A stable data acquisition method based on multi-frequency adaptive grounding of audio magnetotelluric sounding method

Abstract

The application is suitable for the field of geophysical exploration technology, and provides an audio magnetotelluric sounding method stable data acquisition method based on multi-frequency adaptive grounding, which comprises the following steps: constructing a multi-frequency adaptive grounding system at an AMT measuring point, including an environment adaptive control unit, an intelligent grounding impedance matching module, a signal quality monitoring and feedback module, and a conductive gel automatic release device; selecting a grounding mode and performing initial impedance matching according to environmental parameters and AMT signal frequency; collecting electromagnetic field signals and monitoring grounding state parameters in real time; when the grounding impedance exceeds a threshold value, releasing conductive gel and / or dynamically adjusting impedance matching parameters, and feeding back optimization; outputting stable AMT data when the data quality meets the conditions, otherwise repeating feedback optimization until the conditions are met. The application guarantees the stability and reliability of the output data, and significantly improves the quality and stability of AMT data acquisition.

Description

Technical Field

[0001] This application relates to the field of geophysical exploration technology, and in particular to a stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding. Background Technology

[0002] Audio-frequency magnetotelluric (AMT) is a geophysical exploration method that utilizes natural electromagnetic fields within a preset operating frequency band to study the electrical structure of underground structures. It is widely used in mineral resource exploration, geological structure research, and geothermal resource surveys. In this method, a grounding device is used to electrically connect the AMT signal acquisition host to the earth, providing a reference potential for the electromagnetic field signal and forming a measurement loop. Existing AMT grounding devices typically employ metal electrodes or metal grounding grids. At the measurement point, the electrodes are inserted into the ground surface or buried in shallow soil, forming a grounding path through the contact between the electrodes and the soil. To reduce contact resistance, some existing technologies increase the contact area between the electrodes and the soil, increase the number of electrodes, or add conductive media around the electrodes to create an electrical connection between the electrodes and the earth. Subsequently, the AMT signal acquisition host acquires the electromagnetic field signal through this grounding path.

[0003] In certain special regions, such as the mountainous areas of Guangxi Zhuang Autonomous Region with exposed gravel, the surface cover is thin and the resistivity of the gravel layer is extremely high. Poor contact between the electrodes and the ground results in generally high grounding impedance across the entire frequency band for existing grounding devices. Furthermore, the grounding impedance in the high-frequency band is significantly higher than in the low-frequency band, causing severe attenuation of the AMT signal at high frequencies, reduced signal-to-noise ratio, and decreased effective data acquisition rate. Discontinuities or jumps appear in the apparent resistivity and phase curves at high frequencies, affecting the accuracy of subsequent inversion interpretation. The fundamental reason is that existing grounding devices mostly use electrodes made of a single material or with a single structure, which cannot simultaneously meet the grounding requirements of low-frequency, mid-frequency, and high-frequency signals across the entire AMT frequency band. They also lack dynamic response capabilities to changes in environmental parameters and grounding impedance in gravelly mountainous areas, causing the grounding impedance to fluctuate with frequency and environmental conditions, making it difficult to maintain a stable low-impedance grounding state across the entire frequency band. Summary of the Invention

[0004] This application provides a stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding, which is used to solve the problem of how to achieve stable, low-impedance grounding in the entire AMT frequency band under the conditions of high resistance and poor contact in rocky, bare mountainous terrain, so as to improve the quality and stability of AMT data acquisition.

[0005] The first aspect of this application provides a stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding, including: A multi-band adaptive grounding system is constructed at the AMT measurement point. The multi-band adaptive grounding system includes an environmental adaptive control unit, an intelligent grounding impedance matching module, a signal quality monitoring and feedback module, and an automatic conductive gel release device. Based on the environmental parameters and AMT signal frequency of the AMT measurement point, the grounding mode is selected by the environmental adaptive control unit, and initial impedance matching is performed by the intelligent grounding impedance matching module to obtain the matched multi-band adaptive grounding system. The matched multi-band adaptive grounding system collects electromagnetic field signals within the preset AMT operating frequency band, and the grounding status parameters of the multi-band adaptive grounding system are monitored in real time through the signal quality monitoring and feedback module. When the grounding impedance in the grounding status parameters exceeds a set threshold, the conductive gel automatic release device is controlled to release conductive gel around the electrode, and / or the impedance matching parameters are dynamically adjusted through the intelligent grounding impedance matching module, and the multi-band adaptive grounding system is optimized based on the monitoring results. When the AMT data quality meets the preset conditions, output the stably acquired AMT data; when the AMT data quality does not meet the preset conditions, repeat the feedback optimization until the AMT data quality meets the preset conditions.

[0006] Furthermore, the multi-band adaptive grounding system also includes a wideband low-impedance grounding electrode array and a distributed capacitive coupling network; wherein, the wideband low-impedance grounding electrode array and the distributed capacitive coupling network are arranged at the AMT measurement point, forming a multi-band grounding path in the AMT operating frequency band through the wideband low-impedance grounding electrode array, and providing a low-impedance coupling path for high-frequency signals through the distributed capacitive coupling network.

[0007] Furthermore, the broadband low-impedance grounding electrode array includes a high-frequency response layer, a mid-frequency conduction layer, and a low-frequency penetration layer; the distributed capacitive coupling network includes multiple capacitive coupling units; the broadband low-impedance grounding electrode array and the distributed capacitive coupling network are arranged at the AMT measurement point, including: The high-frequency response layer is laid flat on the ground surface of the AMT measuring point, the mid-frequency conduction layer is implanted into the wet soil layer under the gravel layer of the AMT measuring point, and the low-frequency penetration layer is buried around the broadband low-impedance grounding electrode array. The multiple capacitive coupling units are arranged radially around the wideband low impedance grounding electrode array, and each capacitive coupling unit is connected to the other. The high-frequency response layer is used to optimize the grounding of high-frequency signals, the intermediate-frequency conduction layer is used to optimize the conduction of intermediate-frequency signals, the low-frequency penetration layer is used to optimize the grounding of low-frequency signals by releasing conductive ions, and the multiple capacitive coupling units are used to provide a low-impedance path for high-frequency signals through capacitive coupling effect.

[0008] Furthermore, the step of selecting the grounding mode through the environmental adaptive control unit based on the environmental parameters of the AMT measurement point and the AMT signal frequency includes: The environmental parameters of the AMT measurement point are collected by the environmental adaptive control unit, including at least one of temperature, humidity and soil resistivity, and the AMT signal frequency is detected. Based on the environmental parameters and the AMT signal frequency, a grounding mode that matches the current environmental parameters and AMT signal frequency is selected from a variety of preset grounding modes; wherein, different grounding modes correspond to different grounding electrode array configurations, distributed capacitive coupling network access methods, or conductive gel release strategies.

