Attenuation of Rayleigh Surface Waves in a Porous Material
DEBBOUB Salima; BOUMA(I)ZA Youcef; BOUDOUR Amar; TAHRAOUI Tarek
2012-01-01
Using acoustic microscopy at higher frequency,we show the velocity evolutions of surface acoustic waves,in particular Rayleigh waves that depend on porosity for a mesoporous silicon layer.The velocities are obtained from different V(z) curves,which are determined experimentally at a frequency of 600MHz.The analysis of V(z) data yields attenuation that is directly dependent on porosity.On the other hand,αN attenuation has been modeled and allows us to investigate its influence on the velocity VR of the propagation for Rayleigh waves.%Using acoustic microscopy at higher frequency, we show the velocity evolutions of surface acoustic waves, in particular Rayleigh waves that depend on porosity for a mesoporous silicon layer. The velocities are obtained from different V(z) curves, which are determined experimentally at a frequency of 600 MHz. The analysis of V(z) data yields attenuation that is directly dependent on porosity. On the other hand, αN attenuation has been modeled and allows us to investigate its influence on the velocity VR of the propagation for Rayleigh waves.
Nonlinear mixing of laser generated narrowband Rayleigh surface waves
Bakre, Chaitanya; Rajagopal, Prabhu; Balasubramaniam, Krishnan
2017-02-01
This research presents the nonlinear mixing technique of two co-directionally travelling Rayleigh surface waves generated and detected using laser ultrasonics. The optical generation of Rayleigh waves on the specimen is obtained by shadow mask method. In conventional nonlinear measurements, the inherently small higher harmonics are greatly influenced by the nonlinearities caused by coupling variabilities and surface roughness between the transducer and specimen interface. The proposed technique is completely contactless and it should be possible to eliminate this problem. Moreover, the nonlinear mixing phenomenon yields not only the second harmonics, but also the sum and difference frequency components, which can be used to measure the acoustic nonlinearity of the specimen. In this paper, we will be addressing the experimental configurations for this technique. The proposed technique is validated experimentally on Aluminum 7075 alloy specimen.
Zhang, Xiaoming
2016-11-01
The purpose of this Letter to the Editor is to demonstrate an effective method for estimating viscoelasticity based on measurements of the Rayleigh surface wave speed. It is important to identify the surface wave mode for measuring surface wave speed. A concept of start frequency of surface waves is proposed. The surface wave speeds above the start frequency should be used to estimate the viscoelasticity of tissue. The motivation was to develop a noninvasive surface wave elastography (SWE) technique for assessing skin disease by measuring skin viscoelastic properties. Using an optical based SWE system, the author generated a local harmonic vibration on the surface of phantom using an electromechanical shaker and measured the resulting surface waves on the phantom using an optical vibrometer system. The surface wave speed was measured using a phase gradient method. It was shown that different standing wave modes were generated below the start frequency because of wave reflection. However, the pure symmetric surface waves were generated from the excitation above the start frequency. Using the wave speed dispersion above the start frequency, the viscoelasticity of the phantom can be correctly estimated.
Rayleigh waves ellipticity and mode mis-identification in multi-channel analysis of surface waves
Boaga, Jacopo; Cassiani, Giorgio; Strobbia, Claudio
dispersion curve which is then inverted. Typically, single component vertical and multi channel receivers are used. In most cases the inversion of the dispersion properties is carried out assuming that the experimental dispersion curve corresponds to a single mode, mostly the fundamental Rayleigh mode......-identification known as ‘osculation’ (‘kissing’). In general it is called ‘osculation point’ the point where the energy peak shifts at low frequencies from the fundamental to the first higher mode. This jump occurs, with a continuous smooth transition, around a well-define frequency where the two modes get very close...... the vertical component of ground motion, as the mode osculation is linked to the Rayleigh wave ellipticity polarization, and therefore we conclude that multi-component data, using also horizontal receivers, can help discern the multi-modal nature of surface waves. Finally we introduce a-priori detectors...
Rayleigh surface waves, phonon mode conversion, and thermal transport in nanostructures
Maurer, Leon; Knezevic, Irena
We study the effects of phonon mode conversion and Rayleigh (surface) waves on thermal transport in nanostructures. We present a technique to calculate thermal conductivity in the elastic-solid approximation: a finite-difference time-domain (FDTD) solution of the elastic or scalar wave equations combined with the Green-Kubo formula. The technique is similar to an equilibrium molecular dynamics simulation, captures phonon wave behavior, and scales well to nanostructures that are too large to simulate with many other techniques. By imposing fixed or free boundary conditions, we can selectively turn off mode conversion and Rayleigh waves to study their effects. In the example case of graphenelike nanoribbons with rough edges, we find that mode conversion among bulk modes has little effect on thermal transport, but that conversion between bulk and Rayleigh waves can significantly reduce thermal conductivity. With increasing surface disorder, Rayleigh waves readily become trapped by the disorder and draw energy away from the propagating bulk modes, which lowers thermal conductivity. We discuss the implications on the accuracy of popular phonon-surface scattering models that stem from scalar wave equations and cannot capture mode conversion to Rayleigh waves.
Estimation of near-surface shear-wave velocity by inversion of Rayleigh waves
Xia, J.; Miller, R.D.; Park, C.B.
1999-01-01
The shear-wave (S-wave) velocity of near-surface materials (soil, rocks, pavement) and its effect on seismic-wave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh-wave phase velocity of a layered-earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity, density, and thickness of layers. Analysis of the Jacobian matrix provides a measure of dispersion-curve sensitivity to earth properties. S-wave velocities are the dominant influence on a dispersion curve in a high-frequency range (>5 Hz) followed by layer thickness. An iterative solution technique to the weighted equation proved very effective in the high-frequency range when using the Levenberg-Marquardt and singular-value decomposition techniques. Convergence of the weighted solution is guaranteed through selection of the damping factor using the Levenberg-Marquardt method. Synthetic examples demonstrated calculation efficiency and stability of inverse procedures. We verify our method using borehole S-wave velocity measurements.Iterative solutions to the weighted equation by the Levenberg-Marquardt and singular-value decomposition techniques are derived to estimate near-surface shear-wave velocity. Synthetic and real examples demonstrate the calculation efficiency and stability of the inverse procedure. The inverse results of the real example are verified by borehole S-wave velocity measurements.
Propagation of Rayleigh surface waves with small wavelengths in nonlocal visco-elastic solids
D P Acharya; Asit Mondal
2002-12-01
This paper investigates Rayleigh waves, propagating on the surface of a visco-elastic solid under the linear theory of nonlocal elasticity. Dispersion relations are obtained. It is observed that the waves are dispersive in nature for small wavelengths. Numerical calculations and discussions presented in this paper lead us to some important conclusions.
Impact of density information on Rayleigh surface wave inversion results
Ivanov, Julian; Tsoflias, Georgios; Miller, Richard D.; Peterie, Shelby; Morton, Sarah; Xia, Jianghai
2016-12-01
We assessed the impact of density on the estimation of inverted shear-wave velocity (Vs) using the multi-channel analysis of surface waves (MASW) method. We considered the forward modeling theory, evaluated model sensitivity, and tested the effect of density information on the inversion of seismic data acquired in the Arctic. Theoretical review, numerical modeling and inversion of modeled and real data indicated that the density ratios between layers, not the actual density values, impact the determination of surface-wave phase velocities. Application on real data compared surface-wave inversion results using: a) constant density, the most common approach in practice, b) indirect density estimates derived from refraction compressional-wave velocity observations, and c) from direct density measurements in a borehole. The use of indirect density estimates reduced the final shear-wave velocity (Vs) results typically by 6-7% and the use of densities from a borehole reduced the final Vs estimates by 10-11% compared to those from assumed constant density. In addition to the improved absolute Vs accuracy, the resulting overall Vs changes were unevenly distributed laterally when viewed on a 2-D section leading to an overall Vs model structure that was more representative of the subsurface environment. It was observed that the use of constant density instead of increasing density with depth not only can lead to Vs overestimation but it can also create inaccurate model structures, such as a low-velocity layer. Thus, optimal Vs estimations can be best achieved using field estimates of subsurface density ratios.
Xu, Yanlong
2015-01-21
We report high quality broadband spatial reflections of Rayleigh surface acoustic waves (SAWs) through a graded grooved surface. High quality means that no wave is allowed to transmit and the incident wave is nearly all reflected to the input side. The graded grooved surface is structured by drilling one dimensional array of graded grooves with increased depths on a flat surface. We investigate SAW dispersion relations, wave field distribution at several typical SAW wavelengths, and time evolution of a Gaussian pulse through the graded grooved surface. Results show that the input broadband Rayleigh SAWs can be slowed, spatially enhanced and stopped, and finally reflected to the input side. The study suggests that engraving the flat surface can be used as an efficient and economical way to manipulate Rayleigh SAWs, which has potential application in novel SAW devices such as filters, reflectors, sensors, energy harvesters, and diodes.
Assessment of Reinforced Concrete Surface Breaking Crack Using Rayleigh Wave Measurement.
Lee, Foo Wei; Chai, Hwa Kian; Lim, Kok Sing
2016-03-05
An improved single sided Rayleigh wave (R-wave) measurement was suggested to characterize surface breaking crack in steel reinforced concrete structures. Numerical simulations were performed to clarify the behavior of R-waves interacting with surface breaking crack with different depths and degrees of inclinations. Through analysis of simulation results, correlations between R-wave parameters of interest and crack characteristics (depth and degree of inclination) were obtained, which were then validated by experimental measurement of concrete specimens instigated with vertical and inclined artificial cracks of different depths. Wave parameters including velocity and amplitude attenuation for each case were studied. The correlations allowed us to estimate the depth and inclination of cracks measured experimentally with acceptable discrepancies, particularly for cracks which are relatively shallow and when the crack depth is smaller than the wavelength.
Roux-Marchand, Thibaut; Beyssen, Denis; Sarry, Frederic; Elmazria, Omar
2015-04-01
When a microdroplet is put on the Rayleigh surface acoustic wave path, longitudinal waves are radiated into the liquid and induce several phenomena such as the wellknown surface acoustic wave streaming. At the same time, the temperature of the microdroplet increases as it has been shown. In this paper, we study the temperature uniformity of a microdroplet heated by Rayleigh surface acoustic wave for discrete microfluidic applications such as biological reactions. To precisely ascertain the temperature uniformity and not interfere with the biological reaction, we used an infrared camera. We then tested the temperature uniformity as a function of three parameters: the microdroplet volume, the Rayleigh surface acoustic wave frequency, and the continuous applied radio frequency power. Based on these results, we propose a new device structure to develop a future lab on a chip based on reaction temperatures.
