Frequency Surface Wave Research Articles

Novel Frame-Type Seismic Surface Wave Barrier with Ultra-Low-Frequency Bandgaps for Rayleigh Waves

Seismic surface waves carry significant energy that poses a major threat to structures and may trigger damage to buildings. To address this issue, the implementation of periodic barriers around structures has proven effective in attenuating seismic waves and minimizing structural dynamic response. This paper introduces a framework for seismic surface wave barriers designed to generate multiple ultra-low-frequency band gaps. The framework employs the finite-element method to compute the frequency band gap of the barrier, enabling a deeper understanding of the generation mechanism of the frequency band gap based on vibrational modes. Subsequently, the transmission rates of elastic waves through a ten-period barrier were evaluated through frequency–domain analysis. The attentional effects of the barriers were investigated by the time history analysis using site seismic waves. Moreover, the influence of the soil damping and material damping are separately discussed, further enhancing the assessment. The results demonstrate the present barrier can generate low-frequency band gaps and effectively attenuate seismic surface waves. These band gaps cover the primary frequencies of seismic surface waves, showing notable attenuation capabilities. In addition, the soil damping significantly contributes to the attenuation of seismic surface waves, resulting in an attenuation rate of 50%. There is promising potential for the application of this novel isolation technology in seismic engineering practice.

Effect of Anisotropy on Residual Stress Measurement of 316L Stainless Steel by Ultrasonic Surface Wave

Fe–Cr alloys are widely used in power, petroleum, and manufacturing industries for their good resistance to corrosion and oxidation at high temperatures. Ultrasound is the only nondestructive method so far to measure the residual stress of in-service components. However, for parts with material anisotropy, such as materials processed by rolling, the measurement accuracy is highly restrained. In this paper, a rolled 316L stainless steel sample is used to study the influence of texture on the measurement of residual stress by ultrasonic surface wave. The experimental results show that the propagation velocity of surface waves in the sample has anisotropic characteristics. The wave velocity parallel to the rolling direction (0°) is the maximum, and the wave velocity perpendicular to the rolling direction (90°) is the minimum, thereby affecting the measurement accuracy. It is found that reducing the frequency of surface waves can reduce the influence of anisotropy. Therefore, a low-frequency method and modified formula are used to improve the measurement accuracy. The maximum error in the rolling direction is reduced from 21.3 to 3.6 MPa, and the maximum relative error is also reduced from 45.4 to 9.0%. The modified formula can further reduce the influence of anisotropy, with the maximum error value further reduced to 2.3 MPa, the maximum relative error reduced to 4.9%, and the surface wave detection accuracy effectively improved.

Topography‐Incorporated Adjoint‐State Surface Wave Traveltime Tomography: Method and a Case Study in Hawaii

AbstractIn this study we recast surface wave traveltime tomography as an inverse problem constrained by an eikonal equation and solve it using the efficient adjoint‐state method. Specifically, recognizing that large topographic variations and high surface wave frequencies can make the topographic effect too significant to ignore, we employ an elliptically anisotropic eikonal equation to describe the traveltime fields of surface waves on undulated topography. The sensitivity kernel of the traveltime objective function with respect to shear wave velocity is derived using the adjoint‐state method. As a result, the newly developed method is inherently applicable to any study regions, whether with or without significant topographic variations. Hawaii is one of the most seismically and magmatically active regions. However, its significant topographic variations have made it less accurate to investigate using conventional surface wave traveltime tomography methods. To tackle this problem, we applied our new method to invert ambient noise Rayleigh wave phase traveltimes and construct a 3D shear wave velocity model. Our results reveal features that are consistent with geological structures and previous tomography results, including high velocities below Mauna Loa Volcano and Kilauea Volcano, and low velocities beneath the Hilina Fault Zone. Additionally, our model reveals a high‐velocity anomaly to the South of Hualalai's summit, which may be related to a buried rift zone. Our findings further demonstrate that including topography can lead to a correction of up to 0.8% in the shear wave velocity model of Hawaii, an island spanning approximately 100 km with volcanoes reaching elevations exceeding 4 km.

