Manipulation of seismic Rayleigh waves using a phase-gradient rubber metasurface

2020 ◽  
Vol 34 (13) ◽  
pp. 2050142
Author(s):  
Yanbin He ◽  
Tianning Chen ◽  
Xinpei Song
Keyword(s):  
Phase Shift ◽  
Rayleigh Wave ◽  
Surface Waves ◽  
Rayleigh Waves ◽  
Evanescent Waves ◽  
Smart Device ◽  
Phase Gradient ◽  
Seismic Surface Waves ◽  
Seismic Rayleigh Waves ◽  
Specific Phase

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.

Anomalous surface waves from underground explosions

1979 ◽  
Vol 69 (6) ◽  
pp. 1995-2002 ◽  
Author(s):  
Eivind Rygg
Keyword(s):  
Rayleigh Wave ◽  
Surface Waves ◽  
Rayleigh Waves ◽  
Major Part ◽  
Wave Generation ◽  
Love Waves ◽  
Phase Reversal ◽  
Wave Phase ◽  
Anomalous Surface

abstract The Rayleigh waves at Δ ∼40° from an eastern Kazakh explosion are shown to be polarity reversed and delayed relative to the Rayleigh waves from two other explosions of comparable magnitudes in the same area. The event generating the anomalous Rayleigh waves excited very strong Love waves which were not delayed. The Rayleigh wave phase reversal is shown to be a source phenomenon and it is suggested that in this particular case, spall closure was responsible for a major part of the Rayleigh-wave generation.

scholarly journals Rayleigh wave at the surface of a general anisotropic poroelastic medium: derivation of real secular equation

2018 ◽  
Vol 474 (2211) ◽  
pp. 20170589 ◽  
Author(s):  
M. D. Sharma
Keyword(s):  
Porous Media ◽  
Phase Velocity ◽  
Rayleigh Wave ◽  
Surface Waves ◽  
Rayleigh Waves ◽  
Secular Equation ◽  
Poroelastic Medium ◽  
Numerical Example ◽  
True Surface

A secular equation governs the propagation of Rayleigh wave at the surface of an anisotropic poroelastic medium. In the case of anisotropy with symmetry, this equation is obtained as a real irrational equation. But, in the absence of anisotropic symmetries, this secular equation is obtained as a complex irrational equation. True surface waves in non-dissipative materials decay only with depth. That means, propagation of Rayleigh wave in anisotropic poroelastic solid should be represented by a real phase velocity. In this study, the determinantal system leading to the complex secular equation is manipulated to obtain a transformed equation. Even for arbitrary (triclinic) anisotropy, this transformed equation remains real for the propagation of true surface waves. Such a real secular equation is obtained with the option of boundary pores being opened or sealed. A numerical example is solved to study the existence and propagation of Rayleigh waves in porous media for the top three (i.e. triclinic, monoclinic and orthorhombic) anisotropies.

Semiclassical inverse spectral problem for seismic surface waves in isotropic media: part II. Rayleigh waves

2020 ◽  
Vol 36 (7) ◽  
pp. 075016
Author(s):  
Maarten V de Hoop ◽  
Alexei Iantchenko ◽  
Robert D van der Hilst ◽  
Jian Zhai
Keyword(s):  
Surface Waves ◽  
Spectral Problem ◽  
Rayleigh Waves ◽  
Inverse Spectral Problem ◽  
Isotropic Media ◽  
Seismic Surface Waves ◽  
Inverse Spectral

scholarly journals Local Coupling and Conversion of Surface Waves due to Earth’s Rotation. Part 1: Theory

2020 ◽  
Author(s):  
Roel Snieder ◽  
Christoph Sens-Schönfelder
Keyword(s):  
Rayleigh Wave ◽  
Surface Waves ◽  
Coriolis Force ◽  
Rayleigh Waves ◽  
Love Wave ◽  
Mode Conversion ◽  
Love Waves ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Phase Velocities

