Estimation of near‐surface shear‐wave velocity by inversion of Rayleigh waves

Abstract

The shear-wave (S-wave) velocity of near-surface materials (soil, rocks, pavement) and its effect on seismicwave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh-wave phase velocity of a layered-earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion-curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high-frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the weighted equation proved very effective in the high-frequency range when using the Levenberg-Marquardt and singular-value decomposition techniques. Convergence of the weighted solution is guaranteed through selection of the damping factor using the Levenberg-Marquardt method. Synthetic examples demonstrated calculation efficiency and stability of inverse procedures. We verify our method using borehole S-wave velocity measurements.

Validity of the Refraction Microtremors (ReMi) Method for Determining Shear Wave Velocities for Different Soil Types in Egypt

“…This code produces results identical to those of the forward-modeling codes used by Iwata et al (1998) [17], and by [18] within their inversion procedure. The modeling iterates on phase velocity at each period (or frequency), reports when a solution has not been found within the iteration parameters, and can model velocity reversals with depth.…”

Fast Inversion of Air-Coupled Spectral Analysis of Surface Wave (SASW) Using in situ Particle Displacement

“…Since the wave in the penetrated layers travel with the same wave number, it is probable that some kind of average of the shear velocities of these layers dominates the phase velocity. This assumption was confirmed by Xia et al [26] whose research discovered that compared with P-wave velocity, density, and layer thickness, the shear wave velocity is the dominant parameter influencing changes in Rayleigh-wave phase velocity in the high-frequency range (>5 Hz). Moreover, from the energy concept of view, the particle vibrating with larger displacement must contribute more to determine the velocity of the entire surface wave.…”

Interferometría de ruido sísmico para la caracterización de la estructura de velocidad 3D de un talud en la 3ª Sección del Bosque de Chapultepec, Ciudad de México

“…En ambos casos se requiere de arreglos de geófonos de baja frecuencia que permitan registrar longitudes de onda que proporcionen información de las estructuras más profundas. La sísmica activa utiliza una fuente de percusión para generar ondas de tipo Rayleigh cuyas propiedades de dispersión son extraídas siguiendo métodos de análisis espectral de ondas superficiales (método SASW; Xia et al, 1999;método MASW;Miller et al, 1999). La sísmica pasiva hace uso de las ondas superficiales contenidas en el ruido sísmico.…”