A method and system for terrain correction of transient electromagnetic data applied to complex terrain

Abstract

The present invention proposes a terrain correction method and system for transient electromagnetic data applied to complex terrain, belonging to the technical field of transient electromagnetic data correction. A complex terrain model including the terrain of a target area is constructed to perform three-dimensional forward simulation calculation to obtain transient electromagnetic data of the complex terrain with terrain; on this basis, a three-dimensional forward simulation calculation of the same transient electromagnetic parameters is performed on a flat terrain model that does not contain any terrain at all to obtain transient electromagnetic data of the flat terrain without terrain; the transient electromagnetic data of the flat terrain without terrain is subtracted from the transient electromagnetic data of the complex terrain with terrain to obtain a complex terrain response caused purely by the complex terrain; and the complex terrain response is eliminated from the measured transient electromagnetic data to complete the terrain correction of the measured transient electromagnetic data; the complex terrain response is eliminated from the measured transient electromagnetic data in the complex terrain area, the error caused by the terrain effect is reduced, and the credibility of the transient electromagnetic data is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of transient electromagnetic data correction, and in particular to a transient electromagnetic data terrain correction method and system applied to complex terrain. Background Art

[0002] Transient electromagnetic method is an electromagnetic exploration method. The basic principle is to use a grounded or ungrounded transmitting source to establish a primary current pulse field in the detection area, and observe the secondary electromagnetic field generated by the induced eddy current in the conductive earth during the power outage. By observing and recording the secondary field response, the electrical distribution of the underground medium can be further inferred. However, when working in complex terrain areas, in addition to the normal transient electromagnetic response, the complex terrain in the complex terrain area also produces a time-varying secondary field under the stimulation of the field source. This phenomenon is called the terrain effect. The terrain effect will be superimposed on the transient electromagnetic response, causing a strong distortion of the transient electromagnetic response curve, resulting in a significant increase in data complexity and an inability to effectively explain the electrical distribution of the underground medium. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for terrain correction of transient electromagnetic data applied to complex terrain, which eliminates the terrain response caused by terrain effects in the measured transient electromagnetic data in complex terrain areas and improves the credibility of the data.

[0004] To achieve the above object, on the one hand, the present invention provides the following scheme:

[0005] A transient electromagnetic data terrain correction method applied to complex terrain, the transient electromagnetic data terrain correction method comprising the following steps:

[0006] Pulse excitation is performed on the target area according to preset transient electromagnetic parameters, and transient electromagnetic data of the target area is collected to obtain measured transient electromagnetic data;

[0007] According to the terrain characteristics of the target area, a complex terrain model and a flat terrain model are established respectively;

[0008] According to the preset transient electromagnetic parameters, the transient electromagnetic data of the complex terrain model and the flat terrain model are simulated and calculated to obtain the transient electromagnetic data of the complex terrain and the transient electromagnetic data of the flat terrain;

[0009] Obtaining a complex terrain response according to the complex terrain transient electromagnetic data and the flat terrain transient electromagnetic data;

[0010] Corrected transient electromagnetic data are obtained according to the measured transient electromagnetic data and the complex terrain response.

[0011] Optionally, the preset transient electromagnetic parameters include resistivity, relative magnetic permeability and relative dielectric constant.

[0012] Optionally, before obtaining the complex terrain response according to the complex terrain transient electromagnetic data and the flat terrain transient electromagnetic data, the transient electromagnetic data terrain correction method further includes:

[0013] The valid data interval of the complex terrain transient electromagnetic data, the valid data interval of the flat terrain transient electromagnetic data and the valid data interval of the measured transient electromagnetic data are determined respectively.

[0014] Optionally, the respectively determining the valid data interval of the complex terrain transient electromagnetic data, the valid data interval of the flat terrain transient electromagnetic data, and the valid data interval of the measured transient electromagnetic data specifically includes:

[0015] Determine the shut-off time of the complex terrain transient electromagnetic data as the starting point of the valid data interval of the complex terrain transient electromagnetic data;

[0016] Determining a shut-off time of the flat terrain transient electromagnetic data as a starting point of a valid data interval of the flat terrain transient electromagnetic data;

[0017] The shut-off time of the measured transient electromagnetic data is determined as the starting point of the valid data interval of the measured transient electromagnetic data.

