CN116736385A - Fault fracture focus characterization system and method based on waveform characteristic - Google Patents
Fault fracture focus characterization system and method based on waveform characteristic Download PDFInfo
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Abstract
The invention relates to a fault fracture seismic source characterization system and method based on waveform characteristics, comprising a plurality of sensors and at least one processor, wherein the processor is configured to: receiving amplitude data of waves acquired by a plurality of the sensors; constructing a three-dimensional ellipsoidal basic equation capable of covering space radiation; the source location, energy, and/or shatter location is determined based on the spatial geometry of the ellipsoid in three dimensions. The invention fits to obtain a uniquely determined ellipsoid, and describes the physical information of the seismic source through the space geometrical parameters of the ellipsoid. Such as describing the location, energy, spatial extent of disruption, etc. of the source. The calculation process of ellipsoid fitting is simple and easy to understand.
Description
Technical Field
The invention relates to the technical field of elastic wave detection, in particular to a fault fracture seismic source characterization system and method based on waveform characteristics.
Background
When a solid such as rock is subjected to an external force, the solid cracks and fissures are generated. Elastic waves are also generated during the fracture generation. At different scales, elastic waves can manifest themselves as natural earthquakes, microseismic and acoustic emissions. The elastic wave is generally detected by a detector, so that the characteristic analysis of the elastic wave is performed on the crack generating the seismic source. And characterizing the fault fracture seismic source based on waveform characteristics, and judging relevant information of the seismic source to study the seismic source.
Current technology for elastic wave detection generally uses a vibration detector for detection. However, the vibration detector scans the solid structure by using earthquake waves or ultrasonic waves, and the crack structure information in the solid is measured by using the change of wave velocity. The detection accuracy and range of the vibration detector are related to the wavelength, and the smaller the wavelength is, the higher the detection accuracy is, but the smaller the detection range is. According to the characteristics of the detected elastic waves, the representation and description of the seismic source with the three-dimensional structure cannot be performed at present. In particular, the dynamic course of the three-dimensional structure of the seismic source and its fissures cannot be described.
For example, chinese patent publication No. CN111965696a discloses a dynamic disaster prediction method based on elastic wave multi-objective analysis, which includes the steps of: s1: during operation, an acoustic emission monitoring device is used for collecting and transmitting an elastic wave signal propagated in a measured object; s2: the ground comprehensive signal processing device receives and analyzes the elastic wave signal to obtain abnormal geologic body and dynamic inversion imaging of stress variation in the measured object, and simultaneously extracts acoustic emission characteristic parameters of the elastic wave signal; s3: the ground comprehensive signal processing device carries out disaster judgment and intelligent early warning according to the change condition of abnormal geologic body dynamic inversion imaging or stress change dynamic inversion imaging or acoustic emission characteristic parameter in the measured object. Although the invention can carry out comprehensive and accurate prediction and early warning on dynamic disasters, the prediction accuracy is greatly improved, the prediction work efficiency is greatly improved, and the prediction cost is reduced. However, since inversion is performed only on the basis of the elastic wave signal, there is no ellipsoidal model capable of describing dynamic changes, and thus dynamic inversion imaging can be achieved only by constantly updating the inversion imaging of abnormal geologic bodies and stress changes. The invention has the advantages that the data volume to be processed is large, and if one inversion data has problems, the larger deviation of dynamic inversion imaging can be caused.
Based on the defects of the prior art, the method hopes to realize the representation of the seismic source through the dynamic description of the change of the crack of the three-dimensional structure, and improves the representation progress of the seismic source and the crack thereof.
Furthermore, there are differences in one aspect due to understanding to those skilled in the art; on the other hand, since the applicant has studied a lot of documents and patents while making the present invention, the text is not limited to details and contents of all but it is by no means the present invention does not have these prior art features, but the present invention has all the prior art features, and the applicant remains in the background art to which the right of the related prior art is added.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a fault fracture seismic source characterization system based on waveform characteristics, which comprises a plurality of sensors and at least one processor, wherein the sensors and the processor establish a connection relationship in a wired and/or wireless manner, and the processor is configured to: receiving amplitude data of waves acquired by a plurality of the sensors; constructing a three-dimensional ellipsoidal basic equation capable of covering space radiation; the source location, energy, and/or shatter location is determined based on the spatial geometry of the ellipsoid in three dimensions.
The three axes of the seismic source ellipsoid can represent stress triaxial degree, stress state and/or stress azimuth, and the relation between the energy and the stress is established on the three axes through fitting of the relation between the energy and the stress, so that a stress tensor can be completely determined, which is not possible by all the current ground stress measuring means. The invention is basically applied to estimating the stress state of a seismic source area according to the front earthquake, the azimuth of the stress can be directly determined by using an ellipsoid of the seismic source, and the magnitude and the direction of the main stress can be represented by the magnitude and the azimuth of the ellipsoid.
Preferably, the processor is configured to: and judging the change state of the crack and/or the seismic source based on the change of the space geometrical parameter of the ellipsoid in the time dimension. On the basis of characterizing the position and/or stress state, stress orientation and/or stress tensor of the source and its variations by means of spatial geometrical parameters, the various physical quantities of the source can be described in terms of time-based variations in combination with the dimensions of time.
