Periodic in-filled pipes embedded in semi-infinite space as seismic metamaterials for filtering ultra-low-frequency surface waves

2021 ◽  
Vol 313 ◽  
pp. 125498
Author(s):  
Xiao Wang ◽  
Shui Wan ◽  
Yuze Nian ◽  
Peng Zhou ◽  
Yingbo Zhu
Keyword(s):  
Surface Waves ◽  
Low Frequency ◽  
Infinite Space

Fundamental properties of surface waves in lossless stratified structures

2010 ◽  
Vol 466 (2120) ◽  
pp. 2447-2469 ◽  
Author(s):  
Guido Valerio ◽  
David R. Jackson ◽  
Alessandro Galli
Keyword(s):  
Surface Waves ◽  
Dispersion Equation ◽  
High Frequency ◽  
Low Frequency ◽  
Layered Structures ◽  
Graphical Solution ◽  
Fundamental Properties ◽  
The Past ◽  
Permittivity And Permeability ◽  
Constitutive Parameters

This paper is focused on dispersive properties of lossless planar layered structures with media having positive constitutive parameters (permittivity and permeability), possibly uniaxially anisotropic. Some of these properties have been derived in the past with reference to specific simple layered structures, and are here established with more general proofs, valid for arbitrary layered structures with positive parameters. As a first step, a simple application of the Smith chart to the relevant dispersion equation is used to prove that evanescent (or plasmonic-type) waves cannot be supported by layers with positive parameters. The main part of the paper is then focused on a generalization of a common graphical solution of the dispersion equation, in order to derive some general properties about the behaviour of the wavenumbers of surface waves as a function of frequency. The wavenumbers normalized with respect to frequency are shown to be always increasing with frequency, and at high frequency they tend to the highest refractive index in the layers. Moreover, two surface waves with the same polarization cannot have the same wavenumber at a given frequency. The low-frequency behaviours are also briefly addressed. The results are derived by means of a suitable application of Foster’s theorem.

Excitation of lower hybrid waves by electron beams in finite geometry plasmas. Part 2. Surface waves

1978 ◽  
Vol 19 (2) ◽  
pp. 295-299
Author(s):  
Réal R. J. Gagné ◽  
Magdi M. Shoucri
Keyword(s):  
Electron Beam ◽  
Surface Waves ◽  
Electron Beams ◽  
Low Frequency ◽  
Finite Geometry ◽  
Dispersion Relations ◽  
Lower Hybrid ◽  
Small Density ◽  
Hybrid Waves ◽  
Lower Hybrid Waves

The dispersion relations for the quasi-static lower hybrid surface waves are derived. Conditions for their existence and their linear excitation by a small density electron beam are discussed. Instabilities appearing in low-frequency surface waves are also discussed.

Shallow seismic detection of the fault zone associated with a high scarp in southwestern Montana

2015 ◽  
Vol 3 (1) ◽  
pp. T25-T41
Author(s):  
Jose Pujol ◽  
Mervin J. Bartholomew ◽  
Andrew Mickelson ◽  
Michael Bone
Keyword(s):  
Surface Waves ◽  
Fault Zone ◽  
Synthetic Data ◽  
Low Frequency ◽  
Normal Fault ◽  
Actual Data ◽  
Southwestern Montana ◽  
Velocity Models ◽  
Reflection Data ◽  
High Pass

We collected shallow reflection data in southwestern Montana, USA, across a 5.4-m-high tectonic scarp. The goal was to image the normal fault associated with the scarp, observed in an adjacent trench. Processing of the data was challenging because the height of the scarp was comparable to the depths of the reflectors of interest. To find out how to proceed, we processed synthetic data generated using velocity models derived in part from actual shot gathers. The actual data are dominated by large-amplitude low-frequency surface waves, but clear high-frequency reflections are seen in the more distant geophones. Common-offset gathers for the raw and high-pass filtered data reveal sharp discontinuities in arrival times and a strong decrease in amplitudes, respectively, under the scarp. These changes in the wavefield are indicative of lateral variations in elastic properties and are consistent with the presence of a fault zone seen in the trench. The actual data were stacked after the surface waves were removed with a narrow f-k filter. Severe muting was applied to isolate the reflections seen in the high-pass filtered data. The stacked data reveal a clear and fairly continuous horizontal reflector on the downthrown side of the fault and more disrupted reflectors on the upthrown side, with truncated reflections and changes in amplitude roughly across the projection of the fault mapped in the trench. These observations are consistent with faulting and would be difficult to explain if the scarp were an erosional feature.

