An alternating electromagnetic field seismic monitoring and observation network

Abstract

This invention discloses an alternating electromagnetic field seismic monitoring network, comprising receiving electromagnetic field signals from high-power artificial and natural sources, and an alternating electromagnetic observation network composed of multiple receiving stations. The network receives electromagnetic field signals from artificial and natural sources through multiple observation stations deployed based on seismic distribution trends, and processes the observation data, including spectral analysis of the observed electromagnetic field time series to obtain the spectrum and self-power spectrum of each electromagnetic field component, as well as the cross-power spectrum between different components. This allows for the calculation of impedance reflecting underground electrical properties, as well as parameters such as apparent resistivity and impedance phase. Inversion is performed on apparent resistivity and impedance phase at different frequencies to obtain electrical structural parameters at different underground depths. This invention utilizes a wide frequency range of alternating electromagnetic field signals, which are most sensitive to earthquakes, and achieves comprehensive three-dimensional earthquake monitoring through long-term continuous observation by deploying an observation network in seismically active areas and key defense zones.

Description

Technical Field

[0001] This invention relates to the field of earthquake monitoring technology, and in particular to an alternating electromagnetic field earthquake monitoring and observation network that simultaneously receives signals from artificial and natural sources. Background Technology

[0002] Located in two major global seismic belts, my country experiences frequent, intense, shallow-focused, and widely distributed earthquakes. Earth's electromagnetic method is an important geophysical method for earthquake monitoring and prediction. Methods used for earthquake monitoring include DC resistivity sounding, geomagnetic field monitoring, and geoelectric field monitoring.

[0003] Although there is no seismic monitoring network that utilizes alternating electromagnetic fields, a large number of anomalies have been discovered in the alternating electromagnetic field frequency band through mobile observations or temporary single-point observations. Existing monitoring methods include DC resistivity sounding, geomagnetic field observation, and geoelectric field methods. Among them, DC resistivity sounding, which draws on the electrical sounding method used in mineral deposit exploration, sends DC current to the ground through electrodes at both ends of AB, measures the voltage value through MN, and obtains the resistivity of the ground using the coefficient of the observation device. It studies the change of resistivity over time to conduct earthquake monitoring and prediction. The disadvantages of DC resistivity sounding are: (1) due to the shielding of the underground high-pressure layer, the exploration depth is shallow, and the underground structure it reflects is only a few hundred meters deep, which cannot reach the depth of more than 10 kilometers for most shallow earthquakes; (2) it can only monitor changes in underground resistivity and cannot monitor changes in the spatial electromagnetic field; (3) it observes a constant DC field and cannot observe alternating fields; (4) it is often affected by non-seismic factors such as seasonal changes, weather changes, and grounding metallic facilities in the site.

[0004] Geomagnetic field observation utilizes traditional geomagnetic observation methods and has deployed dozens of observation stations across the country. Geomagnetic observation is divided into two categories: one is to observe the basic field, that is, to observe the Earth's absolute magnetic field, which is mainly used for the study of the global geomagnetic field. The other is to observe the changing magnetic field using fluxgate instruments, but the frequency range is low, with the highest sampling rate being 1Hz or 60 seconds. By observing the changes in the geomagnetic field over time, seismic anomalies can be studied. The disadvantages are: (1) The observed absolute field or very low frequency magnetic field does not include the alternating electromagnetic field in the frequency band above 1Hz, which has caused many seismic anomalies; (2) Geomagnetic observation rarely analyzes the alternating field components and their spectra that change over time, and mainly reflects the magnetic field above the ground, and is not sensitive to the underground electrical properties and their changes; (3) Due to the lack of synchronous observation of the electric field, it is not possible to monitor the impedance or resistivity of the ground and their changes; (4) Since the magnetic field signal mainly comes from the magnetosphere and ionosphere above the Earth, the random variation characteristics are obvious, and due to the influence of other interferences, it masks the identification of anomalies caused by seismic activity.