无
2011-01-01
This letter reports experimental observation of a direct correlation between the acoustic nonlinearity parameter (NP) measured with nonlinear Rayleigh waves and the accumulation of plasticity damage in an AZ31 magnesium alloy plate specimen.Rayleigh waves are generated and detected with wedge transducers,and the NPs are measured at different stress levels.The results show that there is a significant increase in the NPs with monotonic tensile loads surpassing the material's yielding stress.The research sugge...
Assessment of precipitation in alloy steel using nonlinear Rayleigh surface waves
Thiele, Sebastian; Matlack, Kathryn H.; Kim, Jin-Yeon; Qu, Jianmin; Wall, James J.; Jacobs, Laurence J.
2014-02-01
Nonlinear ultrasonic waves have shown to be sensitive to various microstructural changes in metals including coherent precipitates; these precipitates introduce a strain field in the lattice structure. The thermal aging of certain alloy steels leads to the formation of coherent precipitates, which pin dislocations and contribute to the generation of a second harmonic component. A precipitate hardenable material namely 17-4 PH stainless steel is thermally treated in this research to obtain different precipitation stages, and then the influence of precipitates on the acoustic nonlinearity parameter is assessed. Conclusions about the microstrucutural changes in the material are drawn based on the results from a nonlinear Rayleigh surface wave measurement and complementary thermo-electric power, hardness and ultrasonic velocity measurements. The results show that the nonlinear parameter is sensitive to coherent precipitates in the material and moreover that precipitation characteristics can be characterized based on the obtained experimental data.
Detection of near-surface cavities by generalized S-transform of Rayleigh waves
Shao, Guang-zhou; Tsoflias, George P.; Li, Chang-jiang
2016-06-01
The near-surface cavities can cause a huge hidden trouble for urban infrastructure construction, such as, foundation settlement and roadbed subsidence, and so on. So, it is an important task to detect the underground cavities effectively for many engineering projects. At the same time, because of the complexity of near-surface materials and the limited resolution of geophysical methods, detecting the location of the hidden cavities quantitatively is still a technical challenge which needs to be studied further. Base on the study of Xia et al. (Xia et al., 2007), we performed a little modification to the travel time equation for the Rayleigh-wave diffraction. We put forward another way to detect the shallow subsurface voids. The generalized S-transform was adopted to extract the arrival times of the diffracted Rayleigh waves from the near and far-offset boundaries of the void at a certain receiver. Then the arrival times were used to calculate the boundary locations of the void. Three half-space void models and a two-layered void model were used to demonstrate the feasibility and effect of detecting a void with the generalized S-transform. A rotated staggered-grid finite-difference method was adopted in wave field modeling to obtain the synthetic seismic record. Finally, a real world field data was used to verify the detecting effect. The theoretical models and the real world example showed that it is feasible and effective to use the generalized S-transform to detect the near-surface cavities.
Rayleigh surface wave interaction with the 2D exciton Bose-Einstein condensate
Boev, M. V.; Kovalev, V. M., E-mail: vadimkovalev@isp.nsc.ru [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)
2015-06-15
We describe the interaction of a Rayleigh surface acoustic wave (SAW) traveling on the semiconductor substrate with the excitonic gas in a double quantum well located on the substrate surface. We study the SAW attenuation and its velocity renormalization due to the coupling to excitons. Both the deformation potential and piezoelectric mechanisms of the SAW-exciton interaction are considered. We focus on the frequency and excitonic density dependences of the SAW absorption coefficient and velocity renormalization at temperatures both above and well below the critical temperature of Bose-Einstein condensation of the excitonic gas. We demonstrate that the SAW attenuation and velocity renormalization are strongly different below and above the critical temperature.
Analysis of group-velocity dispersion of high-frequency Rayleigh waves for near-surface applications
Luo, Y.; Xia, J.; Xu, Y.; Zeng, C.
2011-01-01
The Multichannel Analysis of Surface Waves (MASW) method is an efficient tool to obtain the vertical shear (S)-wave velocity profile using the dispersive characteristic of Rayleigh waves. Most MASW researchers mainly apply Rayleigh-wave phase-velocity dispersion for S-wave velocity estimation with a few exceptions applying Rayleigh-wave group-velocity dispersion. Herein, we first compare sensitivities of fundamental surface-wave phase velocities with group velocities with three four-layer models including a low-velocity layer or a high-velocity layer. Then synthetic data are simulated by a finite difference method. Images of group-velocity dispersive energy of the synthetic data are generated using the Multiple Filter Analysis (MFA) method. Finally we invert a high-frequency surface-wave group-velocity dispersion curve of a real-world example. Results demonstrate that (1) the sensitivities of group velocities are higher than those of phase velocities and usable frequency ranges are wider than that of phase velocities, which is very helpful in improving inversion stability because for a stable inversion system, small changes in phase velocities do not result in a large fluctuation in inverted S-wave velocities; (2) group-velocity dispersive energy can be measured using single-trace data if Rayleigh-wave fundamental-mode energy is dominant, which suggests that the number of shots required in data acquisition can be dramatically reduced and the horizontal resolution can be greatly improved using analysis of group-velocity dispersion; and (3) the suspension logging results of the real-world example demonstrate that inversion of group velocities generated by the MFA method can successfully estimate near-surface S-wave velocities. ?? 2011 Elsevier B.V.
Ekaterina I. Radeva; Esmeryan, Karekin D.; Avramov, Ivan D.
2012-01-01
Temperature induced frequency shifts may compromise the sensor response of polymer coated acoustic wave gas-phase sensors operating in environments of variable temperature. To correct the sensor data with the temperature response of the sensor the latter must be known. This study presents and discusses temperature frequency characteristics (TFCs) of solid hexamethyldisiloxane (HMDSO) polymer coated sensor resonators using the Rayleigh surface acoustic wave (RSAW) mode on ST-cut quartz. Using ...
High-Frequency Rayleigh-Wave Method
Jianghai Xia; Richard D Millerg; Xu Yixian; Luo Yinhe; Chen Chao; Liu Jiangping; Julian Ivanov; Chong Zeng
2009-01-01
High-frequency (≥2 Hz) Rayleigh-wave data acquired with a multichannei recording sys-tem have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave tech-niques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a nou-iuvasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution.
Paffenholz, Joseph; Fox, Jon W.; Gu, Xiaobai; Jewett, Greg S.; Datta, Subhendu K.
1990-01-01
Scattering of Rayleigh-Lamb waves by a normal surface-breaking crack in a plate has been studied both theoretically and experimentally. The two-dimensionality of the far field, generated by a ball impact source, is exploited to characterize the source function using a direct integration technique. The scattering of waves generated by this impact source by the crack is subsequently solved by employing a Green's function integral expression for the scattered field coupled with a finite element representation of the near field. It is shown that theoretical results of plate response, both in frequency and time, are similar to those obtained experimentally. Additionally, implication for practical applications are discussed.
The viscous surface-internal wave problem: nonlinear Rayleigh-Taylor instability
Wang, Yanjin
2011-01-01
We consider the free boundary problem for two layers of immiscible, viscous, incompressible fluid in a uniform gravitational field, lying above a rigid bottom in a three-dimensional horizontally periodic setting. The effect of surface tension is either taken into account at both free boundaries or neglected at both. We are concerned with the Rayleigh-Taylor instability, so we assume that the upper fluid is heavier than the lower fluid. When the surface tension at the free internal interface is below a critical value, which we identify, we establish that the problem under consideration is nonlinearly unstable.
Zhang, Benfeng; Han, Tao; Tang, Gongbin; Zhang, Qiaozhen; Omori, Tatsuya; Hashimoto, Ken-ya
2017-07-01
In this paper, we investigate the impact of the coupling with shear horizontal (SH) surface acoustic wave (SAW) on the propagation of Rayleigh SAW in periodic grating structures on 128°YX-LiNbO3. First, the frequency dispersion behavior with longitudinal and lateral wavenumbers of Rayleigh SAW is calculated using the finite element method (FEM) software COMSOL. It is shown that the coupling causes (1) the satellite stopband and (2) variation of the anisotropy factor. It is also shown these phenomena remain even when the electromechanical coupling factor of SH SAW is zero. Then, the extended thin plate model which can take coupling between two SAWs into account, is applied to simulate the result of FEM. Good agreement between these results indicated that the mechanical coupling is responsible for these two phenomena. Finally, including electrical excitation and detection, the model is applied to the infinitely long interdigital transducer (IDT) structure and the calculated result is compared with that obtained by the three-dimensional FEM. The excellent agreement of both results confirms the effectiveness of the extended thin plate model.
Acoustical breakdown of materials by focusing of laser-generated Rayleigh surface waves
Veysset, David; Maznev, A. A.; Veres, István A.; Pezeril, Thomas; Kooi, Steven E.; Lomonosov, Alexey M.; Nelson, Keith A.
2017-07-01
Focusing of high-amplitude surface acoustic waves leading to material damage is visualized in an all-optical experiment. The optical setup includes a lens and an axicon that focuses an intense picosecond excitation pulse into a ring-shaped pattern at the surface of a gold-coated glass substrate. Optical excitation induces a surface acoustic wave (SAW) that propagates in the plane of the sample and converges toward the center. The evolution of the SAW profile is monitored using interferometry with a femtosecond probe pulse at variable time delays. The quantitative analysis of the full-field images provides direct information about the surface displacement profiles, which are compared to calculations. The high stress at the focal point leads to the removal of the gold coating and, at higher excitation energies, to damage of the glass substrate. The results open the prospect for testing material strength on the microscale using laser-generated SAWs.
Leaky Rayleigh wave investigation on mortar samples.
Neuenschwander, J; Schmidt, Th; Lüthi, Th; Romer, M
2006-12-01
Aggressive mineralized ground water may harm the concrete cover of tunnels and other underground constructions. Within a current research project mortar samples are used to study the effects of sulfate interaction in accelerated laboratory experiments. A nondestructive test method based on ultrasonic surface waves was developed to investigate the topmost layer of mortar samples. A pitch and catch arrangement is introduced for the generation and reception of leaky Rayleigh waves in an immersion technique allowing the measurement of their propagation velocity. The technique has been successfully verified for the reference materials aluminium, copper, and stainless steel. First measurements performed on mortar specimens demonstrate the applicability of this new diagnostic tool.
