scholarly journals Horizontal Acoustic Barriers for Protection from Seismic Waves

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Sergey V. Kuznetsov ◽  
Aybek E. Nafasov
Keyword(s):  
Surface Layer ◽  
Numerical Simulations ◽  
Half Space ◽  
Rayleigh Waves ◽  
Seismic Waves ◽  
Specific Region ◽  
Love Waves ◽  
Thin Surface Layer

The basic idea of a seismic barrier is to protect an area occupied by a building or a group of buildings from seismic waves. Depending on nature of seismic waves that are most probable in a specific region, different kinds of seismic barriers can be suggested. Herein, we consider a kind of a seismic barrier that represents a relatively thin surface layer that prevents surface seismic waves from propagating. The ideas for these barriers are based on one Chadwick's result concerning nonpropagation condition for Rayleigh waves in a clamped half-space, and Love's theorem that describes condition of nonexistence for Love waves. The numerical simulations reveal that to be effective the length of the horizontal barriers should be comparable to the typical wavelength.

scholarly journals Surface waves in multilayered elastic media I. Rayleigh and Love waves from buried sources in a multilayered elastic half-space

1964 ◽  
Vol 54 (2) ◽  
pp. 627-679
Author(s):  
David G. Harkrider
Keyword(s):  
Surface Waves ◽  
Frequency Domain ◽  
Half Space ◽  
Rayleigh Waves ◽  
Elastic Half Space ◽  
Love Waves ◽  
Displacement Fields ◽  
Matrix Formulation ◽  
Total Displacement ◽  
Rayleigh And Love Waves

ABSTRACT A matrix formulation is used to derive integral expressions for the time transformed displacement fields produced by simple sources at any depth in a multilayered elastic isotropic solid half-space. The integrals are evaluated for their residue contribution to obtain surface wave displacements in the frequency domain. The solutions are then generalized to include the effect of a surface liquid layer. The theory includes the effect of layering and source depth for the following: (1) Rayleigh waves from an explosive source, (2) Rayleigh waves from a vertical point force, (3) Rayleigh and Love waves from a vertical strike slip fault model. The latter source also includes the effect of fault dimensions and rupture velocity. From these results we are able to show certain reciprocity relations for surface waves which had been previously proved for the total displacement field. The theory presented here lays the ground work for later papers in which theoretical seismograms are compared with observations in both the time and frequency domain.

Abnormal Structural Strength of Topocomposites

2012 ◽  
Vol 560-561 ◽  
pp. 338-343 ◽  
Author(s):  
Nikolay A. Voronin
Keyword(s):  
Surface Layer ◽  
Bearing Capacity ◽  
Half Space ◽  
Contact Interaction ◽  
Solid Body ◽  
Mechanical Characteristics ◽  
Structural Strength ◽  
Layered Material ◽  
Thin Surface Layer ◽  
Layer Coating

The mechanics of contact interaction of rigid spherical indenter with two-layer elastic - plastic half-space, simulating a surface of a solid body with a thin surface layer is considered. Analytical dependences of critical indentation and bearing capacity on mechanical characteristics of materials of a base and a coating, and as well as that for thickness of top layer (coating) in all region of possible thickness are received and analyzed. Existence of regions of the abnormal structural strength allowing the surface layered material to identify unequivocally as a topocomposite is shown. Theoretical dependences were verified by a final elements method.

4. Seismic waves

2018 ◽  
pp. 53-61
Author(s):  
Mike Goldsmith
Keyword(s):  
Seismic Wave ◽  
Rayleigh Waves ◽  
Seismic Waves ◽  
Shear Waves ◽  
Free Vibrations ◽  
Love Waves ◽  
Sound Waves ◽  
P Waves ◽  
Tectonic Plates ◽  
S Waves

Sound waves travel very easily underground, often for many thousands of kilometres. These are usually referred to as a kind of seismic wave and are most often triggered by earthquakes, which result from a sudden slip of tectonic plates, down to about 700 kilometres below the Earth’s surface. ‘Seismic waves’ describes the four types of seismic wave generated by earthquakes: P-waves (primary waves), S-waves (shear waves), Love waves (usually the most powerful and destructive of seismic waves), and Rayleigh waves, which are created when P and S waves reach the Earth’s surface together, combining to form undulating ground rolls. Free vibrations and star waves are also described.

