Chapter 2: Estimation of Near-surface Shear-wave Velocity and Quality Factor by Inversion of High-frequency Rayleigh Waves
Jianghai Xia, Richard D. Miller, 2010. "Estimation of Near-surface Shear-wave Velocity and Quality Factor by Inversion of High-frequency Rayleigh Waves", Advances in Near-surface Seismology and Ground-penetrating Radar, Richard D. Miller, John H. Bradford, Klaus Holliger
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Near-surface shear-wave (S-wave) velocities and quality factors are key parameters for a wide range of geotechnical, environmental, and hydrocarbon-exploration research and applications. High-frequency Rayleigh-wave data acquired with a multichannel recording system have been used to determine near-surface S-wave velocities since the early 1980s. Multichannel analysis of surface waves —MASW — is a noninvasive, nondestructive, and cost-effective acoustic approach to estimating near-surface S-wave velocity. Inversion of high-frequency surface waves has been achieved by the geophysics research group at Kansas Geological Survey during the past 15 years, using surface-wave inversion algorithms of both a layered-earth model (commonly used in the MASW method) and a continuously layered-earth model (Gibson half-space). Comparison of the MASW results with direct borehole measurements reveals that the differences between the two are approximately 15% or less and have a random distribution. Studies show that simultaneous inversion of higher modes and the fundamental mode increases model resolution and investigation depth. Another important seismic property—quality factor (Q)—can be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. A practical algorithm uses the trade-off between model resolution and covariance to assess an inverted model. Real-world examples demonstrate the applicability of inverting high-frequency Rayleigh waves as part of routine MASW applications.
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Advances in Near-surface Seismology and Ground-penetrating Radar
Near-surface seismology and ground-penetrating radar (GPR) have enjoyed success and increasing popularity among a wide range of geophysicists, engineers, and hydrologists since their emergence in the latter half of the twentieth century. With the common ground shared by near-surface seismology and GPR, their significant upside potential, and rapid developments in the methods, a book bringing together the most current trends in research and applications of both is fitting and timely. Conceptually, near-surface seismology and GPR are remarkably similar, and they share a range of attributes and compatibilities that provides opportunities to integrate processing and interpretation workflows, which makes them a perfect pair to share pages in a book.
With growth in numbers and professional emphasis have come sections, focus groups, and even professional societies specifically promoting near-surface geophysics. The emergence of near-surface geophysics groups, beginning in the late 1990s and extending into the early twenty-first century, has fueled a diversity of opportunities for professional collaborations. A range of workshops and shared publications has been the fruit of collaborative efforts. The near-surface community continues to extend and develop methods and approaches necessary to satisfy increasing demands in some of the socioeconomically pertinent disciplines such as civil and environmental engineering and hydrology. This book represents the first formal cooperative effort undertaken by the near-surface communities of the Society of Exploration Geophysicists, the American Geophysical Union, and the Environmental and Engineering Geophysical Society.