[0005] The seismic station employs the geoelectric field method, which observes the natural electric field or voltage between two electrodes at a certain distance. Its observation equipment is... Figure 1 Similar to the MN measurement device. The measured signal is a natural source field, mainly the Earth's induced electric field generated by changes in the magnetic field, which is different from the DC resistivity method for observing artificial source signals. The highest sampling rate of the observed signal is 1Hz. In my country, geoelectric field stations usually use minute values, and the effective signal frequency band is less than 1Hz. By studying the changes of the observed electric field over time, earthquake prediction and monitoring are studied. The shortcomings are: (1) It is difficult to detect short-term earthquake anomalies of alternating electromagnetic fields higher than 1Hz when observing and studying electric fields with very low frequencies; (2) Since only the electric field is observed, it is impossible to determine whether the observed signal is generated by the observation system itself or caused by changes in the external field; (3) The observed electric field is greatly affected by electromagnetic field sources near the Earth's surface and observation point, as well as above the ground, and is not sensitive enough to underground electrical changes; (4) The observed electric field is highly random and easily interfered with, affecting the identification of earthquake anomalies.

[0006] Semi-continuous or mobile magnetotelluric observations are conducted using a single station or a few stations. This method observes five (two mutually orthogonal horizontal electric field components and two horizontal magnetic field components, and one vertical magnetic field component) or four electromagnetic field components (observing two mutually orthogonal horizontal electric field components and two horizontal magnetic field components) of natural source electromagnetic fields. The spectrum of the electromagnetic field is obtained through spectral analysis of the alternating electromagnetic field, and then the impedance and apparent resistivity reflecting the low electrical properties are obtained. The main purpose is to observe the changes in underground resistivity in the area where the station is located and to study seismic anomalies that may occur during earthquakes. The defects of single-point mobile magnetotelluric observations are: (1) These stations are mobile observation points, and repeated observations are conducted within a period of time without continuous observation. There are very few observation points, generally only one or two measurement points; (2) Only natural source signals are observed, which are easily affected by electromagnetic field interference caused by human activities, which is not conducive to the identification of anomalies that may be related to earthquakes; (3) Only the changes in typical parameters such as underground resistivity are studied, and the changes from space and underground electromagnetic fields are not considered. Therefore, an alternating electromagnetic field seismic monitoring and observation network is needed. Summary of the Invention

[0007] The purpose of this invention is to provide an alternating electromagnetic field seismic monitoring network based on simultaneous observation of artificial and natural sources, which can simultaneously monitor the magnetic fields of natural and artificial sources as well as the continuous changes of underground structures over time, and obtain earthquake precursors and related electromagnetic information.

[0008] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0009] The first aspect of this invention provides a seismic monitoring and observation network that simultaneously receives alternating electromagnetic fields from both artificial and natural sources. This network includes multiple stations capable of receiving high-power artificial electromagnetic fields and electromagnetic signals from natural sources. Subsurface resistivity anomalies and electromagnetic field anomalies in the seismic source area are processed using observation data from multiple stations deployed based on seismic distribution trends to obtain electromagnetic anomaly information beneficial for earthquake prediction. The network includes the following steps:

[0010] By performing spectral analysis on the observed electromagnetic field time series, the spectrum and self-power spectrum of each electromagnetic field component, as well as the cross-power spectrum of different components, can be obtained. The impedance reflecting the underground electrical properties, as well as the apparent resistivity and impedance phase parameters, can be calculated.

[0011] By inverting apparent resistivity and other parameters, underground electrical structure parameters are obtained, and the alternating electromagnetic field earthquake is determined by the abnormal changes in the parameters of the underground electrical structure.

[0012] The formula for calculating impedance from the spectrum of each component of the electromagnetic field is as follows:

[0013] Ex=Zxx Hx+ZxyHy

[0014] Ey=Zyx Hx+ZyyHy

[0015] Hz = A Hx + B Hy

[0016] In the formula, Zxx, Zxy, Zyx, Zyy are impedance tensor elements, and A and B are magnetic field transfer functions;

[0017] Apparent resistivity and impedance phase can be calculated from the impedance tensor elements using the following formula:

[0018] ρ ij =0.2T|Z ij | 2

[0019] φ ij =arctan(Z) ij )

[0020] Where, ρ ij φ represents apparent resistivity. ij This indicates the impedance phase, and the subscript ij indicates x or y.