Stoklasová, Pavla; Sedlák, Petr; Seiner, Hanuš; Landa, Michal
2015-02-01
We show that the Ritz-Rayleigh method can be used for calculation of velocity of surface acoustic waves (SAWs) propagating in a general direction of an anisotropic medium of arbitrary symmetry class. The main advantage of this method is that expanding the displacement field of SAW into a fixed functional basis transforms the calculation of SAW velocities into a simple linear eigenvalue problem. The correctness and reliability of the proposed approach are verified on experimental SAW data obtained for generally oriented planes of an indium phosphide single crystal. The same experimental datasets are then used to discuss the invertibility of the method, i.e. the possibility of determination of elastic coefficients from SAW measurements in general directions. It is shown that the SAW data obtained on a single generally oriented plane are sufficient for such an inverse calculation for a cubic material only if they are complemented by measurements of velocities of bulk quasi-longitudinal (qL) waves propagating along the same free surface. Moreover, when the SAW and qL data are available from three almost perpendicular faces of a single specimen, the complete elastic tensor (21 independent constants) can be inversely determined, without considering a priori any symmetry constraints to the material.
Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets.
Alghane, M; Chen, B X; Fu, Y Q; Li, Y; Desmulliez, M P Y; Mohammed, M I; Walton, A J
2012-11-01
We report an experimental and numerical characterization of three-dimensional acoustic streaming behavior in small droplets of volumes (1-30 μl) induced by surface acoustic wave (SAW). We provide a quantitative evidence of the existence of strong nonlinear nature of the flow inertia in this SAW-driven flow over a range of the newly defined acoustic parameter F{NA}=Fλ/(σ/R_{d})≥0.01, which is a measure of the strength of the acoustic force to surface tension, where F is the acoustic body force, λ is the SAW wavelength, σ is the surface tension, and R{d} is the droplet radius. In contrast to the widely used Stokes model of acoustic streaming, which generally ignores such a nonlinearity, we identify that the full Navier-Stokes equation must be applied to avoid errors up to 93% between the computed streaming velocities and those from experiments as in the nonlinear case. We suggest that the Stokes model is valid only for very small acoustic power of ≤1 μW (F{NA}droplets.
Imaging Rayleigh wave attenuation with USArray
Bao, Xueyang; Dalton, Colleen A.; Jin, Ge; Gaherty, James B.; Shen, Yang
2016-07-01
The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle at an unprecedented scale. The majority of mantle models derived from USArray data to date contain spatial variations in seismic-wave speed; however, in many cases these data sets do not by themselves allow a non-unique interpretation. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. The surface wave amplitudes that constrain upper-mantle attenuation are sensitive to factors in addition to attenuation, including the earthquake source excitation, focusing and defocusing by elastic structure, and local site amplification. Because of the difficulty of isolating attenuation from these other factors, little is known about the attenuation structure of the North American upper mantle. In this study, Rayleigh wave traveltime and amplitude in the period range 25-100 s are measured using an interstation cross-correlation technique, which takes advantage of waveform similarity at nearby stations. Several estimates of Rayleigh wave attenuation and site amplification are generated at each period, using different approaches to separate the effects of attenuation and local site amplification on amplitude. It is assumed that focusing and defocusing effects can be described by the Laplacian of the traveltime field. All approaches identify the same large-scale patterns in attenuation, including areas where the attenuation values are likely contaminated by unmodelled focusing and defocusing effects. Regionally averaged attenuation maps are constructed after removal of the contaminated attenuation values, and the variations in intrinsic shear attenuation that are suggested by these Rayleigh wave attenuation maps are explored.
Ekaterina I. Radeva
2012-05-01
Full Text Available Temperature induced frequency shifts may compromise the sensor response of polymer coated acoustic wave gas-phase sensors operating in environments of variable temperature. To correct the sensor data with the temperature response of the sensor the latter must be known. This study presents and discusses temperature frequency characteristics (TFCs of solid hexamethyldisiloxane (HMDSO polymer coated sensor resonators using the Rayleigh surface acoustic wave (RSAW mode on ST-cut quartz. Using a RF-plasma polymerization process, RSAW sensor resonators optimized for maximum gas sensitivity have been coated with chemosensitive HMDSO films at 4 different thicknesses: 50, 100, 150 and 250 nm. Their TFCs have been measured over a (−100 to +110 °C temperature range and compared to the TFC of an uncoated device. An exponential 2,500 ppm downshift of the resonant frequency and a 40 K downshift of the sensor’s turn-over temperature (TOT are observed when the HMDSO thickness increases from 0 to 250 nm. A partial temperature compensation effect caused by the film is also observed. A third order polynomial fit provides excellent agreement with the experimental TFC curve. The frequency downshift due to mass loading by the film, the TOT and the temperature coefficients are unambiguously related to each other.
Seismic Rayleigh Wave Digital Processing Technology
Jie, Li
2013-04-01
In Rayleigh wave exploration, the digital processing of data plays a very important position. This directly affects the interpretation of ground effect. Therefore, the use of accurate processing software and effective method in the Rayleigh wave exploration has important theoretical and practical significance. Previously, Rayleigh wave dispersion curve obtained by the one-dimensional phase analysis. This method requires channel spacing should be less than the effective wavelength. And minimal phase error will cause great changes in the phase velocity of Rayleigh wave. Damped least square method is a local linear model. It is easy to cause that inversion objective function cannot find the global optimal solution. Therefore, the method and the technology used in the past are difficult to apply the requirements of the current Rayleigh wave exploration. This study focused on the related technologies and algorithms of F-K domain dispersion curve extraction and GA global non-linear inversion, and combined with the impact of Rayleigh wave data acquisition parameters and the characteristics. Rayleigh wave exploration data processing software design and process technology research is completed. Firstly, the article describes the theoretical basis of Rayleigh wave method. This is also part of the theoretical basis of following treatment. The theoretical proof of existence of Rayleigh wave Dispersive in layered strata. Secondly, F-K domain dispersion curve extraction tests showed that the method can overcome the one-dimensional digital processing technology deficiencies, and make full use of multi-channel Rayleigh wave data record information. GA global non-linear inversion indicated that the inversion is not easy getting into local optimal solution. Thirdly, some examples illustrate each mode Rayleigh wave dispersion curve characteristics in the X-T domain. Tests demonstrated the impact on their extraction of dispersion curves. Parameters change example (including the X
Pollitz, F.F.; Snoke, J. Arthur
2010-01-01
We utilize two-and-three-quarter years of vertical-component recordings made by the Transportable Array (TA) component of Earthscope to constrain three-dimensional (3-D) seismic shear wave velocity structure in the upper 200 km of the western United States. Single-taper spectral estimation is used to compile measurements of complex spectral amplitudes from 44 317 seismograms generated by 123 teleseismic events. In the ﬁrst step employed to determine the Rayleigh-wave phase-velocity structure, we implement a new tomographic method, which is simpler and more robust than scattering-based methods (e.g. multi-plane surface wave tomography). The TA is effectively implemented as a large number of local arrays by deﬁning a horizontal Gaussian smoothing distance that weights observations near a given target point. The complex spectral-amplitude measurements are interpreted with the spherical Helmholtz equation using local observations about a succession of target points, resulting in Rayleigh-wave phase-velocity maps at periods over the range of 18–125 s. The derived maps depend on the form of local ﬁts to the Helmholtz equation, which generally involve the nonplane-wave solutions of Friederich et al. In a second step, the phase-velocity maps are used to derive 3-D shear velocity structure. The 3-D velocity images conﬁrm details witnessed in prior body-wave and surface-wave studies and reveal new structures, including a deep (>100 km deep) high-velocity lineament, of width ∼200 km, stretching from the southern Great Valley to northern Utah that may be a relic of plate subduction or, alternatively, either a remnant of the Mojave Precambrian Province or a mantle downwelling. Mantle seismic velocity is highly correlated with heat ﬂow, Holocene volcanism, elastic plate thickness and seismicity. This suggests that shallow mantle structure provides the heat source for associated magmatism, as well as thinning of the thermal lithosphere, leading to relatively high
Reflectometry using longitudinal, shear and Rayleigh waves.
Chen, W; Wu, J
2000-09-01
A new technique of reflectometry using longitudinal, shear and Rayleigh waves is presented. Reflection coefficient as a function of angle incidence of an ultrasound beam with a finite beamwidth was measured for water-aluminum, water-brass, and water-glass interfaces. The measured values have matched very favorably with the results of numerical calculations based on the angular spectrum of waves method. It has been shown that the speeds of longitudinal, shear and Rayleigh waves of a solid can be determined very accurately by measuring a spectacularly reflected signal versus angle of incidence.
Seismic metasurfaces: Sub-wavelength resonators and Rayleigh wave interaction
Colquitt, D J; Craster, R V; Roux, P; Guenneau, S R L
2016-01-01
We consider the canonical problem of an array of rods, which act as resonators, placed on an elastic substrate; the substrate being either a thin elastic plate or an elastic half-space. In both cases the flexural plate, or Rayleigh surface, waves in the substrate interact with the resonators to create interesting effects such as effective band-gaps for surface waves or filters that transform surface waves into bulk waves; these effects have parallels in the field of optics where such sub-wavelength resonators create metamaterials, and metasurfaces, in the bulk and at the surface respectively. Here we carefully analyse this canonical problem by extracting the dispersion relations analytically thereby examining the influence of both the flexural and compressional resonances on the propagating wave. For an array of resonators atop an elastic half-space we augment the analysis with numerical simulations. Amongst other effects, we demonstrate the striking effect of a dispersion curve that transitions from Rayleigh...