[0018] Optionally, the respectively determining the valid data interval of the complex terrain transient electromagnetic data, the valid data interval of the flat terrain transient electromagnetic data, and the valid data interval of the measured transient electromagnetic data specifically includes:

[0019] The complex terrain transient electromagnetic data is subjected to a channel extraction process; the channel extraction process is to randomly extract a number of time channels from all the time channels of the complex terrain transient electromagnetic data;

[0020] Performing extraction processing on the flat terrain transient electromagnetic data;

[0021] The flat terrain transient electromagnetic data is subjected to extraction processing.

[0022] Optionally, the complex terrain response is calculated according to the following formula:

[0023] dB z / dt (topography) =dB z / dt (hill-in) -dB z / dt (hill-off)

[0024] Where, dBz / dt (topography) is the complex terrain response, dB z / dt (hill-in) For complex terrain transient electromagnetic data, dB z / dt (hill-off) Transient electromagnetic data for flat terrain.

[0025] Optionally, the corrected transient electromagnetic data is calculated according to the following formula:

[0026] dB z / dt (corrected) =dB z / dt (measured) -dB z / dt (topography)

[0027] Where, dB z / dt (corrected) To correct transient electromagnetic data, dB z / dt (measured) is the measured transient electromagnetic data, dB z / dt (topography) Response to complex terrain.

[0028] Corresponding to the aforementioned transient electromagnetic data terrain correction method applied to complex terrain, the present invention also provides a transient electromagnetic data terrain correction system applied to complex terrain. When the transient electromagnetic data terrain correction system applied to complex terrain is run by a computer, it executes the transient electromagnetic data terrain correction method applied to complex terrain as described above.

[0029] On the other hand, the present invention also provides a method for determining the electrical distribution of underground media, comprising:

[0030] Execute the transient electromagnetic data terrain correction method as described above to obtain corrected transient electromagnetic data of the target area;

[0031] The corrected transient electromagnetic data are processed and interpreted to obtain the electrical distribution of the underground medium in the target area.

[0032] Corresponding to the aforementioned method for determining the electrical property distribution of underground media, a system for determining the electrical property distribution of underground media is also provided. When the electrical property distribution determination system is run by a computer, it executes the aforementioned method for determining the electrical property distribution of underground media.

[0033] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0034] The present invention provides a terrain correction method and system for transient electromagnetic data applied to complex terrain. A complex terrain model including the terrain of a target area is constructed and three-dimensional forward simulation calculation is performed to obtain transient electromagnetic data of the complex terrain with terrain. On this basis, a three-dimensional forward simulation calculation of the same transient electromagnetic parameters is performed on a flat terrain model that does not contain any terrain at all to obtain transient electromagnetic data of the flat terrain without terrain. The transient electromagnetic data of the flat terrain without terrain is subtracted from the transient electromagnetic data of the complex terrain with terrain to obtain a complex terrain response caused purely by the complex terrain. The complex terrain response is then eliminated from the measured transient electromagnetic data to complete the terrain correction of the measured transient electromagnetic data. The complex terrain response is eliminated from the measured transient electromagnetic data in the complex terrain area, thereby reducing the error caused by the terrain effect and improving the credibility of the transient electromagnetic data. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A flowchart of a method for terrain correction of transient electromagnetic data applied to complex terrain provided in Example 1 of the present invention;

[0037] Figure 2 A schematic diagram of the layout of a transient electromagnetic data acquisition device in the method provided in Example 1 of the present invention;

[0038] Figure 3a A schematic diagram of a complex terrain model in the method provided in Example 1 of the present invention;

[0039] Figure 3b A schematic diagram of a flat terrain model in the method provided in Example 1 of the present invention;

[0040] Figure 4 A comparison diagram of transient electromagnetic data of a flat terrain model and a mountain terrain model in the method provided in Example 1 of the present invention;

[0041] Figure 5a A multi-channel map of transient electromagnetic data of a mountain terrain model in the method provided in Example 1 of the present invention;

[0042] Figure 5b A multi-channel map of transient electromagnetic data of a flat terrain model in the method provided in Example 1 of the present invention;

[0043] Figure 6A complex terrain response curve diagram in the method provided in Example 1 of the present invention;

[0044] Figure 7 A graph showing corrected transient electromagnetic data in the method provided in Example 1 of the present invention;

[0045] Figure 8 A multi-channel map of transient electromagnetic data after correction in the method provided in Example 1 of the present invention;

[0046] Fig. 9 A schematic diagram of the structure of a transient electromagnetic data terrain correction system applied to complex terrain provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] In terms of current data interpretation technology, traditional electromagnetic exploration methods such as apparent resistivity imaging and one-dimensional inversion methods are generally used to process and interpret transient electromagnetic data in complex terrain areas. However, transient electromagnetic data in complex terrain areas are severely distorted due to the influence of terrain effects, which greatly increases the complexity of the data and makes it impossible to effectively interpret the electrical distribution of underground media.