[0021] By using apparent resistivity and impedance phase, we can qualitatively analyze the underground electrical structure information of observation stations and quantitatively invert the underground resistivity structure.

[0022] Furthermore, the observed quantities include the north-south electric field Ex component, the magnetic field Hx component, the east-west electric field Ey component, the magnetic field Hy component, and the vertical magnetic field Hz component.

[0023] Electric field component measurements are performed by connecting the instrument and a grounding electrode 25-50 meters apart using cables to collect electric field signals. Magnetic field signals are received using an inductive magnetic probe.

[0024] Furthermore, the station equipment employs 10 observation channels, of which 5 channels are used for continuous 24-hour observation of low-frequency natural fields, and the other 5 channels are used for segmented observation of artificial sources and high-frequency and mid-frequency natural sources during non-artificial source observation periods.

[0025] To ensure rapid transmission of observational data, electromagnetic field signals were received at different sampling rates in different time periods. For artificial source data, signals were transmitted at fixed times in the morning and evening, and the receiver used different sampling rates to receive artificial source signals of different frequencies. For low-frequency signals from natural sources, the receiver used a lower sampling rate for continuous 24-hour observation. For high-frequency and mid-frequency signals from natural sources, during non-artificial source signal transmission periods, the receiver was received every 10 minutes, collecting at least 4 segments of 4096 data samples to ensure uniform distribution of high and mid-frequency data throughout the day.

[0026] Furthermore, the effective frequency range of natural source electromagnetic fields observed by the seismic network covers 0.001 to 1000 Hz, while the effective frequency range of artificial source electromagnetic fields is 0.1 to 300 Hz.

[0027] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0028] This invention utilizes the frequency range of alternating electromagnetic fields most sensitive to earthquakes. By deploying an observation network in seismically active areas and key defense zones for long-term continuous observation, it can observe both natural and artificial electromagnetic field signals, as well as underground electrical structures and their changes, and spatial electromagnetic fields and their changes, thereby achieving comprehensive three-dimensional monitoring of earthquakes.

[0029] This invention can be used to compare ground-based and satellite observation data and their anomalies, and can also utilize satellite observations of electromagnetic field signals artificially emitted from the ground; it can also be used for observational research on underground resources and deep crustal structures; it is beneficial for studying the mechanism of seismic electromagnetic anomaly response across the entire space-space lithosphere-atmosphere-ionosphere. Furthermore, it can facilitate interdisciplinary research and applications in fields such as communications and the space electromagnetic environment.

[0030] This invention expands the distribution range of the seismic network to cover as many areas as possible that are active in strong earthquakes and key monitoring areas.

[0031] 1) For artificial source signals, the transmitting equipment can be improved to extend the frequency range to both high and low frequencies.

[0032] 2) Different types of transmitters can be used, such as magnetohydrodynamic transmitters, nuclear power transmitters, and industrial power transmitters, while the receiving network scheme remains basically unchanged. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the alternating electromagnetic field network composition of an alternating electromagnetic field seismic monitoring and observation network according to the present invention;

[0034] Figure 2 This is a schematic diagram of the observation system composition of each station in the electromagnetic network of the alternating electromagnetic field seismic monitoring and observation network of the present invention.

[0035] Figure 3 This invention relates to a time series of electromagnetic field signals of five components and four frequencies from natural and artificial sources that can be received by a station in an alternating electromagnetic field seismic monitoring and observation network.

[0036] The five components, from top to bottom, are Ex, Ey, Hx, Hy, Hz, and artificial source signals at four frequencies (F1 to F4) were transmitted within 1.5 hours.

[0037] Figure 4 This invention relates to an electromagnetic field processing and analysis process for an alternating electromagnetic field seismic monitoring and observation network.

