A fault fracture seismic source characterization system and method based on waveform features

Abstract

The present application relates to a kind of fault fissure seismic source characterization system and method based on waveform feature, including several sensors and at least one processor, the processor is configured as: receiving the amplitude data of wave collected by several sensors;Construct three-dimensional ellipsoid basic equation capable of covering space radiation;Determine the position of seismic source, energy and / or fissure orientation based on the spatial geometric parameters of three-dimensional ellipsoid.The present application fits to obtain uniquely determined ellipsoid, and the physical information of seismic source is described by the spatial geometric parameters of ellipsoid.For example, the position of seismic source, energy, spatial damage range and the like.The calculation process of ellipsoid fitting is simple, and easy to understand.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of elastic wave detection, and in particular to a fault fracture source characterization system and method based on waveform characteristics. BACKGROUND

[0002] When a solid such as rock is subjected to external force, it will crack and produce a fracture. In the process of fracture generation, elastic waves will also be generated. On different scales, elastic waves can manifest as natural earthquakes, microseisms, and acoustic emission. Generally, a detector is used to detect elastic waves, and the fracture that generates the source is analyzed in terms of elastic wave characteristics. Based on waveform characteristics, the fault fracture source is characterized, and relevant information of the source is judged to study the source.

[0003] The current technical means for detecting elastic waves is generally to use a vibration detector for detection. However, the vibration detector scans the solid structure by means of seismic waves or ultrasonic waves, and the fracture structure information inside the solid is measured by means of wave velocity change. The detection accuracy and range of the vibration detector are related to the wavelength. The smaller the wavelength, the higher the detection accuracy, but the smaller the detection range. According to the characteristics of the detected elastic waves, the current technology cannot characterize and describe the three-dimensional structure of the source. In particular, it cannot describe the dynamic process of the three-dimensional structure of the source and its fracture.

[0004] For example, Chinese Patent No. CN111965696A discloses a dynamic disaster prediction method based on elastic wave multi-target analysis, comprising the following steps: S1: during the operation, an acoustic emission monitoring device is used to collect and send the elastic wave signals propagating in the measured target body; S2: a ground comprehensive signal processing device receives and analyzes the elastic wave signals to obtain the dynamic inversion imaging of the abnormal geological body and stress change in the measured target body, and extracts the acoustic emission characteristic parameters of the elastic wave signals; S3: the ground comprehensive signal processing device performs disaster identification and intelligent early warning according to the change of the dynamic inversion imaging of the abnormal geological body in the measured target body or the change of the dynamic inversion imaging of the stress change or the change of the acoustic emission characteristic parameters. Although this invention can comprehensively and accurately predict and warn dynamic disasters, greatly improve the prediction accuracy, greatly improve the prediction work efficiency and reduce the prediction cost. However, since the inversion is only based on the elastic wave signals, the ellipsoidal model of dynamic change cannot be described, so the dynamic inversion imaging can only be realized by continuously updating the inversion imaging of the abnormal geological body and the stress change. This invention not only needs to process a large amount of data, but also if there is a problem with the inversion data at one time, it will cause a large deviation in the dynamic inversion imaging.

[0005] Based on the defects of the prior art, the present application hopes to realize the characterization of the source by dynamically describing the changes of the three-dimensional structure of the fracture, and to improve the characterization of the source and its fracture.

[0006] In addition, on the one hand, there are differences in the understanding of those skilled in the art; on the other hand, a large number of literatures and patents are studied by the applicant when making the invention, but due to the limitation of space, all details and contents are not listed in detail, but this does not mean that the invention does not have these prior art characteristics, on the contrary, the invention has all the characteristics of the prior art, and the applicant reserves the right to add relevant prior art in the background art. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a fault fracture seismic source characterization system based on waveform characteristics, comprising a plurality of sensors and at least one processor, the sensors and the processor are connected in a wired and / or wireless manner, the processor is configured to: receive the amplitude data of the wave collected by the plurality of sensors; construct a three-dimensional ellipsoid basic equation capable of covering spatial radiation; determine the source position, energy and / or fracture orientation based on the spatial geometric parameters of the three-dimensional ellipsoid.

[0008] The three axes of the source ellipsoid can represent the stress triaxiality, stress state and / or stress orientation. By fitting the relationship between energy and stress, the relationship between the three axes and stress can be established, so that a stress tensor can be completely determined, which is also not achieved by all current geostress measurement methods. One basic application of the present application is to estimate the stress state of the source area according to the pre-seismic, and the orientation of the stress can be directly determined by the source ellipsoid, while the size and direction of the principal stress can be represented by the size and orientation of the ellipsoid.

[0009] Preferably, the processor is configured to determine the change state of the fracture and / or the source based on the change of the spatial geometric parameters of the ellipsoid in the time dimension. Based on the representation of the position and / or stress state, stress orientation and / or stress tensor of the source by the spatial geometric parameters, and combined with the time dimension, the changes of various physical quantities of the source based on time can be described.

[0010] Preferably, the processor is configured to represent the stress triaxiality, stress state and / or stress orientation based on the three axis parameters of the ellipsoid, and to establish the relationship between the three axis parameters of the ellipsoid and the stress based on the fitting relationship between energy and stress, so as to determine the stress tensor and its change. The present application represents the physical characteristics of the source by the ellipsoid, which can still accurately describe the energy, tensor and the like of the source after the current source energy exceeds the eight-level vibration, making up for the deficiency of the prior art in describing the energy of the super large earthquake.

[0011] Preferably, the way of constructing the ellipsoid capable of covering the spatial radiation comprises: fitting the coefficients of the ellipsoid basic equation; calculating the spatial geometric parameters of the ellipsoid; the spatial geometric parameters at least include: the central coordinates, three semi-axes and / or the half focal length.

