A method for identifying the metastability stage based on improved microseismic activity parameters

Abstract

This invention discloses a method for identifying sub-instability stages based on improved microseismic activity parameters, relating to the field of geological hazard technology. The method includes the following steps: acquiring continuous vibration waveform-time curves during fault friction processes; identifying each mainshock event and each acoustic emission event occurring during each foreshock activity period; aligning the foreshock event-time catalog corresponding to each mainshock event in time sequence; calculating the magnitude of each foreshock event in the superimposed foreshock event-time catalog to obtain a superimposed magnitude-time curve; using a sliding window method to slide across the superimposed magnitude-time curve to obtain several analysis windows; calculating the improved microseismic activity parameters for each analysis window to obtain an improved microseismic activity parameter-time curve; and obtaining the sub-instability stage based on the improved microseismic activity parameter-time curve. This invention can identify sub-instability stages using widely deployable monitoring methods in nature.

Description

Technical Field

[0001] This invention relates to the field of geological disaster technology, and more specifically to a method for identifying sub-instability stages based on improved microseismic activity parameters. Background Technology

[0002] Currently, short-term prediction of geological disasters is a key scientific challenge in mitigating disaster losses, and the identification of the sub-instability stage of faults is of great significance for earthquake disaster early warning. In a laboratory environment, the sub-instability stage can be identified through various observation methods such as strain field, displacement field, and temperature field; however, the observation equipment that laboratory methods rely on is difficult to deploy on a large scale in nature, which limits its application in natural fault monitoring.

[0003] Therefore, how to provide a method for identifying sub-instability stages that can be identified based on widely deployable monitoring methods in nature is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for identifying the sub-instability stage based on improved microseismic activity parameters.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for identifying the sub-instability stage based on improved microseismic activity parameters includes the following steps:

[0007] S1: Obtain the continuous vibration waveform-time curve during the fault friction process;

[0008] S2: Identify each main shock event and each acoustic emission event occurring during each foreshock activity period in the continuous vibration waveform-time curve, and obtain the foreshock event-time catalog corresponding to each main shock event; wherein, the foreshock activity period is a period of time before the occurrence of the main shock event; each main shock event corresponds to a foreshock activity period; an acoustic emission event occurring during a foreshock activity period represents a foreshock event.

[0009] S3: Using the occurrence time of each mainshock event as the 0 reference point, align the foreshock events-time catalog corresponding to each mainshock event in time sequence to obtain the superimposed foreshock events-time catalog;

[0010] S4: Calculate the magnitude of each foreshock event in the superimposed foreshock event-time catalog to obtain the superimposed magnitude-time curve;

[0011] S5: Use the sliding window method to slide across the superimposed magnitude-time curve to obtain several analysis windows;

[0012] S6: Calculate the improved microseismic activity parameters for each analysis window and obtain the improved microseismic activity parameter-time curve;

[0013] S7: Obtain the sub-instability stage based on the improved microseismic activity parameter-time curve.

[0014] Preferably, the improved microseismic activity parameters for each analysis window are calculated based on the following formula:

[0015] ;

[0016] in, , Indicates the total number of analysis windows; This represents the improved microseismic activity parameter for the m-th analysis window, indicating the level of microseismic activity. This represents the time corresponding to the last foreshock event in the m-th analysis window; This represents the time corresponding to the first foreshock event in the m-th analysis window; This indicates that the magnitude in the m-th analysis window is greater than the number of foreshock events; Indicates the global minimum complete magnitude; This indicates that the magnitude in the m-th analysis window is greater than The average magnitude of foreshock events; The base of the natural logarithm; This represents the correction constant.

[0017] Preferably, the global minimum complete magnitude is obtained based on the following steps:

[0018] Obtain the minimum complete magnitude for each analysis window;

[0019] The largest magnitude among the various minimum complete magnitudes is selected as the global minimum complete magnitude.

[0020] Preferably, the improved microseismic activity parameter-time curve is obtained based on the following steps:

[0021] Using the improved microseismic activity parameters after the m-th analysis window as the ordinate and the end time after alignment of the m-th analysis window as the abscissa, a modified microseismic activity parameter-time curve is constructed; where, , This indicates the total number of analysis windows.

[0022] Preferably, S7 specifically includes the following steps:

[0023] Identify the peak points in the improved microseismic activity parameter-time curve;

[0024] Identify the first and second sharp decline points after the peak point; wherein, the time period between the peak point and the first sharp decline point is the sub-instability period I; the time period between the first and second sharp decline points is the sub-instability period II; the sub-instability period I and the sub-instability period II constitute the sub-instability stage; the first and second sharp decline points are non-trough points; the sharp decline point is a point where the decline is greater than a preset threshold.