[0038] Figure 5 This is a distribution map of 15 stations in a certain region of the alternating electromagnetic field seismic monitoring and observation network of the present invention;

[0039] Figure 6 The apparent resistivity and impedance phase curves of the Jinggu station within a regional seismic monitoring and observation network of an alternating electromagnetic field according to the present invention are shown.

[0040] Figure 7 This is a planar distribution diagram of the 216Hz Hx spectrum of a certain network area of ​​an alternating electromagnetic field seismic monitoring and observation network according to the present invention.

[0041] Figure 8 This is a planar contour map of the apparent resistivity at 120Hz in a certain area of ​​an alternating electromagnetic field seismic monitoring and observation network according to the present invention.

[0042] Figure 9 This is a resistivity distribution map at a depth of 15 km obtained by inversion from an alternating electromagnetic field seismic monitoring and observation network according to the present invention.

[0043] Figure 10 This is a resistivity distribution map at different depths (1km, 2km, 5km, 10km, 15km) obtained by inversion of a certain area of ​​an alternating electromagnetic field seismic monitoring and observation network according to the present invention.

[0044] Figure 11This invention relates to the changes in the 4Hz Hx component spectrum of the Jinggu station before and after the 5.1 magnitude earthquake at Shengtang, which occurred at 1:23 AM on September 23, 2016, according to an alternating electromagnetic field seismic monitoring and observation network of the present invention. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] The following defines the abbreviations and key terms used in this technical solution:

[0047] Alternating electromagnetic field: An electromagnetic field that varies with time; its study and application conform to the law of electromagnetic induction.

[0048] A network of observatories: A network of observatories arranged over a certain area on the ground for one or more specific purposes.

[0049] Seismic electromagnetic anomalies: Electromagnetic field phenomena with abnormal background changes associated with seismic activity.

[0050] Electromagnetic field spectrum: The electromagnetic field in the frequency domain is obtained by spectral analysis of the time-domain electromagnetic field signal.

[0051] Apparent resistivity and impedance phase: Impedance, which reflects the underground resistivity structure, is calculated from electromagnetic field data observed on the ground. The resistivity data obtained from further calculations is called apparent resistivity. Phase is calculated from the real and imaginary parts of the impedance element. The underground resistivity distribution can be obtained through techniques such as inversion.

[0052] Resistivity: A parameter reflecting the electrical conductivity of rocks and minerals, which is related to the composition, porosity, structure, and water content of the rocks and minerals.

[0053] "Cloud map": Borrowing terminology from meteorology and other fields, it reflects the spatial distribution characteristics of regional physical properties such as electromagnetic field spectrum, resistivity, and other parameters.

[0054] Three-dimensional monitoring of earthquake anomalies: This method monitors earthquake anomalies from multiple angles and using multiple parameters to more accurately identify anomalies.

[0055] A schematic diagram of the alternating electromagnetic field network is shown below. Figure 1 As shown.

[0056] Figure 1T: High-power artificial electromagnetic field signal transmitter; R: A network of stations, which can be regularly distributed, arbitrarily shaped, or laid out according to earthquake distribution or geological structure; Wa: The propagation path of the artificial electromagnetic field in the waveguide layer, which can reach thousands of kilometers; Wn: The network area where the natural electromagnetic field propagates to the ground; Wi: The transmission of artificial and natural electromagnetic fields underground; Ws: When an earthquake occurs, the electromagnetic field excited by seismic activity propagates to the ground, and the electrical properties of the source area, such as resistivity, also change.

[0057] like Figure 1 As shown, ground-based alternating electric field (AEF) networks can simultaneously observe both natural and artificial electromagnetic field signals. These networks can be deployed over a distance of thousands of kilometers. When an earthquake occurs, the resistivity of the epicenter changes, which can be observed through ground-based networks. Electromagnetic anomalies are also generated in the epicenter, and these can also be observed through the ground-based networks. Due to the large coverage area of ​​the networks, the spatial distribution differences and characteristics of electromagnetic anomalies can be comprehensively analyzed. By observing underground resistivity anomalies and ground-based electromagnetic anomalies, the characteristics of the anomalies can be analyzed in three dimensions, and the authenticity of the anomalies can be identified. High-power artificial source signals can significantly suppress the influence of other interference factors.