[0049] The traditional ratio correction method is a correction method that uses empirical correction coefficients to reset the apparent resistivity parameters. The main feature of this type of method is fast correction speed, but the correction effect depends on the selection of correction coefficients. There are currently many ways to select correction coefficients, and the correction accuracy is generally not high. The apparent resistivity parameter is not the true resistivity of a certain rock, but a parameter calculated based on electromagnetic response to reflect the comprehensive reflection of underground electrical inhomogeneities. The parameter itself has introduced certain errors. Transient electromagnetic data correction calculation based on apparent resistivity will affect the correction effect to a certain extent and reduce the accuracy of data interpretation.

[0050] With the development of transient electromagnetic forward and inversion technology and computer hardware and software in recent years, three-dimensional inversion methods with terrain have been realized. This type of method can well restore the real information of underground anomalies in complex terrain conditions by selecting appropriate initial models and parameters. However, when performing three-dimensional inversion of transient electromagnetic data in complex terrain areas, the numerical simulation of pure terrain is extremely computationally intensive and the calculation time is generally long. It has extremely high requirements on computer hardware conditions and the selection of initial models. If a horizontal surface model is used to force fitting of terrain response data during the inversion process, "false anomalies" are very likely to occur, which will affect the final inversion effect.

[0051] The purpose of the present invention is to provide a method and system for terrain correction of transient electromagnetic data applied to complex terrain, which eliminates the terrain response caused by terrain effects in the measured transient electromagnetic data in complex terrain areas and improves the credibility of the data.

[0052] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] Embodiment 1:

[0054] This embodiment provides a method for terrain correction of transient electromagnetic data applied to complex terrain. Figure 1 As shown in the flowchart, the transient electromagnetic data terrain correction method includes the following steps:

[0055] Before executing the transient electromagnetic data terrain correction method, a transient electromagnetic data acquisition device is deployed in the target area to collect transient electromagnetic data, such as Figure 2 As shown in the figure, a three-dimensional coordinate system is established in the target area, with the X axis along the laying direction of the transmitter, the Y axis perpendicular to the laying direction of the transmitter, and the Z axis vertically downward. The overall coordinate system meets the right-hand coordinate system criterion. The excitation transceiver includes a transmitter and a receiver; the transmitter is a 1000m long wire, the transmitting current is 10A, the transmitting waveform is a step wave, the center point coordinates are (0m, -500m, 0m), the receiving device has a total of 33 measuring points, the measuring point spacing is 50m, and the sampling time is 10 -7 s~10 -1 s, which is discretized into 1200 time steps. The total length of the survey line is 1600m, located at Y = 500m. During the measurement process, the height of the transceiver above the ground is approximately regarded as 0m.

[0056] S1. Collecting measured transient electromagnetic data; performing pulse excitation on the target area according to preset transient electromagnetic parameters, collecting transient electromagnetic data of the target area, and obtaining measured transient electromagnetic data; in this embodiment, the preset transient electromagnetic parameters include resistivity, relative magnetic permeability and relative dielectric constant.

[0057] S2, establish a complex terrain model with terrain and a flat terrain model without terrain; according to the terrain characteristics of the target area, respectively establish a complex terrain model and a flat terrain model; in this embodiment, by obtaining the DEM elevation data of the target area, a complex terrain model that conforms to the terrain characteristics of the target area is established. Figure 3a and Figure 3b As shown, Figure 3a For complex terrain models, Figure 3b is a flat terrain model, where the air resistivity is 10 8 Ω·m, relative magnetic permeability is 1H / m, the resistivity of the mountain and the underground medium are both 100Ω·m, the relative magnetic permeability is 1H / m, the highest peak is 200m, the slope angle is 45°, and the top of the mountain is located at (0m, 500m, -200m).

[0058] S3. Perform simulation calculations to obtain transient electromagnetic data of complex terrain and flat terrain; perform simulation calculations of transient electromagnetic data on the complex terrain model and the flat terrain model according to the preset transient electromagnetic parameters to obtain transient electromagnetic data of complex terrain and transient electromagnetic data of flat terrain.