CHARACTERIZATION OF SURFACE-WAVES IN THE CENTRAL SWAMP DEPOBELT IN THE NIGER DELTA, NIGERIA

This paper presents a detailed study on refraction survey carried out in the Central Swamp Depobelt of the Niger Delta in order to compute the characteristics of the surface waves. Twenty-seven (27) boreholes were each drilled in the Central Swamp Depobelt of the Niger Delta to 66m. The borehole data were acquired using Seismograph McSeis-160MX Recorder, hydrophone detector and electric detonator as the source. Analysis of the results shows two-layer refractors. The consolidated-layer velocities range between 1580 and 1906ms-1with an average of 1737.78ms-1. Weathered-layer (surface) velocities range between 213 and 781ms-1 with an average of 504.81ms-1. Air-blast low velocities range between 213 and 377ms-1 with an average of 307.33ms-1. Depths from refracting surfaces range between 2.25 and 6.12m with an average of 4.58m. Dominant surface wave frequencies range between 5 and 10Hz. The layer thickness and velocity parameters can be applied in static correction in the processing of seismic reflection survey data. The dominant frequency information can also be integrated with the other parameters in detector and source arrays design necessary for attenuating the ground roll noise in the study area.

Electric field tuning of a nickel zinc ferrite resonator by non-linear magnetoelectric effects

The nature of nonlinear magnetoelectric (NLME) effect has been investigated at room-temperature in a single-crystal Zn substituted nickel ferrite. Tuning of the frequency of magnetostatic surface wave (MSSW) modes under an applied pulsed DC electric field/current has been utilized to probe the effect. The frequencies of the modes at 8–20 GHz were found to decrease by ~ 400 MHz for an applied DC power P of ~ 100 mW and the frequency shift was the same for all of the MSSW modes and linearly proportional to P. A model is proposed for the effect and the NLME phenomenon was interpreted in terms of a reduction in the saturation magnetization due to the DC current. The decrease of magnetization with applied electric power, estimated from data on mode frequency versus P, was − 2.50 G/mW. The frequency tuning efficiency of the MSSW modes due to NLME effects in the ferrite resonator was found to be 4.1 MHz/mW which is an order of magnitude higher than the shift reported for M-type strontium and barium hexaferrite resonators investigated earlier. The spinel ferrite resonator discussed here has the potential for miniature, electric field tunable, planar microwave devices for the 8–20 GHz frequency range.

Screened plasmons of graphene near a perfect electric conductor

Screened plasmon properties of graphene near a perfect electric conductor (PEC) are investigated taking into account the retardation effects. A detailed discussion of the dispersion relation of the mentioned screened plasmonic waves is presented and illustrated graphically using classical electrodynamics and a linearized hydrodynamic model that includes Fermi correction. The result indicates that for realistic wavenumbers, the dispersion relation of plasmonic waves of isolated graphene is almost unaffected by the Fermi correction, while this correction is an important factor for the screened plasmons of graphene near a PEC, where it increases the frequency of surface waves. The results show that near the graphene neutrality point, the surface wave has linear dispersion with a universal speed close to vF/2. Such linear dispersion for surface waves (also known as energy waves) appears to be a common occurrence when splitting of plasma frequencies occurs, e.g., in the electron–hole plasma of graphene [Zhao et al., Nature 614, 688 (2023)]. Furthermore, analytical expressions for the energy parameters (the power flow, energy density, and energy velocity) of screened plasmons of the system are derived. Also, the analytical expressions are derived and analyzed for the damping function and surface plasmon and electromagnetic field strength functions of surface waves of the system with small intrinsic damping.