Rayleigh surface wave modeling by finite difference method in biphasic media%双相介质瑞雷面波有限差分正演模拟
张伟; 甘伏平; 刘伟; 郑智杰
2014-01-01
为了研究双相介质瑞雷面波的形成机制及传播规律，促进瑞雷面波资料处理方法的发展。文章根据弹性波动方程，采用交错网格有限差分算法，对二维各向同性弹性介质做解析解与数值解的对比，在此基础上，将PML吸收边界条件，改进的镜像法应用于双相介质波动方程中，并作了稳定性分析，对双相介质水平层状、起伏分界面等典型模型瑞雷面波及体波在内的全波场进行研究。结果表明：基于弹性介质解析解与数值解的对比，在误差接受范围内，研究双相介质是可行的；把稍作改进的镜像法应用于双相介质中，能够有效地处理瑞雷面波自由边界问题；通过详细分析双相介质瑞雷面波及体波在内的全波场的信息，对以双相介质为基础的地震波勘探有一定的指导作用。%In order to study the mechanism and propagation of Rayleigh surface wave in biphasic media and promote the development of data⁃processing method of Rayleigh surface wave, the authors applied finite difference method with staggered grids to simulate the 2D i⁃sotropic elastic media based on the elastic wave equation, and made a comparison between the analytical and numerical solutions. On such a basis, the PML absorbing boundary condition and improved image method can be applied to the two⁃phase medium wave equa⁃tion to simulate the typical media model including horizontal layer and undulating interface, analyze the full wave information including the Rayleigh surface wave and body wave, and make a stability analysis. The results show that, on the basis of the comparison between the numerical solution and the analytical solution of the elastic media within the acceptable range of the error, the study of biphasic me⁃dium is feasible. The slight improvement of the image method can be applied to biphasic media to deal with free boundary condition problem of the Rayleigh surface wave
Retrieval of Rayleigh Wave Ellipticity from Ambient Vibration Recordings
Maranò, Stefano; Hobiger, Manuel; Fäh, Donat
2017-01-01
The analysis of ambient vibrations is a useful tool in microzonation and geotechnical investigations. Ambient vibrations are composed to a large part of surface waves, both Love and Rayleigh waves. One reason to analyse surface waves is that they carry information about the subsurface. The dispersion curve of Rayleigh waves and Love waves can be retrieved using array processing techniques. The Rayleigh wave ellipticity, including the sense of rotation of the particle motion, can also be retrieved using array techniques. These quantities are used in an inversion procedure aimed at obtaining a structural model of the subsurface. The focus of this work is the retrieval of Rayleigh wave ellipticity. We show applications of the (ML) method presented in Maranó et al. (2012) to a number of sites in Switzerland. The sites examined are chosen to reflect a wide range of soil conditions that are of interest in microzonation studies. Using a synthetic wavefield with known structural model, we compare our results with theoretical ellipticity curves and we show the accuracy of the considered algorithm. The sense of rotation of the particle motion (prograde vs. retrograde) is also estimated. In addition, we show that by modelling the presence of both Love and Rayleigh waves it is possible to mitigate the disruptive influence of Love waves on the estimation of Rayleigh wave ellipticity. Using recordings from several real sites, we show that it is possible to retrieve the ellipticity curve over a broad range of frequencies. Fundamental modes and higher modes are retrieved. Singularities of the ellipticity, corresponding to a change of the sense of rotation from prograde to retrograde (or vice versa), are detected with great accuracy. Knowledge of Rayleigh wave ellipticity, including the sense of rotation, is useful in several ways. The ellipticity angle allows us to pinpoint accurately the frequency of singularities (i.e., peaks and zeros of the H/V representation of the
Chen, Shi; Zhang, Yinhong; Lin, Shuyu; Fu, Zhiqiang
2014-02-01
The electromechanical coupling coefficient of Rayleigh-type surface acoustic waves in semi-infinite piezoelectrics/non-piezoelectrics superlattices is investigated by the transfer matrix method. Research results show the high electromechanical coupling coefficient can be obtained in these systems. The optimization design of it is also discussed fully. It is significantly influenced by electrical boundary conditions on interfaces, thickness ratios of piezoelectric and non-piezoelectric layers, and material parameters (such as velocities of pure longitudinal and transversal bulk waves in non-piezoelectric layers). In order to obtain higher electromechanical coupling coefficient, shorted interfaces, non-piezoelectric materials with large velocities of longitudinal and transversal bulk waves, and proper thickness ratios should be chosen.
RAYLEIGH LAMB WAVES IN MICROPOLAR ISOTROPIC ELASTIC PLATE
Rajneesh Kumar; Geeta Partap
2006-01-01
The propagation of waves in a homogeneous isotropic micropolar elastic cylindrical plate subjected to stress free conditions is investigated. The secular equations for symmetric and skew symmetric wave mode propagation are derived. At short wave limit,the secular equations for symmetric and skew symmetric waves in a stress free circular plate reduces to Rayleigh surface wave frequency equation. Thin plate results are also obtained. The amplitudes of displacements and microrotation components are obtained and depicted graphically. Some special cases are also deduced from the present investigations. The secular equations for symmetric and skew symmetric modes are also presented graphically.
Zhang, Yu; Xu, Yixian; Xia, Jianghai
2012-12-01
A better understanding of the influences of different surface fluid drainage conditions on the propagation and attenuation of surface waves as the stipulated frequency is varied is a key issue to apply surface wave method to detect subsurface hydrological properties. Our study develops three-dimensional dynamical Green's functions in poroelastic media for Rayleigh waves of possible free surface conditions: permeable - "open pore," impermeable - "closed pore," and partially permeable boundaries. The full transient response of wave fields and spectra due to a stress impulse wavelet on the surface are investigated in the exploration seismic frequency band for typical surface drainage conditions, viscous coupling-damping, solid frame properties and porous fluid flowing configuration. Our numerical results show that, due to the slow dilatational wave - P2 wave, two types of Rayleigh waves, designated as R1 and R2 waves, exist along the surface. R1 wave possesses high energy as classic Rayleigh waves in pure elastic media for each porous materials. A surface fluid drainage condition is a significant factor to influence dispersion and attenuation, especially attenuation of R1 waves. R2 wave for closed pore and partially permeable surfaces is only observed for a low coupling-damping coefficient. The non-physical wave for partially surface conditions causes the R1 wave radiates into the R2 wave in the negative attenuation frequency range. It makes weaker R1 wave and stronger R2 wave to closed pore surface. Moreover, it is observed that wave fields and spectra of R1 wave are sensitive to frame elastic moduli change for an open pore surface, and to pore fluid flow condition change for closed pore and partially permeable surface.
On Lamb and Rayleigh wave convergence in viscoelastic tissues
Nenadic, Ivan Z; Urban, Matthew W; Aristizabal, Sara; Mitchell, Scott A; Humphrey, Tye C; Greenleaf, James F, E-mail: Nenadic.Ivan@mayo.edu [Department of Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905 (United States)
2011-10-21
Characterization of the viscoelastic material properties of soft tissue has become an important area of research over the last two decades. Our group has been investigating the feasibility of using a shear wave dispersion ultrasound vibrometry (SDUV) method to excite Lamb waves in organs with plate-like geometry to estimate the viscoelasticity of the medium of interest. The use of Lamb wave dispersion ultrasound vibrometry to quantify the mechanical properties of viscoelastic solids has previously been reported. Two organs, the heart wall and the spleen, can be readily modeled using plate-like geometries. The elasticity of these two organs is important because they change in pathological conditions. Diastolic dysfunction is the inability of the left ventricle (LV) of the heart to supply sufficient stroke volumes into the systemic circulation and is accompanied by the loss of compliance and stiffening of the LV myocardium. It has been shown that there is a correlation between high splenic stiffness in patients with chronic liver disease and strong correlation between spleen and liver stiffness. Here, we investigate the use of the SDUV method to quantify the viscoelasticity of the LV free-wall myocardium and spleen by exciting Rayleigh waves on the organ's surface and measuring the wave dispersion (change of wave velocity as a function of frequency) in the frequency range 40-500 Hz. An equation for Rayleigh wave dispersion due to cylindrical excitation was derived by modeling the excised myocardium and spleen with a homogenous Voigt material plate immersed in a nonviscous fluid. Boundary conditions and wave potential functions were solved for the surface wave velocity. Analytical and experimental convergence between the Lamb and Rayleigh waves is reported in a finite element model of a plate in a fluid of similar density, gelatin plate and excised porcine spleen and left-ventricular free-wall myocardium.
On Lamb and Rayleigh wave convergence in viscoelastic tissues.
Nenadic, Ivan Z; Urban, Matthew W; Aristizabal, Sara; Mitchell, Scott A; Humphrey, Tye C; Greenleaf, James F
2011-10-21
Characterization of the viscoelastic material properties of soft tissue has become an important area of research over the last two decades. Our group has been investigating the feasibility of using a shear wave dispersion ultrasound vibrometry (SDUV) method to excite Lamb waves in organs with plate-like geometry to estimate the viscoelasticity of the medium of interest. The use of Lamb wave dispersion ultrasound vibrometry to quantify the mechanical properties of viscoelastic solids has previously been reported. Two organs, the heart wall and the spleen, can be readily modeled using plate-like geometries. The elasticity of these two organs is important because they change in pathological conditions. Diastolic dysfunction is the inability of the left ventricle (LV) of the heart to supply sufficient stroke volumes into the systemic circulation and is accompanied by the loss of compliance and stiffening of the LV myocardium. It has been shown that there is a correlation between high splenic stiffness in patients with chronic liver disease and strong correlation between spleen and liver stiffness. Here, we investigate the use of the SDUV method to quantify the viscoelasticity of the LV free-wall myocardium and spleen by exciting Rayleigh waves on the organ's surface and measuring the wave dispersion (change of wave velocity as a function of frequency) in the frequency range 40–500 Hz. An equation for Rayleigh wave dispersion due to cylindrical excitation was derived by modeling the excised myocardium and spleen with a homogenous Voigt material plate immersed in a nonviscous fluid. Boundary conditions and wave potential functions were solved for the surface wave velocity. Analytical and experimental convergence between the Lamb and Rayleigh waves is reported in a finite element model of a plate in a fluid of similar density, gelatin plate and excised porcine spleen and left-ventricular free-wall myocardium.
On Lamb and Rayleigh Wave Convergence in Viscoelastic Tissues
Nenadic, Ivan Z.; Urban, Matthew W.; Aristizabal, Sara; Mitchell, Scott A.; Humphrey, Tye C.; Greenleaf, James F.