[0059] Since transient electromagnetic data are sampled densely and the data volume is large, it will take a lot of time to process all of these data. Therefore, before analyzing the transient electromagnetic data, it is necessary to pre-process the transient electromagnetic data of each model and the measured transient electromagnetic data to determine the effective data interval of complex terrain transient electromagnetic data, the effective data interval of flat terrain transient electromagnetic data, and the effective data interval of measured transient electromagnetic data. Specifically, it includes:

[0060] Determine the off-time of complex terrain transient electromagnetic data as the starting point of the valid data interval of the complex terrain transient electromagnetic data; perform channel extraction processing on the complex terrain transient electromagnetic data; the channel extraction processing is to randomly extract a number of time channels from all time channels of the complex terrain transient electromagnetic data.

[0061] The off-time of the flat terrain transient electromagnetic data is determined as the starting point of the valid data interval of the flat terrain transient electromagnetic data; and the flat terrain transient electromagnetic data is subjected to channel extraction processing.

[0062] The off-time of the measured transient electromagnetic data is determined as the starting point of the effective data interval of the measured transient electromagnetic data; and the flat terrain transient electromagnetic data is subjected to channel extraction processing.

[0063] In this embodiment, taking a single measuring point as an example, the off-time of the data of the measuring point is determined as the starting position of the valid data interval, and the end position is determined with reference to the commonly used sampling time of the current transient electromagnetic instrument, and data extraction is performed; then the responses of the same time channel of the entire measuring line are connected, and different line segments represent different time channels, so that the change of transient electromagnetic data with time can be obtained.

[0064] S4, extracting complex terrain response; in this embodiment, the complex terrain response is obtained according to the complex terrain transient electromagnetic data and the flat terrain transient electromagnetic data; specifically, the complex terrain transient electromagnetic data and the flat terrain transient electromagnetic data are subtracted to obtain the complex terrain response, and the complex terrain response is calculated according to the following formula:

[0065] dB z / dt (topography) =dB z / dt (hill-in) -dB z / dt (hill-off)

[0066] Where, dB z / dt (topography) is the complex terrain response, dB z / dt (hill-in) For complex terrain transient electromagnetic data, dB z / dt (hill-off) Transient electromagnetic data for flat terrain.

[0067] S5. Correcting the measured transient electromagnetic data; in this embodiment, corrected transient electromagnetic data are obtained according to the measured transient electromagnetic data and the complex terrain response; specifically, the correction can be completed by eliminating the complex terrain response from the measured transient electromagnetic data. In this embodiment, the corrected transient electromagnetic data are calculated according to the following formula:

[0068] dB z / dt (corrected) =dB z / dt (measured) -dB z / dt (topography)

[0069] Where, dB z / dt (corrected) To correct transient electromagnetic data, dB z / dt (measured) is the measured transient electromagnetic data, dB z / dt (topography) Response to complex terrain.

[0070] Several common cases of complex terrain models include mountain terrain models and valley terrain models. In this embodiment, the target area is a mountain terrain; Figure 4 This is a comparison chart of transient electromagnetic data of flat terrain model and mountain terrain model, with the X-axis representing time and the Y-axis representing transient electromagnetic data, where the solid line and the dashed line represent the transient electromagnetic data of flat terrain model and mountain terrain model respectively. The measuring point is located at the top of the mountain terrain. Compared with the transient electromagnetic data of flat terrain, it can be seen that there is a significant difference between the early data of the two, which is manifested as an increase in amplitude. As the elevation of the measuring point decreases, the amplitude gradually decreases, but the mountain terrain is still stronger than the flat terrain. The gap between the two gradually narrows in the middle period, and the mountain terrain and the flat terrain gradually tend to coincide in the late period, indicating that in the late period, the influence of the terrain gradually disappears.

[0071] like Figure 5a and Figure 5b The figures shown are the multi-channel transient electromagnetic data of the mountain terrain model and the flat terrain model. Figure 5a ) and data for the flat terrain model ( Figure 5b )visible, Figure 5a The data distortion caused by the moderate terrain is mainly concentrated near the mountains. In the early stage, there is an obvious feature of amplitude enhancement, and the abnormal shape is similar to a "peak". As time goes by, the response amplitude weakens. In addition, there is a feature of abnormal amplitude decrease at the foot of the mountains on both sides, and the abnormal shape is similar to a "reverse peak". It can be seen that the mountain terrain causes a "false anomaly" phenomenon in the transient electromagnetic response.

