PURPOSE: An apparatus, a method and a recording medium for imaging an underground structure using waveform inversion of a Laplace-Fourier domain are provided to stably obtain a speed model with long wavelength information and middle wavelength information. CONSTITUTION: An apparatus for imaging an underground structure using waveform inversion of a Laplace-Fourier domain includes a receiver and a signal processing unit. The signal processing unit comprises an input unit, a converting unit(202), a modeling data generating unit(203), and a parameter update unit(206). The converting unit converts measurement data in a time domain into measurement data in a Laplace-Fourier domain using an attenuation constant of a complex number. The modeling data generating unit sets an equation including a parameter by receiving a parameter showing a feature of a measurement target region. The modeling data generating unit calculates the equation in the Laplace-Fourier domain to calculate modeling data.

Apparatus, methods and recording medium for imaging a subsurface using the waveform inversion in the laplace-fourier domain

Reverse time migration (RTM) for attenuating media should take amplitude compensation and phase correction into consideration. However, attenuation compensation during seismic propagation s...

Adaptive stabilization for Q-compensated reverse time migration

Anisotropic and attenuating properties of subsurface media cause amplitude loss and waveform distortion in seismic wave propagation, resulting in negative influence on seismic imaging. To correct the anisotropy effect and compensate amplitude attenuation, a compensated-amplitude vertical transverse isotropic (VTI) least-squares reverse time migration (LSRTM) method is adopted. In this method, the attenuation term of an attenuated acoustic wave equation is extended to a VTI quasi-differential wave equation, which takes care of effects from anisotropy and attenuation. The finite-difference method is used to solve the equation, in which attenuation terms are solved in the wavenumber domain, and other terms are solved in the space or wavenumber domain. Stable regularization operators are derived and introduced to the equations to eliminate severe numerical noise in high-frequency components during backward propagation. Meanwhile, a demigration operator, migration operator, and gradient formula for att...

Attenuation compensation in anisotropic least-squares reverse time migration

Time-domain elastic least-squares reverse time migration (LSRTM) is formulated as a linearized elastic full-waveform inversion problem. The elastic Born approximation and elastic reverse time migration (RTM) operators are derived from the time-domain continuous adjoint-state method. Our approach defines P- and S-wave impedance perturbations as unknown elastic images. Our algorithm is obtained using continuous functional analysis in which the problem is discretized at the final stage (optimize-before-discretize approach). The discretized numerical versions of the elastic Born operator and its adjoint (elastic RTM operator) pass the dot-product test. The conjugate gradient least-squares method is used to solve the least-squares migration quadratic optimization problem. In other words, the Hessian operator for elastic LSRTM is implicitly inverted via a matrix-free algorithm that only requires the action of forward and adjoint operators on vectors. The diagonal of the pseudo-Hessian operator is used t...

/pdf/elastic-least-squares-reverse-time-migration-via-linearized-2iomxjon2l.pdf

Elastic least-squares reverse time migration via linearized elastic full-waveform inversion with pseudo-Hessian preconditioning

The calculation of the gradient in full-waveform inversion (FWI) usually involves crosscorrelating the forward-propagated source wavefield and the back-propagated data residual wavefield at...

https://library.seg.org/doi/pdf/10.1190/geo2017-0469.1

Accelerating full-waveform inversion with attenuation compensation

Research progress on seismic imaging technology

A hybrid grid method in an auxiliary coordinate system for irregular fluid-solid interface modelling

Elastic full-waveform inversion (EFWI) attempts to find high-resolution model parameters that are able to match observed data exactly by minimizing residuals between the observed and predicted data. However, irregular surface topography can generate problematic EFWI results. To resolve this issue, an EFWI method in the curvilinear system is presented to invert velocities for areas with surface topography. This method meshes the regions near the surface topography into body-fitted grids, and areas off surface regions into rectangular grids. We derived the gradient formulas with respect to multiple parameters in the curvilinear system and developed a step-search method to calculate the corresponding step lengths. Wiener filtering is performed on a multiscale decomposition method to invert the velocity from a low to a high wavenumber. Error analysis, using a homogeneous model with a surface topography, demonstrates the accuracy and validity of our methods. Numerical experiments with an elastic hill g...

Elastic full-waveform inversion for surface topography

Viscoacoustic anisotropic full waveform inversion

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