[0009] Furthermore, the initial impedance matching through the intelligent grounding impedance matching module to obtain the matched multi-band adaptive grounding system includes: The initial grounding impedance of the multi-band adaptive grounding system is measured by the impedance monitoring circuit of the intelligent grounding impedance matching module. The DSP processor of the intelligent grounding impedance matching module calculates the initial matching parameters based on the initial grounding impedance and the AMT signal frequency. Based on the adjustable matching network of the intelligent grounding impedance matching module, the matching state is adjusted according to the initial matching parameters, so that the multi-band adaptive grounding system is in the initial matching state.

[0010] Furthermore, the matching multi-band adaptive grounding system acquires electromagnetic field signals within a preset AMT operating frequency band, and monitors the grounding status parameters of the multi-band adaptive grounding system in real time through the signal quality monitoring and feedback module, including: With the support of the matched multi-band adaptive grounding system, the AMT signal acquisition host and magnetic sensor acquire electric field and magnetic field signals in the AMT operating frequency band according to the preset acquisition parameters. The potential difference monitoring circuit of the signal quality monitoring and feedback module monitors the ground electrode potential difference of the wideband low impedance ground electrode array in real time, the ground current monitoring circuit of the signal quality monitoring and feedback module monitors the ground current through the multi-band adaptive grounding system in real time, and the signal analysis module of the signal quality monitoring and feedback module calculates the signal-to-noise ratio and spectral characteristics of the AMT signal in real time to obtain the grounding state parameters.

[0011] Furthermore, the step of controlling the conductive gel automatic release device to release conductive gel around the electrode when the grounding impedance in the grounding state parameters exceeds a set threshold includes: When the grounding impedance in the grounding state parameters exceeds a set threshold, the amount of conductive gel released is determined based on the degree to which the grounding impedance exceeds the set threshold. The control valve of the automatic conductive gel release device is opened according to the release amount, and the conductive gel in the storage tank is uniformly released to the surrounding area of ​​the electrodes through the conductive gel release hole of the broadband low impedance grounding electrode array via the pressure release mechanism of the automatic conductive gel release device.

[0012] Furthermore, the dynamic adjustment of impedance matching parameters through the intelligent grounding impedance matching module includes: The impedance monitoring circuit of the intelligent grounding impedance matching module measures the current grounding impedance of the multi-band adaptive grounding system in real time at the current AMT signal frequency. The DSP processor of the intelligent grounding impedance matching module calculates dynamic matching parameters based on the current grounding impedance and the current AMT signal frequency. The adjustable matching network of the intelligent grounding impedance matching module adjusts the matching state according to the dynamic matching parameters to reduce the grounding impedance at the current AMT signal frequency.

[0013] Furthermore, the step of performing feedback optimization of the multi-band adaptive grounding system based on monitoring results includes: Based on the signal-to-noise ratio and / or spectral characteristics in the grounding state parameters, feedback optimization instructions are generated through the feedback control algorithm of the signal quality monitoring and feedback module; According to the feedback optimization instructions, at least one of the following is adjusted: the grounding mode selected by the environmental adaptive control unit, the impedance matching parameters of the intelligent grounding impedance matching module, the conductive gel release strategy of the conductive gel automatic release device, and the access method of the distributed capacitive coupling network.

[0014] Furthermore, the step of outputting stably acquired AMT data when the AMT data quality meets preset conditions includes: Based on at least one of the following factors of the currently acquired AMT data: continuity of the apparent resistivity curve, quality of the phase curve, signal-to-noise ratio, and effective data acquisition rate, determine whether the currently acquired AMT data meets the preset conditions. When the currently acquired AMT data meets the preset conditions, the currently acquired AMT data is output to the data processing terminal as the stably acquired AMT data.

[0015] As can be seen from the above technical solutions, this application has the following advantages: This application constructs a multi-band adaptive grounding system at the AMT measurement point, comprising an environmental adaptive control unit, an intelligent grounding impedance matching module, a signal quality monitoring and feedback module, and an automatic conductive gel release device. This enables the grounding system to possess multiple functions, including environmental adaptation, impedance matching, signal monitoring, and conductive gel release, thus providing a system foundation for achieving stable grounding across the entire frequency band in rocky, exposed mountainous terrain. Based on the environmental parameters and AMT signal frequency at the AMT measurement point, the environmental adaptive control unit selects the grounding mode, and the intelligent grounding impedance matching module performs initial impedance matching. This allows the grounding system to automatically select a matching grounding mode and complete initial impedance matching as environmental conditions and signal frequency change. Electromagnetic field signals are acquired and transmitted via the matched multi-band adaptive grounding system. The signal quality monitoring and feedback module monitors grounding status parameters in real time, enabling data acquisition and grounding status monitoring to proceed synchronously. When the grounding impedance exceeds a set threshold, the system controls an automatic conductive gel release device to release conductive gel around the electrodes, and / or dynamically adjusts impedance matching parameters through an intelligent grounding impedance matching module. Based on the monitoring results, feedback optimization is performed, enabling the grounding system to automatically respond when the grounding impedance increases. This maintains a low-impedance grounding state across the entire frequency band without manual intervention, reducing signal attenuation caused by poor contact. When the AMT data quality meets preset conditions, stable AMT data is output. If the preset conditions are not met, feedback optimization is repeated until the preset conditions are met, ensuring the stability and reliability of the output data and significantly improving the quality and stability of AMT data acquisition. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding, as described in this application. Figure 2 This is a comparison diagram of impedance-frequency characteristics in this application; Figure 3(a) is a bar chart comparing the signal-to-noise ratio in this application; Figure 3(b) is a bar chart comparing the effective data acquisition rate in this application; Figure 4(a) is a comparison of the apparent resistivity curves in this application; Figure 4(b) is a comparison diagram of phase curves in this application; Figure 5 This is the convergence graph for the feedback optimization iteration in this application. Detailed Implementation

[0017] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “corresponding to,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0018] Please see Figure 1 The present application provides a method for stable data acquisition using audio magnetotelluric sounding based on multi-band adaptive grounding, comprising the following steps: 101. Construct a multi-band adaptive grounding system at the AMT measurement point. The multi-band adaptive grounding system includes an environmental adaptive control unit, an intelligent grounding impedance matching module, a signal quality monitoring and feedback module, and an automatic conductive gel release device. In this embodiment, the multi-band adaptive grounding system provides a stable low-impedance grounding path for AMT signal acquisition at the AMT measurement point. Specifically, the environmental adaptive control unit collects environmental parameters at the AMT measurement point and detects the AMT signal frequency to select the grounding mode; the intelligent grounding impedance matching module performs impedance matching to maintain low impedance of the grounding system within the AMT operating frequency band; the signal quality monitoring and feedback module monitors grounding status parameters in real time and generates feedback optimization instructions; and the conductive gel automatic release device releases conductive gel around the electrodes when the grounding impedance exceeds a set threshold.