[0072] Figure 6 The complex terrain response curve in transient electromagnetic data is obtained by subtracting the response of the flat terrain model from the response of the mountain terrain model, that is, dB z / dt (hill-in) -dBz / dt (hill-off) It can be seen that the complex terrain response produced by the terrain effect is very strong in the early stage. As time goes on, there is an obvious "polarity reversal" phenomenon in the middle stage, which also means that the terrain effect is gradually disappearing.

[0073] Figure 7 This is a curve diagram of the corrected transient electromagnetic data of the measuring point at the top of the mountain after terrain correction processing. It can be seen that correction is made for the phenomenon of enhanced response amplitude in the early and middle stages. The corrected transient electromagnetic data is in good agreement with the transient electromagnetic data of the flat terrain model, which shows the effectiveness of the present invention.

[0074] right Figure 3a The pre-processed data of all the measuring points in the model are corrected to obtain the transient electromagnetic data at each extraction time. Figure 8 As shown. Figure 5aCompared with the above, the corrected transient electromagnetic data ( Figure 8 ) can effectively eliminate Figure 5a The response distortion of the "peak" shape in the early and middle stages. Figure 5b It can be seen that Figure 8 The structural features of the flat terrain model are retained. It can be seen that the present invention corrects the terrain effects existing at different measuring points, retains the real structural features of the underground, and basically eliminates the terrain effect caused by complex terrain such as mountains as abnormal bodies near the surface.

[0075] In this embodiment, a complex terrain model including the terrain of the target area is constructed for three-dimensional forward simulation calculation to obtain transient electromagnetic data of the complex terrain with terrain; on this basis, a three-dimensional forward simulation calculation of the same transient electromagnetic parameters is performed on a flat terrain model that does not contain any terrain at all to obtain transient electromagnetic data of the flat terrain without terrain; the transient electromagnetic data of the flat terrain without terrain is subtracted from the transient electromagnetic data of the complex terrain with terrain to obtain a complex terrain response caused purely by the complex terrain; and the complex terrain response is eliminated from the measured transient electromagnetic data to complete the terrain correction of the measured transient electromagnetic data; the complex terrain response is eliminated from the measured transient electromagnetic data in the complex terrain area, thereby reducing the error caused by the terrain effect, thereby improving the credibility of the transient electromagnetic data.

[0076] Embodiment 2:

[0077] The method of embodiment 1 of the present invention can also be used by Fig. 9 The architecture of the transient electromagnetic data terrain correction system applied to complex terrain is implemented as shown in FIG. Fig. 9 As shown, the transient electromagnetic data terrain correction system applied to complex terrain may include a measured data acquisition module, a model building module, a simulation calculation module, a terrain response extraction module and a measured data correction module; some modules may also have sub-units for realizing their functions, for example, the model building module may also include a non-terrain model building unit and a terrain model building unit. Of course, Fig. 9 The architecture shown is only exemplary. In some implementations, other units may be added to some modules. In addition, when different functions need to be implemented, some modules may be omitted according to actual needs. Fig. 9 One or at least two components of the system shown.

[0078] Embodiment 3:

[0079] This embodiment provides an example of a method for terrain correction of transient electromagnetic data applied to complex terrain provided in Example 1, which is a method for determining the electrical distribution of underground media, including the following steps:

[0080] Q1. Execute the transient electromagnetic data terrain correction method as described in Example 1 to obtain corrected transient electromagnetic data of the target area.

[0081] Q2. Process and interpret the corrected transient electromagnetic data to obtain the electrical distribution of the underground medium in the target area.

[0082] It should be understood that the application of the transient electromagnetic data terrain correction method provided in Example 1 in this embodiment is only a reference scheme, and it cannot be considered that the method provided in Example 1 can only be applied to determine the electrical distribution of terrain media.

[0083] Embodiment 4:

[0084] Corresponding to the relationship between the above-mentioned embodiments 1 and 2, the method of embodiment 3 of the present invention can also be implemented with the aid of an electrical distribution determination system for underground media; the electrical distribution determination system may include several modules for executing some steps; in some embodiments, other units may be added to some of the modules; in addition, when different functions need to be implemented, one or at least two components may be omitted according to actual needs.