Preferably, the processor is configured to: the stress triaxial degree, the stress state and/or the stress azimuth are characterized based on three axis parameters of the ellipsoid, and the relationship between the three axis parameters of the ellipsoid and the stress is established based on the fitting relationship between the energy and the stress, so that the stress tensor and the change thereof are determined. The physical characteristics of the seismic source are represented by the ellipsoids, so that the energy, tensor and the like of the seismic source can still be accurately described after the current energy of the seismic source exceeds eight-level vibration, and the defect of the energy description of the super-large seismic in the prior art is overcome.
Preferably, the way to construct a three-dimensional ellipsoidal basic equation capable of covering spatial radiation includes: fitting coefficients of the ellipsoidal basic equation; calculating the space geometrical parameters of the ellipsoids; the spatial geometrical parameters at least comprise: center coordinates, three half-axis lengths, and/or mid-focal distances.
The spatial geometry of an ellipsoid that can cover an amplitude vector is related to the physical characteristics of the source. It is necessary to obtain the spatial geometry of the ellipsoids. According to the method, the ellipsoids which can be covered by all the amplitude vectors are obtained by fitting coefficients of an ellipsoid basic equation, so that the effect of the ellipsoids on covering the amplitude vectors is better.
Preferably, the fitting of the coefficients of the ellipsoidal basic equation at least includes:
under the condition that the received data quantity is not less than a preset data quantity threshold value, directly fitting coefficients of the ellipsoidal basic equation; and under the condition that the received data quantity is less than a preset data quantity threshold value, fitting coefficients of the ellipsoidal basic equation based on a principal plane random complement method.
Preferably, the preset number threshold is 10. That is, when the number of data channels is 10 or more, the data is relatively rich, and random dot filling is not required. In the case where the number of data channels is smaller than 10, the data is relatively small, and the coefficients of ellipsoids need to be calculated by random complements.
In the present invention, setting the preset number threshold to 10 is based on the result of a sufficient analysis of a large amount of experimental data. For data with data channel smaller than 10, if random point complement is not performed, the fitting deviation between the data channel and the corresponding ellipsoid is larger, and the effect is poor. For data with the data channel not smaller than 10, no matter the points are complemented, an ellipsoid with better fitting effect can be obtained. Therefore, the invention sets the preset number threshold to 10, and reduces the calculated amount of the processor in the fitting process.
Preferably, the way of calculating the spatial geometrical parameters of the ellipsoids comprises at least:
the basic equation of an 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 ；
Simplifying each coefficient of the ellipsoidal basic equation into a matrix form:
K 3 ＝|A|，I 3 ＝|A*|；
wherein a represents a coefficient, I 3 The third invariant, K, representing matrix a × 3 Then the third semi-invariant of matrix a is represented; calculating eigenvalues (lambda) corresponding to matrix a 1 ,λ 2 ,λ 3 ) And a unit feature vector (eta) 1 ,η 2 ,η 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Based on matrix a, eigenvalues, and third invariant of matrix aAnd calculating the space geometrical parameters of the ellipsoids.
The basic equation (1) of the ellipsoid is required to be corrected into a standard form, so that the spatial geometrical parameters related to the amplitude vector can be obtained, and meanwhile, the ellipsoid with large coverage deviation cannot be obtained.
Preferably, the method for calculating the space geometrical parameters of the ellipsoid according to the matrix a, the eigenvalue and the third invariant of the matrix a is as follows:
X c T ＝-(A * ) - [a 14 a 24 a 34 ] T ；
X c T representing the center coordinates of an ellipsoid (x 0 ,y 0 ,z 0 ) The method comprises the steps of carrying out a first treatment on the surface of the a. b and C respectively represent the half-axis length in the three-dimensional direction of the ellipsoid, C 0 Representing the half focal length of an ellipsoid.
The spatial geometrical parameters of the present invention are related to the individual coefficients of the ellipsoidal basic equation. The use of spatial geometric parameters to characterize the various physical quantities of the seismic source, rather than directly using coefficients, can simplify the characterization information, be straightforward, and even laypersons can easily understand the characterization content.
The invention also provides a fault fracture seismic source characterization method based on waveform characteristics, which at least comprises the following steps:
s1: receiving amplitude data of waves acquired by a plurality of the sensors;
s2: constructing a three-dimensional ellipsoidal basic equation capable of covering space radiation;
s3: the source location, energy, and/or shatter location is determined based on the spatial geometry of the ellipsoid in three dimensions.
The characterization method of the invention is basically applied to estimating the stress state of the seismic source area according to the front earthquake, the direction of the stress can be directly determined by using the seismic source ellipsoid, and the magnitude of the stress is actually required to be combined with the damage evolution characteristic, which cannot be achieved by the prior art.
Preferably, the method further comprises: and judging the change state of the crack and/or the seismic source based on the change of the space geometrical parameter of the ellipsoid in the time dimension.
The physical characteristics of the seismic source are accurately and dynamically described based on the time dimension, which is a dynamic description which cannot be performed by adopting a plane ellipse or a plurality of ellipse filling methods in the prior art.
Preferably, the method further comprises: the stress triaxial degree, the stress state and/or the stress azimuth are characterized based on three axis parameters of the ellipsoid, and the relationship between the three axis parameters of the ellipsoid and the stress is established based on the fitting relationship between the energy and the stress, so that the stress tensor and the change thereof are determined.