2012-01-01
Characterization of the viscoelastic material properties of soft tissue has become an important area of research over the last two decades. Our group has been investigating the feasibility of using Shearwave Dispersion Ultrasound Vibrometry (SDUV) method to excite Lamb waves in organs with plate-like geometry to estimate the viscoelasticity of the medium of interest. The use of Lamb wave Dispersion Ultrasound Vibrometry (LDUV) to quantify mechanical properties of viscoelastic solids has previously been reported. Two organs, the heart wall and the spleen, can be readily modeled using plate-like geometries. The elasticity of these two organs is important because they change in pathological conditions. Diastolic dysfunction is the inability of the left ventricle (LV) of the heart to supply sufficient stroke volumes into the systemic circulation and is accompanied by the loss of compliance and stiffening of the LV myocardium. It has been shown that there is a correlation between high splenic stiffness in patients with chronic liver disease and strong correlation between spleen and liver stiffness. Here, we investigate the use of the SDUV method to quantify viscoelasticity of the LV free-wall myocardium and spleen by exciting Rayleigh waves on the organ’s surface and measuring the wave dispersion (change of wave velocity as a function of frequency) in the frequency range 40–500 Hz. An equation for Rayleigh wave dispersion due to cylindrical excitation was derived by modeling the excised myocardium and spleen with a homogenous Voigt material plate immersed in a nonviscous fluid. Boundary conditions and wave potential functions were solved for the surface wave velocity. Analytical and experimental convergence between the Lamb and Rayleigh waves is reported in a finite element model of a plate in a fluid of similar density, gelatin plate and excised porcine spleen and left-ventricular free-wall myocardium. PMID:21970846
RAYLEIGH WAVE STUDIES OF CATHODIC H-CHARGING OF Fe
Lunarska, E.; Fiore, N.
1981-01-01
The attenuation of 2-6 MHz Rayleigh waves /RW/ was measured in sheet samples of Fe which were undergoing electrolytic charging with H. The cathodic polarization and As2O3 addition into electrolyte were found to effect the attenuation and velocity of the surface waves. The attenuation changes were retarded by the deposition of a thin /2µm/ layer of Cu on the Fe surface, with the Cu acting as a H-permeation barrier. The decrease in attenuation was caused by the entry of H into solid solution at...
Rayleigh-type waves in nonlocal micropolar solid half-space.
Khurana, Aarti; Tomar, S K
2017-01-01
Propagation of Rayleigh type surface waves in nonlocal micropolar elastic solid half-space has been investigated. Two modes of Rayleigh-type waves are found to propagate under certain approximations. Frequency equations of these Rayleigh type modes and their conditions of existence have been derived. These frequency equations are found to be dispersive in character due to the presence of micropolarity and nonlocality parameters in the medium. One of the frequency equations is a counterpart of the classical Rayleigh waves and the other is new and has appeared due to micropolarity of the medium. Phase speeds of these waves are computed numerically for Magnesium crystal and their variation against wavenumber are presented graphically. Comparisons have been made between the phase speeds of Rayleigh type waves through nonlocal micropolar, local micropolar and elastic solid half-spaces. Copyright © 2016 Elsevier B.V. All rights reserved.
Rayleigh wave scattering at the foot of a mountain
P. S. Deshwal
1987-01-01
Full Text Available A theoretical study of scattering of seismic waves at the foot of a mountain is discussed here. A mountain of an arbitrary shape and of width a (0≤x≤a, z=0 in the surface of an elastic solid medium (z≥0 is hit by a Rayleigh wave. The method of solution is the technique of Wiener and Hopf. The reflected, transmitted and scattered waves are obtained by inversion of Fourier transforms. The scattered waves behave as decaying cylindrical waves at distant points and have a large amplitude near the foot of the mountain. The transmitted wave decreases exponentially as its distance from the other end of the mountain increases.
Experimental and theoretical study of Rayleigh-Lamb wave propagation
Rogers, Wayne P.; Datta, Subhendu K.; Ju, T. H.
1990-01-01
Many space structures, such as the Space Station Freedom, contain critical thin-walled components. The structural integrity of thin-walled plates and shells can be monitored effectively using acoustic emission and ultrasonic testing in the Rayleigh-Lamb wave frequency range. A new PVDF piezoelectric sensor has been developed that is well suited to remote, inservice nondestructive evaluation of space structures. In the present study the new sensor was used to investigate Rayleigh-Lamb wave propagation in a plate. The experimental apparatus consisted of a glass plate (2.3 m x 25.4 mm x 5.6 mm) with PVDF sensor (3 mm diam.) mounted at various positions along its length. A steel ball impact served as a simulated acoustic emission source, producing surface waves, shear waves and longitudinal waves with dominant frequencies between 1 kHz and 200 kHz. The experimental time domain wave-forms were compared with theoretical predictions of the wave propagation in the plate. The model uses an analytical solution for the Green's function and the measured response at a single position to predict response at any other position in the plate. Close agreement was found between the experimental and theoretical results.
Rayleigh-Wave Group-Velocity Tomography of Saudi Arabia
Tang, Zheng; Mai, P. Martin; Chang, Sung-Joon; Zahran, Hani
2017-04-01
We use surface-wave tomography to investigate the lithospheric structure of the Arabian plate, which is traditionally divided into the Arabian shield in the west and the Arabian platform in the east. The Arabian shield is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks. The Arabian platform is primarily covered by very thick Paleozoic, Mesozoic and Cenozoic sediments. We develop high-resolution tomographic images from fundamental-mode Rayleigh-wave group-velocities across Saudi Arabia, utilizing the teleseismic data recorded by the permanent Saudi National Seismic Network (SNSN). Our study extends previous efforts on surface wave work by increasing ray path density and improving spatial resolution. Good quality dispersion measurements for roughly 3000 Rayleigh-wave paths have been obtained and utilized for the group-velocity tomography. We have applied the Fast Marching Surface Tomography (FMST) scheme of Rawlinson (2005) to obtain Rayleigh-wave group-velocity images for periods from 8 s to 40 s on a 0.8° 0.8° grid and at resolutions approaching 2.5° based on the checkerboard tests. Our results indicate that short-period group-velocity maps (8-15 s) correlate well with surface geology, with slow velocities delineating the main sedimentary features including the Arabian platform, the Persian Gulf and Mesopotamia. For longer periods (20-40 s), the velocity contrast is due to the differences in crustal thickness and subduction/collision zones. The lower velocities are sensitive to the thicker continental crust beneath the eastern Arabia and the subduction/collision zones between the Arabian and Eurasian plate, while the higher velocities in the west infer mantle velocity.
Selective Manipulation of Microscopic Particles with Precursor Swirling Rayleigh Waves
Riaud, Antoine; Baudoin, Michael; Bou Matar, Olivier; Becerra, Loic; Thomas, Jean-Louis
2017-02-01
Contactless manipulation of microparticles is demonstrated with single-beam acoustical tweezers based on precursor swirling Rayleigh waves. These surface waves degenerate into acoustical vortices when crossing a stack made of a fluid layer and its solid support, hence creating a localized acoustical trap in a fluid cavity. They can be synthesized with a single interdigitated transducer whose spiraling shape encodes the phase of the field like a hologram. For applications, these tweezers have many attractive features: they are selective, flat, easily integrable, and compatible with disposable substrates.
Demonstration of Shear Waves, Lamb Waves, and Rayleigh Waves by Mode Conversion.
Leung, W. P.
1980-01-01
Introduces an experiment that can be demonstrated in the classroom to show that shear waves, Rayleigh waves, and Lamb waves can be easily generated and observed by means of mode conversion. (Author/CS)
Pseudo Rayleigh wave in a partially saturated non-dissipative porous solid
Sharma, M. D.
2016-09-01
Propagation of surface waves is studied at the pervious boundary of a porous solid saturated with a mixture of two immiscible fluids. An approach, based on continuum mixture theory, is used to derive a secular equation for the propagation of harmonic waves at the stress-free plane surface of this non-dissipative medium. Numerical analysis shows that this secular equation may not represent the propagation of true surface wave in the porous aggregate. Then, this equation is solved numerically for the propagation of pseudo Rayleigh wave or the leaky surface waves. To ensure the existence of pseudo Rayleigh wave, capillary effect between two (wetting and non-wetting) pore-fluids is related to the partial saturation. Effects of porosity and partial saturation coupled with capillary effect are observed on the phase velocity of pseudo Rayleigh waves in sandstone saturated with water-CO2 mixture.
Modeling of Rayleigh wave dispersion in Iberia
José Badal
2011-01-01
Full Text Available Phase and group velocities of 15–70 s Rayleigh waves propagating across the Iberian Peninsula have been transformed into local dispersion curves by linear inversion of travel times. The procedure permits that the waveform dispersion to be obtained as a continuous period-dependent velocity function at grid points belonging to the area probed by the waves, thus providing phase- and group-velocity contour maps for several periods within the interval of interest. The regionalization process rests on a homogeneous initial data set in which the number of observations remains almost constant for all periods of reference. Damped least-squares inversion of the local dispersion curves for shear-wave velocity structure is performed to obtain depth-dependent S-wave velocity profiles at the grid points covering the model region. The reliability of the results should improve significantly owing to the use of phase and group velocities simultaneously. On this basis, we have built horizontal depth sections that give an updated view of the seismic velocity structure of the peninsula at lithospheric and upper mantle depths (20–200 km. After averaging all the pure-path S-wave velocities previously determined at each grid point, the velocity-depth models so obtained for major tectonic units allow the comparison between the Hercynian basement and other areas of Mesozoic folding and Tertiary basins.
Rayleigh Waves in a Rotating Orthotropic Micropolar Elastic Solid Half-Space
Baljeet Singh
2013-01-01
Full Text Available A problem on Rayleigh wave in a rotating half-space of an orthotropic micropolar material is considered. The governing equations are solved for surface wave solutions in the half space of the material. These solutions satisfy the boundary conditions at free surface of the half-space to obtain the frequency equation of the Rayleigh wave. For numerical purpose, the frequency equation is approximated. The nondimensional speed of Rayleigh wave is computed and shown graphically versus nondimensional frequency and rotation-frequency ratio for both orthotropic micropolar elastic and isotropic micropolar elastic cases. The numerical results show the effects of rotation, orthotropy, and nondimensional frequency on the nondimensional speed of the Rayleigh wave.