[0012] The spatial geometric parameters of the ellipsoid capable of covering the amplitude vector are related to the physical characteristics of the seismic source. It is necessary to obtain the spatial geometric parameters of the ellipsoid. The present application obtains the ellipsoid capable of covering each amplitude vector by fitting the coefficients of the ellipsoid basic equation, so that the effect of the ellipsoid covering the amplitude vector is better.

[0013] Preferably, the way of fitting the coefficients of the ellipsoid basic equation at least includes:

[0014] In the case that the amount of received data is not less than the preset data amount threshold, the coefficients of the ellipsoid basic equation are directly fitted; in the case that the amount of received data is less than the preset data amount threshold, the coefficients of the ellipsoid basic equation are fitted based on the main plane random point supplement method.

[0015] Preferably, the preset number threshold is 10. That is, in the case that the number of data channels is greater than or equal to 10, the data is relatively rich, and random point supplement is not needed. In the case that the number of data channels is less than 10, the data is relatively less, and random point supplement is needed to calculate the coefficients of the ellipsoid.

[0016] In the present application, the preset number threshold is set to 10 based on the results of sufficient analysis of a large amount of experimental data. For data with less than 10 data channels, if random point supplement is not performed, the deviation of the fitted ellipsoid corresponding thereto is relatively large, and the effect is not good. For data with not less than 10 data channels, an ellipsoid with good fitting effect can be obtained regardless of whether the point is supplemented or not. Therefore, the present application sets the preset number threshold to 10, thereby reducing the amount of calculation of the processor in the fitting process.

[0017] Preferably, the way of calculating the spatial geometric parameters of the ellipsoid at least includes:

[0018] The basic equation of the ellipsoid is F(x, y, z) = a 11 x 2 +a 22 y 2 +a 33 z 2 +2a 12 xy+2a 13 xz+2a 23 yz+2a 14 x+2a 24 y+2a 34 z+a 44 ;

[0019] Simplify the coefficients of the basic equation of the ellipsoid into a matrix form:

[0020]

[0021] K3=|A|, I3=|A*|;

[0022] Wherein, a represents a coefficient, I3 represents the third invariant of the matrix A*, and K3 represents the third semi-invariant of the matrix A; the eigenvalues (λ1, λ2, λ3) and unit eigenvectors (η1, η2, η3) corresponding to the matrix A* are calculated; the spatial geometric parameters of the ellipsoid are calculated according to the matrix A*, the eigenvalues and the third invariant of the matrix A*.

[0023] The spatial geometric parameters of the ellipsoid cannot be directly obtained based on the basic equation of the ellipsoid, and the basic equation (1) of the ellipsoid needs to be modified into a standard form in the application, so that the spatial geometric parameters related to the amplitude vector can be obtained, and at the same time an ellipsoid with a large coverage deviation is not obtained.

[0024] Preferably, the way of calculating the spatial geometric parameters of the ellipsoid according to the matrix A*, the eigenvalues and the third invariant of the matrix A* is:

[0025] X c T =-(A * ) - [a 14 a 24 a 34 ] T ;

[0026]

[0027]

[0028] X c T (x0, y0, z0) represent the center coordinates of the ellipsoid; a, b and c respectively represent the semi-axes of the three-dimensional direction of the ellipsoid, and C0 represents the semi-focal distance of the ellipsoid.

[0029] The spatial geometric parameters of the application are related to each coefficient of the basic equation of the ellipsoid. Using the spatial geometric parameters to represent each physical quantity of the seismic source instead of directly using the coefficients to represent can simplify the representation information and is simple and easy to understand, and even an outsider can easily understand the representation content.

[0030] The application further provides a fault fracture seismic source representation method based on waveform characteristics, and the method at least comprises:

[0031] S1: receiving the amplitude data of the wave collected by a plurality of sensors;

[0032] S2: constructing a three-dimensional ellipsoid basic equation capable of covering spatial radiation;

[0033] S3: determining a source location, energy and / or a fracture orientation based on a spatial geometric parameter of the three-dimensional ellipsoid.

[0034] The basic application of the characterization method of the present application is to estimate the stress state of a source area according to a precursor, and the orientation of the stress can be directly determined by the source ellipsoid, while the size of the stress actually needs to be combined with the damage evolution characteristics, which cannot be achieved by the prior art.

[0035] Preferably, the method further comprises judging a change state of a fracture and / or a source based on a change of the spatial geometric parameter of the ellipsoid in a time dimension.

[0036] The present application accurately and dynamically describes the physical characteristics of a source based on a time dimension, which cannot be achieved by the dynamic description of the prior art using a planar ellipse or a plurality of ellipse filling methods.

[0037] Preferably, the method further comprises characterizing a stress triaxiality, a stress state and / or a stress orientation based on three axis parameters of the ellipsoid, establishing a relationship between the three axis parameters of the ellipsoid and the stress based on a fitting relationship between the energy and the stress, and determining a stress tensor and a change thereof.