[0025] Preferably, the time alignment involves shifting the foreshock event-time catalog corresponding to each main shock event to the target time, so that the occurrence time of each main shock event is 0.

[0026] Preferably, each sliding window in the sliding window method contains G foreshock events;

[0027] The sliding window method uses H foreshock events as the step size each time;

[0028] in, ; And both G and H are integers.

[0029] Preferably, G=150, H=1.

[0030] Preferably, the foreshock activity period is 70 seconds before the main shock event.

[0031] Preferably, the value of the correction constant is 0.1.

[0032] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a method for identifying the sub-instability stage based on improved microseismic activity parameters, which can identify the sub-instability stage based on monitoring methods that can be widely deployed in nature. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1 A flowchart illustrating a method for identifying the sub-instability stage based on improved microseismic activity parameters provided by this invention;

[0035] Figure 2 A schematic diagram of the superimposed magnitude-time curve provided by the present invention;

[0036] Figure 3 This is a schematic diagram illustrating the acquisition of the minimum complete magnitude of a certain analysis window provided by the present invention.

[0037] Figure 4 A schematic diagram of the improved microseismic activity parameter-time curve provided by the present invention;

[0038] Figure 5 This is a comparison diagram of the sub-instability stage obtained using the method of the present invention and the method obtained using the shear stress-time curve. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, this invention discloses a method for identifying the sub-instability stage based on improved microseismic activity parameters, comprising the following steps:

[0041] S1: Obtain the continuous vibration waveform-time curve during the fault friction process;

[0042] S2: Identify each main shock event and each acoustic emission event occurring during each foreshock activity period in the continuous vibration waveform-time curve, and obtain the foreshock event-time catalog corresponding to each main shock event; wherein, the foreshock activity period is a period of time before the occurrence of the main shock event; each main shock event corresponds to a foreshock activity period; an acoustic emission event occurring during a foreshock activity period represents a foreshock event.

[0043] In one embodiment, the integrated deep learning model in the authorized patent CN117609874B is used to identify each acoustic emission event occurring during each foreshock activity period in the continuous vibration waveform-time curve.

[0044] In one embodiment, the foreshock activity period is 70 seconds before the main shock event occurs.

[0045] Specifically, assuming eight mainshock events are identified, the occurrence times (in seconds) of the eight mainshock events are as follows: ;

[0046] The foreshock activity periods of the eight mainshock events are as follows: .

[0047] S3: Using the occurrence time of each mainshock event as the 0 reference point, align the foreshock events-time catalog corresponding to each mainshock event in time sequence to obtain the superimposed foreshock events-time catalog;

[0048] In one embodiment, the time alignment involves shifting the foreshock event-time catalog corresponding to each mainshock event to the target time, so that the occurrence time of each mainshock event is 0.

[0049] Specifically, assuming the foreshock activity periods of the eight mainshock events are as follows: ;

[0050] The aforementioned time alignment involves shifting the foreshock events and time catalogs corresponding to the eight main shock events to [the specified timeline]. Time period.

[0051] S4: Calculate the magnitude of each foreshock event in the superimposed foreshock event-time catalog to obtain the superimposed magnitude-time curve;

[0052] Assuming eight mainshock events are identified, the superimposed magnitude-time curve would be as follows: Figure 2 As shown, Figure 2 In the diagram, E1-E8 represent the magnitudes of the foreshocks corresponding to the eight main shock events, and the red circle represents the average magnitude of the eight main shock events.

[0053] S5: Use the sliding window method to slide across the superimposed magnitude-time curve to obtain several analysis windows;

[0054] In one embodiment, each sliding window in the sliding window method contains G foreshock events;

[0055] The sliding window method uses H foreshock events as the step size each time;

[0056] in, ; And both G and H are integers.

[0057] In one embodiment, G=150, H=1.

[0058] That is, each sliding window in the sliding window method contains 150 foreshock events; the sliding window method uses a step size of 1 foreshock event at a time; the present invention sets the sliding window to contain 150 foreshock events, which can ensure that there are enough statistically significant events in each window; the sliding step size is set to 1 foreshock event, so that the sliding window can be advanced event by event, which can ensure that the influence of each foreshock event in the process of the main shock on the fault instability state can be captured, providing high temporal resolution for accurate identification of the sub-instability stage.