Quasi-Rayleigh waves in butt-welded thick steel plate
Kamas, Tuncay; Giurgiutiu, Victor; Lin, Bin
2015-03-01
This paper discusses theoretical and experimental analyses of weld guided surface acoustic waves (SAW) through the guided wave propagation (GWP) analyses. The GWP analyses have been carried out by utilizing piezoelectric wafer active sensors (PWAS) for in situ structural inspection of a thick steel plate with butt weld as the weld bead is ground flush. Ultrasonic techniques are commonly used for validation of welded structures in many in-situ monitoring applications, e.g. in off-shore structures, in nuclear and pressure vessel industries and in a range of naval applications. PWAS is recently employed in such ultrasonic applications as a resonator as well as a transducer. Quasi-Rayleigh waves a.k.a. SAW can be generated in relatively thick isotropic elastic plate having the same phase velocity as Rayleigh waves whereas Rayleigh waves are a high frequency approximation of the first symmetric (S0) and anti-symmetric (A0) Lamb wave modes. As the frequency becomes very high the S0 and the A0 wave speeds coalesce, and both have the same value. This value is exactly the Rayleigh wave speed and becomes constant along the frequency i.e. Rayleigh waves are non-dispersive guided surface acoustic waves. The study is followed with weld-GWP tests through the pitch-catch method along the butt weld line. The tuning curves of quasi-Rayleigh wave are determined to show the tuning and trapping effect of the weld bead that has higher thickness than the adjacent plates on producing a dominant quasi-Rayleigh wave mode. The significant usage of the weld tuned and guided quasi-Rayleigh wave mode is essentially discussed for the applications in the in-situ inspection of relatively thick structures with butt weld such as naval offshore structures. The paper ends with summary, conclusions and suggestions for future work.
Quasi-Rayleigh waves in butt-welded thick steel plate
Kamas, Tuncay, E-mail: kamas@email.sc.edu, E-mail: victorg@sc.edu, E-mail: linbin@cec.sc.edu; Giurgiutiu, Victor, E-mail: kamas@email.sc.edu, E-mail: victorg@sc.edu, E-mail: linbin@cec.sc.edu; Lin, Bin, E-mail: kamas@email.sc.edu, E-mail: victorg@sc.edu, E-mail: linbin@cec.sc.edu [Mechanical Engineering University of South Carolina, 300 Main Str., Columbia, SC 29208 (United States)
2015-03-31
This paper discusses theoretical and experimental analyses of weld guided surface acoustic waves (SAW) through the guided wave propagation (GWP) analyses. The GWP analyses have been carried out by utilizing piezoelectric wafer active sensors (PWAS) for in situ structural inspection of a thick steel plate with butt weld as the weld bead is ground flush. Ultrasonic techniques are commonly used for validation of welded structures in many in-situ monitoring applications, e.g. in off-shore structures, in nuclear and pressure vessel industries and in a range of naval applications. PWAS is recently employed in such ultrasonic applications as a resonator as well as a transducer. Quasi-Rayleigh waves a.k.a. SAW can be generated in relatively thick isotropic elastic plate having the same phase velocity as Rayleigh waves whereas Rayleigh waves are a high frequency approximation of the first symmetric (S0) and anti-symmetric (A0) Lamb wave modes. As the frequency becomes very high the S0 and the A0 wave speeds coalesce, and both have the same value. This value is exactly the Rayleigh wave speed and becomes constant along the frequency i.e. Rayleigh waves are non-dispersive guided surface acoustic waves. The study is followed with weld-GWP tests through the pitch-catch method along the butt weld line. The tuning curves of quasi-Rayleigh wave are determined to show the tuning and trapping effect of the weld bead that has higher thickness than the adjacent plates on producing a dominant quasi-Rayleigh wave mode. The significant usage of the weld tuned and guided quasi-Rayleigh wave mode is essentially discussed for the applications in the in-situ inspection of relatively thick structures with butt weld such as naval offshore structures. The paper ends with summary, conclusions and suggestions for future work.
Enhanced sensing and conversion of ultrasonic Rayleigh waves by elastic metasurfaces.
Colombi, Andrea; Ageeva, Victoria; Smith, Richard J; Clare, Adam; Patel, Rikesh; Clark, Matt; Colquitt, Daniel; Roux, Philippe; Guenneau, Sebastien; Craster, Richard V
2017-07-28
Recent years have heralded the introduction of metasurfaces that advantageously combine the vision of sub-wavelength wave manipulation, with the design, fabrication and size advantages associated with surface excitation. An important topic within metasurfaces is the tailored rainbow trapping and selective spatial frequency separation of electromagnetic and acoustic waves using graded metasurfaces. This frequency dependent trapping and spatial frequency segregation has implications for energy concentrators and associated energy harvesting, sensing and wave filtering techniques. Different demonstrations of acoustic and electromagnetic rainbow devices have been performed, however not for deep elastic substrates that support both shear and compressional waves, together with surface Rayleigh waves; these allow not only for Rayleigh wave rainbow effects to exist but also for mode conversion from surface into shear waves. Here we demonstrate experimentally not only elastic Rayleigh wave rainbow trapping, by taking advantage of a stop-band for surface waves, but also selective mode conversion of surface Rayleigh waves to shear waves. These experiments performed at ultrasonic frequencies, in the range of 400-600 kHz, are complemented by time domain numerical simulations. The metasurfaces we design are not limited to guided ultrasonic waves and are a general phenomenon in elastic waves that can be translated across scales.
Sensitivity comparisons of layered Rayleigh wave and Love wave acoustic devices
Pedrick, Michael K.; Tittmann, Bernhard R.
2007-04-01
Due to their high sensitivity, layered Surface Acoustic Wave (SAW) devices are ideal for various film characterization and sensor applications. Two prominent wave types realized in these devices are Rayleigh waves consisting of coupled Shear Vertical and Longitudinal displacements and Love waves consisting of Shear Horizontal displacements. Theoretical calculations of sensitivity of SAW devices to pertubations in wave propagation are limited to idealized scenarios. Derivations of sensitivity to mass change in an overlayer are often based on the effect of rigid body motion of the overlayer on the propagation of one of the aforementioned wave types. These devices often utilize polymer overlayers for enhanced sensitivity. The low moduli of such overlayers are not sufficiently stiff to accommodate the rigid body motion assumption. This work presents device modeling based on the Finite Element Method. A coupled-field model allows for a complete description of device operation including displacement profiles, frequency, wave velocity, and insertion loss through the inclusion of transmitting and receiving IDTs. Geometric rotations and coordinate transformations allow for the modeling of different crystal orientations in piezoelectric substrates. The generation of Rayleigh and Love Wave propagation was realized with this model by examining propagation in ST Quartz both normal to and in the direction of the X axis known to support Love Waves and Rayleigh Waves, respectively. Sensitivities of layered SAW devices to pertubations in mass, layer thickness, and mechanical property changes of a Polymethyl methacrylate (PMMA) and SU-8 overlayers were characterized and compared. Experimental validation of these models is presented.
Tanimoto, T; Hadziioannou, C; H. Igel; Wasserman, J.; U. Schreiber; Gebauer, A.
2015-01-01
©2015. American Geophysical Union. All Rights Reserved. Using a colocated ring laser and an STS-2 seismograph, we estimate the ratio of Rayleigh-to-Love waves in the secondary microseism at Wettzell, Germany, for frequencies between 0.13 and 0.30 Hz. Rayleigh wave surface acceleration was derived from the vertical component of STS-2, and Love wave surface acceleration was derived from the ring laser. Surface wave amplitudes are comparable; near the spectral peak about 0.22 Hz, Rayleigh wave a...
Rayleigh-type Surface Quasimodes in General Linear Elasticity
Hansen, Sönke
2010-01-01
Rayleigh-type surface waves correspond to the characteristic variety, in the elliptic boundary region, of the displacement-to-traction map. In this paper, surface quasimodes are constructed for the reduced elastic wave equation, anisotropic in general, with traction-free boundary. Assuming a global variant of a condition of Barnett and Lothe, the construction is reduced to an eigenvalue problem for a selfadjoint scalar first order pseudo-differential operator on the boundary. The principal and the subprincipal symbol of this operator are computed. The formula for the subprincipal symbol seems to be new even in the isotropic case.
Rayleigh wave inversion using heat-bath simulated annealing algorithm
Lu, Yongxu; Peng, Suping; Du, Wenfeng; Zhang, Xiaoyang; Ma, Zhenyuan; Lin, Peng
2016-11-01
The dispersion of Rayleigh waves can be used to obtain near-surface shear (S)-wave velocity profiles. This is performed mainly by inversion of the phase velocity dispersion curves, which has been proven to be a highly nonlinear and multimodal problem, and it is unsuitable to use local search methods (LSMs) as the inversion algorithm. In this study, a new strategy is proposed based on a variant of simulated annealing (SA) algorithm. SA, which simulates the annealing procedure of crystalline solids in nature, is one of the global search methods (GSMs). There are many variants of SA, most of which contain two steps: the perturbation of model and the Metropolis-criterion-based acceptance of the new model. In this paper we propose a one-step SA variant known as heat-bath SA. To test the performance of the heat-bath SA, two models are created. Both noise-free and noisy synthetic data are generated. Levenberg-Marquardt (LM) algorithm and a variant of SA, known as the fast simulated annealing (FSA) algorithm, are also adopted for comparison. The inverted results of the synthetic data show that the heat-bath SA algorithm is a reasonable choice for Rayleigh wave dispersion curve inversion. Finally, a real-world inversion example from a coal mine in northwestern China is shown, which proves that the scheme we propose is applicable.
Passive retrieval of Rayleigh waves in disordered elastic media.
Larose, Eric; Derode, Arnaud; Clorennec, Dominique; Margerin, Ludovic; Campillo, Michel
2005-10-01
When averaged over sources or disorder, cross correlation of diffuse fields yields the Green's function between two passive sensors. This technique is applied to elastic ultrasonic waves in an open scattering slab mimicking seismic waves in the Earth's crust. It appears that the Rayleigh wave reconstruction depends on the scattering properties of the elastic slab. Special attention is paid to the specific role of bulk to Rayleigh wave coupling, which may result in unexpected phenomena, such as a persistent time asymmetry in the diffuse regime.
Estimating the location of a tunnel using correlation and inversion of Rayleigh wave scattering
Kasililar, A.; Harmankaya, U.; Wapenaar, C.P.A.; Draganov, D.S.
2013-01-01
The investigation of near-surface scatterers, such as cavities, tunnels, abandoned mine shafts, and buried objects, is important to mitigate geohazards and environmental hazards. By inversion of travel times of cross-correlated scattered waves, due to the incident Rayleigh waves, we estimate the loc
Zeng, C.; Xia, J.; Miller, R.D.; Tsoflias, G.P.