[0038] The fault fracture source characterization method based on waveform characteristics of the present application can not only characterize a rupture process of a source fracture, but also can characterize a source energy based on an ellipsoid volume. The calculation of the source energy of the present application can make up for the saturation of the Richter magnitude and the moment magnitude for earthquakes of eight levels and above. The present application can directly calculate the source energy and can characterize the energy of a source of eight levels and above, thereby providing more accurate characterization content for subsequent research of an earthquake. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a schematic diagram of one of the fitted ellipsoids of the present application;

[0040] Figure 2 is a schematic diagram of a sensor arrangement of one of the preferred embodiments of the present application;

[0041] Figure 3 is a schematic diagram of a sensor arrangement of another preferred embodiment of the present application;

[0042] Figure 4 is an exemplary first source direction finding vector diagram of the present application formed based on six-channel amplitude data;

[0043] Figure 5 is a source ellipsoid diagram of the present application corresponding to the first source direction finding vector diagram;

[0044] Figure 6 is an exemplary second source vector map based on eight-channel amplitude data according to the present application;

[0045] Figure 7 is a shear-type source ellipsoid map corresponding to the second source vector map according to the present application;

[0046] Figure 8 is an exemplary third source vector map based on eight-channel amplitude data according to the present application;

[0047] Figure 9 is a shear-type source ellipsoid map corresponding to the third source vector map according to the present application;

[0048] Figure 10 is an exemplary fourth source vector map based on eight-channel amplitude data according to the present application;

[0049] Figure 11 is a tension-type source ellipsoid map corresponding to the fourth source vector map according to the present application;

[0050] Figure 12 is an exemplary fifth source vector map based on eight-channel amplitude data according to the present application;

[0051] Figure 13 is a tension-type source ellipsoid map corresponding to the fifth source vector map according to the present application;

[0052] Figure 14 is a schematic diagram of main plane determination according to the present application;

[0053] Figure 15 is a schematic diagram of random point generation according to the present application;

[0054] Figure 16 is an analysis schematic diagram of source rupture velocity derivation according to the present application.

[0055] LIST OF REFERENCE NUMERALS

[0056] 10: sensor; 20: processor. DETAILED DESCRIPTION

[0057] The present application will be described in detail below with reference to the accompanying drawings.

[0058] The present application provides a fault fracture source characterization system and method based on waveform characteristics. The present application can also provide a source energy calculation method and system.

[0059] The system of the present application comprises several sensors and at least one processor. The sensors are connected to the processor in wired and / or wireless manner. The wired manner is, for example, communication connection through optical fiber. The wireless manner is, for example, wireless communication connection through Bluetooth communication component, WIFI communication component, ZigBee communication component, infrared communication component and the like communication elements.

[0060] The sensors are used to collect the elastic waves of the seismic source. The sensors are preferably broadband vibration sensors, and the frequency range is 0-2 kHz (low frequency) and 2 kHz-500 kHz (high frequency) according to different monitoring objects. For example, the high frequency can select R6 type piezoelectric ceramic sensor, or W800 type piezoelectric ceramic sensor, and the low frequency sensor can select all-fiber microseismic probe.

[0061] Preferably, the processor refers to a special integrated chip and / or server, CPU, single-chip microcomputer and the like capable of running the program of the fault fracture seismic source characterization method based on waveform characteristics of the present application. Preferably, the processor can also be an integration of several microprocessors. Preferably, the processor is not limited to a single processing element, and can also include servers, computers and other devices with data processing capabilities containing processing elements.

[0062] The present application makes the following explanations on some noun terms.

[0063] Seismic source: refers to the position of solid rupture, which is represented by coordinates (x, y, z) in space. In the present application, the seismic source is represented by an ellipsoid, also known as a seismic source ellipsoid, and the position of the seismic source is the focal point coordinate of the ellipsoid. It includes but is not limited to acoustic emission, microseismic and natural earthquake. Acoustic source, acoustic emission source, represents the movement process of the rupture process and the rupture surface.

[0064] Source probe vector: its direction is from the seismic source to the probe, and the size is represented by amplitude.

[0065] Seismic source ball: a spherical body (radius can be arbitrary, preferably greater than wavelength) centered on the seismic source. The waveforms of sensors in different directions and different distances in space are detected with the spherical body as a reference to calibrate their attenuation. The waveforms in different directions on the ball are obtained, and the present application refers to this ball as a seismic source ball.

[0066] Attenuation: refers to the phenomenon that the amplitude of the wave becomes smaller due to propagation consumption.

[0067] Ellipsoid: the elastic wave generated by explosion propagates uniformly in space in the form of a spherical surface, and the rupture feature corresponding to the explosion is a spherical shape. When the rupture becomes a directional fracture, the elastic wave generated by the rupture will be distorted into an ellipsoid, which corresponds to the fracture process.

[0068] The ellipsoid based on the elastic wave mentioned in the prior art can only realize the characterization of the static crack structure, and multiple ellipsoids are needed to fill the crack to completely cover the crack, so the fault crack source cannot be accurately characterized based on the waveform characteristics. The application optimizes the calculation process of the ellipsoid, thereby characterizing the fault crack source based on the ellipsoid basic equation in a new way, improving the quantitative description of the source and the accuracy of the characterization.

[0069] Unlike the defects in the prior art that can only characterize a certain static state of the crack, the application constructs a new ellipsoid basic equation based on the waveform characteristics to characterize the crack process dynamic description of the source. The application is not a dynamic description of the crack, but a description of the crack process of the source itself. The application uses ellipsoid to characterize the crack process of the source, and characterizes the rupture velocity and rupture length. The ratio of the rupture length to the rupture velocity is the rupture time. The application can also represent the energy of the source by the volume of the ellipsoid. After obtaining the energy of the source, the crack strength can be judged. For example, when the source is a seismic crack, the crack strength can be quantified by the volume of the ellipsoid.

[0070] In the prior art, the Richter magnitude is determined by the horizontal displacement generated when the earthquake occurs. The Richter magnitude table is divided into 9 levels. The larger the earthquake, the larger the number of the magnitude. When the magnitude increases by one level, the energy released by the earthquake increases by about 32 times. The moment magnitude is determined by the size of the seismic moment. The seismic moment is a physical quantity (similar to the concept of moment) that describes the mechanical strength when an earthquake occurs, which is determined by the product of the rupture area of the earthquake fault, the average displacement and the shear modulus of the rock. The seismic moment and the moment magnitude can be obtained by comprehensive inversion of the seismic wave spectrum, or by the rupture characteristics of the earthquake (earthquake fault size, source depth, displacement and rock mechanical properties, etc.). The defects of the Richter magnitude or the moment magnitude of the prior art in determining the size of the earthquake are that the energy of the source is not directly calculated to determine the magnitude, and when the strength of the source exceeds eight levels, the representation of the increase in energy is not sensitive.