The fault fracture seismic source characterization method based on waveform characteristics not only can be used for indicating the fracture process of the seismic source fracture, but also can be used for characterizing the energy of the seismic source based on the volume of an ellipsoid. The method can be used for calculating the seismic source energy, and can be used for supplementing the defect of saturation of the traditional Rich's magnitude and moment magnitude on the seismic level of more than eight-magnitude earthquakes. The method can directly calculate the energy of the seismic source, can characterize the energy of the seismic source with more than eight levels, and provides more accurate characterization content for subsequent researches of the seismic.
Drawings
FIG. 1 is a schematic representation of one of the fitted ellipsoids of the present invention;
FIG. 2 is a schematic view of a sensor arrangement of one preferred embodiment of the present invention;
FIG. 3 is a schematic view of a sensor arrangement of another preferred embodiment of the present invention;
FIG. 4 is a first source probe vector diagram formed based on six-channel amplitude data, which is exemplary of the present invention;
FIG. 5 is a view of a source ellipsoid corresponding to the first source probe vector map of the present invention;
FIG. 6 is a second source probe vector diagram formed based on eight-channel amplitude data, which is exemplary of the present invention;
FIG. 7 is a view of a shearing type source ellipsoid corresponding to the second source detection vector diagram of the present invention;
FIG. 8 is a third source probe vector diagram formed based on eight-channel amplitude data, which is exemplary of the present invention;
FIG. 9 is a view of a shear-type source ellipsoid corresponding to the third source probe vector diagram of the present invention;
FIG. 10 is a fourth source probe vector diagram formed based on eight-channel amplitude data, which is exemplary of the present invention;
FIG. 11 is a drawing of a stretched source ellipsoid corresponding to a fourth source probe vector diagram of the present invention;
FIG. 12 is a fifth source probe vector diagram formed based on eight-channel amplitude data, which is exemplary of the present invention;
FIG. 13 is a drawing of a stretched source ellipsoid corresponding to the fifth source probe vector diagram of the present invention;
FIG. 14 is a schematic illustration of the principal plane determination of the present invention;
FIG. 15 is a schematic view of a random papermaking point of the present invention;
FIG. 16 is a schematic representation of an analysis of the present invention to derive source break up velocity.
List of reference numerals
10: a sensor; 20: a processor.
Detailed Description
The following detailed description refers to the accompanying drawings.
The invention provides a fault fracture seismic source characterization system and a fault fracture seismic source characterization method based on waveform characteristics. The invention also provides a method and a system for calculating the energy of the seismic source.
The system of the present invention includes a number of sensors and at least one processor. The sensor establishes a connection with the processor in a wired and/or wireless manner. The wired mode is, for example, communication connection through optical fibers. The wireless mode is, for example, wireless communication connection is performed through communication elements such as a Bluetooth communication assembly, a WIFI communication assembly, a ZigBee communication assembly, an infrared communication assembly and the like.
The sensor is used for collecting the elastic wave of the seismic source. The sensor is preferably a broadband vibration sensor, and the frequency range is 0-2kHz (low frequency) and 2-500 kHz (high frequency) according to the monitoring object. For example, the high frequency can be R6 type piezoelectric ceramic sensor or W800 type piezoelectric ceramic sensor, and the low frequency can be all-fiber microseismic probe.
Preferably, the processor refers to an application specific integrated chip and/or a server, a CPU, a single-chip microcomputer, etc. capable of running the program of the fault fracture source characterization method based on waveform characteristics of the present invention. Preferably, the processor may also be an integration of several microprocessors. Preferably, the processor is not limited to appear as a single processing element, but may include a server, computer, or like device having data processing capabilities including a processing element.
The invention will now be described with reference to certain terminology.
A seismic source: refers to the location where the solid breaks, and is spatially represented by coordinates (x, y, z). In the present invention, the seismic source is represented by an ellipsoid, also known as a seismic source ellipsoid, the location of which is the focal coordinates of the ellipsoid. Including but not limited to acoustic emissions, microseismic, and natural seismic. A sound source, an acoustic emission source, representing the rupture process and the movement process of the rupture face.
Source probe vector: the direction of which is from the source to the probe, the magnitude being expressed in amplitude.
Seismic source ball: the method takes a seismic source as a center to serve as a sphere (the radius can be arbitrary and is better than the wavelength), sensors in different directions and at different distances in space are used for detecting waveforms, attenuation of the sphere is calibrated by taking the sphere as a reference, and waveforms in different directions are obtained on the sphere.
Attenuation: the phenomenon that the amplitude of the finger wave becomes small due to propagation loss.
Ellipsoid: the elastic wave generated by explosion uniformly propagates to space in the form of sphere, and the corresponding rupture characteristic of explosion is a sphere. When the fracture becomes a directional fracture, the generated elastic wave will be distorted into an ellipsoid, corresponding to the fracture process.
Ellipsoids calculated based on elastic waves mentioned in the prior art generally can only realize the characterization of a static fracture structure, and a plurality of ellipsoids are needed to fill the fracture to completely cover the fracture, so that the fault fracture seismic source cannot be accurately characterized based on waveform characteristics. According to the invention, through optimizing the calculation process of the ellipsoid, the fault fracture seismic source is characterized in a new mode based on an ellipsoid basic equation, and the quantitative description and the characterization accuracy of the seismic source are improved.
