13 results about "Phase velocity" patented technology

This paper provides a high-resolution frequency-wavenumber method capable of modal separation. Based on the frequency, wavenumber, and phase velocity characteristics of multimodal Rayleigh surface waves, a method for enhancing high-modal energy by weighting the F-K spectrum with a two-dimensional Gaussian window is proposed. This algorithmic approach enhances high-modal Rayleigh wave information, resulting in simple computation and clear physical meaning. Using probability distribution statistics, a frequency-phase velocity probability distribution is plotted. All extreme points are statistically analyzed, and the median of their phase velocity intervals is taken as the phase velocity of the frequency point in that mode. This more accurately separates and extracts multimodal dispersion curves.

To improve estimation accuracy of an underground structure.SOLUTION: In the underground structure estimation method, micromotion of the soil at observation points P1 to P6 is observed by a micromotion array 10, and at least an S-wave speed Vs1 in a base layer 1 and a depth H to an upper surface 1a of the base layer 1 are calculated by inverse analysis using a relationship between a frequency and a phase speed of a wave propagating through the soil G from the observed micromotion, thereby estimating an underground structure at the observation points P1 to P6. In the subsurface structure estimation method, predetermined observation points among the plurality of observation points P1 to P6 are grouped as group observation points Pg, inverse analysis is performed assuming that the S-wave velocities Vs1 in the base layer 1 at all the grouped group observation points Pg are the same, and the S-wave velocities Vs1 in the base layer 1 and the depth H to the upper surface 1a of the base layer 1 at each of the group observation points Pg are calculated.SELECTED DRAWING: Figure 1

The invention discloses an underground structure scanning method for a controlled active source. According to the method, a known signal generated by an active source is equivalent to a record of a virtual station, the virtual station and an actual six-component seismograph station form a station pair, and the phase velocity of a wave under the distance is estimated through a phase difference / travel time difference between the virtual station and the actual six-component seismograph station and a geometric distance relationship between the source and the station; the obtained phase velocity is actually equivalent to a frequency dispersion curve at the midpoint of the connecting line of the source and the station, so that the phase velocity-depth structure from the source to the midpoint of the station can be obtained by performing inversion by using the obtained frequency dispersion curve; as the active source moves in the measurement area, a group of signals can be generated at different positions respectively, and a series of virtual midpoints are formed for the single-station six-component seismograph, so that the density of measurement points is remarkably increased in space. On the basis, through combination with an inversion result of a single station, three-dimensional underground velocity structure modeling with high credibility and high spatial resolution can be realized.

Shear wave phase velocity is estimated from measurements of shear wave motion obtained using ultrasound shear wave elastography or other suitable elastography techniques. Shear wave dispersion curves are generated using a combined generalized Stockwell transform and slant wave number-frequency analysis. A modified version of the S-transform is used to control the time-frequency resolution of a time-frequency decomposition of a signal.

The invention discloses a surface wave frequency dispersion energy spectrum imaging method, system and device for improving F-K transformation resolution based on normalization preprocessing and a medium, and belongs to the technical field of surface wave exploration, and the method comprises the steps: collecting a plurality of seismic records of an acquisition domain; performing normalization preprocessing on the selected seismic record data to obtain preprocessed surface wave data; performing two-dimensional Fourier transform to obtain domain data, and transforming a domain into a domain according to the frequency dispersion characteristic of the surface wave data; and in the phase velocity range of the surface wave, determining a frequency dispersion curve recorded by the surface wave by selecting a peak point corresponding to any frequency in a domain. According to the method, by introducing a normalization preprocessing process, the comprehensive performance of a traditional F-K transformation method in surface wave frequency dispersion energy spectrum imaging is improved, the overall resolution of a frequency dispersion energy spectrum can be enhanced, the recognition capability of high-order mode frequency dispersion energy is improved, and energy spectrum distribution of a base order and a high-order mode is clearly separated.

The invention discloses a surface wave frequency dispersion image generation method, a medium, equipment and a product, and relates to the field of surface wave exploration, and the method comprises the steps: obtaining time domain surface wave signals received by a geophone, and arranging the time domain surface wave signals according to spatial positions to form a gather; performing S transformation on the time domain surface wave signal of each seismic channel to obtain a complex value time-frequency spectrum; based on the time-frequency spectrum, extracting a complex frequency spectrum corresponding to main energy on each frequency point of each seismic channel, and performing normalization processing to obtain a phase spectrum; selecting a plurality of heuristic phase velocities in a preset phase velocity scanning range, performing coherent superposition on phase spectrums corresponding to all seismic traces for each frequency and the heuristic phase velocity, and constructing an energy function of a frequency-phase velocity domain; and when the tentative phase velocity is consistent with the actual surface wave phase velocity, obtaining a surface wave phase velocity frequency dispersion energy image based on an energy function of a frequency-phase velocity domain. According to the invention, the anti-interference capability and stability of surface wave frequency dispersion imaging under complex geology or noise conditions can be improved.

The invention belongs to the technical field of rock physics and multiphase flow coupling seismic wave propagation simulation, and discloses a wave velocity-attenuation whole-process calculation method based on an Lo two-phase fluid model. According to the method, thermodynamic characteristics of CO2-saline two-phase fluid are obtained by utilizing temperature and pressure conditions of a target reservoir, seepage characteristics are fitted according to experimental data, and a unified medium physical property layer is constructed by combining fluid parameters and rock skeleton parameters; after an elastic matrix, an inertia matrix and a viscosity matrix of a multiphase medium are calculated according to physical property parameters, phase velocity and attenuation characteristics of three types of longitudinal waves and one type of transverse waves are obtained through a Lo two-phase fluid model control equation. According to the method, a complete technical process from physical property construction, control equation solution to sensitivity judgment and mechanism analysis is formed, the method can be used for seismic monitoring, reservoir feature recognition and relevant parameter inversion in the CO2 geological storage process, and the method has good engineering applicability and popularization value.