[0071] The application can take the absolute value of the energy, and use the absolute energy value to objectively represent the strength of the earthquake. When the earthquake exceeds eight levels, the absolute value of the energy of the source can be used to directly judge the strength and change of the earthquake, which is more objective and accurate.

[0072] As Figure 2 and Figure 3As shown, the rock is provided with a plurality of sensors 10. Assuming that the rock is in a cubic geometry, the plurality of sensors 10 are arranged in a central symmetric manner on the surface of the rock and / or around the rock. In the present application, the cubic geometry is an ideal structure and is exemplary. In reality, the rock-like solid can be a regular cube or an irregular cube structure. In the case of an irregular cube, the plurality of sensors 10 can also be arranged in a manner as close to central symmetry as possible, so as to collect the elastic waves emitted in various directions by the cracks in the rock. The elastic waves propagate outward and form a radiation field of elastic waves.

[0073] The longitudinal wave and the transverse wave in the elastic wave are both body waves, and the point source propagates outward from the source in the form of a sphere, and the energy and displacement in each direction are equal, and such a source is called a sound monopole. The energy and displacement of the crack source in each direction are distorted into an ellipsoid. Due to energy attenuation during propagation, the amplitude of the elastic wave will continuously decrease. Arranging a plurality of sensors 10 around the source is beneficial to collecting amplitude data of elastic waves of different sizes from the source in multiple directions, i.e., detecting the spatial radiation displacement field.

[0074] The sensor 10 sends the collected amplitude data to the processor 20 through the communication component. The processor 20 processes the amplitude data to ultimately realize the construction of the basic equation of the ellipsoid. Preferably, the processor 20 processes the amplitude data according to the following steps.

[0075] As shown in Tables 1, 2 and 3, after receiving the data collected by the sensors, the processor extracts all events from the acoustic emission waveform data through short-time Fourier transform, and stores the amplitude of each channel received, the time, coordinates and amplitude data of all events.

[0076] S1: Construct a spatial propagation vector of the source.

[0077] As shown in Tables 1, 2 and 3, after receiving the data collected by the sensors, the processor extracts all events from the acoustic emission waveform data through short-time Fourier transform, and stores the amplitude of each channel received, the time, coordinates and amplitude data of all events. Figure 4 , Figure 6 , Figure 8 , Figure 10 and Figure 12 , a spatial coordinate system is established. The origin of the coordinates is determined by the constructor, and the spatial coordinates x, y and z are used to represent the source position. In the figure, the amplitude is used to represent the displacement of the spatial radiation displacement field of the source. The amplitude is connected with the source to obtain the spatial propagation direction of the source, i.e., the direction of the source probe vector. After considering the attenuation of the wave along the source probe vector direction, the initial displacement emitted from the source in each direction can be obtained, i.e., the size of the source probe vector. In the case that more than 4 sensors receive waveform data radiated by the source, the source position is determined by the time difference positioning method. In the present application, if the channel data is relatively small and the average coverage is small, the fitting effect of the ellipsoid is not good. Especially in the case of only 4 data channels, the average coverage of the ellipsoid and the amplitude vector is small.

[0078] As shown in Figure 4 , there are five source-probe vectors with different directions. The size of each source-probe vector represents the initial displacement of the elastic wave in the corresponding direction.

[0079] S2: Construct a spherical ball covering the spatial radiation of the source.

[0080] As shown in Figure 1 , a spherical ball is set to enclose the spatial radiation of the source. For example, a spherical ball is formed with the source as the center and a radius. Preferably, the radius of the spherical ball can be set arbitrarily. Preferably, the radius of the spherical ball is greater than the wavelength of the elastic wave. The waveforms of the elastic wave collected by the sensors 10 at different spatial positions with different directions are calibrated in terms of their attenuation with the spherical ball as the reference. The amplitudes of the waveforms in different directions are obtained on the spherical ball. The acoustic monopole mentioned in the present application has a source ball which is also a spherical ball. The spatial radiation of the elastic wave generated by the crack process is an ellipsoid. By using the amplitudes of the elastic wave on the source ball, the basic equation of the ellipsoid and the standard form can be obtained, and the structural characteristics of the crack can be characterized.

[0081] S3: Calculate the basic equation of the ellipsoid of the present application.

[0082] S31: Establish the basic equation of the ellipsoid.

[0083] The basic equation of the ellipsoid can be expressed as:

[0084] F(x,y,z)=a 11 x 2 +a 22 y 2 +a 33 z 2 +2a 12 xy+2a 13 xz+2a 23 yz+2a 14 x+2a 24 y+2a 34 z+a 44 (1)

[0085] wherein x, y, z coordinates represent the amplitude coordinates on the source ball. The size of x, y, z is calculated as follows: the source-probe vector is multiplied by the cosine of its direction. a represents the coefficient, which is calculated based on the amplitude data collected by the sensors.

[0086] S32: Correct the basic equation of the ellipsoid to the standard form.

[0087] The basic equation of ellipsoid cannot directly obtain the space geometry parameters of ellipsoid, so the basic equation (1) of ellipsoid is modified to standard form. The space geometry parameters of ellipsoid include at least the center of ellipsoid, the axis length, the focal point coordinate and the like.