2011-01-01
Conventional surface wave inversion for shallow shear (S)-wave velocity relies on the generation of dispersion curves of Rayleigh waves. This constrains the method to only laterally homogeneous (or very smooth laterally heterogeneous) earth models. Waveform inversion directly fits waveforms on seismograms, hence, does not have such a limitation. Waveforms of Rayleigh waves are highly related to S-wave velocities. By inverting the waveforms of Rayleigh waves on a near-surface seismogram, shallow S-wave velocities can be estimated for earth models with strong lateral heterogeneity. We employ genetic algorithm (GA) to perform waveform inversion of Rayleigh waves for S-wave velocities. The forward problem is solved by finite-difference modeling in the time domain. The model space is updated by generating offspring models using GA. Final solutions can be found through an iterative waveform-fitting scheme. Inversions based on synthetic records show that the S-wave velocities can be recovered successfully with errors no more than 10% for several typical near-surface earth models. For layered earth models, the proposed method can generate one-dimensional S-wave velocity profiles without the knowledge of initial models. For earth models containing lateral heterogeneity in which case conventional dispersion-curve-based inversion methods are challenging, it is feasible to produce high-resolution S-wave velocity sections by GA waveform inversion with appropriate priori information. The synthetic tests indicate that the GA waveform inversion of Rayleigh waves has the great potential for shallow S-wave velocity imaging with the existence of strong lateral heterogeneity. ?? 2011 Elsevier B.V.
Pseudospectral modeling and dispersion analysis of Rayleigh waves in viscoelastic media
Zhang, K.; Luo, Y.; Xia, J.; Chen, C.
2011-01-01
Multichannel Analysis of Surface Waves (MASW) is one of the most widely used techniques in environmental and engineering geophysics to determine shear-wave velocities and dynamic properties, which is based on the elastic layered system theory. Wave propagation in the Earth, however, has been recognized as viscoelastic and the propagation of Rayleigh waves presents substantial differences in viscoelastic media as compared with elastic media. Therefore, it is necessary to carry out numerical simulation and dispersion analysis of Rayleigh waves in viscoelastic media to better understand Rayleigh-wave behaviors in the real world. We apply a pseudospectral method to the calculation of the spatial derivatives using a Chebyshev difference operator in the vertical direction and a Fourier difference operator in the horizontal direction based on the velocity-stress elastodynamic equations and relations of linear viscoelastic solids. This approach stretches the spatial discrete grid to have a minimum grid size near the free surface so that high accuracy and resolution are achieved at the free surface, which allows an effective incorporation of the free surface boundary conditions since the Chebyshev method is nonperiodic. We first use an elastic homogeneous half-space model to demonstrate the accuracy of the pseudospectral method comparing with the analytical solution, and verify the correctness of the numerical modeling results for a viscoelastic half-space comparing the phase velocities of Rayleigh wave between the theoretical values and the dispersive image generated by high-resolution linear Radon transform. We then simulate three types of two-layer models to analyze dispersive-energy characteristics for near-surface applications. Results demonstrate that the phase velocity of Rayleigh waves in viscoelastic media is relatively higher than in elastic media and the fundamental mode increases by 10-16% when the frequency is above 10. Hz due to the velocity dispersion of P
Rayleigh-wave mode separation by high-resolution linear radon transform
Luo, Y.; Xia, J.; Miller, R.D.; Xu, Y.; Liu, J.; Liu, Q.
2009-01-01
Multichannel analysis of surface waves (MASW) method is an effective tool for obtaining vertical shear wave profiles from a single non-invasive measurement. One key step of the MASW method is generation of a dispersion image and extraction of a reliable dispersion curve from raw multichannel shot records. Because different Rayleigh-wave modes normally interfere with each other in the time and space domain, it is necessary to perform mode separation and reconstruction to increase the accuracy of phase velocities determined from a dispersion image. In this paper, we demonstrate the effectiveness of high-resolution linear Radon transform (LRT) as a means of separating and reconstructing multimode, dispersive Rayleigh-wave energy. We first introduce high-resolution LRT methods and Rayleigh-wave mode separation using high-resolution LRT. Next, we use synthetic data and a real-world example to demonstrate the effectiveness of Rayleigh-wave mode separation using high-resolution LRT. Our synthetic and real-world results demonstrate that (1) high-resolution LRT successfully separates and reconstructs multimode dispersive Rayleigh-wave energy with high resolution allowing the multimode energy to be more accurately determined. The horizontal resolution of the Rayleigh-wave method can be increased by extraction of dispersion curves from a pair of traces in the mode-separated shot gather and (2) multimode separation and reconstruction expand the usable frequency range of higher mode dispersive energy, which increases the depth of investigation and provides a means for accurately determining cut-off frequencies. ?? 2009 The Authors Journal compilation ?? 2009 RAS.
Lognonné, Philippe; Karakostas, Foivos; Rolland, Lucie; Nishikawa, Yasuhiro
2016-08-01
Acoustic coupling between solid Earth and atmosphere has been observed since the 1960s, first from ground-based seismic, pressure, and ionospheric sensors and since 20 years with various satellite measurements, including with global positioning system (GPS) satellites. This coupling leads to the excitation of the Rayleigh surface waves by local atmospheric sources such as large natural explosions from volcanoes, meteor atmospheric air-bursts, or artificial explosions. It contributes also in the continuous excitation of Rayleigh waves and associated normal modes by atmospheric winds and pressure fluctuations. The same coupling allows the observation of Rayleigh waves in the thermosphere most of the time through ionospheric monitoring with Doppler sounders or GPS. The authors review briefly in this paper observations made on Earth and describe the general frame of the theory enabling the computation of Rayleigh waves for models of telluric planets with atmosphere. The authors then focus on Mars and Venus and give in both cases the atmospheric properties of the Rayleigh normal modes and associated surface waves compared to Earth. The authors then conclude on the observation perspectives especially for Rayleigh waves excited by atmospheric sources on Mars and for remote ionospheric observations of Rayleigh waves excited by quakes on Venus.
Declercq, Nico Felicien
2014-02-01
When a bounded beam is incident on an immersed plate Lamb waves or Rayleigh waves can be generated. Because the amplitude of a bounded beam is not constant along its wave front, a specific beam profile is formed that influences the local efficiency of energy conversion of incident sound into Lamb waves or Rayleigh waves. Understanding this phenomenon is important for ultrasonic immersion experiments of objects because the quality of such experiments highly depends on the amount of energy transmitted into the object. This paper shows by means of experiments based on monochromatic Schlieren photography that the area within the bounded beam responsible for Lamb wave generation differs from that responsible for Rayleigh wave generation. Furthermore it provides experimental verification of an earlier numerical study concerning Rayleigh wave generation.
Nonlinear dynamic acousto-elasticity measurement by Rayleigh wave in concrete cover evaluation
Vu, Quang Anh; Garnier, Vincent; Payan, Cédric; Chaix, Jean-François; Lott, Martin; Eiras, Jesús N.
2015-10-01
This paper presents local non-destructive evaluation of concrete cover by using surface Rayleigh wave in nonlinear Dynamic Acousto-Elasticity (DAE) measurement. Dynamic non classical nonlinear elastic behavior like modulus decrease under applied stress and slow dynamic process has been observed in many varieties of solid, also in concrete. The measurements conducted in laboratory, consist in qualitative evaluation of concrete thermal damage. Nonlinear elastic parameters especially conditioning offset are analyzed for the cover concrete by Rayleigh wave. The results of DAE method show enhanced sensitivity when compared to velocity measurement. Afterward, this technique broadens measurements to the field.
Rayleigh scattering of a spherical sound wave.
Godin, Oleg A
2013-02-01
Acoustic Green's functions for a homogeneous medium with an embedded spherical obstacle arise in analyses of scattering by objects on or near an interface, radiation by finite sources, sound attenuation in and scattering from clouds of suspended particles, etc. An exact solution of the problem of diffraction of a monochromatic spherical sound wave on a sphere is given by an infinite series involving products of Bessel functions and Legendre polynomials. In this paper, a simple, closed-form solution is obtained for scattering by a sphere with a radius that is small compared to the wavelength. Soft, hard, impedance, and fluid obstacles are considered. The solution is valid for arbitrary positions of the source and receiver relative to the scatterer. Low-frequency scattering is shown to be rather sensitive to boundary conditions on the surface of the obstacle. Low-frequency asymptotics of the scattered acoustic field are extended to transient incident waves. The asymptotic expansions admit an intuitive interpretation in terms of image sources and reduce to classical results in appropriate limiting cases.
Wave Equation Inversion of Skeletonized SurfaceWaves
Zhang, Zhendong
2015-08-19
We present a surface-wave inversion method that inverts for the S-wave velocity from the Rayleigh dispersion curve for the fundamental-mode. We call this wave equation inversion of skeletonized surface waves because the dispersion curve for the fundamental-mode Rayleigh wave is inverted using finite-difference solutions to the wave equation. The best match between the predicted and observed dispersion curves provides the optimal S-wave velocity model. Results with synthetic and field data illustrate the benefits and limitations of this method.
Krylov, Victor V
2015-01-01
In the present paper, the effects of focusing of Rayleigh waves generated by high speed trains in the supporting ground under the condition of ground vibration boom are considered theoretically. These effects are similar to the effects of focusing of sound waves radiated by aircraft under the condition of sonic boom. In particular, if a railway track has a bend to provide the possibility of changing direction of train movement, the Rayleigh surface waves generated by high-speed trains under the condition of ground vibration boom may become focused. This results in concentration of their energy along a simple caustic line at one side of the track and in the corresponding increase in ground vibration amplitudes. The effect of focusing of Rayleigh waves may occur also if a train moves along a straight line with acceleration and its current speed is higher than Rayleigh wave velocity in the ground. The obtained results are illustrated by numerical calculations.