[0059] S6: Calculate the improved microseismic activity parameters for each analysis window and obtain the improved microseismic activity parameter-time curve;

[0060] In one embodiment, the improved microseismic activity parameters for each analysis window are calculated based on the following formula:

[0061] ;

[0062] in, , Indicates the total number of analysis windows; This represents the improved microseismic activity parameter for the m-th analysis window, indicating the level of microseismic activity. This represents the time corresponding to the last foreshock event in the m-th analysis window; This represents the time corresponding to the first foreshock event in the m-th analysis window; This indicates that the magnitude in the m-th analysis window is greater than the number of foreshock events; Indicates the global minimum complete magnitude; This indicates that the magnitude in the m-th analysis window is greater than The average magnitude of foreshock events; The base of the natural logarithm; This represents the correction constant.

[0063] In one embodiment, the value of the correction constant is 0.1.

[0064] In one embodiment, the global minimum complete magnitude is obtained based on the following steps:

[0065] Obtain the minimum complete magnitude for each analysis window;

[0066] It is understandable that: Figure 3 As shown, the present invention can calculate the minimum complete magnitude for each analysis window using the following two methods:

[0067] The first method is to use the maximum curvature method to calculate the point with the maximum curvature of the magnitude-cumulative frequency in the analysis window, and the corresponding magnitude is the minimum complete magnitude.

[0068] The second method is to calculate the non-cumulative frequency of each magnitude, and the magnitude with the highest non-cumulative frequency is the minimum complete magnitude.

[0069] In one embodiment, the minimum complete magnitude Mc of a certain analysis window is 1.5.

[0070] The largest magnitude among the various minimum complete magnitudes is selected as the global minimum complete magnitude.

[0071] In one embodiment, the improved microseismic activity parameter-time curve is obtained based on the following steps:

[0072] Using the improved microseismic activity parameters after the m-th analysis window as the ordinate and the end time after alignment of the m-th analysis window as the abscissa, a modified microseismic activity parameter-time curve is constructed; where, , This indicates the total number of analysis windows.

[0073] It is understandable that the improved microseismic activity parameters calculated for each analysis window are taken from the end time of the analysis window, which can ensure that each improved microseismic activity parameter can reflect the microseismic activity characteristics within the window duration before that time point.

[0074] S7: Obtain the sub-instability stage based on the improved microseismic activity parameter-time curve.

[0075] In one embodiment, S7 specifically includes the following steps:

[0076] Identify the peak points in the improved microseismic activity parameter-time curve;

[0077] Identify the first and second sharp decline points after the peak point; wherein, the time period between the peak point and the first sharp decline point is the sub-instability period I; the time period between the first and second sharp decline points is the sub-instability period II; the sub-instability period I and the sub-instability period II constitute the sub-instability stage; the first and second sharp decline points are non-trough points; the sharp decline point is a point where the decline is greater than a preset threshold.

[0078] like Figure 4 As shown, assuming eight mainshock events are identified, Figure 4 In the diagram, point O represents the peak point, point A represents the first sharp decline point, point B represents the second sharp decline point, t1 represents the duration of sub-instability phase I, t2 represents the duration of sub-instability phase II, and t0 represents the total duration of the sub-instability phase.

[0079] The preset threshold ;in, This represents the scaling factor (in one embodiment, =0.2); Represents the peak point (i.e. Figure 4 The improved microseismic activity parameters corresponding to point O in the diagram; This represents the last point in the improved microseismic activity parameter-time curve (i.e. Figure 4 The improved microseismic activity parameters corresponding to point C in the diagram.

[0080] It should be noted that in nature, seismic networks can be deployed on both sides of a fault to monitor and obtain continuous vibration waveform-time curves during the fault friction process. However, shear stress-time curves can only be obtained in the laboratory and cannot be obtained in nature. But the sub-instability stage can be identified based on the shear stress-time curves.

[0081] To verify the effectiveness of this invention, the effectiveness of the method of this invention was verified in the laboratory:

[0082] Specifically: A large-scale (0.85-meter rock) fault friction experiment was carried out using a high sampling rate (3 MHz) acoustic emission monitoring system to obtain continuous vibration waveform-time curves during the fault friction process; a horizontal dual-axis hydraulic servo control loading device was used to synchronously obtain shear stress-time curves during the fault friction process, and a total of 8 main shock events were identified during the experiment.