[0088] The standard form of ellipsoid can be expressed as:

[0089]

[0090] In the formula, x0, y0, z0 represent the coordinates of the center of ellipsoid, a, b, c represent the long, medium and short half axis length of ellipsoid respectively. In the case of determining the center of ellipsoid, the crack propagation direction can be characterized based on the source position.

[0091] The coefficients of the basic equation of ellipsoid are simplified as follows:

[0092]

[0093] Wherein, I3 represents the third invariant of matrix A*, and K3 represents the third semi-invariant of A, and their values are the determinants of the corresponding matrix respectively.

[0094] Meanwhile, the eigenvalue (λ1, λ2, λ3) and unit eigenvector (η1, η2, η3) corresponding to A* are also obtained.

[0095] Using the above parameters, the center coordinate X c =(x c ,y c ,z c ) of ellipsoid, the half axis length (a, b, c) and the half focal length (pseudo) are obtained respectively as follows:

[0096] X c T =(A * ) - [a 14 a 24 a 34 ] T (4)

[0097]

[0098]

[0099] X c TThe center coordinates (x0, y0, z0) of the ellipsoid, a, b, c respectively represent the semi-axis lengths of the three-dimensional directions of the ellipsoid, and C0 represents the half focal length of the main plane of the ellipsoid. The direction corresponding to the first principal axis (i.e. the long axis) of the ellipsoid is determined by the characteristic vector η1. The focal point of the ellipsoid is on its long axis, and its coordinates can be calculated using the spherical center coordinates. At this point, all the spatial geometric parameters of the ellipsoid are calculated.

[0100] The determination method of the spatial geometric parameters of the source ellipsoid of the application has a simple calculation method and an intuitive geometric shape.

[0101] First, the main method for determining the spatial geometric parameters of the source in current seismology is to perform moment tensor inversion on the seismic waveforms collected by multiple seismic stations (more than 6), to determine the magnitude and source type, and to calculate the spatial geometric characteristics of the source through complex dynamics methods on the basis of certain theoretical assumptions. The calculation program is complicated, the source geometric parameters are separated from the physical process, and deep professional background knowledge is required to understand. Petra Adamová et al. perform source ellipsoid fitting through high-order Green's function, only indicate that the principal axis of the source ellipsoid represents the source expansion direction, and do not combine other ellipsoid geometric characteristics with the source physical characteristics. Moreover, this method needs high-order inversion fitting of the moment tensor, and the calculation method is complicated. In this method, the ellipsoid shape and spatial trend obtained by fitting different frequency components vary, and the result is not unique.

[0102] Second, the present application uses the source spatial radiation amplitude (maximum amplitude) as the original data for fitting, and the maximum amplitude is obtained by performing fast Fourier transform on the waveforms collected by the sensor. At least 4 waveform data collected by the sensor is needed, and the ellipsoid least square fitting is performed on the maximum amplitude to uniquely determine the ellipsoid geometric parameters. The volume of the ellipsoid can represent the size of the source energy. The spatial distribution of the ellipsoid can represent the spatial damage range of the source. The first principal plane of the ellipsoid can represent the spatial distribution direction of the fault. The ratio of the first principal axis and the third principal axis of the ellipsoid can represent the source type. The position of the source to the center of the ellipsoid represents the crack expansion direction. In summary, the present application obtains the source physical parameters through the spatial geometric parameters of the ellipsoid, the calculation is simple, the physical process is clear and intuitive, and it can be understood without professional background.

[0103] Taking the source as the focal point on the long axis of the ellipsoid, the parameters of the ellipsoid are the parameters of the source crack, that is, the crack can be quantitatively described by the amplitude ellipsoid parameters of the source. For example, Table 1 shows the amplitude data of 6 channels.

[0104] Table 1 6-channel amplitude data sample

[0105]

[0106] In Table 1, the first column indicates the time when the event occurs. The X, Y and Z columns represent the coordinates of the source respectively. The channels 1-6 represent the amplitude data of each channel. The source probe vectors constructed from the data in Table 1 are shown in Figure 6 . Figure 6 The six source probe vectors with different directions are included in the ellipsoid.

[0107] In Table 2, the first three columns are the coordinates of the center of the ellipsoid, the fourth to sixth columns are the lengths of the major, intermediate and minor axes, the seventh to ninth columns are the unit vectors of the first, second and third principal axes respectively, and the tenth column is the average coverage rate. The processor 20 constructs Figure 4 and Figure 5 based on the data samples in Table 1. The processor 20 calculates the spatial geometric parameters of the ellipsoid based on the standard form of the ellipsoid, as shown in Table 2.

[0108] Geometric parameters of the fitted ellipsoid in Table 2

[0109]

[0110] As shown in Figure 1 , when the data channels are less than 4, the amount of data is insufficient, and it is difficult to fit the ellipse. When the data channels are greater than or equal to 4, the amount of data is sufficient to achieve the fitting of the ellipse. However, the fitting effect of the ellipse is quite different. The present application evaluates the fitting effect of the ellipsoid by the coverage rate of the amplitude vector by the ellipsoid. Through analysis of a large amount of experimental data, it is shown that when more than 6 channels of data can be collected, the ellipsoid coverage rate is greater than 90%, and the fitting effect is good. When the channels are less than 6, the ellipsoid coverage rate is less than 80%, and the fitting effect is poor.

[0111] Preferably, the processor 20 calculates the spatial geometric parameters of the ellipsoid based on the least square method.

[0112] Without the need for point supplement, the spatial geometric parameters of the ellipsoid are obtained by the following calculation.

[0113]

[0114] Wherein, minG(A) represents the objective function, a represents the length of the major axis, b represents the length of the intermediate axis, and c represents the length of the minor axis.

