A Fidelity Imaging Method Based on Scalar Wavefield Extrapolation

Abstract

The invention relates to a fidelity imaging method based on wave field extrapolation of scalar wave. The method comprises the following steps: deriving a scalar wave equation describing the propagation law of a seismic wave field excited by an earthquake source in an underground medium according to the Newton's second law and the Hooke's law by assuming the underground medium as isotropy, uniformness and constant density; solving the scalar wave equation by using a finite difference method after knowing the underground smooth background speed and a seismic source sub-wave function, thereby obtaining the wave field amplitudes of the wave field at underground different space points at any time, and recording the wave field amplitude at a boundary when the wave field is propagated to the boundary of the numerical simulation; solving the scalar wave equation by regarding wave field amplitude at the boundary as a boundary value condition, thereby recovering the seismic source point end wavefield; solving the scalar wave equation by regarding the wave field received by a surface wave detector as the boundary value condition, thereby constructing a wave detection point end wave field; and performing the fidelity imaging on the seismic source point end wave field and the wave detection point end wave field through the fidelity imaging formula based on the wave field extrapolation of the scalar wave, thereby obtaining a fidelity imaging result of an underground reflection coefficient.

Description

technical field [0001] The invention relates to a fidelity imaging method based on scalar wave field extrapolation, and relates to the technical field of seismic exploration data processing. Background technique [0002] Seismic wave imaging has now developed to the stage where the FWI (Full Waveform Inversion) + LS_RTM (LeastSquare Reverse Time Migration) method is the core; among them, FWI mainly uses the transmitted wave information to estimate the background velocity; LS_RTM is an imaging method based on the idea of ​​inverse scattering , trying to estimate wave impedance perturbations or velocity perturbations at high wavenumbers. The FWI method essentially includes the LS_RTM method, which is theoretically a nonlinear inversion method that can estimate all components from background parameter changes to high wavenumber parameter changes. LS_RTM is a linearized inversion under the assumption that the background parameters are correct and known, and can be considered as...

AI Technical Summary

Problems solved by technology

However, the perfect inversion imaging theory does not bring reliable technology that can be applied in practice, and the technical combination of FWI+LS_RTM is far from reaching the level that can produce obvious application effects on any data volume

In essence, there is another important issue that has not been mentioned. In the case of seismic exploration, only geophones are deployed on the ground (or in the well) to observe the seismic wave field propagating backward, which does not match the data requirements of the FWI+LS_RTM method itself.

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