The invention discloses a method for determining the thickness of a covering layer below a power grid facility based on seismic surface wave exploration. The method comprises the steps of collecting original three-component continuous waveform data and dividing the data into an active source and a passive source; calculating a Rayleigh surface wave frequency dispersion energy diagram based on the active source multichannel seismic record, picking up a frequency dispersion curve of a base-order Rayleigh surface wave from the Rayleigh surface wave frequency dispersion energy diagram, determining a phase velocity corresponding to a high-frequency asymptote of the base-order Rayleigh surface wave, and estimating a shear wave velocity of a covering layer according to the obtained phase velocity; based on passive source single-channel observation data, measuring an HVSR curve of the position of each channel changing along with frequency, and determining the peak frequency of the HVSR curve; and based on the obtained peak frequency of the HVSR curve and the transverse wave velocity of the covering layer, determining the thickness of the covering layer below each channel. The method provided by the invention does not involve inversion calculation, and has the characteristics of stability and high efficiency.

The invention discloses a phase velocity imaging method based on Rayleigh wave time-frequency characteristic similarity analysis, and the method comprises the steps: firstly, designing a reasonable working frequency band, and collecting a seismic signal; secondly, de-noising the seismic original signal by using wavelet transform; then, intercepting Rayleigh waves in a time domain; thirdly, obtaining the time waveform of each frequency component of each Rayleigh wave through time-frequency analysis, calculating the time difference through similarity analysis, and obtaining a frequency dispersion curve between two channels; and finally, in combination with a plurality of Rayleigh wave frequency dispersion curves, obtaining a phase velocity imaging graph below the seismic arrangement. The method is good in effect when applied to engineering investigation.

The application discloses a wave front fast advancing algorithm suitable for anisotropic media, and is implemented according to the following steps: step 1, rewriting the eikonal equation, discretizing the eikonal equation by using the fast advancing algorithm, and initializing a source point as a known point; step 2, obtaining a function relation about an incident angle, an incident phase angle and a stratum dip angle by using the known point; step 3, obtaining a travel time of a to-be-solved point by using a phase angle and a phase velocity of the to-be-solved point, and calculating travel times of all grid nodes; and step 4, after the wave front time field is solved by using steps 1 and 3, determining a phase velocity field, calculating a group velocity field by using the phase velocity field, and finally completing ray tracing by using the group velocity. The application shapes the exit direction and exit velocity of the to-be-solved point as known quantities by using the snell equation, and then obtains high-precision travel times of all grid nodes, determines more accurate time field gradients of all grid nodes to determine group velocity vectors, and performs ray tracing.

The application discloses a kind of inversion initial model fast establishment, inversion method and system of seismic transverse wave velocity, comprising: first, extracting surface wave dispersion curve from original surface wave data, and the phase velocity in surface wave dispersion curve, frequency is converted into apparent transverse wave velocity and depth.Then, based on the converted surface wave dispersion curve, according to the depth corresponding to the layer depth array in initial model, the apparent transverse wave velocity in the converted surface wave dispersion curve is assigned to each layer depth array using interpolation algorithm, and the inversion initial model of seismic transverse wave velocity is established.Because the apparent transverse wave velocity and the actual transverse wave velocity are consistent in variation trend, the inversion initial model thus established can ensure the convergence of algorithm to remain stable when seismic transverse wave velocity is inverted, and avoid inversion into local minimum value or not convergent.

The application discloses a kind of continental slope sea area underwater very low frequency line spectrum target positioning method.The method first constructs the three-dimensional sound field model based on spatial coordinate rotation transformation, solves the problem that the element position of horizontal receiving array cannot accurately fall on the calculation grid point, simultaneously realizes the fast prediction to the element receiving signal of horizontal receiving array.Then the MVDR algorithm is used to estimate the multi-path wave arrival angle of each order mode, and combined with the vertical mode-horizontal ray theory, the underwater sound source position is accurately positioned by horizontal sound line backtracking.Finally, the average mode phase velocity is introduced to improve the accuracy of multi-path wave arrival angle estimation, and the multi-path wave arrival angle of each order mode is more accurately estimated, and the positioning error of underwater sound source position is further reduced.

The invention relates to the technical field of mechanical equipment state monitoring and fault diagnosis, and discloses a bearing damage positioning method based on modal acoustic emission and normalized cross correlation. The method comprises the following steps: firstly, establishing a bearing three-dimensional model, and solving a phase velocity frequency dispersion curve of an acoustic emission signal in the bearing by adopting a semi-analytical finite element method; according to the frequency dispersion curve, Lamb waves with different frequencies in the same mode are excited in the model, simulation signals at different positions are extracted, and the propagation speeds of the simulation signals are calculated; the simulation signal is used as a template, and the arrival time with the maximum correlation with the template in the acoustic emission signal is determined by using a normalized cross-correlation method; and the distance between the damage position and the sensor is calculated by combining the propagation velocity difference and the time difference of the Lamb waves with different frequencies, so that the precise positioning of the bearing damage is realized. According to the method, the problem that the multi-frequency Lamb wave propagation velocity in the bearing is difficult to solve is solved, the calculation precision of the time difference of arrival is improved through normalized cross-correlation, damage positioning can be completed by using a single sensor, and the installation difficulty and the detection cost are reduced.