[0115] In the case where the objective function is set to the volume of the ellipsoid, then:

[0116]

[0117] minG'(A) represents the volume of the ellipsoid.

[0118] The above formula is further simplified, which is equivalent to:

[0119] minG"(A) = |I3| (7-3)

[0120] minG"(A) represents the ellipsoid volume, I3 = |A*|.

[0121] The first constraint condition is n linear equations established by the radiation vector of the channel source, i.e. n ellipsoid basic equations. At this time, the variable is the element of matrix A, x, y and z are the radiation coordinate values collected by the sensors on the source sphere. Namely:

[0122] a 11 x 2 +a 22 y 2 +a 33 z 2 +a 12 xy+a 13 xz+a 23 yz+a 14 x+a 24 y+a 34 z+a 44 =0 (8)

[0123] The second constraint condition is the coefficient condition of the standard form of the ellipsoid equation, i.e.:

[0124]

[0125] The third constraint condition is the condition of the solution of the characteristic equation of the quadratic term coefficient matrix of the ellipsoid equation, i.e. the condition that the monomial cubic equation has three real roots, i.e.:

[0126] Δ = 4I1 3 I3-I1 2 I2 2 -18I1I2I3+27I3 2 ≤0 (10)

[0127] Wherein, I1 represents the first invariant of matrix A*; I2 represents the second invariant of matrix A*; I3 represents the third invariant of matrix A*.

[0128] The fourth constraint condition is the focal point condition, the source point coordinates (x c ,y c ,z c ) are the same as the focal point coordinates calculated by the semi-axis length and the semi-focal distance, and the expression is:

[0129] x c =x0-C0η1(1),y c =y0-C0η1(2),z c =z0-C0η1(3) (11)

[0130] wherein x0, y0, z0 represent the coordinates of the center of the ellipsoid, C0 represents the half focal length, and η1 represents a unit principal vector in the principal axis direction. (1), (2), and (3) in the formula represent that there are three direction vectors in the formula, and each direction vector is represented by three components.

[0131] The long axis direction of the ellipsoid radiation has the strongest radiation energy, and is marked as the crack propagation direction. The position of the focus point to the center of the ellipsoid determined by the first and second principal axes of the ellipsoid, i.e. the pseudo focal length, is the length of the crack propagation (or sliding). The ratio of the first axis and the third axis of the ellipsoid can be used to determine the type of the source: when the percentage of the middle axis / long axis of the ellipsoid is greater than 50%, it is a shear type crack, otherwise it is a tensile type crack, as shown in Table 3.

[0132] Table 3: Source type calculation table

[0133]

[0134] Table 4 is 8-channel 2-group amplitude data sample 1 of the present application, and the corresponding source probe vector and ellipsoid are Figure 6 and Figure 7 , Figure 8 and Figure 9 .

[0135] Table 4: 8-channel amplitude data sample 1

[0136]

[0137] As shown in Table 3, Figure 7 the percentage of the middle axis / long axis of the ellipsoid in the Figure 9 is 60.01%, which are all shear type cracks.

[0138] Table 5: 8-channel amplitude data sample 2

[0139]

[0140] Table 5 is 8-channel 2-group amplitude data sample 2 of the present application, and the corresponding source probe vector and ellipsoid are Figure 10 and Figure 11 , Figure 12 and Figure 13 .

[0141] As shown in Table 3, Figure 11 the percentage of the middle axis / long axis of the ellipsoid in the Figure 13 is 45.89%, which are all tensile type cracks.

[0142] Preferably, when the data channel is greater than or equal to 10, the processor does not need to randomly supplement the principal plane of the ellipsoid. When the data channel is less than 10, the processor needs to randomly supplement the principal plane of the ellipsoid.

[0143] Preferably, when supplement is needed, the step of randomly supplementing the ellipsoid of the present application is as follows.

[0144] S51: Determine the principal plane.

[0145] As shown in Figure 14 , the maximum amplitude direction is the first principal direction of the ellipsoid, and the maximum value of the maximum amplitude is the major axis, i.e. The maximum value of the modulus of the cross product of the other amplitude vectors and the maximum amplitude vector is The corresponding amplitude vector The amplitude vector The unit vector obtained by the cross product of the maximum amplitude vector is the principal plane normal, i.e. The other amplitude vectors are represented by The crack vector with the maximum modulus is represented by The modulus of is represented. The direction perpendicular to the first principal axis on the principal plane is the second principal axis direction. The projection size of the amplitude vector on the second principal axis is the second principal axis size, i.e. The second principal axis size is represented by

[0146] S52: Randomly create points.

[0147] As shown in Figure 15 , within a 5-degree range in the first principal direction, 2 points are randomly generated with a size of 0.9-1.1 Within a 15-degree range in the opposite direction of the first principal direction, 2 points are randomly generated with a size of 0.9-1.1 Two points are randomly created in the second principal direction with a size of 0.9-1.1

[0148] In addition to the two amplitude vectors that determine the principal plane, the other amplitude vectors are generated by mirror points, which have an angle of α with the principal plane normal. When the angle α is less than , points are created in the direction with an angle of π-2α with the amplitude vector with a size of 0.9-1.1 When the angle is greater than , points are created in the direction with an angle of 2α-π with the amplitude vector with a size of 0.9-1.1

[0149] S53: Judge the fitting effect.

[0150] ​The smaller the ellipsoid area and the more amplitude vectors the ellipsoid can cover, the better the fitting result.