Unlike available technology, which can only characterize some static state of the crack, the present invention constructs new ellipsoid basic equation via waveform characteristic to characterize the crack process dynamic description of the seismic source. The present invention is not a description of the dynamic changes of the fracture, but rather a description of the fracture process of the source itself. The invention adopts ellipsoids to represent the crack process of the seismic source, and represents the cracking speed and the cracking length. The ratio of the burst length to the burst speed is the burst time. The invention can also represent the energy of the seismic source by the volume of the ellipsoid. After the energy of the seismic source is obtained, the intensity of the shatter can be judged. For example, when the source is a seismic fracture, the fracture intensity can be quantified by the volume of the ellipsoid.
In the prior art, the level of the Rich earthquake takes the horizontal displacement generated when the earthquake occurs as a judgment standard. The Rich jar scale table is divided into 9 scales. The greater the earthquake, the greater the number of magnitude. For each level increase, the energy released by the earthquake increases by a factor of about 32. Moment magnitude is the magnitude of the seismic moment that is used to determine the magnitude. The seismic moment is a physical quantity (similar to the concept of moment) describing the mechanical strength of an earthquake as it occurs, and is determined by the product of the fracture area of the seismic fault, the average amount of dislocation, and the shear modulus of the rock. The moment and magnitude of the earthquake can be obtained by the comprehensive inversion of the earthquake spectrum or by the fracture characteristics of the earthquake (such as the earthquake fault scale, the depth of the earthquake source, the amount of misplacement, the rock mechanical property and the like). The disadvantage of the prior art in determining the magnitude of the earthquake from the Rich magnitude or the moment magnitude is that the magnitude judgment is not directly performed by calculating the energy of the earthquake source, and the earthquake source is insensitive to the representation of the increase of the energy after the intensity of the earthquake source exceeds eight levels.
The invention can measure the absolute value of energy, and objectively characterize the earthquake intensity by adopting the absolute energy value. After the earthquake exceeds eight levels, the intensity and the change of the earthquake can be judged directly through the energy absolute value of the earthquake source, and the earthquake is more objective and accurate.
As shown in fig. 2 and 3, a number of sensors 10 are provided on the rock. Assuming a cubic geometry of the rock, several sensors 10 are arranged on the surface of and/or around the rock in a centrosymmetric manner. In the present invention, the cube geometry is an ideal structure, and is an exemplary structure. The rock solid in reality can be regular cubes or irregular cube structures. Even in the case of irregular cubes, the plurality of sensors 10 can be arranged as close to the central symmetry as possible, so that the elastic waves emitted from the crack development in the rock in each direction can be collected. The elastic wave propagates outward and forms a radiation field of the elastic wave.
The longitudinal wave and the transverse wave in the elastic wave are bulk waves, the point source propagates outwards from the source in a spherical form, the energy and displacement in all directions are equal, and the source is called an acoustic monopole. The energy and displacement of the split source in each direction will be distorted into ellipsoids. The amplitude of the elastic wave is continuously reduced due to the energy attenuation during propagation. The arrangement of several sensors 10 around the source facilitates the acquisition of amplitude data of elastic waves of different sizes of the source from multiple directions, i.e. the detection of a spatially radiated displacement field.
The sensor 10 sends the acquired amplitude data to the processor 20 via the communication assembly. The processor 20 processes the amplitude data to ultimately effect the construction of the basic equations for the ellipsoids. Preferably, the processor 20 processes the amplitude data as follows.
As shown in tables 1, 2 and 3, after receiving the data acquired by the sensors, the processor extracts all events and amplitudes received by each channel from the acoustic emission waveform data by short-time fourier transform, and stores all event time, coordinates and amplitude data.
S1: constructing a spatial propagation vector of the seismic source.
As shown in fig. 4, 6, 8, 10 and 12, a spatial coordinate system is established. The origin of coordinates is determined by the constructor and the spatial coordinates x, y, z are used to characterize the source location. In the figure, the displacement of the spatially radial displacement field of the seismic source is represented by amplitude. And connecting the amplitude with the seismic source to obtain the spatial propagation direction of the seismic source, namely the direction of a source detection vector. The initial displacement emitted from the source in all directions, i.e. the magnitude of the source probe vector, can be obtained by considering the attenuation of the wave in the direction of the source probe vector. In the case where more than 4 sensors receive waveform data of the source radiation, the source location is determined by time difference localization. In the invention, if the channel data are less, the average coverage rate is smaller, and the ellipsoidal fitting effect is poor. Especially in the case of only 4 data channels, the average coverage of ellipsoids with the amplitude vector is small.
As shown in fig. 4, there are 5 source probe vectors in different directions. The magnitude of each source probe vector represents the initial displacement of the elastic wave in that corresponding direction.
S2: a sphere is constructed that covers the spatial radiation of the source.
As shown in fig. 1, a sphere is provided that is capable of enclosing the spatial radiation of the source. For example, a radius is set centered on the source to form a sphere. Preferably, the radius of the sphere can be arbitrarily set. Preferably, the radius of the sphere is greater than the wavelength of the elastic wave. The waveforms of the elastic waves acquired by the sensors 10 at different spatial positions with different directions and distances are used as a reference to calibrate the attenuation of the spherical body. Waveform amplitudes in different directions are obtained on the sphere. The sound monopole of the invention is also a sphere itself. The elastic wave space radiation generated by the fracture process is an ellipsoid. The basic equation and standard equation of the ellipsoid can be obtained by utilizing the amplitude of the elastic wave on the seismic focus sphere, so that the structural characteristics of the crack can be further represented.
S3: the ellipsoid basic equation of the present invention for an ellipsoid is calculated.
S31: and establishing an ellipsoidal basic equation.