Crossover of surface waves and capillary-viscous-elastic transition in soft biomaterials detected by resonant acoustic rheometry

Viscoelastic properties of hydrogels are important for their application in science and industry. However, rheological assessment of soft hydrogel biomaterials is challenging due to their complex, rapid, and often time-dependent behaviors. Resonant acoustic rheometry (RAR) is a newly developed technique capable of inducing and measuring resonant surface waves in samples in a non-contact fashion. By applying RAR at high temporal resolution during thrombin-induced fibrin gelation and ultraviolet-initiated polyethylene glycol (PEG) polymerization, we observed distinct changes in both frequency and amplitude of the resonant surface waves as the materials changed over time. RAR detected a series of capillary-elastic, capillary-viscous, and visco-elastic transitions that are uniquely manifested as crossover of different types of surface waves in the temporally evolving materials. These results reveal the dynamic interplay of surface tension, viscosity, and elasticity that is controlled by the kinetics of polymerization and crosslinking during hydrogel formation. RAR overcomes many limitations of conventional rheological approaches by offering a new way to comprehensively and longitudinally characterize soft materials during dynamic processes.

Laboratory study of instability-driven mixing of fluid mud under surface wave motion

Motivated by the role of interfacial instabilities in sediment resuspension in coastal areas, this paper provides quantitative measurements of fluid mud density profile during motion of a surface wave over a muddy bed in a wave flume. Following a fluidization process, a quasi-standing interfacial wave grew owing to a resonant wave interaction with the surface wave. In the process, the quasi-standing wave reached a maximum amplitude and then approached a steady state. The long-time behavior of the resonantly generated interfacial wave and the changes in vertical density profile during wave motion were recorded. Increasing the surface wave frequency led to a higher initial growth rate of the interfacial wave within the experimental range, but the faster growth rate did not result in a larger final amplitude. The results show that excitation of the interfacial wave results in increasing water turbidity such that the water column becomes turbid in a matter of a few minutes. In general, the change in the fluid density profile is highly correlated with the quasi-standing interfacial wave amplitude during the resonant interaction. The amount of entrained mud particles into the clear water by the end of each experiment was determined. The ultimate amplitude of the quasi-standing interfacial wave was found to be a major factor in sediment resuspension.

Prevention of Wave Propagation via Circular Arrangement of Seismic Metamaterials Formed with Concrete Piles

It is known that the low frequencies of seismic surface waves have a destructive effect. The main purpose of seismic metamaterials is to protect structures from seismic waves at low frequencies, especially in a wide band. In this study, the effects of seismic metamaterials formed using circular array concrete piles on surface waves were investigated. Each concrete pile has been selected due to symmetric properties to investigate the band diagram. Therefore, the direction independence can also be determined with respect to frequency. This study was conducted both numerically and experimentally in the low-frequency range of 5–15 Hz. Two fields, with and without metamaterials, have been designed and compared. In numerical analysis, transmission loss graphs were drawn using the finite element method (FEM), and wave propagation at frequencies where the loss happened was simulated. In numerical analysis, optimum dimensions such as radius and depth were determined, and these dimensions were applied exactly in the experimental field. The results obtained from the experiment using a harmonic vibration device are mapped. In this numerical and experimental study, it has been revealed that the proposed structure prevents the propagation of seismic surface waves.

Experimental investigations on dynamic wave structures of a prefilming atomizer

An experimental study was performed on a planar prefilming airblast atomizer to investigate the dynamic wave behavior on a prefilmer. Using a high-speed camera, backlighting visualization and reflection imaging were applied to record the breakup process of the liquid film and the temporary evolution of wave structures. Image post-processing methods were used to obtain the film thickness, surface wave frequency, breakup length, and ligament breakup frequency. Depending on non-dimensional aerodynamic numbers, surface waves on the prefilmer were classified into three mechanisms. In addition, correlations were derived from experimental data and used to predict atomization characteristics. The deviations of surface wave frequency and breakup length were limited to ±10%. These predictive correlations can assist in resolving engineering issues regarding prefilming atomizers.