[0019] In this embodiment, the multi-band adaptive grounding system also includes a wideband low-impedance grounding electrode array and a distributed capacitive coupling network; wherein, the wideband low-impedance grounding electrode array and the distributed capacitive coupling network are arranged at the AMT measurement point, forming a multi-band grounding path in the AMT operating frequency band through the wideband low-impedance grounding electrode array, and providing a low-impedance coupling path for high-frequency signals through the distributed capacitive coupling network.

[0020] Specifically, the operating frequency band of an AMT can be divided into high-frequency, mid-frequency, and low-frequency bands. For example, the high-frequency band can be 1kHz to 10kHz, the mid-frequency band can be 10Hz to 1kHz, and the low-frequency band can be 0.1Hz to 10Hz. A wideband low-impedance grounding electrode array is configured with a high-frequency response layer, a mid-frequency conduction layer, and a low-frequency penetration layer for each of these different frequency bands to form a good grounding path in all frequency bands.

[0021] In this embodiment, the broadband low-impedance grounding electrode array includes a high-frequency response layer, a mid-frequency conduction layer, and a low-frequency penetration layer; the distributed capacitive coupling network includes multiple capacitive coupling units; the broadband low-impedance grounding electrode array and the distributed capacitive coupling network are arranged at the AMT measurement point, including: 1. Lay the high-frequency response layer flat on the ground surface of the AMT measurement point, embed the mid-frequency conduction layer into the wet soil layer under the gravel layer of the AMT measurement point, and bury the low-frequency penetration layer around the broadband low-impedance grounding electrode array. 2. Multiple capacitive coupling units are laid out radially around a wideband low-impedance grounding electrode array, and each capacitive coupling unit is connected to the other accordingly. Among them, the high-frequency response layer is used to optimize the grounding of high-frequency signals, the intermediate-frequency conduction layer is used to optimize the conduction of intermediate-frequency signals, the low-frequency penetration layer is used to optimize the grounding of low-frequency signals by releasing conductive ions, and multiple capacitive coupling units are used to provide a low-impedance path for high-frequency signals through capacitive coupling effect.

[0022] Specifically, the high-frequency response layer can be a copper mesh structure with a surface covered by a nano-conductive coating, 1-3 mm thick, laid flat on the surface of the AMT measurement point to ensure full contact with the ground; the mid-frequency conduction layer can be a copper-steel composite rod electrode, 10-20 mm in diameter and 0.8-1.5 m in length, with a spiral groove structure on the surface, pressed into the underlying relatively moist soil layer under the gravel layer using a special hydraulic tool, to a depth of 0.8-1.2 m; the low-frequency penetration layer can be a porous conductive ceramic tube with a built-in special conductive gel, buried around the electrode array to a depth of 0.3-0.5 m, optimizing low-frequency signal grounding by slowly releasing conductive ions; each capacitive coupling unit in the distributed capacitive coupling network can include a conductive foil, an insulating medium, and a protective layer, laid radially around the electrode array, covering an area of ​​approximately 2-4 m², ensuring good connection between units. The above specific structures and dimensions are merely examples and should not be construed as limiting this application.

[0023] In this embodiment, the acquired AMT signals include electric field and magnetic field signals. Subsequent steps will use an AMT signal acquisition host and a magnetic sensor to acquire these signals within the AMT operating frequency band. The multi-band adaptive grounding system constructed in this step provides a grounding path and reference potential for subsequent AMT data acquisition.

[0024] 102. Based on the environmental parameters of the AMT measurement point and the AMT signal frequency, the grounding mode is selected through the environmental adaptive control unit, and the initial impedance matching is performed through the intelligent grounding impedance matching module to obtain the matched multi-band adaptive grounding system. The environmental adaptive control unit selects the grounding mode based on the environmental parameters and AMT signal frequency of the AMT measurement point, enabling the multi-band adaptive grounding system to adapt to the geological and electromagnetic environment of the current measurement point. Specifically, the environmental adaptive control unit integrates at least one of a temperature sensor, a humidity sensor, and a soil resistivity sensor, and includes a signal frequency detection module. The environmental adaptive control unit collects environmental parameters of the AMT measurement point through these sensors, including at least one of temperature, humidity, and soil resistivity; simultaneously, it detects the current AMT signal frequency through the signal frequency detection module. The environmental adaptive control unit matches the collected environmental parameters and the detected AMT signal frequency with multiple preset grounding modes, selecting the grounding mode that best matches the current environmental parameters and AMT signal frequency.

[0025] Multiple preset grounding modes are pre-defined based on different combinations of environmental parameters and AMT signal frequencies. Different grounding modes correspond to different grounding electrode array configurations, distributed capacitive coupling network access methods, or conductive gel release strategies. For example, when soil resistivity is high and AMT signal frequencies are predominantly high-frequency, a grounding mode that enhances high-frequency response layer access, increases the number of distributed capacitive coupling network units, and increases conductive gel release can be selected. When soil moisture is high and AMT signal frequencies are predominantly low-frequency, a grounding mode that enhances low-frequency penetration layer access, reduces the number of distributed capacitive coupling network units, and decreases conductive gel release can be selected. The above examples are only for illustrating the configuration differences corresponding to different grounding modes and do not constitute a limitation on this embodiment.

[0026] In this embodiment, an initial impedance matching is performed using an intelligent grounding impedance matching module to obtain a matched multi-band adaptive grounding system, including: 1. Measure the initial grounding impedance of the multi-band adaptive grounding system using the impedance monitoring circuit of the intelligent grounding impedance matching module; The impedance monitoring circuit is connected to a wideband low-impedance grounding electrode array and a distributed capacitive coupling network. After the environmental adaptive control unit selects the grounding mode, it injects a test signal into the multi-band adaptive grounding system to measure the initial grounding impedance of the multi-band adaptive grounding system at the current AMT signal frequency. The initial grounding impedance may include grounding resistance and grounding reactance components. The impedance monitoring circuit outputs the measured initial grounding impedance to the DSP processor.

[0027] 2. The DSP processor of the intelligent grounding impedance matching module calculates the initial matching parameters based on the initial grounding impedance and the AMT signal frequency; The DSP processor receives the initial grounding impedance output from the impedance monitoring circuit and the AMT signal frequency provided by the environmental adaptive control unit. Based on the initial grounding impedance and the AMT signal frequency, it calculates the initial matching parameters according to a preset impedance matching algorithm. The initial matching parameters may include the values ​​of at least one of the adjustable capacitor, adjustable inductor, and adjustable resistor in the adjustable matching network. When calculating the initial matching parameters, the DSP processor aims to make the grounding impedance of the multi-band adaptive grounding system approach the preset target impedance at the AMT signal frequency.

[0028] 3. An adjustable matching network based on an intelligent grounding impedance matching module adjusts the matching state according to the initial matching parameters, so that the multi-band adaptive grounding system is in the initial matching state.