SEISMIC WAVES FROM A TRANSDUCER AT THE SURFACE OF STRATIFIED GROUND

Geophysics ◽  
1956 ◽  
Vol 21 (4) ◽  
pp. 939-959 ◽  
Author(s):  
F. F. Evison
Keyword(s):  
Surface Layer ◽  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Seismic Waves ◽  
Ground Surface ◽  
Shear Velocity ◽  
Critical Distance ◽  
Variable Frequency ◽  
Independent Estimate ◽  
Refracted Waves

Vibration impulses of variable frequency and duration have been generated by means of an electrically excited vibrator and the resulting seismic waves recorded at the ground surface along a 200‐ft traverse. The first arrivals were refractions from the water table and a deeper clay‐siltstone interface, and these checked with the results of a standard refraction survey. The amplitudes of displacement of the refracted waves varied in each case with approximately the inverse square of distance; the critical distance was marked by a discontinuity of amplitude. Two later impulsive arrivals recorded within 50 msec of the first were interpreted respectively as a transformed reflection from 85 ft depth and an ordinary compressional reflection from 200 ft depth. A dispersive Rayleigh wave gave an independent estimate of the shear velocity and thickness of the surface layer. Air‐coupled waves of frequencies 70.8 cps and 330 cps were recorded and have been related to the first‐ and third‐mode Rayleigh waves respectively.

Finite-amplitude Love waves in a pre-stressed compressible elastic half-space with a double surface layer

Wave Motion ◽  
2015 ◽  
Vol 56 ◽  
pp. 205-220 ◽  
Author(s):  
Priza Kayestha ◽  
Elizabete Rodrigues Ferreira ◽  
Anil C. Wijeyewickrema
Keyword(s):  
Surface Layer ◽  
Half Space ◽  
Finite Amplitude ◽  
Elastic Half Space ◽  
Love Waves ◽  
Double Surface

scholarly journals Numerical simulations to explain the coseismic electromagnetic signals: a case study for a M5.4 aftershock of the 2016 Kumamoto earthquake

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Yao-Chong Sun ◽  
Makoto Uyeshima ◽  
Hengxin Ren ◽  
Qinghua Huang ◽  
Koki Aizawa ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Half Space ◽  
Rayleigh Waves ◽  
Volcanic Area ◽  
2016 Kumamoto Earthquake ◽  
Electrokinetic Effect ◽  
Space Model ◽  
Scattering Effect ◽  
Magnetic Components ◽  
The 2016 Kumamoto Earthquake

AbstractCoseismic electromagnetic (EM) signals that appear from the P arrival were observed in a volcanic area during the 2016 Kumamoto earthquake. In this study, we conduct numerical simulations to explain the coseismic EM signals observed for a M5.4 aftershock of the earthquake. Initially, we adopt a water-saturated half-space model, and its simulation result for a receiver with a depth of 0.1 m suggests that the magnetic signals do not show up at the arrivals of P, refracted SV–P and Rayleigh waves because the evanescent EM waves just counterbalance the localized magnetic signals that accompany P, refracted SV–P and Rayleigh waves. Then, we conduct numerical simulations on a seven-layer half-space model in which the second layer corresponds to an aquifer analogy and the six other layers refer to air-saturated porous media. When only the electrokinetic effect is considered, the simulated coseismic magnetic signals still appear from the S arrival. The combination of electrokinetic effect and surface-charge assumption is also tested. We find that signals before the S arrival are missing on the transverse seismic, transverse electric, radial magnetic and vertical magnetic components, although the situation on horizontal magnetic components is improved to an extent. Then, we introduce an artificial scattering effect into our numerical simulations given that the scattering effect should exist in the volcanic area. New numerical result shows good agreement with the observation result on the signal appearance time. Hence, the combination of electrokinetic and scattering effects is a plausible explanation of coseismic EM signals. Further investigations indicate that coseismic electric and/or magnetic signals are more sensitive to the scattering effect and the aquifer thickness than seismic signals.