Finite-frequency surface waves on current sheets

1991 ◽  
Vol 45 (3) ◽  
pp. 389-406 ◽  
Author(s):  
K. P. Wessen ◽  
N. F. Cramer
Keyword(s):  
Magnetic Field ◽  
Dispersion Relation ◽  
Surface Waves ◽  
Cyclotron Frequency ◽  
Low Frequency ◽  
Dielectric Tensor ◽  
Magnetic Field Direction ◽  
Field Reversal ◽  
Ion Cyclotron ◽  
The Magnetic Field

The dispersion relation for low-frequency surface waves at a current sheet between two magnetized plasmas is derived using the cold-plasma dielectric tensor with finite ion-cyclotron frequency. The magnetic field direction is allowed to change discontinuously across the sheet, but the plasma density remains constant. The cyclotron frequency causes a splitting of the dispersion relation into a number of mode branches with frequencies both less than and greater than the ion-cyclotron frequency. The existence of these modes depends in particular upon the degree of magnetic field discontinuity and the direction of wave propagation in the sheet relative to the magnetic field directions. Sometimes two modes can exist for the same direction of propagation. The existence of modes undamped by Alfvén resonance absorption is predicted. Analytical solutions are obtained in the low-frequency and magnetic-field-reversal limits. The solutions are obtained numerically in the general case.

scholarly journals EXPERIMENTAL STUDIES OF THE DISTRIBUTION OF VARIOUS SPECIES OF SEISMOACOUSTIC WAVES IN THE COASTAL ZONE

2020 ◽  
Author(s):  
А.Н. Самченко ◽  
А.А. Пивоваров ◽  
А.Н. Швырев ◽  
И.О. Ярощук
Keyword(s):  
Surface Waves ◽  
Coastal Zone ◽  
Sea Of Japan ◽  
Peter The Great Bay ◽  
Experimental Studies ◽  
Low Frequency ◽  
Acoustic Signals ◽  
The Sea Of Japan ◽  
Preliminary Results ◽  
Peter The Great

В статье приводятся результаты экспериментальных исследований распространения низкочастотных акустических сигналов (33 Гц) на побережье залива Петра Великого Японского моря. Источник акустических сигналов опускался с борта маломерного судна в воду, а приемные системы были у береговой черты в воде и на суше. За счет использования трехкомпонентных виброметров стало возможно разделить принятые сигналы на различные типы волн (продольные, поперечные и поверхностные). Получены предварительные результаты расчета скоростных характеристик приходов различного типа волн на виброметры. The article presents the results of experimental studies on the propagation of low-frequency acoustic signals (33 Hz) on the coast of Peter the Great Bay of the Sea of Japan. The source of acoustic signals descended from the board of a small boat into the water, and the receiving systems were at the coastline in water and on land. Through the use of three component vibrometers, it has become possible to divide the received signals into various types of waves (longitudinal, transverse and surface waves). The preliminary results of calculating the speed characteristics of the arrival of various types of waves on vibrometers are obtained.

scholarly journals Low-Frequency Earthquakes along the Ryukyu Islands Triggered by Teleseismic Earthquakes

2021 ◽  
Author(s):  
Ayumi Kinjo ◽  
Mamoru Nakamura
Keyword(s):  
Surface Waves ◽  
Low Frequency ◽  
Stress Sensitivity ◽  
Peak Ground Velocity ◽  
Ryukyu Islands ◽  
Plate Interface ◽  
Okinawa Island ◽  
Short Period ◽  
Ryukyu Arc ◽  
The Ryukyu Islands

Abstract Tremors and low-frequency earthquakes (LFEs), which occur in the plate interface, can provide useful information about the state of aseismic stress transfer in mega-earthquake fault zones. We estimated the distribution of stress sensitivity in the subducted plate interface by using triggered LFEs. Specifically, we detected LFEs in the Ryukyu Trench triggered by the surface waves of large teleseismic earthquakes by using the waveform records of broadband and short-period seismometers installed in the Ryukyu Arc. We selected a total of 45 teleseismic earthquakes with magnitudes of more than 7.5, which occurred between 2004 and 2017, for the analysis. We could detect the triggered LFEs for five teleseismic earthquakes. Then, we determined the hypocenters of LFEs by using the relative arrival times of LFEs for each station. The LFEs were distributed in the south of Okinawa Island and the Yaeyama area. Moreover, they were distributed around the source fault of the slow slip events. These were almost the same as the position of LFEs accompanying very low-frequency earthquakes (VLFEs). However, the epicenters of the triggered LFEs were concentrated near the locations of the most active LFE clusters accompanying VLFEs. This suggests that the sensitivity for inducing LFEs was higher near the most active clusters of the LFEs accompanying the VLFEs. The amplitudes of the triggered LFEs were proportional to the peak ground velocity of the surface waves. This indicates that the LFEs accompanying VLFEs are activated by stress acceleration in the Yaeyama and Okinawa areas and the triggered LFEs observed in these areas can be a result of the activation of the ambient tremors due to increased stress.

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