[0058] A schematic diagram of the observation system composition of each station in the electromagnetic network is shown below. Figure 2 The receiving equipment at the observation station can be located inside the seismic station, or elsewhere outside the station, or in a blank area when needed. The observations include five components: north-south electric field (Ex) and magnetic field (Hx) components, east-west electric field (Ey) and magnetic field (Hy) components, and a vertical magnetic field component (Hz). Electric field component measurements use cables to connect the instrument to grounded electrodes 50-100 meters apart to collect signals. Magnetic field signals are received using an inductive magnetic probe (magnetic rod). To ensure uninterrupted continuous observation and prevent interference from power sources, solar power is used. The main observation unit is housed in a room or other windproof and rainproof facility or container (referred to as the observation room).

[0059] The station equipment employs 10 observation channels, with 5 channels used for continuous 24-hour observation of low-frequency natural fields, and the other 5 channels used for segmented observation of artificial sources and high-frequency and mid-frequency natural sources during non-artificial source observation periods. This allows the same instrument to simultaneously observe electromagnetic field signals from both natural and artificial sources. To ensure rapid data transmission, different sampling rates are used to receive electromagnetic field signals at different times. For artificial source data, signals are transmitted at fixed times in the morning and evening, and the receiver uses different sampling rates to receive signals from different frequencies of artificial sources. For low-frequency natural source signals, the receiver uses a lower sampling rate for continuous 24-hour observation. For high-frequency and mid-frequency natural source signals, during non-artificial source signal transmission periods, reception is performed every 10 minutes, collecting at least 4 segments totaling 4096 data points to ensure uniform distribution of high and mid-frequency data throughout the day.

[0060] The effective frequency range of natural electromagnetic fields observed by the seismic network covers 1000–0.001 Hz, while the effective frequency range of artificial electromagnetic fields is 300–0.1 Hz. The observed data can be transmitted to data processing, analysis, and forecasting departments via wired or wireless networks for real-time or near-real-time processing and analysis.

[0061] The original time series of observed natural and artificial source field signals are as follows: Figure 2 The horizontal axis represents time, and the vertical axis represents signal amplitude. The graph shows artificial source signals at four frequencies and natural source signals between and outside of them. The amplitude of the artificial source signals is greater than that of the natural source signals.

[0062] like Figure 3 As shown, by performing spectral analysis on the observed electromagnetic field time series, the spectrum of each electromagnetic field component can be obtained. This allows for the calculation of parameters reflecting subsurface electrical properties, such as impedance, apparent resistivity, and impedance phase. These parameters are fundamental to reflecting subsurface electrical properties and the changes in the spatial electromagnetic field. Inversion of apparent resistivity and other parameters yields the subsurface electrical structure, enabling the observation network to directly monitor anomalous changes in this structure.

[0063] The formula for calculating impedance from the spectrum of each component of the electromagnetic field (Ex, Ey, Hx, Yy, and Hz) is as follows:

[0064] Ex=Zxx Hx+ZxyHy

[0065] Ey=Zyx Hx+ZyyHy

[0066] Hz = A Hx + B Hy

[0067] In the formula, Zxx, Zxy, Zyx, and Zyy are the impedance tensor elements, and A and B are the magnetic field transfer functions. The apparent resistivity and impedance phase can be calculated from the impedance tensor elements using the following formula:

[0068] ρ ij =0.2T|Z ij | 2 φ ij =arctan(Z) ij )

[0069] Where, ρ ij φ represents apparent resistivity. ij This indicates the impedance phase, and the subscript ij indicates x or y.

[0070] Apparent resistivity, impedance phase, and magnetic field transfer function can be used to qualitatively analyze the underground electrical structure information of observation stations and quantitatively invert the underground resistivity structure.