The basic equation for an ellipsoid can be expressed as:
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)
wherein x, y, z coordinates represent the amplitude coordinates on the source sphere. The calculation modes of the x, y and z are as follows: the source probe vector is multiplied by the cosine of its direction. a represents a coefficient calculated based on amplitude data acquired by the sensor.
S32: the modified ellipsoidal basic equation is in a standard form.
The basic equation based on the ellipsoid cannot directly obtain the space geometric parameters of the ellipsoid, so the invention needs to correct the basic equation (1) of the ellipsoid into a standard form. The space geometrical parameters of the ellipsoid at least comprise the center of the ellipsoid, the axial length, the focal point coordinates and the like.
The standard form of an ellipsoid can be expressed as:
wherein x is 0 、y 0 、z 0 The coordinates of the center of the ellipsoid are represented, and a, b, and c represent the long, medium, and short half-axis lengths of the ellipsoid, respectively. In determining the center of the ellipsoid, the crack propagation direction can be characterized based on the source location.
The coefficients of the basic equation of an ellipsoid are reduced to the following form:
L 3 ＝|A|，I 3 ＝|A*| (3)
wherein I is 3 The third invariant representing matrix a, and K 3 The third semi-invariant of a is represented and their values are the determinant of the corresponding matrix, respectively.
At the same time, also find the corresponding AEigenvalue (lambda) 1 ,λ 2 ,λ 3 ) And a unit feature vector (eta) 1 ,η 2 ,η 3 )。
The central coordinate X of the ellipsoid can be obtained by using the above parameters c ＝(x c ,y c ,z c ) The half-axis lengths (a, b and c) and the semicoke distances (pseudo) are respectively as follows:
X c T ＝-(A * ) - [a 14 a 24 a 34 ] T (4)
X c T represents the center coordinates (x 0 ,y 0 ,z 0 ) A, b and C respectively represent the half axis length of the ellipsoid in the three-dimensional direction, C 0 Representing the semicoke distance of the major plane of the ellipsoid. The direction corresponding to the first principal axis (i.e., major axis) of the ellipsoid is defined by the eigenvector eta 1 And (5) determining. The focal point of the ellipsoid is on its long axis and its coordinates can be calculated using the coordinates of the sphere center. So far, all the space geometrical parameters of the ellipsoids are all calculated.
The method for determining the geometrical parameters of the space of the focus ellipsoid is simple and convenient in calculation method and visual in geometrical morphology.
Firstly, the main method for determining the space geometrical parameters of the seismic source in the seismology at present is to perform moment tensor inversion on the seismic wave waveforms acquired by a plurality of seismic stations (more than 6), determine the magnitude and the type of the seismic source, calculate the space geometrical characteristics of the seismic source through a complex dynamics method on the basis of a certain theoretical assumption, have complicated calculation procedures, separate the geometrical parameters of the seismic source from the physical process, require deep professional background knowledge to understand, perform the fitting of the ellipsoid of the seismic source through Gao Jiege forest functions by Petra Adamov et al, only indicate that the principal axis of the ellipsoid of the seismic source represents the expansion direction of the seismic source, not combine other geometrical characteristics of the ellipsoid with the physical characteristics of the seismic source, and have complex calculation methods. In the method, the ellipsoidal shape and the spatial trend obtained by fitting different frequency components are changed, and the result is not unique.
Second, the invention uses the source spatial radiation amplitude (maximum amplitude) as the raw data for the fit, with the maximum amplitude obtained by performing a fast fourier transform on the waveforms acquired by the sensors. The minimum needs 4 waveform data acquired by the sensor, and the geometrical parameters of the ellipsoid can be uniquely determined by carrying out least square fitting on the ellipsoid with the maximum amplitude. The ellipsoidal volume can characterize the magnitude of the source energy. The spatial spread of ellipsoids may characterize the spatial extent of disruption of the source. The ellipsoidal first principal plane can characterize the spatial direction of spread of the fault. The ratio of the first principal axis and the third principal axis of the ellipsoid may characterize the source type. The crack propagation direction is characterized by the position of the source to the center of the ellipsoid. In conclusion, the method acquires the physical parameters of the seismic source through the space geometrical parameters of the ellipsoid, is simple to calculate, has clear and vivid physical process, and can be understood without professional background.
The focus is taken as a focus on the long axis of the ellipsoid, and then each parameter of the ellipsoid is the parameter of the focus slit, namely the slit can be quantitatively described by the amplitude ellipsoid parameter of the focus. For example, table 1 shows amplitude data for 6 channels.
Table 16 channel amplitude data sample
In table 1, the first column indicates the time at which the event occurred. X, Y and Z columns represent the coordinates of the seismic source, respectively. Channels 1-6 represent the amplitude data for each channel. The source probe vectors constructed from the data of table 1 are shown in fig. 6. Fig. 6 includes 6 source probe vectors having different directions. The origin of the 6 source probe vectors is the source.
In Table 2, columns 1 to 3 are ellipsoidal center coordinates, columns 4 to 6 are long, medium, and short half-axis lengths, columns 7 to 9 are unit vectors of the first principal axis, the second principal axis, and the third principal axis, respectively, and column 10 is average coverage. Processor 20 constructs fig. 4 and 5 based on the data samples of table 1. The processor 20 calculates the spatial geometry of the ellipsoid based on a standard form of the ellipsoid, as shown in table 2.
