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.