[0071] The data processing and analysis process can be described as follows: Figure 4 It is indicated that the alternating electromagnetic field network method is used, with stations distributed in the seismically active zone (a certain region) and the metropolitan area, each region including 15 stations. Figure 5 This is a distribution map of 15 stations in a certain region's network area (marked in yellow).

[0072] Figure 6 This indicates the apparent resistivity and impedance phase curves obtained from the Jinggu station within a certain regional seismic network. These are fundamental parameters for seismic anomaly detection in surface observation data. They reflect the subsurface electrical structure, and by inverting these parameters, the electrical distribution of the baseline, i.e., the electrical structure, can be obtained. If the subsurface structure remains unchanged, the subsurface electrical structure is stable, and the apparent resistivity and phase curves will not change. When earthquakes or other events occur, the subsurface structure changes, and the apparent resistivity and phase parameters will also change.

[0073] A planar electromagnetic field energy cloud map can be calculated from the spectrum of the observed frequency range, which includes five components. This spectrum map is similar to a meteorological "cloud map." Under normal circumstances, the cloud map should be stable. When anomalies occur, such as earthquakes, the cloud map will change, thus allowing the identification of the frequency and region of the anomaly. Figure 7 The given image is a spectral plane distribution map of the Hx spectrum at 216Hz for a certain network area. Similar cloud maps can be obtained for other components.

[0074] It resembles the clouds in the electromagnetic power spectrum above. Figure 1 Similarly, cloud maps reflecting the electrical structure at different underground depths can be obtained, and when anomalies occur, the frequency and location of the anomalies can be identified from the map. Figure 8 The apparent resistivity ρ of a certain region at 120Hz yx A plane contour map.

[0075] By inverting the apparent resistivity and phase obtained from ground observations, the underground electrical (resistivity) structure of the network area can be obtained (e.g., ...). Figure 9 When the underground structure remains unchanged, the inverted underground resistivity distribution is stable. However, when earthquakes or other events occur, the underground structure is damaged or fractured, the porosity of the rock changes, and the distribution of underground fluids also changes, thus altering the underground resistivity.

[0076] Resistivity distribution maps at different depths, based on Figure 10 When an earthquake anomaly occurs, in addition to identifying the area where the anomaly occurs, the depth at which the anomaly occurs can also be identified, allowing for earthquake anomaly monitoring from a three-dimensional perspective.

[0077] For a specific earthquake, data from various stations within the seismic network can be analyzed to explore whether there are any abnormal changes in the parameters of the corresponding stations before and after the earthquake. This allows for the study of the characteristics of the anomalies in relevant parameters before and after the earthquake, thus contributing to earthquake prediction. Figure 11 The graph shows the changes in the 4Hz Hx component spectrum at Jinggu station before and after the 5.1 magnitude earthquake at Shengtang at 1:23 AM on September 23, 2016. The black line represents changes in the spectrum of natural sources, and the red line represents changes in the spectrum of artificial sources. As can be seen from the graph, it is difficult to detect any abnormal changes in the spectrum of natural sources, while the spectrum of artificial sources gradually increased three days before the earthquake, and then returned to normal values ​​after the earthquake.

[0078] The alternating electromagnetic field network was proposed to address the shortcomings of existing methods. Its advantages include: (1) It can observe underground electrical structures and their continuous changes, reaching depths below the source depth of most earthquakes, and even below the crust. It can also monitor changes in electromagnetic fields from space and underground on the ground, forming a true three-dimensional observation. (2) The frequency band of the observed alternating electromagnetic field is very wide. Currently, the high frequency band reaches several kilohertz, and the low frequency band can reach below 1000 seconds, covering the main frequency bands and adjacent frequency bands of previously discovered earthquake anomalies. (3) The observation is carried out in a network manner, with many stations observing simultaneously over a range of several thousand kilometers. This allows for comparison of the characteristics of electromagnetic anomaly data in different regions (earthquake zones and areas far from earthquakes), which is beneficial for capturing the location and spatial distribution of earthquake anomalies and their temporal variation characteristics. (4) It can observe both natural source electromagnetic fields and artificial source electromagnetic fields. Currently, the signal of high-power artificial electromagnetic field propagates thousands of kilometers away through the waveguide layer between the Earth and the ionosphere, with a frequency range of 300 to 0.1 Hz. Future technological developments can make the frequency range wider; (5) Observing artificial source signals can greatly suppress the influence of interference signals, highlight useful signals, and improve the ability to identify and capture earthquake anomalies; (6) Long-term continuous observation by the network can compare data at different times (day and night, different dates, different seasons, earthquake and non-earthquake times, etc.), which is conducive to comparing and identifying the authenticity of earthquake anomalies and to identifying and capturing the temporal distribution characteristics of earthquake anomalies.

