Multi-scale step type layer-stripping full-waveform inversion method for ground penetrating radar data

A full-waveform inversion and ground penetrating radar technology, applied in radio wave measurement systems, instruments, etc., can solve the problems of local minimum, unreliable and difficult hierarchical full-waveform inversion processing, etc., to reduce the gap, The effect of improving inversion and improving stability

Inactive Publication Date: 2018-07-06
JILIN UNIV
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Problems solved by technology

However, choosing an appropriate offset-time window to extract a specific waveform above a certain fixed depth is usually not easy and may lead to unreliability of the layered full waveform inversion process in strongly heterogeneous media
In addition, under this strategy, when there is a large difference in the inversion frequencies of two adjacent layers, a local minimum may appear near the boundary between the two layers

Method used

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  • Multi-scale step type layer-stripping full-waveform inversion method for ground penetrating radar data
  • Multi-scale step type layer-stripping full-waveform inversion method for ground penetrating radar data
  • Multi-scale step type layer-stripping full-waveform inversion method for ground penetrating radar data

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Embodiment 1

[0078] a, input ground radar record, initial model and wavelet as observation data; The present invention has set up the true model of inversion ( Figure 4 (a)), to test and evaluate the workflow and effect of the stepped layer stripping full waveform inversion. Real permittivity model: two high-value anomalous objects at the center of the model with a layered background. Except for two higher anomalous regions, the permittivity increases with depth, and the maximum and minimum values ​​of the model permittivity are ε max =29,ε min =6. The size of the model is 8.64m×34.02m, with h on top of the model a =0.45m air layer, finite difference grid spacing h=9cm, so the model totals N M =97×379=36763 grid points; the ground observation system consists of 76 transmitting antennas with a distance of 5 grid points and 190 receiving antennas with a distance of 1 grid point, and the signal transmitted by each antenna can be detected by all Receive antenna records; input the synthet...

Embodiment 2

[0103] a, input ground radar record, initial model and wavelet as observation data; The present invention has established random soil medium model as the true model of inversion based on multi-parameter coupling equation ( Figure 7 (a)). The size of the model is 9.54m*9m, with h on top of the model a =0.36m air layer; finite difference grid spacing h=9cm, so the model totals N M =107×105=11235 grid points; the ground observation system consists of 36 transmitting antennas with a distance of 3 grid points and 107 receiving antennas with a distance of 1 grid point, and the signal transmitted by each antenna can be detected by all Receive antenna records; input the synthetic data calculated by the real model as the inverted observation data; input the large-scale smoothing results of the real model as the initial model ( Figure 7 (b)); The input center frequency is a wavelet of 120MHz;

[0104] b. After comprehensive consideration of factors such as model size, structural co...

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Abstract

The invention relates to a multi-scale step type layer-stripping full-waveform inversion method for ground penetrating radar data. The method comprises the following steps: firstly, selecting layeringnumber and inversion frequency of a model and a single-frequency and single-layer inversion number of times, and determining an inversion serial number of each layer in each frequency according to anew inversion sequence; secondly, filtering radar observation data and sub-waves to different frequency bands by virtue of a Wiener filter, and adding a space window in a corresponding layer to the calculated gradient by virtue of a dielectric constant gradient formula, so as to obtain a gradient value of the current layer; and finally, calculating the updating amount of the model, and finishing iterative operation layer by layer and frequency by frequency. By utilizing a multi-scale strategy, the independence on an initial model is reduced, and the cycle skip problem is effectively solved; the method is different from an existing offset-time window, and the gradient of a specific layer is acquired by virtue of a space window, so that convergence can be rapidly realized; by utilizing a newstep type inversion sequence, the difference between the inversion frequencies of two adjacent layers is effectively reduced, so that a relatively good inversion effect is achieved, the deep inversion effect of the model is effectively improved, and the stability of full-waveform inversion is improved.

Description

Technical field: [0001] The invention relates to a time-domain full-waveform imaging method for reconstructing permittivity in the field of ground-penetrating radar. Combining the frequency multi-scale strategy with the conventional layer stripping inversion sequence, a new stepped inversion sequence is proposed to improve the stability of the full waveform inversion and reduce the cycle jumping problem. Background technique: [0002] Full Waveform Inversion (FWI) of Ground Penetrating Radar (GPR) data is a promising technology for near-surface parametric imaging. The full waveform inversion method based on the generalized least squares method first appeared in the pioneering paper of Tarantola (1984.Linearized inversion of seismic reflection data.GEOPHYSICAL PROSPECTING 32(6).998-1015), which is a time-domain full waveform inversion Technology has laid a solid theoretical foundation. Then it is widely used in seismic exploration data processing, but it is still relatively...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01S7/41
CPCG01S7/41
Inventor 槐楠曾昭发
Owner JILIN UNIV
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