[0029] The adjustable matching network includes at least one of adjustable capacitors, adjustable inductors, and adjustable resistors. The DSP processor sends the calculated initial matching parameters to the adjustable matching network. The adjustable matching network adjusts the values ​​of its internal adjustable components according to the initial matching parameters, thereby changing the impedance characteristics of the multi-band adaptive grounding system. This reduces the grounding impedance of the multi-band adaptive grounding system at the AMT signal frequency to near the preset target impedance. At this point, the multi-band adaptive grounding system is in the initial matching state, which is the matched multi-band adaptive grounding system. The matched multi-band adaptive grounding system is used for subsequent AMT data acquisition.

[0030] In this embodiment, after selecting a grounding mode, the environmental adaptive control unit sends the selected grounding mode information to the intelligent grounding impedance matching module. The intelligent grounding impedance matching module, during initial impedance matching, incorporates this grounding mode information to employ corresponding matching strategies for different grounding modes. For example, when different grounding modes correspond to different distributed capacitive coupling network access methods, the adjustable matching network adjusts the number or connection method of the connected capacitive coupling units accordingly to achieve better impedance matching performance in the initial matching state.

[0031] 103. Electromagnetic field signals are collected within the preset AMT operating frequency band through the matched multi-band adaptive grounding system, and the grounding status parameters of the multi-band adaptive grounding system are monitored in real time through the signal quality monitoring and feedback module; In this embodiment, after obtaining the matched multi-band adaptive grounding system, electromagnetic field signals are collected in the preset AMT working frequency band by the AMT signal acquisition host and magnetic sensor, and the grounding status parameters of the multi-band adaptive grounding system are monitored in real time by the signal quality monitoring and feedback module, so as to grasp the working status of the grounding system in real time during the acquisition process.

[0032] In this embodiment, using an AMT signal acquisition host and a magnetic sensor, and with the support of a matched multi-band adaptive grounding system, electric and magnetic field signals are acquired within the AMT operating frequency band according to preset acquisition parameters, including: Specifically, the AMT signal acquisition host is connected to a broadband low-impedance grounding electrode array and a magnetic sensor, respectively. The electrodes in the broadband low-impedance grounding electrode array are used to measure electric field signals, and the magnetic sensor is used to measure magnetic field signals. A multi-band adaptive grounding system provides a reference potential and grounding loop for the AMT signal acquisition host, enabling it to acquire electric field signals based on the reference potential. The magnetic sensor can be placed near the AMT measurement point to acquire magnetic field signals. The AMT signal acquisition host acquires the electric and magnetic field signals according to preset acquisition parameters. These preset acquisition parameters include at least one of a frequency band range and a sampling rate. For example, the frequency band range can be from 0.1 Hz to 10 kHz, and the sampling rate can be 20 kHz. These specific values ​​are merely examples and should not be construed as limitations on this application. The AMT signal acquisition host outputs the acquired electric and magnetic field signals to a subsequent data processing terminal or storage unit.

[0033] In this embodiment, the grounding status parameters of the multi-band adaptive grounding system are monitored in real time through the signal quality monitoring and feedback module, including: The potential difference of the grounding electrode array of the broadband low impedance grounding electrode array is monitored in real time by the potential difference monitoring circuit of the signal quality monitoring and feedback module, the grounding current of the multi-band adaptive grounding system is monitored in real time by the grounding current monitoring circuit of the signal quality monitoring and feedback module, and the signal analysis module of the signal quality monitoring and feedback module calculates the signal-to-noise ratio and spectral characteristics of the AMT signal in real time to obtain the grounding status parameters.

[0034] Specifically, the signal quality monitoring and feedback module includes a potential difference monitoring circuit, a ground current monitoring circuit, and a signal analysis module. The potential difference monitoring circuit is connected to the grounding electrode and the far reference electrode in the wideband low-impedance grounding electrode array, measuring the potential difference between the grounding electrode and the far reference electrode in real time to obtain the grounding electrode potential difference. The ground current monitoring circuit is connected in series in the grounding loop of the multi-band adaptive grounding system, measuring the ground current passing through the multi-band adaptive grounding system in real time. The signal analysis module is connected to the AMT signal acquisition host, receiving the electric field and magnetic field signals acquired by the AMT signal acquisition host, and performing time-frequency analysis on the electric field and magnetic field signals, such as calculating the signal-to-noise ratio and spectral characteristics of the AMT signal through Fourier transform. The signal-to-noise ratio can be calculated based on the ratio of signal power to noise power within the signal frequency band; the spectral characteristics can include at least one of amplitude-frequency characteristics and phase-frequency characteristics. The signal analysis module outputs the calculated signal-to-noise ratio and spectral characteristics. The outputs of the potential difference monitoring circuit, the ground current monitoring circuit, and the signal analysis module together constitute the grounding status parameters. The grounding status parameters are used in subsequent steps to determine whether the grounding impedance exceeds a set threshold and to perform feedback optimization.

[0035] In this embodiment, the grounding status parameters may further include the grounding impedance measured by the impedance monitoring circuit of the intelligent grounding impedance matching module. During AMT data acquisition, the impedance monitoring circuit continuously measures the grounding impedance of the multi-band adaptive grounding system at the current AMT signal frequency and uses this grounding impedance as part of the grounding status parameters. Thus, the signal quality monitoring and feedback module and the intelligent grounding impedance matching module jointly provide real-time monitoring data for subsequent feedback optimization.

[0036] 104. When the grounding impedance in the grounding status parameters exceeds the set threshold, control the conductive gel automatic release device to release conductive gel around the electrode, and / or dynamically adjust the impedance matching parameters through the intelligent grounding impedance matching module, and perform feedback optimization of the multi-band adaptive grounding system based on the monitoring results; During AMT data acquisition, the signal quality monitoring and feedback module monitors the grounding status parameters of the multi-band adaptive grounding system in real time. When the grounding impedance in the grounding status parameters exceeds a set threshold, it indicates that the grounding performance of the multi-band adaptive grounding system has deteriorated under the current environment or the current AMT signal frequency. At this time, the conductive gel automatic release device can be controlled to release conductive gel around the electrodes, and / or the impedance matching parameters can be dynamically adjusted through the intelligent grounding impedance matching module to reduce the grounding impedance. Simultaneously, the multi-band adaptive grounding system is optimized based on the monitoring results to maintain a stable low-impedance grounding state across the entire frequency band.

[0037] In this embodiment, when the grounding impedance in the grounding status parameters exceeds a set threshold, the conductive gel automatic release device is controlled to release conductive gel around the electrode, including: 1. When the grounding impedance in the grounding status parameters exceeds the set threshold, the amount of conductive gel released is determined according to the degree to which the grounding impedance exceeds the set threshold; The threshold value can be preset according to the quality requirements of AMT data acquisition, for example, set to 500Ω, but is not limited to this. The degree to which the grounding impedance exceeds the set threshold can be expressed by the excess amount or the excess ratio. The release amount of conductive gel is positively correlated with the excess amount, that is, the greater the excess amount, the greater the release amount. In this embodiment, a mapping relationship table between the excess amount and the release amount can be established in advance, for example, the excess amount can be divided into multiple intervals, each interval corresponding to a release amount level. When the grounding impedance exceeds the set threshold, the mapping relationship table is consulted according to the difference or ratio between the current grounding impedance and the set threshold to determine the corresponding release amount. The release amount can be expressed in terms of volume or release time. For example, when the excess ratio is less than 10%, the release amount is level one; when the excess ratio is between 10% and 30%, the release amount is level two; when the excess ratio is greater than 30%, the release amount is level three. The above examples are for illustration only and do not constitute a limitation of this application.