Transmission of Love waves in a half-space with a surface layer whose thickness varies hyperbolically

1964 ◽  
Vol 54 (2) ◽  
pp. 611-625
Author(s):  
Takehito Takahashi
Keyword(s):  
Surface Layer ◽  
Phase Velocity ◽  
Half Space ◽  
Lower Boundary ◽  
Approximate Solutions ◽  
Love Waves ◽  
Curvilinear Coordinates ◽  
Harmonic Waves ◽  
Straight Line

ABSTRACT The Propagation of Love waves in a layer over a half-space is theoretically studied for cases where the upper or lower boundary of the layer can be represented by a hyporbola. Curvilinear coordinates are used. Approximate solutions of various modes exist. Among the component harmonic waves of a mode, the representative one for each given position can be specified. This explains the position dependancy of phase velocity. The condition of transmission and refiection of Love waves for this model and the case in which one-half of the hyperbola is replaced by a straight line are discussed.

scholarly journals Seismic barriers: theory and numerical simulations

2019 ◽  
Vol 97 ◽  
pp. 03005 ◽  
Author(s):  
Vladimir Bratov ◽  
Alla Ilyashenko ◽  
Nikita Morozov ◽  
Tursunbai Rashidov
Keyword(s):  
Physical Properties ◽  
Numerical Simulations ◽  
Wave Energy ◽  
Seismic Waves ◽  
Fem Simulation ◽  
Specific Region ◽  
Bulk Waves ◽  
Vertical Barriers

The basic idea of a seismic barrier is to protect an area occupied by a building or a group of buildings from seismic waves. Depending on the nature of seismic waves that are the most probable in a specific region, different kinds of seismic barriers are suggested. For example, vertical barriers resembling a wall in a soil can protect from Rayleigh and bulk waves. The FEM simulation reveals that to be effective, such a barrier should be (i) composed of layers with contrast physical properties allowing “trapping” of the wave energy inside some of the layers, and (ii) depth of the barrier should be comparable or greater than the considered seismic wavelength.

Surface-wave propagation under initial tension or compression

1973 ◽  
Vol 63 (6-1) ◽  
pp. 1895-1899
Author(s):  
E. J. Brunelle
Keyword(s):  
Wave Propagation ◽  
Surface Wave ◽  
Initial Stress ◽  
Half Space ◽  
Rayleigh Waves ◽  
Love Waves ◽  
Initial Tension ◽  
Linearized Equations ◽  
Compressive Stresses ◽  
Surface Wave Propagation

Abstract The propagation of Rayleigh waves in a half-space and the propagation of Love waves in a welded layer and half-space are examined when initial tensile or compressive stresses are present. Using the perturbed and linearized equations of elasticity, which include the effects of initial stress, a modified Rayleigh equation and a modified Love equation are obtained. The solution of the equations shows a dramatic change in the phase speeds of the two wave types under initial tension or compression. Numerical results are presented.

scholarly journals Seismic Rayleigh waves on an exponentially graded, orthotropic half-space

2006 ◽  
Vol 463 (2078) ◽  
pp. 495-502 ◽  
Author(s):  
Michel Destrade
Keyword(s):  
Half Space ◽  
Rayleigh Waves ◽  
Seismic Waves ◽  
Symmetry Axis ◽  
Mass Density ◽  
Homogeneous Case ◽  
Marked Contrast ◽  
Homogeneous Half Space ◽  
Shear Horizontal ◽  
Exponentially Graded

Efforts at modelling the propagation of seismic waves in half-spaces with continuously varying properties have mostly been focused on shear-horizontal waves. Here, a sagittally polarized (Rayleigh type) wave travels along a symmetry axis (and is attenuated along another) of an orthotropic material with stiffnesses and mass density varying in the same exponential manner with depth. In contrast to what could be expected at first sight, the analysis is very similar to that of the homogeneous half-space, with the main and capital difference that the Rayleigh wave is now dispersive. The results are illustrated numerically for (i) an orthotropic half-space typical of horizontally layered and vertically fractured shales and (ii) for an isotropic half-space made of silica. In both the examples, the wave travels at a slower speed and penetrates deeper than in the homogeneous case. In the second example, the inhomogeneity can force the wave amplitude to oscillate as well as decay with depth, in marked contrast with the homogeneous isotropic general case.

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