Table 2 geometric parameters of the fitted ellipsoids
As shown in fig. 1, when the number of data channels is less than 4, the data amount is insufficient, and it is difficult to fit an ellipse. When the number of data channels is greater than or equal to 4, the amount of data is sufficient to achieve an ellipse fit. However, the fitting effect of ellipses varies greatly. The invention evaluates the effect of ellipsoid fitting through the coverage rate of the ellipsoids to the amplitude vector. A large number of experimental data analysis shows that when more than 6 channels of data can be acquired, the ellipsoidal coverage rate is more than 90%, and the fitting effect is good. When the number of channels is less than 6, the ellipsoid coverage rate is less than 80%, and the fitting effect is poor.
Preferably, the processor 20 calculates the spatial geometry parameters of the ellipsoids based on the least squares method.
The spatial geometry of the ellipsoid is obtained by the following calculation without the need for the complement.
Wherein min G (A) represents an objective function, a represents a major axis half-axis length, b represents a minor axis half-axis length, and c represents a minor axis half-axis length.
In the case where the objective function is set to an ellipsoidal volume, then there are:
min G' (A) represents the ellipsoidal volume.
The above formula is further simplified and is equivalent to:
min G″(A)＝-|I 3 | (7-3)
min G' (A) represents the volume of the ellipsoid, I 3 ＝|A*|。
The first constraint is n linear equations, i.e., n ellipsoid basis equations, established by the channel source radiation vector. At this time, the variables are elements of the matrix A, and x, y and z are radiation coordinate values acquired by the sensors on the focus sphere. Namely:
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)
the second constraint is a coefficient condition in the standard form of an ellipsoidal equation, namely:
the third constraint condition is the condition of solving the characteristic equation of the elliptic equation quadratic coefficient matrix, namely, the condition that the unitary cubic equation has three real roots, namely:
Δ＝4I 1 3 I 3 -I 1 2 I 2 2 -18I 1 I 2 I 3 +27I 3 2 ≤0 (10)
wherein I is 1 The first invariant representing matrix a; i 2 A second invariant representing matrix a; i 3 The third invariant representing matrix a.
The fourth constraint is the focus condition, the source point coordinates (x c ,y c ,z c ) The same as the focal coordinates obtained by the calculation of the half-axis length and the half-focal distance, the expression is as follows:
x c ＝x 0 -C 0 η 1 (1),y c ＝y 0 -C 0 η 1 (2),z c ＝z 0 -C 0 η 1 (3) (11)
wherein x is 0 、y 0 、z 0 Representing the coordinates of the centre of the ellipsoid, C 0 Representing the half focal length, eta 1 Representing a unit principal vector in the principal axis direction. In the expressions (1), (2) and (3), there are 3 direction vectors, each of which is represented by 3 components.
The ellipsoidal radiation has the strongest radiation energy in the long axis direction and is marked as the crack expansion direction. The position of the focus determined by 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 expansion (or sliding). The type of source can be determined by the ratio of the first axis to the third axis of the ellipsoid: when the percentage of the center axis/the long axis of the ellipsoid is greater than 50%, the ellipsoid is a shear fracture, whereas the ellipsoid is a tensile fracture, as shown in table 3.
TABLE 3 calculation of source type
Table 4 shows the 8-channel 2-set amplitude data sample one of the present invention, corresponding to the source probe vector and ellipsoid of fig. 6 and 7, and fig. 8 and 9, respectively.
Sample one of amplitude data of the 4 8 channel
As shown in table 3, the ellipsoids in fig. 7 have a percentage of 90.10% of the central axis/long axis, and the ellipsoids in fig. 9 have a percentage of 60.01% of the central axis/long axis, which are all shear cracks.
Table 5 8 amplitude data sample two of the channels
Table 5 shows the 8-channel 2-set amplitude data samples of the present invention, corresponding to the source vectors and ellipsoids of fig. 10 and 11, and fig. 12 and 13, respectively.
As shown in table 3, the ellipsoids in fig. 11 have a percentage of 42.63% of the central axis/long axis, and the ellipsoids in fig. 13 have a percentage of 45.89% of the central axis/long axis, which are all tensile slits.
Preferably, in the case where the data channel is greater than or equal to 10, the processor does not need to randomly complement the major plane of the ellipsoid. In the case where the data channel is smaller than 10, the processor needs to randomly complement the major plane of the ellipsoid.
Preferably, in the case where the point complement is required, the step of randomly complementing the ellipsoid according to the present invention is as follows.
S51: a principal plane is determined.
As shown in FIG. 14, the first principal direction of the ellipsoid is the direction of maximum amplitude, the maximum of the long axis radiation is the maximum amplitude, i.eMake the other amplitude vector and maximum amplitude vector fork, get +.>Maximum value of the modulus->Corresponding amplitude vector>Amplitude vector->The unit vector obtained by cross multiplication with the maximum amplitude vector is the principal plane normal, i.e. +.> Representing the other respective amplitude vectors +.>Slit vector representing the mode maximum +.> Representation ofIs a mold of (a). The direction perpendicular to the first main axis on the main plane is the direction of the second main axis. Amplitude vector->The projection size on the second principal axis is the second principal axis size, i.e. +.> Representing the second principal axis size.
S52: and (5) randomly creating points.