[0038] 2. The control valve of the conductive gel automatic release device is opened according to the release amount, and the conductive gel in the storage tank is evenly released to the surrounding area of ​​the electrode through the conductive gel release hole of the wideband low impedance grounding electrode array by the pressure release mechanism of the conductive gel automatic release device.

[0039] The automatic conductive gel release device includes a storage tank, a pressure release mechanism, and a control valve. The storage tank, with a capacity of 2-5 liters, is used to store the conductive gel and is made of corrosion-resistant composite material. The control valve, located at the outlet of the storage tank, controls the release rate of the conductive gel. The pressure release mechanism applies pressure to the conductive gel in the storage tank, causing it to flow out through the control valve. A conductive gel release orifice is provided on the broadband low-impedance grounding electrode array, which can be located near the mid-frequency conductive layer and / or the low-frequency penetrating layer. When the control valve opens according to the predetermined release rate, the pressure release mechanism uniformly releases the conductive gel from the storage tank into the surrounding area of ​​the electrodes through the release orifice. After release, the conductive gel permeates into the soil or gravel layer around the electrodes, improving the contact between the electrodes and the ground, thereby reducing the grounding impedance.

[0040] In this embodiment, the impedance matching parameters are dynamically adjusted through the intelligent grounding impedance matching module, including: 1. The impedance monitoring circuit of the intelligent grounding impedance matching module measures the current grounding impedance of the multi-band adaptive grounding system in real time at the current AMT signal frequency; The impedance monitoring circuit continuously monitors the grounding impedance of the multi-band adaptive grounding system at the current AMT signal frequency and outputs the measured current grounding impedance to the DSP processor. The current AMT signal frequency can be provided by the signal frequency detection module of the environmental adaptive control unit, or it can be detected by the impedance monitoring circuit itself.

[0041] 2. The DSP processor of the intelligent grounding impedance matching module calculates dynamic matching parameters based on the current grounding impedance and the current AMT signal frequency; The DSP processor receives the current grounding impedance and the current AMT signal frequency, and calculates dynamic matching parameters according to a preset impedance matching algorithm. Dynamic matching parameters may include updated values ​​of at least one of the adjustable capacitors, adjustable inductors, and adjustable resistors in the adjustable matching network. The DSP processor calculates dynamic matching parameters with the goal of bringing the grounding impedance of the multi-band adaptive grounding system close to a preset target impedance at the current AMT signal frequency. For example, a gradient descent-based optimization algorithm or a lookup table method can be used to calculate the dynamic matching parameters.

[0042] 3. By using the adjustable matching network of the intelligent grounding impedance matching module, the matching state is adjusted according to the dynamic matching parameters to reduce the grounding impedance at the current AMT signal frequency.

[0043] The adjustable matching network includes at least one of an adjustable capacitor, an adjustable inductor, and an adjustable resistor. The DSP processor sends the calculated dynamic matching parameters to the adjustable matching network, which adjusts the values ​​of its internal adjustable components according to the dynamic matching parameters, thereby changing the impedance characteristics of the multi-band adaptive grounding system and reducing the grounding impedance at the current AMT signal frequency. Dynamic adjustment can be performed periodically or triggered when the grounding impedance exceeds a set threshold.

[0044] In this embodiment, the multi-band adaptive grounding system is optimized based on monitoring results, including: 1. Based on the signal-to-noise ratio and / or spectral characteristics in the grounding status parameters, generate feedback optimization instructions through the feedback control algorithm of the signal quality monitoring and feedback module; The signal analysis module of the signal quality monitoring and feedback module calculates the signal-to-noise ratio (SNR) and spectral characteristics of the AMT signal in real time. The feedback control algorithm determines the current AMT data quality based on the SNR and / or spectral characteristics. For example, when the SNR is lower than a preset SNR threshold, or when the spectral characteristics show abnormal attenuation or distortion in the high-frequency band, the feedback control algorithm generates a feedback optimization instruction. The feedback optimization instruction may include at least one of the following: the type of parameter to be adjusted, the adjustment direction, or the adjustment amount.

[0045] 2. Based on the feedback optimization instructions, adjust at least one of the following: the grounding mode selected by the environmental adaptive control unit, the impedance matching parameters of the intelligent grounding impedance matching module, the conductive gel release strategy of the conductive gel automatic release device, and the access method of the distributed capacitive coupling network.

[0046] Feedback optimization commands can be sent to at least one of the following: an environmental adaptive control unit, an intelligent grounding impedance matching module, an automatic conductive gel release device, or a distributed capacitive coupling network. When a feedback optimization command is sent to the environmental adaptive control unit, the unit reselects the grounding mode based on the command. When sent to the intelligent grounding impedance matching module, the module adjusts the impedance matching parameters. When sent to the automatic conductive gel release device, the device adjusts its release strategy, such as increasing or decreasing the release amount or changing the release timing. When sent to the distributed capacitive coupling network, the network adjusts its connection method, such as increasing or decreasing the number of connected capacitive coupling units or changing the connection method. Through these adjustments, feedback optimization is performed on the multi-band adaptive grounding system to improve AMT data quality.

[0047] In this embodiment, releasing the conductive gel, dynamically adjusting the impedance matching parameters, and feedback optimization can be performed individually or in combination. For example, when the grounding impedance exceeds a set threshold, only the conductive gel can be released, only the impedance matching parameters can be dynamically adjusted, or both can be performed simultaneously. If the AMT data quality still does not meet the preset conditions after releasing the conductive gel and / or dynamically adjusting, feedback optimization is further performed to adjust other parameters.

[0048] 105. When the AMT data quality meets the preset conditions, output the stably acquired AMT data; when the AMT data quality does not meet the preset conditions, repeat the feedback optimization until the AMT data quality meets the preset conditions.

[0049] During AMT data acquisition, the grounding status parameters are monitored in real time through the signal quality monitoring and feedback module, and the grounding system can be optimized based on these parameters. After each optimization, the quality of the acquired AMT data is assessed to determine whether to output stable AMT data. When the AMT data quality meets preset conditions, stable AMT data is output; when the AMT data quality does not meet preset conditions, the feedback optimization in step 104 is repeated until the AMT data quality meets the preset conditions.