On research of dispersion characteristics of multi-component surface waves from traffic-induced seismic ambient noise

As one of the commonly used sources in passive surface wave exploration, traffic-induced seismic ambient noise is widely used in urban underground velocity structure detection at present. However, characteristics of the dispersion curve extracted from such kind of ambient noise lack systematical research, especially for the multi-component surface wave. Due to the complex character of the real-world underneath structures, dispersion characteristics concluded from real-world traffic-induced seismic ambient noise that is hard to verify. The numerical simulation technique is a good choice for systematical research of characteristics of dispersion curves extracted from multi-component traffic-induced seismic ambient noise. Most of the numerical examples that appeared in the present literature, however, are based on the dispersion-curve-based numerical simulation technique. Hence, most of these can only simulate the vertical component. In this paper, the two-dimensional finite difference method is used to simulate multi-component traffic seismic ambient noise. The characteristics of original traffic noise are analyzed, and the effect of trace intervals on surface wave imaging of different types of traffic-induced noise is studied. Rayleigh wave dispersion energy image is extracted by the passive surface-wave frequency wavenumber transformed method. The differences in Rayleigh-wave dispersion images in traffic noise with different components are analyzed and compared. The results show that Rayleigh wave dispersion energy images appearing different characteristics in different components. The surface wave dispersion information presented by different types of traffic noise is frequency-dependent. The trace spacing also strongly affect the surface-wave dispersion energy images extracted from different types of traffic-induced noise. The numerical results are significant for guiding the traffic-induced seismic noise data acquisition and processing.

Seismic and ionospheric disturbances caused by the 3 September 2017 underground nuclear test in North Korea

We investigated lithospheric and ionospheric disturbances caused by the 3 September 2017 underground nuclear test (UNT) in North Korea based on data from networks of seismic stations and GPS/GLONASS receivers. We analyzed frequency composition of longitudinal and surface waves detected at more than 40 seismic stations. Low frequencies (∼0.45 ± 0.21 Hz) were found to prevail in the spectrum of longitudinal waves. For both types of waves, frequencies decreased with distance according to the power law. Analysis revealed two trends in the spatial distribution of peak frequencies. First, high and mid-frequencies (0.14–0.50 Hz) are typical for the continental landmass regions, and low frequencies of surface waves (0.13 Hz and below) are more common for the regions adjacent to fringe seas. Second, uneven frequency variations of seismic waves for different azimuths relative to the UNT epicenter (frequencies subside rapidly in the east, southeast, and southwest directions from the epicenter; towards the continental landmass inner parts, frequency variation is much slower). Records of longitudinal waves made at different distances from the epicenter allowed estimating the size of the focal area. Analysis of data from GPS/GLONASS receiving stations near the Korean Peninsula revealed ionospheric disturbances that were most likely caused by UNT. The ionospheric disturbances started to be detected ∼ 8 min after UNT and were observed for about 5 hrs. During the first 1.5–2 hrs after UNT, travelling ionospheric disturbances (TID) were recorded; they propagated from the epicenter at ∼ 600, 250 and 133 m/s. These TIDs had periods of 1–10.5 min and could be associated with acoustic waves induced in the Earth's atmosphere by the underground nuclear test. After TID passage over the UNT site, there was a long-lived (more than 3.5 hrs) region of non-travelling perturbations of ionospheric plasma with the velocity about 7 m/s. This velocity describes not so much the disturbance travel, but the time when the “receiver – satellite” line of sight (LOS) crosses the disturbance. This region can possibly occur due to the formation of standing waves in the atmosphere, development of plasma instabilities or penetration into the ionosphere of an anomalous electric field generated by radioactive substances leaked out onto the surface.

