Sensitivity of ionosonde detection of atmospheric disturbances induced by seismic Rayleigh waves at different latitudes

In this paper, a new method is proposed to manipulate seismic Rayleigh waves using phase-gradient metasurfaces. This highly compact artificial structure enables the anomalous refraction of Rayleigh waves according to the generalized Snell’s law (GSL). The soil-embedded metasurface is composed of only one column of commercial rubber blocks, which can provide an accurate phase shift to the Rayleigh wave. To verify the flexibility of this method, several metasurfaces are designed. Numerical results demonstrate that the Rayleigh waves can be focused, split, or converted into evanescent waves by using specific phase gradient configurations. The investigation also suggests the strong potential of metasurface as a smart device for shielding of seismic surface waves.

Download Full-text

Linear and Nonlinear Seismic Rayleigh Waves with Damping: A Heuristic Direct Method

Journal of Applied Sciences ◽

10.3923/jas.2011.275.283 ◽

2011 ◽

Vol 11 (2) ◽

pp. 275-283

Author(s):

Dennis Ling Chuan Ching ◽

Zainal Abdul Aziz ◽

Faisal Salah Yusof

Keyword(s):

Rayleigh Waves ◽

Direct Method ◽

Linear And Nonlinear ◽

Seismic Rayleigh Waves

Download Full-text

Application of a complete workflow for 2D elastic full-waveform inversion to recorded shallow-seismic Rayleigh waves

Geophysics ◽

10.1190/geo2016-0284.1 ◽

2017 ◽

Vol 82 (2) ◽

pp. R109-R117 ◽

Cited By ~ 40

Author(s):

Lisa Groos ◽

Martin Schäfer ◽

Thomas Forbriger ◽

Thomas Bohlen

Keyword(s):

Wave Velocity ◽

Rayleigh Waves ◽

Waveform Inversion ◽

Velocity Model ◽

Full Waveform Inversion ◽

S Wave ◽

Full Waveform ◽

Shallow Seismic ◽

Lateral Variations ◽

Seismic Rayleigh Waves

The S-wave velocity of the shallow subsurface can be inferred from shallow-seismic Rayleigh waves. Traditionally, the dispersion curves of the Rayleigh waves are inverted to obtain the (local) S-wave velocity as a function of depth. Two-dimensional elastic full-waveform inversion (FWI) has the potential to also infer lateral variations. We have developed a novel workflow for the application of 2D elastic FWI to recorded surface waves. During the preprocessing, we apply a line-source simulation (spreading correction) and perform an a priori estimation of the attenuation of waves. The iterative multiscale 2D elastic FWI workflow consists of the preconditioning of the gradients in the vicinity of the sources and a source-wavelet correction. The misfit is defined by the least-squares norm of normalized wavefields. We apply our workflow to a field data set that has been acquired on a predominantly depth-dependent velocity structure, and we compare the reconstructed S-wave velocity model with the result obtained by a 1D inversion based on wavefield spectra (Fourier-Bessel expansion coefficients). The 2D S-wave velocity model obtained by FWI shows an overall depth dependency that agrees well with the 1D inversion result. Both models can explain the main characteristics of the recorded seismograms. The small lateral variations in S-wave velocity introduced by FWI additionally explain the lateral changes of the recorded Rayleigh waves. The comparison thus verifies the applicability of our 2D FWI workflow and confirms the potential of FWI to reconstruct shallow small-scale lateral changes of S-wave velocity.

Download Full-text