Summary Earth’s rotation affects wave propagation to first order in the rotation through the Coriolis force. The imprint of rotation on wave motion has been accounted for in normal mode theory. By extending the theory to propagating surface waves we account for the imprint of rotation as a function of propagation distance. We describe the change in phase velocity and polarization, and the mode conversion of surface waves by Earth’s rotation by extending the formalism of Kennett (1984) for surface wave mode conversion due to lateral heterogeneity to include the Coriolis force. The wavenumber of Rayleigh waves is changed by Earth’s rotation and Rayleigh waves acquire a transverse component. The wavenumber of Love waves in not affected by Earth’s rotation, but Love waves acquire a small additional Rayleigh wave polarization. In contrast to different Rayleigh wave modes, different Love wave modes are not coupled by Earth’s rotation. We show that the backscattering of surface waves by Earth’s rotation is weak. The coupling between Rayleigh waves and Love waves is strong when the phase velocities of these modes are close. In that regime of resonant coupling, Earth’s rotation causes the difference between the Rayleigh wave and Love wave phase velocities that are coupled to increase through the process of level-repulsion.

Stoneley and Rayleigh waves in thermoelastic materials with voids

2019 ◽  
Vol 25 (14) ◽  
pp. 2053-2062 ◽  
Author(s):  
SS Singh ◽  
Lalawmpuia Tochhawng
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Surface Waves ◽  
Rayleigh Waves ◽  
Frequency Equation ◽  
Attenuation Coefficients ◽  
Stoneley Waves ◽  
Materials With Voids ◽  
Modes Of Vibration ◽  
Phase Velocity And Attenuation

The present paper deals with the propagation of surface waves (Stoneley and Rayleigh waves) in thermoelastic materials with voids. The frequency equations of the Stoneley waves at the bonded and unbonded interfaces between two dissimilar half-spaces of thermoelastic materials with voids are obtained. The numerical values of the determinant for bonded and unbonded interface are calculated for a particular model. We also derived the frequency equation of the Rayleigh wave in thermoelastic materials with voids. The phase velocity and attenuation coefficients have shown that there are two modes of vibration. These two modes are computed and they are depicted graphically. The effect of thermal parameters in these surface waves is discussed.

Tectonic strain-release characteristics of CANNIKIN

1972 ◽  
Vol 62 (6) ◽  
pp. 1425-1438 ◽  
Author(s):  
M. Nafi Toksöz ◽  
Harold H. Kehrer
Keyword(s):  
Rayleigh Wave ◽  
Surface Waves ◽  
Reasonable Agreement ◽  
Wave Amplitude ◽  
Nuclear Explosion ◽  
Arbitrary Orientation ◽  
Amplitude Ratios ◽  
Static Strain ◽  
Seismic Surface Waves ◽  
Strain Release

abstract The tectonic strain-release characteristics of the CANNIKIN nuclear explosion are determined from seismic surface waves and static strain changes associated with the event. The source is considered to be the superposition of an isotropic explosion component and a tectonic component consisting of a fault of arbitrary orientation. From Love-to-Rayleigh-wave amplitude ratios, the strength of the tectonic component (F) relative to the explosion is determined to be 0.6. The parameters of the fault are found to be consistent with nearby faults and displacements observed following the event. Reasonable agreement with observed static strains is also obtained with a fault 20 km long, but of different orientation. Discrepancies between observed and theoretical strains indicate the complexity of strain readjustment. The relatively small amount of tectonic strain release associated with CANNIKIN is probably due either to the low rigidity of the medium or to low ambient stresses near the surface.