[0050] Specifically, the quality of AMT data can be judged based on at least one of the following: the continuity of the apparent resistivity curve, the quality of the phase curve, the signal-to-noise ratio (SNR), and the effective data acquisition rate. The continuity of the apparent resistivity curve characterizes whether the apparent resistivity curve of the AMT data is continuous and smooth within the AMT operating frequency band, and whether there are any discontinuities or jumps. The quality of the phase curve characterizes whether the phase curve of the AMT data is smooth and continuous within the AMT operating frequency band, and whether there are any severe jumps. The SNR characterizes the power ratio of the AMT signal to noise. The effective data acquisition rate characterizes the ratio of the number of effective data points to the total number of acquired data points within the AMT operating frequency band. When at least one of the above indicators meets a preset condition, the AMT data quality is determined to meet the preset condition. For example, the preset condition may include: the apparent resistivity curve is continuous and smooth across the entire frequency band; the phase curve is smooth and continuous across the entire frequency band; the SNR is not lower than a preset SNR threshold; and the effective data acquisition rate is not lower than a preset acquisition rate threshold. The above specific conditions are merely examples and should not be construed as limitations on this application.

[0051] In this embodiment, the determination of whether the currently acquired AMT data meets preset conditions is based on at least one of the following: the continuity of the apparent resistivity curve, the quality of the phase curve, the signal-to-noise ratio, and the effective data acquisition rate. This includes: 1. Based on at least one of the following factors of the currently acquired AMT data: continuity of the apparent resistivity curve, quality of the phase curve, signal-to-noise ratio, and effective data acquisition rate, determine whether the currently acquired AMT data meets the preset conditions. The signal analysis module of the signal quality monitoring and feedback module receives the electric and magnetic field signals acquired by the AMT signal acquisition host and calculates the apparent resistivity curve and phase curve based on these signals. The continuity of the apparent resistivity curve can be determined by detecting whether there are any discontinuities, jumps, or abnormal abrupt changes within the AMT operating frequency band. For example, the difference in the logarithmic values ​​of the apparent resistivity at adjacent frequency points can be calculated; if the difference exceeds a preset difference threshold, a discontinuity or jump is determined at that frequency point. The quality of the phase curve can be determined by detecting whether there are any severe jumps within the AMT operating frequency band. For example, the difference in the phase values ​​at adjacent frequency points can be calculated; if the difference exceeds a preset phase difference threshold, a severe jump is determined at that frequency point. The calculation methods for the signal-to-noise ratio and effective data acquisition rate have been explained in step 103 and will not be repeated here. The signal analysis module compares the above indicators with their respective preset conditions. If at least one indicator meets the preset conditions, the quality of the currently acquired AMT data is determined to meet the preset conditions; otherwise, the quality of the currently acquired AMT data is determined not to meet the preset conditions.

[0052] 2. When the currently acquired AMT data meets the preset conditions, the currently acquired AMT data is output as the stably acquired AMT data to the data processing terminal.

[0053] When the quality of the currently acquired AMT data meets the preset conditions, the signal quality monitoring and feedback module sends an output command to the AMT signal acquisition host. The AMT signal acquisition host then outputs the currently acquired AMT data as stably acquired AMT data to the data processing terminal. The data processing terminal can be a data storage unit or a data processing computer, used to store or subsequently interpret the stably acquired AMT data. When the quality of the currently acquired AMT data does not meet the preset conditions, the signal quality monitoring and feedback module generates a feedback optimization command, triggering the feedback optimization in step 104. This involves adjusting at least one of the following: the grounding mode selected by the environmental adaptive control unit, the impedance matching parameters of the intelligent grounding impedance matching module, the conductive gel release strategy of the conductive gel automatic release device, and the access method of the distributed capacitive coupling network. Then, the AMT data is reacquired and the quality is judged again until the AMT data quality meets the preset conditions.

[0054] Through the above closed-loop control, the multi-band adaptive grounding system can continuously optimize the grounding state during AMT data acquisition until it outputs stable AMT data that meets the preset conditions, thereby improving the quality and stability of AMT data acquisition.

[0055] To verify the technical effectiveness of the multi-band adaptive grounding-based audio magnetotelluric sounding method for stable data acquisition compared to traditional grounding devices, and to verify the synergistic effect of the broadband low-impedance grounding electrode array, distributed capacitive coupling network, intelligent grounding impedance matching module, environmental adaptive control unit, signal quality monitoring and feedback module, and conductive gel automatic release device, a comparative AMT measurement experiment was conducted in a typical gravelly, bare mountainous area in Guangxi Zhuang Autonomous Region. Details are as follows: I. Experimental Site and Geological Conditions: The experimental site was a typical gravelly, bare mountainous area in Guangxi Zhuang Autonomous Region. This region has a thin surface cover, a well-developed gravel layer, and underlying bedrock resistivity greater than 1000 Ω·m, classifying it as a high-resistivity, poor-contact area. Multiple measuring points with similar geological conditions were selected, and environmental parameters such as temperature, humidity, and soil resistivity were recorded during the experiment to ensure comparability of comparative experiments.

[0056] II. Experimental Equipment and Materials: AMT signal acquisition host, magnetic sensor, electric field sensor; Traditional grounding devices: copper rod electrodes or metal grounding grids; The device described in this application includes: a wideband low-impedance grounding electrode array, a distributed capacitive coupling network, an intelligent grounding impedance matching module, an environmental adaptive control unit, a signal quality monitoring and feedback module, and an automatic conductive gel release device. Impedance analyzer, temperature and humidity sensor, soil resistivity tester; Data processing terminal.

[0057] III. Experimental Group Design: A control group and an experimental group were set up, and an ablation group was set up to verify the contribution of each module: Control group A: Traditional grounding device, with copper rod electrodes or metal grounding grids arranged in a conventional manner.

[0058] Experimental Group B: The complete method of this application involves constructing a multi-band adaptive grounding system and performing data acquisition according to steps 101-105 of the instruction manual.

[0059] Ablation group C: Only a wideband low-impedance grounding electrode array is arranged.

[0060] Ablation group D: Based on C, a distributed capacitive coupling network is added.

[0061] Ablation Group E: Enables the intelligent grounding impedance matching module based on D.

[0062] Ablation Group F: Based on E, an automatic conductive gel release device is enabled.

[0063] Ablation group G: Based on F, feedback optimization of the signal quality monitoring and feedback module is enabled, i.e., the complete method of this application (same as experimental group B, used as a control).

[0064] IV. Experimental Procedure: 1. Measurement point preparation: Clean up the loose stones on the surface of the measurement point, prepare an area of ​​about 3m×3m, measure the surface resistivity distribution, and record the environmental parameters.

[0065] 2. Control Group A Deployment and Data Acquisition: At measurement point A, a conventional grounding device was set up using standard methods, and the AMT signal acquisition host and magnetic sensor were connected. Acquisition parameters were set: frequency band range 0.1Hz-10kHz, sampling rate 20kHz. AMT data acquisition was started, recording grounding impedance-frequency characteristics, signal-to-noise ratio, effective data acquisition rate, apparent resistivity curve, phase curve, single-point deployment time, etc.