Smoothed Particle Hydrodynamics Simulation of the Dynamic Water Pressure inside an Arch Rib of an Arch Bridge Subjected to Seismic Excitation

The dynamic pressure exerted on an arch rib by inner water under seismic excitation was studied based on the smoothed particle hydrodynamics (SPH) numerical model. Numerical cases of different seismic excitations in both the horizontal and vertical directions and different water depths were carried out. The fast Fourier transform (FFT) of dynamic pressure exerted on the arch rib showed that the spike frequency is related to the water depth. The surface wave frequency of inner water is very close to the first spike frequency. The first spike frequency comes close to the second and fourth vibration frequencies when the inner water reaches the depth of 18 m and 11.3 m, respectively. This will likely lead to the resonance of the entire arch rib. By considering barely the first spike frequency, when designing a new arch bridge, the possibilities of resonance in its second and fourth modes under seismic excitation cannot be ruled out. Based on the findings of this investigation, the inner water effect should be considered during the arch bridge design stage.

Expression of Concern: “Approximation of surface wave frequency in piezo-composite structure” [JCOMB, Volume 144, 1 July 2018, Pages 19–28

Expression of Concern: “Approximation of surface wave frequency in piezo-composite structure” [JCOMB, Volume 144, 1 July 2018, Pages 19–28

Spectral analysis of localized surface phonon polaritons in resonant silicon carbide hollow cylinder array

Manipulation of the amplitude and frequency of resonant optical surface waves in mid-infrared is of great interest for improvement of photonic devices and vibrational molecule sensing applications. Antennas supporting localized surface phonon polaritons (LSPhPs) fold the optical phonons into periodic pillar array to control the scattering process. Energy exchange, mode evolution and near-field coupling mechanism are investigated thoroughly, and it is demonstrated that the transverse dipole mode in the 6H-silicon carbide hollow cylinder array shows excellent absorption efficiency and tunable capability across a wide spectral range. Dependence of local field on structural parameters in the polarized sub-mode is explored to elucidate the optical properties. Near-field coupling is further evaluated by combining the values of current distribution with multipole decomposition. This study also provides a practical guide to establish a general framework for exploring the spectral tuning and coupling mechanisms of LSPhP modes.

Tunable terahertz Bloch surface waves in one-dimensional photonic crystals with a Dirac semimetal cap layer

The dispersion relation and localization of surface waves in semi-infinite one-dimensional photonic crystals in the presence of Dirac semimetal as a cap layer are theoretically and numerically investigated, using the transfer matrix method at terahertz band. It is demonstrated that the frequency and localization of surface waves can be tuned by changing the cap layer's Fermi energy for both transverse electric and transverse magnetic polarizations. The numerical results show that the dispersion relation of surface waves and consequently their localization are more sensitive to changes in Fermi energy. Therefore, the surface states with the desired localization can be achieved. In addition, the effect of the cap layer's thickness and the arrangement of the photonic crystal layers on surface waves are investigated. The results show that these parameters have considerable effect on modification of surface waves.

The effect of viscosity of saturated soil on the surface wave attenuation by periodic in-filled trench

Investigations on the ambient vibration reduction by periodic wave barriers have been received more and more attention in recent years. However, the role of energy dissipation caused by the viscosity of soil is usually ignored in most of the previous studies. The surface wave attenuation in saturated viscoelastic soil by periodic in-filled trench is investigated in this study. Firstly, the constitutive model of saturated viscoelastic soil is constructed by introducing Kelvin viscoelastic model into the Biot's theory. Secondly, the complex band structure of surface waves propagating in periodic in-filled trench is calculated. A finite model for analyzing ambient vibration isolation is built, and the responses of the site under external excitation are numerically solved both in frequency domain and time domain. The roles of the viscosity of soil and the periodic barrier in the surface wave attenuation are comprehensively discussed, and some findings are obtained. Soil's viscosity reinforces the attenuation when the frequencies of surface waves fall in the attenuation zone. However, the contribution of the viscosity is not obvious. Contrary to the attenuation zone, soil's viscosity plays a key role in the attenuation when the frequencies of surface waves are out of the attenuation zone.