As shown in FIG. 15, 2 points are randomly generated within 5 degrees of the first main direction, and the size is 0.9-1.1Within 15 degrees of the reverse direction of the first main direction, 2 points are randomly generated, which is more than 0.9 to 1.1->Randomly creating 2 points in the second main direction, wherein the size is 0.9-1.1 +.>
In addition to determining two amplitude vectors of the principal plane, other amplitude vectors employ mirror image fabrication points whose normal angles to the principal plane are α. When the included angle alpha is smaller thanAt the time ofThe included angle between the amplitude vector and the amplitude vector is pi-2 alpha, and the size of the point is 0.9 to 1.1 +.>When the included angle is greater than->When the point is made in the direction with the included angle of 2 alpha-pi with the amplitude vector, the size is 0.9 to 1.1 +.>
S53: and judging the fitting effect.
The smaller the ellipsoidal area is and the more amplitude vectors can be covered, the better the fitting effect is.
Specifically, the intersection point of the ellipsoid formed by fitting and each amplitude vector equation is obtained by simultaneous solving, the square sum of the residual error of each amplitude vector and the intersection point is squared, and the average coverage difference of the amplitude vectors is obtained by dividing the sum of squares of the residual errors of each amplitude vector and the intersection point by the number of amplitude channels. The average coverage difference is divided by the sum of the amplitudes and multiplied by the percentage to obtain a coverage difference ratio. Subtracting the value from 1 to obtain the ellipsoid coverage rate. The bigger the ellipsoid coverage, the better the ellipsoid fitting effect.
The amplitude average coverage difference of the main plane dotting method is mostly within 10 mm. The ellipsoidal principal plane can characterize the spatial direction of the fault.
For example, the ellipsoidal expression is:
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。
setting the position M of the seismic source in the space 0 (x 0 ,y 0 ,z 0 ) Amplitude vectorThe amplitude vector vertex coordinates are (x) 2 ,y 2 ,z 2 ) Let M (x, y, z) be any point on the amplitude vector, the amplitudeThe vector equation is
Solving the ellipsoid basic equation and the amplitude vector equation simultaneously to obtain an intersection point M1 (x 1 ,y 1 ,z 1 ) Amplitude vector and intersection residual (distance)The average coverage difference of the amplitude vectors is +.>Amplitude sum is +.>Ellipsoid coverage is->*100％。
Table 6 6 ellipsoidal coverage rate calculation table
The calculated values of the average coverage difference and the associated parameters of ellipsoids fitted based on the source data of 6 data channels are shown in table 6. The average coverage difference is 5.533, the ellipsoid coverage rate is 95.21%, and the ellipsoid fitting effect is good.
S6: and quantitatively describing the seismic source based on the fitted ellipsoid.
The seismic source is quantitatively described as a seismic source ellipsoid through the spatial energy radiation characteristics of the seismic source, and is suitable for seismic source description in which the inside of a solid on all scales takes crack and fault regeneration, connection, sliding, activation and the like as physical processes.
The ellipsoidal radiation has the strongest radiation energy in the long axis direction and is marked as the crack expansion direction. The position of the focus determined by 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 expansion (or sliding). By Doppler effect, the crack extension rate can be calculated from the source radiation, thereby completing the source mechanism solution.
As shown in fig. 16, the calculation formula for the source break velocity can be deduced from the doppler effect as follows:
in the above, f 1 Representing the primary frequency of the seismic source acquired by the first sensor, f 2 Representing the primary frequency of the seismic source acquired by the second sensor, v 0 Representing the wave velocity in the medium. cos alpha 1 Representing alpha 1 Angle at first sensor position S1 and source position O 1 Projection in the direction of the line. cos alpha 2 Representing alpha 2 Angle at first sensor position S1 and source position O 1 Projection in the direction of the line. cos alpha 01 Representing alpha 01 Angle at first sensor position S1 and source position O 1 Projection in the direction of the line. Δf 12 Represents f 1 And f 2 Is a difference in (c). The calculation process is shown in Table 6.
In FIG. 16, S 1 、S 2 Indicating sensor position, O 1 For the source position, L 0 Is the fracture direction determined by the major axis of the ellipsoid. Table 7 shows an example of data for the fracture rate parameters and related parameters for a portion of the seismic source.
TABLE 7 seismic source break up speed calculation table
| f 1 | f 2 | v 0 (km/s) | cosα 1 | cosα 2 | cosα 01 | Δf 12 | u 0 (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 |
Five sets of data examples for calculating the source break up velocity are shown in table 7. In the five sets of data, the source break up velocity is progressively greater.
Further application scenarios of the invention.
The seismic source mechanism can be established through the seismic source ellipsoid itself, moment tensor inversion is not needed, and the moment tensor is used for forward calculation of the radiation of the seismic source ellipsoid, which is not necessary.
The three axes of the seismic source ellipsoid can represent stress triaxial degree, stress state and/or stress azimuth, and the relation between the energy and the stress is established on the three axes through fitting of the relation between the energy and the stress, so that a stress tensor can be completely determined, which is not possible by all the current ground stress measuring means. One basic application of this method is to estimate the stress state of the source region from the front earthquake, the orientation of the stress can be determined directly by the source ellipsoid, and the magnitude and direction of the principal stress can be characterized by the ellipsoid size and orientation.
Based on the ellipsoid model, a statistical rule model of dynamic evolution of dynamic geological disasters is established.
S11: spatial geometric parameters in an ellipsoid model are acquired.
Preferably, spatial geometric parameters associated with the failure feature, such as long axis parameters, are acquired, reliable lesion variables are established, and the lesion parameters are unified.