[0066] 3. Deployment of Experimental Group B: Construct a multi-band adaptive grounding system at measurement point B according to step 101 of the instruction manual, arrange a wideband low-impedance grounding electrode array and a distributed capacitive coupling network, and connect each module.

[0067] 4. Environmental Adaptive Grounding Mode Selection: Follow step 102 in the instruction manual to collect temperature, humidity, and soil resistivity through the environmental adaptive control unit, detect the AMT signal frequency, and select the matching grounding mode.

[0068] 5. Initial impedance matching: The initial grounding impedance is measured by the impedance monitoring circuit of the intelligent grounding impedance matching module, the DSP processor calculates the initial matching parameters, and the adjustable matching network adjusts the matching state to bring the system into the initial matching state.

[0069] 6. AMT Data Acquisition and Real-time Monitoring: Following step 103 in the instruction manual, electric field and magnetic field signals are acquired with the support of the matched system. Grounding status parameters are monitored in real time through the signal quality monitoring and feedback module.

[0070] 7. Threshold Triggering and Feedback Optimization: Following step 104 in the instruction manual, when the grounding impedance exceeds the set threshold, control the conductive gel automatic release device to release the conductive gel, and / or dynamically adjust the impedance matching parameters through the intelligent grounding impedance matching module, and perform feedback optimization based on the monitoring results. Record the release amount, changes in matching parameters, feedback optimization instructions, and adjustment details.

[0071] 8. Quality Judgment and Loop Closure: Following step 105 in the instruction manual, judge the AMT data quality based on at least one of the following: apparent resistivity curve continuity, phase curve quality, signal-to-noise ratio, and effective data acquisition rate. If the preset conditions are met, output the stably acquired AMT data; if not, repeat the feedback optimization in step 7 until the preset conditions are met. Record the number of feedback optimization iterations and the changes in indicators after each iteration.

[0072] 9. Ablation group experiment: Repeat steps 3 to 8 according to the settings of ablation groups C, D, E, F and G respectively, and record the performance indicators of each group.

[0073] 10. Repeat the experiment at multiple measurement points with similar geological conditions, take the average value and calculate the standard deviation.

[0074] V. Measurement Indicators and Data Recording: The various indicators that need to be measured during the experiment and their recording methods are shown in Table 1: Table 1 Measurement Indicators and Data Recording Table VI. Experimental Data and Figure Descriptions: Table 2 shows the performance comparison results of the traditional grounding device and the device proposed in this application under the same AMT acquisition parameters in typical gravelly and bare mountainous conditions in Guangxi Zhuang Autonomous Region: Table 2 Performance Comparison Data Between Traditional Grounding Devices and the Device Applied For To verify the contribution of each module in this application, an ablation experiment was set up, and the performance indicators of each experimental group are shown in Table 3: Table 3 Comparison of Ablation Experiment Performance Data from Figure 2 It is known that the grounding impedance of traditional grounding devices increases significantly with increasing frequency, reaching 3500-5000Ω in the 1k-10kHz high-frequency band, indicating severe degradation of grounding performance in the high-frequency band. The grounding impedance of the device in this application remains flat and low across the entire frequency band, basically stable between 280-400Ω, with no significant increase in the high-frequency band. Therefore, this application effectively solves the problem of high grounding impedance in the high-frequency band of traditional devices through a multi-band adaptive grounding system, achieving low-impedance stable grounding across the entire AMT frequency band. As shown in Figures 3(a) and 3(b), the AMT data signal-to-noise ratio of the device in this application is 28.7dB, while that of the traditional device is 9.3dB, an improvement of 208.6%, indicating that this application significantly improves AMT signal quality and reduces noise interference. The effective data acquisition rate of the device in this application is 96.4%, while that of the traditional device is 62.8%, an improvement of 53.5%, indicating that this application significantly reduces invalid data and improves the effectiveness and completeness of data acquisition. Therefore, this application is significantly superior to traditional devices in all core data quality indicators. As shown in Figures 4(a) and 4(b), the apparent resistivity curve of the traditional device exhibits obvious discontinuities or jumps in the high-frequency band, and the phase curve shows severe fluctuations in the high-frequency band, indicating poor and discontinuous high-frequency data quality. In contrast, the apparent resistivity curve of the device in this application is continuous and smooth across the entire frequency band, and the phase curve is smooth and continuous across the entire frequency band, without any discontinuities or severe fluctuations. Therefore, this application effectively improves the high-frequency data quality, ensures the consistency and reliability of AMT data across the entire frequency band, and provides high-quality basic data for subsequent inversion interpretation. Figure 5 As the number of feedback optimization iterations increases, the grounding impedance gradually decreases from an initial approximately 800Ω and converges to approximately 325Ω, indicating that the feedback optimization in this application can continuously reduce the grounding impedance. Simultaneously, the signal-to-noise ratio gradually increases from an initial approximately 14dB and converges to approximately 28.7dB, indicating that the feedback optimization effectively improves the AMT signal quality while reducing the grounding impedance. Both curves stabilize within a relatively small number of iterations, demonstrating that the closed-loop feedback optimization in this application has rapid convergence and can adjust the grounding state in a timely manner during actual data acquisition, ensuring the stability of data acquisition.

[0075] VII. Conclusion: Through the aforementioned comparative and ablation experiments, under typical gravelly, exposed mountainous conditions in Guangxi Zhuang Autonomous Region, the method described in this application significantly outperforms traditional grounding devices in terms of average grounding impedance, high-frequency impedance, AMT data signal-to-noise ratio, effective data acquisition rate, apparent resistivity curve continuity, phase curve quality, and single-point deployment time. The ablation experiments further demonstrate that the feedback optimization of the broadband low-impedance grounding electrode array, distributed capacitive coupling network, intelligent grounding impedance matching module, conductive gel automatic release device, and signal quality monitoring and feedback module all contribute to performance improvement, with optimal results achieved when all modules work in tandem. This application, through closed-loop control of a multi-band adaptive grounding system, effectively solves the problems of high grounding impedance, severe signal attenuation, and unstable data quality across the entire AMT frequency band under high resistance and poor contact conditions, providing high-quality foundational data for subsequent geological interpretation.

[0076] It is understood that those skilled in the art can combine various implementation methods in the above embodiments under the guidance of the above examples to obtain technical solutions with multiple implementation methods.