[0079] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A seismic monitoring and observation network using alternating electromagnetic fields, characterized in that... This includes multiple stations receiving high-power artificial source electromagnetic fields and natural source electromagnetic signals. Subsurface resistivity and electromagnetic field anomalies in the seismic source area are processed using observation data from multiple stations deployed based on seismic distribution trends to obtain electromagnetic anomaly information beneficial for earthquake prediction. This process includes the following steps: By performing spectral analysis on the observed electromagnetic field time series, the spectrum and self-power spectrum of each electromagnetic field component, as well as the cross-power spectrum of different components, are obtained. The impedance reflecting the underground electrical properties, as well as the apparent resistivity and impedance phase parameters, are calculated. By inverting apparent resistivity, the electrical structural parameters of the subsurface are obtained, and the anomaly changes in these parameters are used to determine the alternating electromagnetic field earthquake. The formula for calculating impedance from the spectrum of electromagnetic field observations is as follows: Ex=Zxx Hx+ZxyHy Ey=Zyx Hx+ZyyHy Hz = A Hx + B Hy In the formula, Zxx, Zxy, Zyx, and Zyy are the impedance tensor elements, and A and B are the magnetic field transfer functions; The apparent resistivity and impedance phase are calculated from the impedance tensor elements using the following formula: ； Where, ρ ij Φ represents apparent resistivity. ij This indicates the impedance phase, and the subscript ij indicates x or y; Qualitative analysis of the underground electrical structure information of the observation station and quantitative inversion of the underground resistivity structure are performed using apparent resistivity and impedance phase. The observed quantities include the north-south electric field Ex component, the magnetic field Hx component, the east-west electric field Ey component, the magnetic field Hy component, and the vertical magnetic field Hz component. Electric field measurements are performed by connecting the instrument and grounding electrodes 30-50 meters apart using cables to collect mutually perpendicular horizontal electric field signals. Magnetic field measurements are performed by using an inductive magnetic field sensor to receive three mutually perpendicular magnetic field signals corresponding to the direction of the electric field. To ensure rapid transmission of observation data, electromagnetic field signals are received at different sampling rates in different time periods. For artificial source data, signals are transmitted at fixed times in the morning and evening, and the receiver uses different sampling rates to receive artificial source transmission signals of different frequencies. For natural source low-frequency signals, the receiver uses a dedicated low-frequency channel for continuous 24-hour observation. For high-frequency and mid-frequency natural source signals, during non-artificial source signal transmission periods, the receiver is received every 10 minutes, collecting at least 4 segments of 4096 data samples to ensure uniform distribution of high and mid-frequency data throughout the day.

2. The alternating electromagnetic field seismic monitoring and observation network according to claim 1, characterized in that, The station equipment uses 10 channels for observation, of which 5 channels are used for continuous low-frequency observation of the natural field 24 hours a day, and the other 5 channels are used for frequency-segmented observation of artificial sources and high-frequency and medium-frequency segmented observation of natural sources during non-artificial source observation periods.

3. The alternating electromagnetic field seismic monitoring and observation network according to claim 1, characterized in that, The effective frequency range of natural source electromagnetic fields observed by the seismic network covers 0.001~1000Hz, while the effective frequency range of artificial source electromagnetic fields is 0.1~300Hz.

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