground 3C-DAS optical cable, characterized in that: The seismic data acquisition device based on the ground 3C-DAS optical cable according to any one of claims 1 to 6 is used, wherein the method comprises the following steps: S1. Digging a shallow trench below the surface along a pre-designed two-dimensional geophone point measurement line or a three-dimensional geophone point measurement network or an orthogonal grid line, burying and compacting a 3C-DAS distributed optical fiber sensor cable (1) in the shallow trench; S2, stimulating the artificial seismic source (4) in sequence along the pre-designed seismic source points on the seismic source line, and synchronously transmitting the trigger signal for stimulating the artificial seismic source (4) to the trigger port of a three-channel, four-channel or five-channel low-frequency 3C-DAS data modulation and demodulation instrument (3) connected to the 3C-DAS distributed optical fiber sensing cable (1) on the ground in a wired or wireless manner; S3, triggering the low-frequency 3C-DAS data modulation and demodulation instrument (3) to start synchronously collecting distributed three-component ground seismic data of the artificial seismic source (4) along the 3C-DAS distributed optical fiber sensing cable (1) at the same time as the ground seismic source is excited; S4. In the absence of an artificial seismic source (4) triggering, manually starting the low-frequency 3C-DAS data modem instrument (3) to continuously acquire distributed three-component ground seismic data excited by natural earthquakes, passive earthquakes, background noise, or fluid noise signals along the 3C-DAS distributed optical fiber sensing cable (1) in an automatic continuous data acquisition mode; S5, a low-frequency 3C-DAS data modulation and demodulation instrument (3) collects the Rayleigh scattered light signal reflected from the optical fiber in the 3C-DAS distributed optical fiber sensor cable (1); S6. By performing modulation and demodulation processing on the phase data of the Rayleigh scattered light signal, the distributed three-component ground seismic data excited by the distributed three-component artificial earthquake, natural earthquake, passive earthquake, background noise or fluid noise signal distributed along the 3C-DAS distributed optical fiber sensing cable (1) is obtained; S7, a low-frequency 3C-DAS data modem instrument (3) and a 3C-DAS distributed optical fiber sensing cable (1) buried under the surface continuously or intermittently measure surface deformation data, distributed three-component strain data, temperature data, distributed three-component SDAS microseismic data, two-dimensional or three-dimensional distributed three-component SDAS seismic data, and distributed three-component time-lapse SDAS seismic data in real time.

8. The seismic data acquisition method based on ground 3C-DAS optical cable according to claim 7, characterized in that: The following steps are also included: S8, shallow surface structure data processing and interpretation system (2), based on the distance from any detection point on the 3C-DAS distributed optical fiber sensor cable (1) to each ground artificial seismic source (4), and the direct longitudinal wave travel time, direct shear wave travel time, surface wave travel time, refracted wave travel time along the underground wave impedance interface to the detection point, and reflected wave travel time data detected from the detection point, the longitudinal wave velocity, shear wave velocity, surface wave velocity, velocity anisotropy of the longitudinal wave velocity in different directions, velocity anisotropy of the shear wave velocity in different directions, attenuation coefficient of the longitudinal wave propagating in the underground medium, and attenuation coefficient of the shear wave propagating in the underground medium are inverted and calculated; S9. For the low-frequency 3C-DAS data modulation and demodulation instrument (3), the distributed three-component ground seismic data or passive source 3C-DAS array seismic data excited by natural earthquakes, passive earthquakes, background noise or fluid noise signals along the 3C-DAS distributed optical fiber sensor cable (1) are continuously collected in an automatic continuous data collection mode. The passive source noise data are first processed, including using AI-based processing technology to perform rapid scanning processing on the energy and amplitude of each component of the continuously collected 3C-DAS passive source noise data, and segmenting each scanned high background noise seismic data to segment the continuously collected 3C-DAS data into independent 3C-DAS high noise source shot gather data. S10, subjecting each independent 3C-DAS high-noise source shot gather data generated in step S9 to special processing using the strain field Green's empirical function; S11, performing surface wave dispersion extraction on each 3C-DAS high-noise source shot gather data after the strain field Green's empirical function processing in step S10; S12, generating a surface wave multi-mode phase velocity dispersion curve using the surface wave dispersion data extracted in step S11; S13, performing surface wave dispersion inversion processing on the surface wave multi-mode phase velocity dispersion curve generated in step S12; S14, the data after the surface wave dispersion inversion processing in step S13 is subjected to shallow surface shear wave velocity V S imaging processing; S15, the shallow surface P-wave velocity V outputted in step S8 and step S14 P Imaging data and shear wave velocity V S The imaging data are fused and interpreted to obtain accurate structural and lithological imaging of the shallow surface structure, fluid distribution imaging, and bedrock surface depth and fluctuation imaging.

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