S12: the seismic source is described.
The length of each stage of the major axis of the ellipsoid conforms to poisson's distribution, but the overall mean of the major axis of the ellipsoid should be continually increased until the characteristic length is reached. When the damage of the characteristic length reaches a certain amount, the whole monitoring area (rock sample, landslide, seismic block and the like) is damaged. In the case of defects, damage corresponding to the order of the characteristic length also occurs in the early stages, which is associated with the final destruction.
The invention enables more accurate grading of the intensity of a seismic source by dynamic representation of the source, for example dynamic description of the seismic source. Compared with the method for evaluating the intensity of the seismic source in the prior art, the method provided by the invention has the advantages that the description of the cracks of the seismic source is more accurate, and the grading can be finer.
It should be noted that the above-described embodiments are exemplary, and that a person skilled in the art, in light of the present disclosure, may devise various solutions that fall within the scope of the present disclosure and fall within the scope of the present disclosure. It should be understood by those skilled in the art that the present description and drawings are illustrative and not limiting to the claims. The scope of the invention is defined by the claims and their equivalents. The description of the invention encompasses multiple inventive concepts, such as "preferably," "according to a preferred embodiment," or "optionally," all means that the corresponding paragraph discloses a separate concept, and that the applicant reserves the right to filed a divisional application according to each inventive concept.
Claims (10)
1. A fault fracture seismic source characterization system based on waveform characteristics comprises a plurality of sensors and at least one processor, wherein the sensors and the processor establish a connection relationship in a wired and/or wireless manner,
the processor is configured to:
receiving amplitude data of waves acquired by a plurality of the sensors;
constructing a three-dimensional ellipsoidal basic equation capable of covering space radiation;
the source location, energy, and/or shatter location is determined based on the spatial geometry of the three-dimensional ellipsoid.
2. The waveform signature based fault source characterization system of claim 1, wherein the processor is configured to:
and judging the change state of the crack and/or the seismic source based on the change of the space geometrical parameter of the ellipsoid in the time dimension.
3. The fault source characterization system based on waveform characteristics of claim 1 or 2, wherein the processor is configured to:
stress triaxial, stress state and/or stress orientation are characterized based on three axis parameters of the ellipsoid,
and establishing the relationship between the three axis parameters of the ellipsoid and the stress based on the fitting relationship between the energy and the stress, thereby determining the stress tensor and the change thereof.
4. A fault fracture source characterization system based on waveform features according to any one of claims 1 to 3, wherein the manner of constructing a three-dimensional ellipsoidal base equation capable of covering spatial radiation comprises: fitting coefficients of the ellipsoidal basic equation;
calculating the space geometrical parameters of the ellipsoids;
the spatial geometrical parameters at least comprise: center coordinates, three half-axis lengths, and/or mid-focal distances.
5. The fault source characterization system based on waveform features of any one of claims 1 to 4, wherein the fitting coefficients of the ellipsoidal basic equation comprises at least:
under the condition that the received data quantity is not less than a preset data quantity threshold value, directly fitting coefficients of the ellipsoidal basic equation;
and under the condition that the received data quantity is less than a preset data quantity threshold value, fitting coefficients of the ellipsoidal basic equation based on a principal plane random complement method.
6. The fault source characterization system based on waveform features of any one of claims 1 to 5, wherein the means for calculating the spatial geometry of the ellipsoid comprises at least:
the basic equation of an 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 ；
Simplifying each coefficient of the ellipsoidal basic equation into a matrix form:
K 3 ＝|A|，I 3 ＝|A*|；
wherein a represents a coefficient, I 3 The third invariant, K, representing matrix a × 3 Then the third semi-invariant of matrix a is represented;
calculating eigenvalues (lambda) corresponding to matrix a 1 ,λ 2 ,λ 3 ) And a unit feature vector (eta) 1 ,η 2 ,η 3 )；
And calculating the space geometrical parameters of the ellipsoid according to the matrix A, the eigenvalue and the third invariant of the matrix A.
7. The fault source characterization system based on waveform features of any one of claims 1 to 6, wherein the way to calculate the spatial geometry parameters of the ellipsoid from the matrix a, the eigenvalue, and the third invariant of the matrix a is:
X c T ＝-(A * ) - [a 14 a 24 a 34 ] T ；
X c T representing the center coordinates of an ellipsoid (x 0 ,y 0 ,z 0 ) The method comprises the steps of carrying out a first treatment on the surface of the a. b and C respectively represent the half-axis length in the three-dimensional direction of the ellipsoid, C 0 Representing the half focal length of an ellipsoid.
8. A fault fracture source characterization method based on waveform characteristics, the method at least comprising:
receiving amplitude data of waves acquired by a plurality of the sensors;
constructing a three-dimensional ellipsoidal basic equation capable of covering space radiation;
the source location, energy, and/or shatter location is determined based on the spatial geometry of the ellipsoid in three dimensions.
9. The method of claim 8, further comprising:
and judging the change state of the crack and/or the seismic source based on the change of the space geometrical parameter of the ellipsoid in the time dimension.
10. The fault source characterization method based on waveform characteristics of claim 8 or 9, further comprising:
stress triaxial, stress state and/or stress orientation are characterized based on three axis parameters of the ellipsoid,
and establishing the relationship between the three axis parameters of the ellipsoid and the stress based on the fitting relationship between the energy and the stress, thereby determining the stress tensor and the change thereof.
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