On the nature of oceanic seismic surface waves with predominant periods of 6 to 8 seconds

1961 ◽  
Vol 51 (3) ◽  
pp. 437-455
Author(s):  
Jack Oliver ◽  
James Dorman
Keyword(s):  
Surface Waves ◽  
Deep Sea ◽  
Rayleigh Waves ◽  
Seismic Refraction ◽  
Normal Modes ◽  
Quantitative Agreement ◽  
Period Range ◽  
Oceanic Surface ◽  
Short Period ◽  
Seismic Surface Waves

Abstract The train of normally-dispersed, short-period, oceanic surface waves, commonly identified by the near-sinusoidal nature of all three components of ground motion in the period range of about 6 to 8 seconds, is shown to correspond to propagation in the first Love and first shear normal modes. Theoretical dispersion curves which agree with the observed dispersion of these short-period waves, as well as with dispersion of Rayleigh waves and Love waves of longer periods, are obtained for layered models of the oceanic crust which are consistent with results of seismic refraction studies. In order to obtain good quantitative agreement between theory and observation, it is essential that the effect of the small but finite rigidity of the deep-sea sedimentary layer be included in the calculations.

The polar phase shift of surface waves on a sphere

1961 ◽  
Vol 51 (2) ◽  
pp. 247-257
Author(s):  
James N. Brune ◽  
John E. Nafe ◽  
Leonard E. Alsop
Keyword(s):  
Phase Shift ◽  
Rayleigh Wave ◽  
Surface Waves ◽  
Free Oscillation ◽  
Wave Length ◽  
Polar Phase ◽  
Wave Phase ◽  
Using Data ◽  
Surface Wave Data ◽  
Rayleigh Wave Phase Velocity

Abstract It has been demonstrated by means of a model experiment that elastic surface waves on a sphere advance in phase by π/2 on each crossing of the polar or antipodal region. Comparison of the asymptotic forms of solutions of the wave equation for displacements and dilatation before the polar crossing with those that apply afterward also show the π/2 phase shift. Similarly a π/4 phase advance occurs for waves leaving a point source. Because of the occurrence of the polar phase shift, it is necessary to correct previously published Rayleigh wave and Love wave phase velocities measured by correlation of phases over complete circumferential paths. The corrected Rayleigh wave phase velocity curve is presented here. The polar phase shift is involved in the determination of periods of free oscillation of the earth from surface wave data. Using data from the great Chilean earthquake of May 22, 1960, it is shown that the ratio of the earth's circumference to the wave length at free oscillation periods gives very nearly half integers in accordance with the formula 2 π a λ = n + 1 2 ·

Quantification of Effects of Ridge and Valley Topography on the Rayleigh Wave Characteristics

2018 ◽  
Vol 12 (03) ◽  
pp. 1850007 ◽  
Author(s):  
J. P. Narayan ◽  
A. Kumar
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Large Scale ◽  
Research Work ◽  
Vertical Component ◽  
Staggered Grid ◽  
Long Span ◽  
Shape Ratio ◽  
Day By Day ◽  
Ridge And Valley

The effects of ridge and valley on the characteristics of Rayleigh waves are presented in this paper. The research work carried out has been stimulated by the day by day increase of long-span structures in the hilly areas which are largely affected by the spatial variability in ground motion caused by the high-frequency Rayleigh waves. The Rayleigh wave responses of the considered triangular and elliptical ridge and valley models were computed using a fourth-order accurate staggered-grid viscoelastic P-SV wave finite-difference (FD) program. The simulated results revealed very large amplification of the horizontal component and de-amplification of the vertical component of Rayleigh wave at the top of a triangular ridge and de-amplification of both the components at the base of the triangular valley. The observed amplification of both the components of Rayleigh wave in front of elliptical valley was larger than triangular valley models. A splitting of the Rayleigh wave wavelet was inferred after interaction with ridge and valley. It is concluded that the large-scale topography acts as a natural insulator for the surface waves and the insulating capacity of the valley is more than that of a ridge. This insulation phenomenon is arising due to the reflection, diffraction and splitting of the surface wave while moving across the topography. It is concluded that insulating potential of the topography for the Rayleigh waves largely depends on their shape and shape-ratio.

scholarly journals Resolving the lithosphere-asthenosphere boundary with seismic Rayleigh waves

2011 ◽  
Vol 186 (3) ◽  
pp. 1152-1164 ◽  
Author(s):  
Stefan Bartzsch ◽  
Sergei Lebedev ◽  
Thomas Meier
Keyword(s):  
Rayleigh Waves ◽  
Seismic Rayleigh Waves
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