[0151] Specifically, the intersection of the ellipsoid formed by the fitting and the amplitude vector equation is solved, the square root of the square sum of the residual of each amplitude vector and the intersection is taken, and then divided by the number of amplitude channels, that is, the average coverage difference of the amplitude vector is obtained. Divide the average coverage difference by the sum of the amplitudes and multiply by the percentage to get the coverage difference ratio. Subtract 1 from this value, and the ellipsoid coverage rate is obtained. The larger the ellipsoid coverage rate, the better the fitting effect of the ellipsoid.

[0152] The amplitude average coverage difference of the main plane point making method of the present application is mostly within 10 mm. The main plane of the ellipsoid can represent the spatial distribution direction of the fault.

[0153] For example, the ellipsoid expression is:

[0154] F(x,y,z)=a 11 x 2 +a 22 y 2 +a 33 z 2 +a 12 xy+a 13 xz+a 23 yz+a 14 x+a 24 y+a 34 z+a 44 =0.

[0155] Set the source position M0(x0,y0,z0) and amplitude vector The vertex coordinates of the amplitude vector are (x2,y2,z2), and M(x,y,z) is any point on the amplitude vector. The amplitude vector equation is

[0156] The intersection M1(x1,y1,z1) of the ellipsoid basic equation and the amplitude vector equation is solved, and the residual (distance) of the amplitude vector and the intersection is The average coverage difference of the amplitude vector is The sum of the amplitudes is The ellipsoid coverage rate is *100%.

[0157] Table 6 6-channel ellipsoid coverage rate calculation table

[0158]

[0159]

[0160] The related parameters of the ellipsoid fitted based on the seismic source data of 6 data channels and the calculated value of the average coverage difference are shown in Table 6. The average coverage difference is 5.533, and the ellipsoid coverage rate is 95.21%, indicating that the fitting effect of the ellipsoid is good.

[0161] S6: Quantitatively describe the seismic source based on the fitted ellipsoid.

[0162] The seismic source is quantitatively described as a seismic source ellipsoid based on its spatial energy radiation characteristics, which is suitable for describing the seismic source of all scales of solid internal physical processes such as crack, fault, connection, sliding, activation, etc.

[0163] The long axis direction of the ellipsoid radiation has the strongest radiation energy, which is marked as the crack propagation direction. The position of the focus point of the first and second principal axes of the ellipsoid to the center of the ellipsoid, i.e. the pseudo focal length, is the length of the crack propagation (or sliding). Through the Doppler effect, the crack propagation rate can be calculated from the seismic source radiation, thereby completing the seismic source mechanism solution.

[0164] As shown in Figure 16 , the calculation formula of the seismic source rupture velocity can be derived through the Doppler effect as follows:

[0165] In the above formula, f1 represents the main frequency of the seismic source obtained by the first sensor, f2 represents the main frequency of the seismic source obtained by the second sensor, v0 represents the wave speed in the medium. cosα1 represents the projection of the angle α1 in the direction of the line connecting the first sensor position S1 and the seismic source position O1. cosα2 represents the projection of the angle α2 in the direction of the line connecting the first sensor position S1 and the seismic source position O1. cosα 01 represents the projection of the angle α 01 in the direction of the line connecting the first sensor position S1 and the seismic source position O1. Δf 12 represents the difference between f1 and f2. The calculation process is shown in Table 6.

[0166] Figure 16 In the above formula, S1, S2 represent the sensor positions, O1 is the seismic source position, and L0 is the rupture direction determined by the ellipsoid principal axis. Table 7 shows data examples of the rupture velocity parameters and related parameters of some seismic sources.

[0167] Table 7 Seismic source rupture velocity calculation table

[0168] f1 f2 [v0 (km / s)] cos α1 cos a2 cos a 01 ]]> Delta F 12 ]] u0 (km / s) 207.0313 203.125 1.933 -0.17443 0.730726 -0.80061 3.90625 0.051107 199.2188 191.4063 1.933 0.433644 0.897576 -0.62257 7.8125 0.283998 93.75 91.79688 1.996 0.843238 -0.69158 0.329559 1.953125 0.08299 41.01563 37.10938 1.996 0.878509 -0.83372 0.851071 3.90625 0.136793 99.60938 93.75 1.996 -0.74028 0.123238 -0.62565 5.859375 0.219167

[0169] Table 7 shows five sets of data examples for calculating the seismic source rupture velocity. In the five sets of data, the seismic source rupture velocity gradually increases.

[0170] Further application scenarios of the present application.

[0171] The focal mechanism can be established by the focal ellipsoid itself, and the moment tensor inversion is not necessary.

[0172] The three axes of the focal ellipsoid can represent the stress triaxiality, stress state and / or stress orientation. Through the fitting of the relationship between energy and stress, the relationship between stress and the three axes can be established, so that a stress tensor can be completely determined. This is also something that all current stress measurement methods cannot do. One basic application of this method is to estimate the stress state of the focal region according to the foreshock. The orientation of the stress can be directly determined by the focal ellipsoid, and the size and direction of the principal stress can be represented by the size and orientation of the ellipsoid.

[0173] Based on the ellipsoid model of the application, a statistical law model of dynamic evolution of dynamic geological disasters is established.

[0174] S11: Collecting the spatial geometric parameters in the ellipsoid model.

[0175] Preferably, the spatial geometric parameters related to the damage characteristics, such as the long axis parameters, are collected to establish a reliable damage variable and unify the damage parameters.

[0176] S12: Describing the focal source.

[0177] The lengths of the long axes of the ellipsoids at different stages conform to the Poisson distribution, but the overall mean of the long axes of the ellipsoids should increase continuously until the characteristic length is reached. When the damage of the characteristic length reaches a certain amount, the overall damage of the monitoring area (rock sample, landslide, seismic block, etc.) will occur. In the case of defects, pre-damage of the order of magnitude of the characteristic length will also appear, which is related to the final damage.

