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This paper presents a novel numerical method for the Newton seismic full-waveform inversion (FWI). The method is based on the full-space approach, where the state, adjoint state, and control variables are optimized simultaneously. Each Newton step is formulated as a PDE-constrained optimization problem, which is cast in the form of the Karush–Kuhn–Tucker (KKT) system of linear algebraic equitations. The KKT system is solved inexactly with a preconditioned Krylov solver. We introduced two preconditioners: the one based on the block-triangular factorization and its variant with an inexact block solver. The method was benchmarked against the standard truncated Newton FWI scheme on a part of the Marmousi velocity model. The algorithm demonstrated a considerable runtime reduction compared to the standard FWI. Moreover, the presented approach has a great potential for further acceleration. The central result of this paper is that it establishes the feasibility of Newton-type optimization of the KKT system in application to the seismic FWI. [ABSTRACT FROM AUTHOR]

In this paper, we consider the problem of constructing a numerical solution to the system of equations of an acoustic medium in a fixed domain with a boundary. Physically, it corresponds to seismic wave propagation in geological media during seismic exploration of hydrocarbon deposits. The system of first-order partial differential equations under consideration is hyperbolic. Its numerical solution is constructed by applying a grid-characteristic method on an extended spatial stencil. This approach yields a higher order approximation scheme at internal points of the computational domain, but requires a careful construction of the numerical solution near the boundaries. In this paper, an approach that preserves the increased approximation order up to the boundary is proposed. Verification numerical simulations were carried out. [ABSTRACT FROM AUTHOR]

In this paper, we consider the problem of seismic wave propagation in gradient geological media. Their dynamic behavior is described using the acoustic approximation and the numerical integration of the initial-boundary value problem for the acoustic wave equation with spatially variable mechanical parameters. A grid-characteristic numerical method is developed that explicitly takes into account the gradient of the medium. The numerical solutions are compared with results obtained using a piecewise constant model of the medium in the one-dimensional case. [ABSTRACT FROM AUTHOR]

The goal of this study is to develop and apply a grid-characteristic numerical algorithm for determining damage to an offshore object (ice island) by computing seismic wave propagation from an earthquake hypocenter located at a depth of several kilometers taking into account specific features of the Northern Seas (shallow depths). The grid-characteristic method on combined grids is used for this purpose. A single run involves more than 25 separate grids differing from each other in the system of equations to be solved, the type of the numerical scheme, and the step sizes in coordinates. Some of these grids make up a set of embedded hierarchical ones with a multiple step in coordinate, while the others are conformal to each other. Additionally, an improved nonreflecting condition is used, which assumes a sharp increase in the step size in coordinate and the application of a dissipative difference scheme. Special attention is given to the computational algorithms used on the boundaries and interfaces of the separate grids, which make it possible to implement the proposed approach with the use of the grid-characteristic method on combined grids. [ABSTRACT FROM AUTHOR]

The problem of seismic wave propagation from a source located in a well is considered. Acoustic equations are used to describe the dynamic behavior of the fluid. The damaged zone is described as a porous fluid-saturated medium by applying the Dorovsky model. The elastic approximation is used to describe the dynamic behavior of the surrounding rock. A unified algorithm based on the grid-characteristic approach with curvilinear grids is proposed for full-wave modeling in the entire computational domain. Its distinctive feature is that the necessary contact conditions on the boundary between media with different rheological properties are stated explicitly. The possibility of acoustic diagnostics of the heterogeneity of the damaged zone is numerically explored. [ABSTRACT FROM AUTHOR]

The grid-characteristic method on a sequence of embedded hierarchical grids is used to study the reflection and diffraction of elastic seismic waves propagating from an earthquake hypocenter to the Earth's surface. More specifically, the destruction caused by seismic waves in complex heterogeneous structures, such as multi-story buildings, is analyzed. This study is based on computer modeling with the use of the grid-characteristic method, which provides a detailed description of wave processes in heterogeneous media, takes into account all types of emerging waves, and relies on algorithms that perform well on the boundaries of the integration domain and material interfaces. Applying a sequence of hierarchical grids makes it possible to simulate seismic wave propagation from an earthquake hypocenter to ground facilities of interest-multi-story buildings-and to investigate their seismic resistance. [ABSTRACT FROM AUTHOR]

Today, the exploration of the Arctic region is one of the most important direction of research in our country, because large amounts of unexplored oil and gas deposits are located there. Large hydrocarbon deposits are situated within the Northern seas. Their development is complicated by gas explosions resulting from an accidental opening and further spread of the gas. Since the region with gas layers cannot be frequently monitored, an area with already detected gas deposits is numerically modeled instead. In this work, seismic waves propagating in multilayered geological models with gas-containing inclusions were numerically modeled over a four-year interval by applying the grid-characteristic method. Wave patterns of seismic reflections and seismograms for the described problem were obtained. The wave patterns and seismograms obtained in the two- and three-dimensional cases were compared. The results were found to be in good agreement. [ABSTRACT FROM AUTHOR]

The article presents a mathematical research which introduces a grid-characteristic method for the numerical simulation of the effects of anisotropic media on seismic wave propagation. Details include the statement of the problem and numerical results for the wave pattern in elastic wave propagation through horizontally transversal and heterogenous anisotropic media. It concludes the development of the grid method through studying the system of equations in anisotropic medium.