McMechan, George A.
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George McMechan is the Ida Green Professor of Geosciences and Director of the Center for Lithospheric Studies. He is considered an expert in seismology, geophysics, ground-penetrating radar, and wave fields. Learn more about Dr. McMechan from his profile and Research Explorer pages
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Recent Submissions
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Reverse Time Migrations in Transversely Isotropic Media: A Comparison between Acoustic and Elastic Wave Equations with Two Wave Mode Separation Algorithms
Anisotropic reverse time migrations (RTMs) using pseudoacoustic or elastic wave equations are tested, and the migrated PP images, obtained using the same data set as input, are compared. In anisotropic elastic RTMs, both ... -
Time-Domain Least-Squares Migration Using the Gaussian Beam Summation Method
With a finite recording aperture, a limited source spectrum and unbalanced illumination, traditional imaging methods are insufficient to generate satisfactory depth profiles with high resolution and high amplitude fidelity. ... -
P- and S-Decomposition in Anisotropic Media with Localized Low-Rank Approximations
(Society of Exploration Geophysicists, 2017-11-13)We have developed a P- and S-wave decomposition algorithm based on windowed Fourier transforms and a localized low-rank approximation with improved scalability and efficiency for anisotropic wavefields. The model and ... -
Combining Multidirectional Source Vector with Antitruncation-Artifact Fourier Transform to Calculate Angle Gathers from Reverse Time Migration in Two Steps
(Society of Exploration Geophysicists, 2017-08-11)Because receiver wavefields reconstructed from observed data are not as stable as synthetic source wavefields, the source-propagation vector and the reflector normal have often been used to calculate angle-domain common-image ... -
Characterization of a Coalesced, Collapsed Paleocave Reservoir Analog Using GPR and Well-Core Data
(Society of Exploration Geophysicists, 2002-07)The three-dimensional architecture, spatial complexity, and pore-type distribution are mapped in a near-surface analog of a coalesced, collapsed paleocave system in the Lower Ordovician Ellenburger Group near the city of ... -
Estimation of Gas Hydrate and Free Gas Saturation, Concentration, and Distribution from Seismic Data
(Society of Exploration Geophysicists, 2018-08-24)Gas hydrates contain a major untapped source of energy and are of potential economic importance. The theoretical models to estimate gas hydrate saturation from seismic data predict significantly different acoustic/ elastic ... -
AVA Analysis and Interpretation of a Carbonate Reservoir: Northwest Java Basin, Indonesia
A detailed analysis is performed of amplitude variation with angle (AVA) observations in six common-midpoint gathers with reflection points that are over and beside carbonate reefs in the Parigi Formation in the northwest ... -
Up/Down and P/S Decompositions of Elastic Wavefields Using Complex Seismic Traces with Applications to Calculating Poynting Vectors and Angle-Domain Common-Image Gathers from Reverse Time Migrations
(Society of Exploration Geophysicists, 2018-06-01)Separations of up- and down-going as well as of P- and S-waves are often a part of processing of multicomponent recorded data and propagating wavefields. Most previous methods for separating up/down propagating wavefields ... -
Efficient Love Wave Modelling via Sobolev Gradient Steepest Descent
(Oxford University Press, 2016-02-22)A new method for finding solutions to ordinary differential equation boundary value problems is introduced, in which Sobolev gradient steepest descent is used to determine eigenfunctions and eigenvalues simultaneously in ... -
Removing Smearing-Effect Artifacts in Angle-Domain Common-Image Gathers from Reverse Time Migration
(Soc Exploration Geophysicists, 2015-03-17)Local plane-wave decomposition (LPWD) and local shift imaging condition (LSIC) methods for extracting angle-domain common-image gathers (ADCIGs) from prestack reverse time migration are based on the local plane-wave ... -
Vector-Based Elastic Reverse Time Migration
(Society of Exploration Geophysicists, 2015-10-15)Prestack elastic reverse time migration (RTM) of multicomponent seismic data requires separating PP and PS reflections before, or as part of, applying the image condition, and using image conditions that preserve the angle ... -
Comparison of Two Algorithms for Isotropic Elastic P and S Vector Decomposition
(Society of Exploration Geophysicists, 2015-06-10)P- and S-wavefield separation is necessary to extract PP and PS images from prestack elastic reverse time migrations. Unlike traditional separation methods that use curl and divergence operators, which do not preserve the ... -
Common-Reflection-Point Migration Velocity Analysis of 2D P-Wave Data From TTI Media
(Soc Exploration Geophysicists, 2014-05)We have developed a common-reflection-point (CRP)-based kinematic migration velocity analysis for 2D P-wave reflection data to estimate the four transversely isotropic (TI) parameters VPo, δ, and ε, and the tilt angle ϕ ... -
Comparison of Methods for Extracting ADCIGS from RTM
(Soc Exploration Geophysicists, 2014-04-01)Methods for extracting angle-domain common-image gathers (ADCIGs) during 2D reverse-time migration fall into three main categories; direction-vector-based methods, local-plane-wave decomposition methods, and local-shift ... -
2d Frequency-Domain Elastic Full-Waveform Inversion Using Time-Domain Modeling and a Multistep-Length Gradient Approach
(Soc Exploration Geophysicists, 2014-02-17)To decouple the parameters in elastic full-waveform inversion (FWI), we evaluated a new multistep-length gradient approach to assign individual weights separately for each parameter gradient and search for an optimal step ... -
Conductivity and Scattering Q in GPR Data: Example from the Ellenburger Dolomite, Central Texas
(2012-06-27)Total attenuation (Qt -1) in ground-penetrating radar (GPR) data is a composite of intrinsic and scattering attenuations (Qin -1 and Qsc -1). For nonmagnetic materials, Qin -1 is a combination of the effects of real ... -
Sensitivity of Estimated Elastic Moduli to Completeness of Wave Type, Measurement Type, and Illumination Apertures at a Receiver in Multicomponent VSP Data
(2012-02-01)Inversion of phase slowness and polarization vectors measured from multicomponent vertical seismic profile data can yield estimates of all 21 density-normalized elastic moduli for anisotropic elastic media in the neighborhood ... -
Tomography of Diffraction-Based Focusing Operators
(2012-08-24)Diffractions carry the same kinematic information provided by common focus point operators (CFPOs). Thus CFPO and diffraction time trajectories may be used separately, or combined into a single unified tomography for ... -
3D, 9C Seismic Modeling and Inversion of Weyburn Field Data
(2012-06-18)Inversion of 3D, 9C wide azimuth vertical seismic profiling (VSP) data from the Weyburn Field for 21 independent elastic tensor elements was performed based on the Christoffel equation, using slowness and polarization ... -
Gas hydrate and free gas petroleum system in 3D seismic data, offshore Angola
(Society of Exploration Geophysicists, 2012-09-26)Evidence of gas hydrate and free gas occurrences in a 3D seismic volume from the West-Central Coastal Province of the Congo Fan, offshore Angola, illustrates all the components of a complete petroleum system. Analysis and ...
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