Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 29 for “"Full waveform inversion"”.
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Full waveform inversion combining rock physics for seismic reservoir characterization and monitoring
… based on amplitude variation with offset (AVO). Full waveform inversion (FWI) methods, although computationally more complex than AVO approaches, can produce more accurate elastic models by extracting the full information content in the seismogram. Progress has been reported in using elastic FWI …
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Machine learning methods modeling waveform, multi-parameter full waveform inversion, and uncertainty quantification
Full waveform inversion (FWI) is a potent technology capable of estimating subsurface parameters using seismic records. However, several challenges hinder its widespread application in large-scale field operations. In this thesis, I introduce strategies that leverage machine learning techniques to …
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Distributed acoustic sensing: modelling, full waveform inversion, and its use in seismic monitoring
… wavefield modes that are crucial to support land full waveform inversion (FWI). The inherently different sampling that DAS fibers provide leads to a requirement for modeling strategies that differ from those used to simulate point sensor data. To maximize the potential of DAS which only samples …
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Full-waveform inversion of time-lapse seismic data using physics-based and data-driven techniques
Time-lapse (4D) full-waveform inversion (FWI) is an advanced seismic technique that can enable accurate estimation of changes in the subsurface properties, such as fluid saturation or reservoir depletion, by utilizing amplitude and phase information in seismic data. However, most existing 4D FWI …
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Viscoelastic full-waveform inversion: treating attenuation uncertainty, characterizing cross-talk, and quantifying confidence in inversion results
Full waveform inversion (FWI) is a powerful technique for estimating the subsurface properties which affect seismic wave propagation but it is often limited by simplistic treatment of wave propagation physics. In particular, attenuation and dispersion, which play major roles in most seismic …
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Full waveform inversion of ultrasonic phased array data for the tomographic reconstruction of heterogeneous media for NDT
… work builds upon that work by creating a full waveform inversion framework to build a tomography method that reconstructs spatially heterogeneous wave speeds maps from simulated ultrasonic phased array data. This framework consists of: a Voronoi tessellation to spatially parametrise the …
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Investigation of Source Extension Methods, the Discrepancy Algorithm, and Noise Estimation to Overcome Cycle Skipping in Full Waveform Inversion
Full waveform inversion (FWI) is a geophysical technique used to create highly detailed mod- els of the Earth’s subsurface which can be used to explore for hydrocarbons and to predict natural hazards such as earthquakes. Seismic waves are generated from controlled sources such as vibroseis trucks …
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Frequency Domain Ultrasound Waveform Tomography Breast Imaging
… detection of disease. Using the principles of full waveform inversion, high-resolution quantitative sound speed and attenuation maps of the breast can be created. In this thesis, we introduce some basic principles of imaging breast disease and the formalism of sound wave propagation. We present …
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Modelling, Migration, and Inversion for Angle Domain Common Image Gathers
… the high accuracy requirements of migration and inversion algorithms. This thesis focuses on developing an new algorithm to integrate the modeling, migration, and inversion of ADCIGs. The modeling of ADCIGs is based on acoustic and elastic wave equations, and the results are compared with the …
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Born Waveform Inversion in Shot Coordinate Domain
The goal of this thesis is to integrate Born waveform inversion, variable projection algorithm and model extension concept to get a method that can improve the long scale background model updates reliably and efficiently from seismic data. Born waveform inversion is a partially linearized version …
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Estratégias de inversão de multiparâmetros utilizando a equação completa da elastodinâmica
… directions for the elastic multiparameters full waveform inversion (FWI), by using the approximate Hessian reparametrization properties, to ensure that the parameters update directions are properly scaled, and also keeping proper physical units of the problem. This study also includes …
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Full wavefield inversion methods for monitoring time-lapse subsurface velocity changes
… to achieve the quantitative analysis using full wavefield inversion methods which are robust in complex geology. We developed several methodologies in both the data domain and image domain to handle different time-lapse seismic acquisitions. In the data domain, we implemented …
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Efficient modeling and waveform inversion of multicomponent seismic data for anisotropic media
… wavefields is crucial for seismic imaging and inversion applications. Incorrect handling of the boundary conditions can distort the wavefield solutions, especially the horizontal displacement and velocity components, which may have serious implications for elastic reverse time migration (ERTM) …
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Novel Application of Nondestructive Testing to Evaluate Anomalous Conditions in Drilled Shafts and the Geologic Materials Underlying Their Excavations
… investigate the improvements offered by using a full waveform inversion (FWI) approach to analyze the stress wave data. A hybrid, multi-scale FWI workflow is recommended to increase the chance of the convergence of the inversion algorithms. Additionally, the benefits of a multi-parameter FWI are …
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Scattering of Seismic Waves from Arbitrary Viscoelastic-Isotropic and Anisotropic Structures with Applications to Data Modelling, FWI Sensitivities and Linearized AVO-AVAz Analysis
It is acknowledged that Full Waveform Inversion (FWI) techniques are sensitive to the set of model parameters that we choose for the minimization procedure. This model parametrization and sensitivity analysis for FWI has been extensively studied for acoustic and isotropic-elastic media. In order to …
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Efficient Tunnel Detection with Waveform Inversion of Back-scattered Surface Waves
… velocity anomaly detection method by using waveform inversion of the back-scattered surface waves (BSWI) is proposed. The main objective of this thesis is to review the theoretical background and study the feasibility of the proposed BSWI method. The proposed BSWI method is tested with …
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Sparse seismic signal processing using adaptive dictionaries
… As a convincing quantitative imaging technique, full waveform inversion (FWI) searches for the correct velocity model that can match the acquired seismic dataset. However, due to the high dimensionality of the model space, FWI is inherently a challenging problem, so that regularization techniques …
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New technologies for unconventional reservoir characterization: Seismic inversion, focal-time estimation, and signal processing to improve reservoir imaging
… seismic events. Constraints obtained from full-waveform inversion provide detailed information about the properties of the Duvernay Formation itself, such as brittle and ductile facies. Accurate microseismic hypocenter determination in the context of seismic analysis identifies which …
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Geometrically-informed methods of wave-based imaging
… adjoint-state method, in the context of full-waveform inversion, a non-linear least-squares problem for estimating material properties within the domain of interest. We analyze the contributions of reflected and transmitted waves to the linearized Hessian operator, demonstrating that …
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