[0178] The application can more accurately classify the intensity of an earthquake by dynamically describing the focal source, such as dynamically describing the focal source of an earthquake. Compared with the evaluation method of the intensity of the focal source of an earthquake in the prior art, the method of the application is more accurate in describing the fissures of the focal source of an earthquake, and the classification can also be more fine.

[0179] It should be noted that the above specific embodiments are exemplary, and those skilled in the art can think of various solutions under the inspiration of the disclosure of the application, and these solutions also belong to the disclosed range of the application and fall within the protection scope of the application. Those skilled in the art should understand that the specification and drawings of the application are illustrative and do not constitute a limitation on the claims. The protection scope of the application is defined by the claims and their equivalents. The specification of the application contains multiple inventive concepts, such as "preferably", "according to a preferred embodiment" or "optionally", which all indicate that the corresponding paragraph discloses an independent concept, and the applicant reserves the right to file a divisional application according to each inventive concept.

Claims

1. A system for characterizing a fault-fracture seismic source based on waveform features, comprising a plurality of sensors (10) and at least one processor (20), the sensors (10) being connected to the processor (20) in a wired and / or wireless manner, characterized in that the processor (20) is configured to: receive amplitude data of waves collected by the plurality of sensors (10); construct a three-dimensional ellipsoid basic equation capable of covering spatial radiation; determine a source location, energy and / or a fracture orientation based on spatial geometric parameters of the three-dimensional ellipsoid; wherein the step of constructing the three-dimensional ellipsoid basic equation capable of covering spatial radiation comprises: setting a source sphere capable of encompassing spatial radiation of a source; calibrating attenuation of waveforms of elastic waves collected by sensors (10) at spatial positions with different directions and distances with the source sphere as a reference; obtaining waveform amplitudes in different directions on the source sphere; and obtaining the basic equation and a standard form of the ellipsoid by using the amplitudes of the elastic waves on the source sphere. The processor (20) is configured to: determine a change state of a fracture and / or a source based on changes of the spatial geometric parameters of the ellipsoid in a time dimension. The processor (20) is configured to: characterize a stress triaxiality, a stress state and / or a stress orientation based on three axis parameters of the ellipsoid, and establish a relationship between the three axis parameters of the ellipsoid and the stress based on a fitting relationship between the energy and the stress, so as to determine a stress tensor and a change thereof. The way of constructing the three-dimensional ellipsoid basic equation capable of covering spatial radiation comprises: fitting coefficients of the ellipsoid basic equation; The spatial geometric parameters of the ellipsoid at least include: a center coordinate, three semi-axis lengths and / or a semi-focal distance. The way of fitting the coefficients of the ellipsoid basic equation at least comprises: In a case where an amount of the received data is not less than a preset data amount threshold, directly fitting the coefficients of the ellipsoid basic equation; In a case where the amount of the received data is less than the preset data amount threshold, fitting the coefficients of the ellipsoid basic equation based on a main plane random point supplement method. The way of calculating the spatial geometric parameters of the ellipsoid at least comprises: The basic equation of the ellipsoid is 2. The waveform feature based fault fracture seismic source characterization system of claim 1, wherein, The coefficients of the ellipsoid basic equation are simplified into a matrix form: The method at least comprises:

3. The waveform feature based fault-fracture seismic source characterization system of claim 1 or 2, wherein, receiving amplitude data of waves collected by the plurality of sensors (10); constructing a three-dimensional ellipsoid basic equation capable of covering spatial radiation; determining a source location, energy and / or a fracture orientation based on spatial geometric parameters of the three-dimensional ellipsoid; 4. The waveform feature based fault fracture seismic source characterization system of claim 1, wherein, wherein the step of constructing the three-dimensional ellipsoid basic equation capable of covering spatial radiation comprises: setting a source sphere capable of encompassing spatial radiation of a source; calibrating attenuation of waveforms of elastic waves collected by sensors (10) at spatial positions with different directions and distances with the source sphere as a reference; 5. The waveform feature based fault fracture seismic source characterization system of claim 4, wherein, obtaining waveform amplitudes in different directions on the source sphere; obtaining the basic equation and a standard form of the ellipsoid by using the amplitudes of the elastic waves on the source sphere. The method further comprises:

6. The waveform feature based fault fracture seismic source characterization system of claim 4, wherein, determining a change state of a fracture and / or a source based on changes of the spatial geometric parameters of the ellipsoid in a time dimension. ​ ； ​ ， ， ， ； where a denotes a coefficient, I3denotes the third invariant of the matrix K3denotes the third semi-invariant of the matrix A. Computing the matrix The corresponding eigenvalue And the unit eigenvector ; According to the matrix , eigenvalues and the third invariant of the matrix calculate the spatial geometric parameters of the ellipsoid.

7. The waveform feature based fault fracture seismic source characterization system of claim 6, wherein, According to the matrix , eigenvalues and the third invariant of the matrix The way to calculate the spatial geometric parameters of the ellipsoid is: ； ； ； representing the center coordinates of the ellipsoid ; a, b, c represent the semi-axes of the ellipsoid in three dimensions, respectively, represents the semi-focal distance of the ellipsoid.

8. A method for representing a fault fracture source based on waveform characteristics, characterized by, ​ ​ ​ ​ ​ ​ ​ ​ ​ 9. The waveform feature based fault fracture seismic source characterization method of claim 8, wherein, ​ ​ 10. The wave shape feature based characterization of a faulted fracture seismic source method of claim 8 or 9, wherein, The method further comprises: characterizing stress triaxiality, stress state and / or stress orientation based on three axis parameters of the ellipsoid, establishing a relationship between the three axis parameters of the ellipsoid and the stress based on a fitted relationship between energy and stress, thereby determining the stress tensor and its variation.

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