[0085] Specific examples are used in this article, but the above description is only to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas; technicians in this field should understand that the modules or steps of the present invention can be implemented by a general computer device, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by a computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps in them can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0086] Meanwhile, for those skilled in the art, according to the concept of the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for terrain correction of transient electromagnetic data applied to complex terrain, characterized in that: The transient electromagnetic data terrain correction method comprises: Pulse excitation is performed on the target area according to preset transient electromagnetic parameters, and transient electromagnetic data of the target area is collected to obtain measured transient electromagnetic data; According to the terrain characteristics of the target area, a complex terrain model and a flat terrain model are established respectively; According to the preset transient electromagnetic parameters, the transient electromagnetic data of the complex terrain model and the flat terrain model are simulated and calculated to obtain the transient electromagnetic data of the complex terrain and the transient electromagnetic data of the flat terrain; Obtaining a complex terrain response according to the complex terrain transient electromagnetic data and the flat terrain transient electromagnetic data; Obtaining corrected transient electromagnetic data according to the measured transient electromagnetic data and the complex terrain response; The complex terrain response is calculated according to the following formula: dB z / dt (topography) =dB z / dt (hill-in) -dB z / dt (hill-off) Where, dB z / dt (topography) is the complex terrain response, dB z / dt (hill-in) For complex terrain transient electromagnetic data, dB z / dt (hill-off) Transient electromagnetic data for flat terrain; The corrected transient electromagnetic data are calculated according to the following formula: dB z / dt (corrected) =dB z / dt (measured) -dB z / dt (topography) Where, dB z / dt (corrected) To correct transient electromagnetic data, dB z / dt (measured) is the measured transient electromagnetic data, dB z / dt (topography) Response to complex terrain.

2. The method for terrain correction of transient electromagnetic data applied to complex terrain according to claim 1, characterized in that: The preset transient electromagnetic parameters include resistivity, relative magnetic permeability and relative dielectric constant.

3. The method for terrain correction of transient electromagnetic data applied to complex terrain according to claim 1, characterized in that: Before obtaining the complex terrain response according to the complex terrain transient electromagnetic data and the flat terrain transient electromagnetic data, the transient electromagnetic data terrain correction method further includes: The valid data interval of the complex terrain transient electromagnetic data, the valid data interval of the flat terrain transient electromagnetic data and the valid data interval of the measured transient electromagnetic data are determined respectively.

4. The method for terrain correction of transient electromagnetic data applied to complex terrain according to claim 3, characterized in that: The respectively determining the valid data interval of the complex terrain transient electromagnetic data, the valid data interval of the flat terrain transient electromagnetic data and the valid data interval of the measured transient electromagnetic data specifically includes: Determine the shut-off time of the complex terrain transient electromagnetic data as the starting point of the valid data interval of the complex terrain transient electromagnetic data; Determining a shut-off time of the flat terrain transient electromagnetic data as a starting point of a valid data interval of the flat terrain transient electromagnetic data; The shut-off time of the measured transient electromagnetic data is determined as the starting point of the valid data interval of the measured transient electromagnetic data.

5. The method for terrain correction of transient electromagnetic data applied to complex terrain according to claim 3, characterized in that: The respectively determining the valid data interval of the complex terrain transient electromagnetic data, the valid data interval of the flat terrain transient electromagnetic data and the valid data interval of the measured transient electromagnetic data specifically includes: The complex terrain transient electromagnetic data is subjected to a channel extraction process; the channel extraction process is to randomly extract a number of time channels from all the time channels of the complex terrain transient electromagnetic data; Performing extraction processing on the flat terrain transient electromagnetic data; The flat terrain transient electromagnetic data is subjected to extraction processing.

6. A transient electromagnetic data terrain correction system applied to complex terrain, characterized in that: When the transient electromagnetic data terrain correction system is run by a computer, it executes the transient electromagnetic data terrain correction method according to any one of claims 1 to 5.

7. A method for determining the electrical distribution of underground media, characterized in that: The electrical property distribution determination method comprises: Execute the transient electromagnetic data terrain correction method according to any one of claims 1 to 5 to obtain corrected transient electromagnetic data of the target area; The corrected transient electromagnetic data are processed and interpreted to obtain the electrical distribution of the underground medium in the target area.

8. A system for determining the electrical distribution of underground media, characterized in that: When the electrical property distribution determination system is run by a computer, it executes the method for determining the electrical property distribution of the underground medium as claimed in claim 7.

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