[0077] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding, characterized in that, include: A multi-band adaptive grounding system is constructed at the AMT measurement point. The multi-band adaptive grounding system includes an environmental adaptive control unit, an intelligent grounding impedance matching module, a signal quality monitoring and feedback module, and an automatic conductive gel release device. Based on the environmental parameters and AMT signal frequency of the AMT measurement point, the grounding mode is selected by the environmental adaptive control unit, and initial impedance matching is performed by the intelligent grounding impedance matching module to obtain the matched multi-band adaptive grounding system. The matched multi-band adaptive grounding system collects electromagnetic field signals within the preset AMT operating frequency band, and the grounding status parameters of the multi-band adaptive grounding system are monitored in real time through the signal quality monitoring and feedback module. When the grounding impedance in the grounding status parameters exceeds a set threshold, the conductive gel automatic release device is controlled to release conductive gel around the electrode, and / or the impedance matching parameters are dynamically adjusted through the intelligent grounding impedance matching module, and the multi-band adaptive grounding system is optimized based on the monitoring results. When the AMT data quality meets the preset conditions, output the stably acquired AMT data; when the AMT data quality does not meet the preset conditions, repeat the feedback optimization until the AMT data quality meets the preset conditions.

2. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding as described in claim 1, characterized in that, The multi-band adaptive grounding system also includes a wideband low-impedance grounding electrode array and a distributed capacitive coupling network; wherein, the wideband low-impedance grounding electrode array and the distributed capacitive coupling network are arranged at the AMT measurement point, and the wideband low-impedance grounding electrode array forms a multi-band grounding path in the AMT operating frequency band, and the distributed capacitive coupling network provides a low-impedance coupling path for high-frequency signals.

3. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding as described in claim 2, characterized in that, The wideband low-impedance grounding electrode array includes a high-frequency response layer, a mid-frequency conduction layer, and a low-frequency penetration layer; the distributed capacitive coupling network includes multiple capacitive coupling units. The broadband low-impedance grounding electrode array and the distributed capacitive coupling network are arranged at the AMT measurement point, including: The high-frequency response layer is laid flat on the ground surface of the AMT measuring point, the mid-frequency conduction layer is implanted into the wet soil layer under the gravel layer of the AMT measuring point, and the low-frequency penetration layer is buried around the broadband low-impedance grounding electrode array. The multiple capacitive coupling units are arranged radially around the wideband low impedance grounding electrode array, and each capacitive coupling unit is connected to the other. The high-frequency response layer is used to optimize the grounding of high-frequency signals, the intermediate-frequency conduction layer is used to optimize the conduction of intermediate-frequency signals, the low-frequency penetration layer is used to optimize the grounding of low-frequency signals by releasing conductive ions, and the multiple capacitive coupling units are used to provide a low-impedance path for high-frequency signals through capacitive coupling effect.

4. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding as described in claim 1, characterized in that, The step of selecting the grounding mode through the environmental adaptive control unit based on the environmental parameters and AMT signal frequency of the AMT measurement point includes: The environmental parameters of the AMT measurement point are collected by the environmental adaptive control unit, including at least one of temperature, humidity and soil resistivity, and the AMT signal frequency is detected. Based on the environmental parameters and the AMT signal frequency, a grounding mode that matches the current environmental parameters and AMT signal frequency is selected from a variety of preset grounding modes; wherein, different grounding modes correspond to different grounding electrode array configurations, distributed capacitive coupling network access methods, or conductive gel release strategies.

5. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding according to claim 4, characterized in that, The process of performing initial impedance matching through the intelligent grounding impedance matching module to obtain a matched multi-band adaptive grounding system includes: The initial grounding impedance of the multi-band adaptive grounding system is measured by the impedance monitoring circuit of the intelligent grounding impedance matching module. The DSP processor of the intelligent grounding impedance matching module calculates the initial matching parameters based on the initial grounding impedance and the AMT signal frequency. Based on the adjustable matching network of the intelligent grounding impedance matching module, the matching state is adjusted according to the initial matching parameters, so that the multi-band adaptive grounding system is in the initial matching state.

6. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding according to claim 1, characterized in that, The matched multi-band adaptive grounding system acquires electromagnetic field signals within a preset AMT operating frequency band, and monitors the grounding status parameters of the multi-band adaptive grounding system in real time through the signal quality monitoring and feedback module, including: With the support of the matched multi-band adaptive grounding system, the AMT signal acquisition host and magnetic sensor acquire electric field and magnetic field signals in the AMT operating frequency band according to the preset acquisition parameters. The potential difference monitoring circuit of the signal quality monitoring and feedback module monitors the ground electrode potential difference of the wideband low impedance ground electrode array in real time, the ground current monitoring circuit of the signal quality monitoring and feedback module monitors the ground current through the multi-band adaptive grounding system in real time, and the signal analysis module of the signal quality monitoring and feedback module calculates the signal-to-noise ratio and spectral characteristics of the AMT signal in real time to obtain the grounding state parameters.

7. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding according to claim 6, characterized in that, When the grounding impedance in the grounding state parameters exceeds a set threshold, the automatic release device for conductive gel is controlled to release conductive gel around the electrode, including: When the grounding impedance in the grounding state parameters exceeds a set threshold, the amount of conductive gel released is determined based on the degree to which the grounding impedance exceeds the set threshold. The control valve of the automatic conductive gel release device is opened according to the release amount, and the conductive gel in the storage tank is uniformly released to the surrounding area of ​​the electrodes through the conductive gel release hole of the broadband low impedance grounding electrode array via the pressure release mechanism of the automatic conductive gel release device.

8. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding according to claim 6, characterized in that, The dynamic adjustment of impedance matching parameters through the intelligent grounding impedance matching module includes: The impedance monitoring circuit of the intelligent grounding impedance matching module measures the current grounding impedance of the multi-band adaptive grounding system in real time at the current AMT signal frequency. The DSP processor of the intelligent grounding impedance matching module calculates dynamic matching parameters based on the current grounding impedance and the current AMT signal frequency. The adjustable matching network of the intelligent grounding impedance matching module adjusts the matching state according to the dynamic matching parameters to reduce the grounding impedance at the current AMT signal frequency.

9. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding according to claim 6, characterized in that, The step of feedback optimization of the multi-band adaptive grounding system based on monitoring results includes: Based on the signal-to-noise ratio and / or spectral characteristics in the grounding state parameters, feedback optimization instructions are generated through the feedback control algorithm of the signal quality monitoring and feedback module; According to the feedback optimization instructions, at least one of the following is adjusted: the grounding mode selected by the environmental adaptive control unit, the impedance matching parameters of the intelligent grounding impedance matching module, the conductive gel release strategy of the conductive gel automatic release device, and the access method of the distributed capacitive coupling network.

10. The stable data acquisition method for audio magnetotelluric sounding based on multi-band adaptive grounding according to claim 1, characterized in that, When the AMT data quality meets preset conditions, the stable acquired AMT data is output, including: Based on at least one of the following factors of the currently acquired AMT data: continuity of the apparent resistivity curve, quality of the phase curve, signal-to-noise ratio, and effective data acquisition rate, determine whether the currently acquired AMT data meets the preset conditions. When the currently acquired AMT data meets the preset conditions, the currently acquired AMT data is output to the data processing terminal as the stably acquired AMT data.

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