Nondestructive evaluation of porosity in additive manufacturing by laser ultrasonic surface wave

A noncontact and nondestructive method based on laser ultrasound is proposed for evaluation of porosity in additive manufacturing components. The 304L stainless steel samples with porosities in the range of 0.1%–5.7 % were fabricated using selective laser melting. Laser ultrasonic surface wave was used to characterize the porosity by the wave speed, peak frequency and wavelet packet energy. The result indicates that the surface wave speed, peak frequency and wavelet packet energy are sensitive to the slight variation of porosity in the samples. Good R-squares of fitting between surface wave velocity and porosity were obtained when it considers the pore irregular morphology. The peak frequency of surface wave decreases as the disappearance of high-frequency signals induced by the scattering attenuation. The wavelet packet analysis result shows that the sum of the percentage energy of the ninth layer of wavelet packet decomposition nodes 2–4 is linearly related to the porosity, and exhibits the highest coefficient of determination (R = 0.98) among the proposed characteristics. It is concluded that the laser ultrasonic surface wave based on wavelet packet energy is recommended to be a promising candidate for the quantitative nondestructive evaluation of the porosity of additive manufacturing components.

Sensitivity of Love surface waves to mass loading

The sensitivity of the phase velocity vp of Love surface waves to mass loading is a very important characteristic of Love wave devices. In this paper, we present a novel approach to evaluate the sensitivity of Love surface waves to loading with an infinitesimal layer of mass of a surface density σkg/m2. To this end, the we developed analytical formulas for the mass coefficient of sensitivity Sσvp=(1/vp)dvp/dσ [m2/kg] and phase velocity gradients −dvp(f)/df and −dvp(h1)/dh1, where f and h1 stand, respectively, for frequency of the Love wave and thickness of the guiding surface layer. We also established analytical formulas that relate the mass sensitivity Sσvp with 1) the relative slope (gradient) −(1/vp)dvp/dh1 of the phase velocity dispersion curve vp(h1), and 2) the relative slope (gradient) −(1/vp)dvp/df of the phase velocity dispersion curve vp(f). These analytical formulas have been developed using full wave theory. We have discovered that the maxima of the mass sensitivity Sσvpf, Sσvph1 and maxima of the relative gradients (-(1/vp)dvp)⁄df, −(1/vp)dvp/dh1, occur virtually at the same values of fandh1. Comparing with the Perturbation Method and Finite Element Method (FEM), the analytical formulas established in this paper display some advantages, such as very low execution time of the mass sensitivity , and perhaps more importantly a possibility for a direct parametric optimization of the Love wave waveguide as a function of its material parameters, thickness of the guiding surface layer and wave frequency .

Hydrodynamic behavior of a circular floating solar pond with an entrapped two-layer fluid

The resonant behavior in a moonpool of a floating circular solar pond, with an entrapped two-layer fluid, is studied. The problem is solved by applying a domain-decomposition method using eigenfunction matching. The surface- and internal-wave elevations and the hydrodynamic coefficients of a typical floating solar pond under forced heave or surge motion are computed. The effects of density stratification on surface-wave elevation, added mass, and damping coefficients are analyzed. A collection of resonance frequencies of surface and internal waves is examined, together with the corresponding variations of modal shapes. For heave resonance, the surface and internal waves are characterized by axisymmetric sloshing modes, as opposed to antisymmetric sloshing modes under surge resonances. A frozen-mode approximation method that treats the moonpool fluid as a density-stratified solid is developed to estimate piston-mode frequencies. Non-dimensional resonance frequencies corresponding to antisymmetric and axisymmetric sloshing modes are estimated based on the standing-wave approximation and reciprocity relations between surface and internal wavenumbers. Satisfactory agreement between the estimated resonance frequencies and those computed by eigenfunction matching method is achieved. It is found that the first resonance of the internal wave, rather than higher-order resonances, is more likely to affect the surface-wave behavior, whereas resonances of the surface-wave modes have significant effects on the internal waves. Parametric analyses are performed to study the effects of geometry configurations of the pond. It is found that the resonance frequencies of internal waves under forced heave or surge motion decrease with an increasing density ratio.