[0083] like Figure 5 As shown, E1-E8 represent the total duration t0, the duration t1 of sub-instability phase I, and the duration t2 of sub-instability phase II corresponding to the eight main shock events obtained using shear stress-time curves, respectively. E represents the total duration t0, the duration t1 of sub-instability phase I, and the duration t2 of sub-instability phase II calculated by the method of this invention. Figure 5 The results show that the duration of the sub-instability stage I identified by the method of the present invention is longer than the duration of the sub-instability stage II (t1>t2), which is consistent with the relationship between the duration of the sub-instability stage identified by the shear stress-time curve. This proves that the method of the present invention can accurately identify the sub-instability stage.

[0084] This invention not only helps to deepen the understanding of the physical mechanism between the mechanical processes in the sub-instability stage and the microseismic activity response, but also has important application value for finding precursory information of impending earthquakes and improving short-term earthquake prediction.

[0085] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0086] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for identifying sub-instability stage based on improved microseismic activity parameter, characterized in that, The method comprises the following steps: S1: obtaining a continuous seismic waveform-time curve in a fault friction process; S2: identifying each main shock event and each acoustic emission event occurring in each foreshock activity period in the continuous seismic waveform-time curve, and obtaining a foreshock event-time catalog corresponding to each main shock event; wherein the foreshock activity period is a certain period before the occurrence of the main shock event; each main shock event corresponds to a foreshock activity period; and one acoustic emission event occurring in a foreshock activity period represents one foreshock event; S3: taking the occurrence time of each main shock event as a 0 reference point, time-aligning the foreshock event-time catalog corresponding to each main shock event, and obtaining a superimposed foreshock event-time catalog; S4: calculating the magnitude of each foreshock event in the superimposed foreshock event-time catalog, and obtaining a superimposed magnitude-time curve; S5: sliding on the superimposed magnitude-time curve by using a sliding window method, and obtaining a plurality of analysis windows; S6: calculating an improved microseismic activity parameter of each analysis window, and obtaining an improved microseismic activity parameter-time curve; S7: obtaining a sub-instability stage based on the improved microseismic activity parameter-time curve.

2. The method of claim 1, wherein the method is characterized by, The improved microseismic activity parameter of each analysis window is calculated based on the following formula: ； wherein, , represents the total number of analysis windows; represents the improved microseismic activity parameter of the mth analysis window, representing the microseismic activity level; represents the time corresponding to the last foreshock event in the mth analysis window; represents the time corresponding to the first foreshock event in the mth analysis window; represents the number of foreshock events with magnitude greater than in the mth analysis window; represents the global minimum complete magnitude; represents the average magnitude of foreshock events with magnitude greater than in the mth analysis window; represents the base of the natural logarithm; represents a correction constant.

3. The method of claim 2, wherein the method is characterized by, The global minimum complete magnitude is obtained based on the following steps: obtaining a minimum complete magnitude of each analysis window; selecting a maximum magnitude in each minimum complete magnitude as the global minimum complete magnitude.

4. The method of claim 3, wherein the method is characterized by, The improved microseismic activity parameter-time curve is obtained based on the following steps: Taking the improved microseismic activity parameter of the mth analysis window as the ordinate and the end time of the mth analysis window after alignment as the abscissa, a microseismic activity parameter-time curve of the improved microseismic activity parameter is constructed; wherein, , represents the total number of analysis windows.

5. The method of claim 1, wherein the method is characterized by, S7 specifically comprises the following steps: identifying a peak point in the improved microseismic activity parameter-time curve; identifying a first sharp drop point and a second sharp drop point after the peak point; wherein the time period between the peak point and the first sharp drop point is the sub-instability I period; the time period between the first sharp drop point and the second sharp drop point is the sub-instability II period; the sub-instability I period and the sub-instability II period constitute the sub-instability stage; the first sharp drop point and the second sharp drop point are non-valley points; and a sharp drop point is a point with a drop greater than a preset threshold.

6. The method of claim 1, wherein the method is characterized by, The time alignment is to respectively translate each foreshock event-time catalog corresponding to each main shock event as a whole to a target time, so that the occurrence time of each main shock event is 0.

7. The sub-instability stage identification method based on an improved microseismic activity parameter according to claim 1, characterized in that: each sliding window in the sliding window method contains G foreshock events; the sliding window method takes H foreshock events as a step length for each sliding; wherein ; ; and G and H are each integers.

8. The method of claim 7, wherein the method is characterized by G = 150, and H = 1.

9. The sub-instability stage identification method based on an improved microseismic activity parameter according to claim 1, wherein the foreshock activity period is 70 seconds before the occurrence of the main shock event.

10. The sub-instability stage identification method based on an improved microseismic activity parameter according to claim 2, wherein the value of the correction constant is 0.1.

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