Application of particle swarm optimization to interpret Rayleigh wave dispersion curves
Song, Xianhai; Tang, Li; Lv, Xiaochun; Fang, Hongping; Gu, Hanming
2012-09-01
Rayleigh waves have been used increasingly as an appealing tool to obtain near-surface shear (S)-wave velocity profiles. However, inversion of Rayleigh wave dispersion curves is challenging for most local-search methods due to its high nonlinearity and to its multimodality. In this study, we proposed and tested a new Rayleigh wave dispersion curve inversion scheme based on particle swarm optimization (PSO). PSO is a global optimization strategy that simulates the social behavior observed in a flock (swarm) of birds searching for food. A simple search strategy in PSO guides the algorithm toward the best solution through constant updating of the cognitive knowledge and social behavior of the particles in the swarm. To evaluate calculation efficiency and stability of PSO to inversion of surface wave data, we first inverted three noise-free and three noise-corrupted synthetic data sets. Then, we made a comparative analysis with genetic algorithms (GA) and a Monte Carlo (MC) sampler and reconstructed a histogram of model parameters sampled on a low-misfit region less than 15% relative error to further investigate the performance of the proposed inverse procedure. Finally, we inverted a real-world example from a waste disposal site in NE Italy to examine the applicability of PSO on Rayleigh wave dispersion curves. Results from both synthetic and field data demonstrate that particle swarm optimization can be used for quantitative interpretation of Rayleigh wave dispersion curves. PSO seems superior to GA and MC in terms of both reliability and computational efforts. The great advantages of PSO are fast in locating the low misfit region and easy to implement. Also there are only three parameters to tune (inertia weight or constriction factor, local and global acceleration constants). Theoretical results exist to explain how to tune these parameters.
A. M. Abd-Alla
2011-01-01
Full Text Available The surface waves propagation in generalized magneto-thermo-viscoelastic granular medium subjected to continuous boundary conditions has been investigated. In addition, it is also subjected to thermal boundary conditions. The solution of the more general equations are obtained for thermoelastic coupling. The frequency equation of Rayleigh waves is obtained in the form of a determinant containing a term involving the coefficient of friction of a granular media which determines Rayleigh waves velocity as a real part and the attenuation coefficient as an imaginary part, and the effects of rotation, magnetic field, initial stress, viscosity, and gravity field on Rayleigh waves velocity and attenuation coefficient of surface waves have been studied in detail. Dispersion curves are computed numerically for a specific model and presented graphically. Some special cases have also been deduced. The results indicate that the effect of rotation, magnetic field, initial stress, and gravity field is very pronounced.
Surface waves in ﬁbre-reinforced anisotropic elastic media
P R Sengupta; Sisir Nath
2001-08-01
The aim of this paper is to investigate surface waves in anisotropic ﬁbre-reinforced solid elastic media. First, the theory of general surface waves has been derived and applied to study the particular cases of surface waves – Rayleigh, Love and Stoneley types. The wave velocity equations are found to be in agreement with the corresponding classical result when the anisotropic elastic parameters tends to zero. It is important to note that the Rayleigh type of wave velocity in the ﬁbre-reinforced elastic medium increases to a considerable amount in comparison with the Rayleigh wave velocity in isotropic materials.
Multichannel analysis of surface waves
Park, C.B.; Miller, R.D.; Xia, J.
1999-01-01
The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and characterizing the shallow subsurface. Most surface-wave analysis relies on the accurate calculation of phase velocities for the horizontally traveling fundamental-mode Rayleigh wave acquired by stepping out a pair of receivers at intervals based on calculated ground roll wavelengths. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the whole wave field. Among these nonplanar, nonfundamental-mode Rayleigh waves (noise) are body waves, scattered and nonsource-generated surface waves, and higher-mode surface waves. The degree to which each of these types of noise contaminates the dispersion curve and, ultimately, the inverted shear-wave velocity profile is dependent on frequency as well as distance from the source. Multichannel recording permits effective identification and isolation of noise according to distinctive trace-to-trace coherency in arrival time and amplitude. An added advantage is the speed and redundancy of the measurement process. Decomposition of a multichannel record into a time variable-frequency format, similar to an uncorrelated Vibroseis record, permits analysis and display of each frequency component in a unique and continuous format. Coherent noise contamination can then be examined and its effects appraised in both frequency and offset space. Separation of frequency components permits real-time maximization of the S/N ratio during acquisition and subsequent processing steps. Linear separation of each ground roll frequency component allows calculation of phase velocities by simply measuring the linear slope of each frequency component. Breaks in coherent surface-wave arrivals, observable on the decomposed record, can be compensated for during acquisition and processing. Multichannel recording permits single-measurement surveying of a broad depth range, high levels of
Rayleigh scattering and nonlinear inversion of elastic waves
Gritto, R.
1995-12-01
Rayleigh scattering of elastic waves by an inclusion is investigated and the limitations determined. In the near field of the inhomogeneity, the scattered waves are up to a factor of 300 stronger than in the far field, excluding the application of the far field Rayleigh approximation for this range. The investigation of the relative error as a function of parameter perturbation shows a range of applicability broader than previously assumed, with errors of 37% and 17% for perturbations of {minus}100% and +100%, respectively. The validity range for the Rayleigh limit is controlled by large inequalities, and therefore, the exact limit is determined as a function of various parameter configurations, resulting in surprisingly high values of up to k{sub p}R = 0.9. The nonlinear scattering problem can be solved by inverting for equivalent source terms (moments) of the scatterer, before the elastic parameters are determined. The nonlinear dependence between the moments and the elastic parameters reveals a strong asymmetry around the origin, which will produce different results for weak scattering approximations depending on the sign of the anomaly. Numerical modeling of cross hole situations shows that near field terms are important to yield correct estimates of the inhomogeneities in the vicinity of the receivers, while a few well positioned sources and receivers considerably increase the angular coverage, and thus the model resolution of the inversion parameters. The pattern of scattered energy by an inhomogeneity is complicated and varies depending on the object, the wavelength of the incident wave, and the elastic parameters involved. Therefore, it is necessary to investigate the direction of scattered amplitudes to determine the best survey geometry.
Field-Correlation Effects on Rayleigh-Enhanced Nondegenerate Four-Wave Mixing
王延帮; 姜谦; 米辛; 俞祖和; 傅盘铭
2002-01-01
We study Rayleigh-enhanced nondegenerate four-wave mixing (NFWM) with time-delayed, correlated fluctuating fields. The importance of the field correlation is revealed in the Rayleigh-enhanced NFWM spectrum when the time delay is varied. The Rayleigh-enhanced NFWM is employed to study the ultrafast processes in the frequency domain. A relaxation time as short as 220 fs was deduced in the Rayleigh-enhanced NFWM experiments in carbon disulphide.
Study on Rayleigh Wave Inversion for Estimating Shear-wave Velocity Profile
T.A. Sanny
2003-05-01
Full Text Available Rayleigh wave or ground roll is a noise in seismic body waves. However, how to use this noise for soil characterization is very interesting since Rayleigh wave phase velocity is a function of compression-wave velocity, shear-wave velocity, density and layer thickness. In layered-medium Rayleigh wave velocity also depends on wavelength or frequency, and this phenomenon is called dispersion. Inversion procedure to get shear-wave velocity profile needs a priori information about the solution of the problem to limit the unknown parameters. The Lagrange multiplier method was used to solve the constrained optimization problems or well known as a smoothing parameter in inversion problems. The advantage of our inversion procedure is that it can guarantee the convergence of solution even though the field data is incomplete, insufficient, and inconsistent. The addition of smoothing parameter can reduce the time to converge. Beside numerical stability, the statistical stability is also involved in inversion procedure. In field experiment we extracted ground roll data from seismic refraction record. The dispersion curves had been constructed by applying f-k analysis and f-k dip filtering. The dispersion curves show the dependence of Rayleigh wave phase velocities in layered media to frequency. The synthetic models also demonstrate the stability and the speed of inversion procedure.
Zhao, Kaifeng; Luo, Yinhe; Xie, Jun
2017-02-01
In this study, we demonstrate the feasibility of imaging broad-band (10-150 s) Rayleigh wave phase velocity maps on a continental scale using ambient noise tomography (ANT). We obtain broad-band Rayleigh waves from cross-correlations of ambient noise data between all station pairs of USArray and measure the dispersion curves from these cross-correlations at a period band of 10-150 s. The large-scale dense USArray enables us to obtain over 500 000 surface wave paths which cover the contiguous United States densely. Using these paths, we generate Rayleigh wave phase velocity maps at 10-150 s periods. Our phase velocity maps are similar to other reported phase velocity maps based on ambient noise data at short periods (phase velocity maps from ANT can be used to construct 3-D lithospheric and asthenospheric velocity structures.
Modelling of Rayleigh-type seam waves in disturbed coal seams and around a coal mine roadway
Essen, Katja; Bohlen, Thomas; Friederich, Wolfgang; Meier, Thomas
2007-08-01
Wave propagation in coal seams is numerically modelled in order to identify approaches towards the reconnaissance beyond the heading face of an advancing coal mine roadway. Complete synthetic wavefields including P-SV body waves and Rayleigh-type seam waves are calculated using a Green's function approach for simple, laterally homogeneous models and a parallel elastic 2-D/3-D finite difference modelling code for more realistic geometries. For a simple three-layer model the wavefield within the seam is dominated by a fundamental Rayleigh seam mode symmetrical with respect to the centre of the seam on the vertical component and antisymmetrical on the horizontal component. If the seam contains an interleaved dirt band with higher velocities and density, higher modes dominate the wave propagation, depending on the thickness of the dirt band. Wave propagation in laterally inhomogeneous coal seam models with disturbances like seam ends, faults, thinning, washouts and seam splitting is strongly influenced by the type of disturbance. Amplitudes of seam waves reflected from these disturbances strongly depend on the fault throw and the degree of thinning or washout. In some cases, conversion to higher modes can occur. In all investigated models, those Rayleigh seam wave phases are preferably reflected, which have frequencies above the fundamental mode Airy phase. Lower frequency phases are preferably transmitted. However, seam waves are not reflected from a seam splitting disturbance. Thus a detection of seam splitting with reflected seam waves appears to be impossible. FD computations for 3-D models containing an ending tunnel parallel to the seam and a source beyond the heading face of the tunnel show that seam waves are converted into Rayleigh waves at the tunnel face. They propagate along the surface of the tunnel and interfere with the seam waves propagating beside the tunnel. This effect has to be taken into account for subsequent treatment of experimental data, where
Control of Rayleigh-like waves in thick plate Willis metamaterials
Diatta, André; Achaoui, Younes; Brûlé, Stéphane; Enoch, Stefan; Guenneau, Sébastien
2016-12-01
Recent advances in control of anthropic seismic sources in structured soil led us to explore interactions of elastic waves propagating in plates (with soil parameters) structured with concrete pillars buried in the soil. Pillars are 2 m in diameter, 30 m in depth and the plate is 50 m in thickness. We study the frequency range 5 to 10 Hz, for which Rayleigh wave wavelengths are smaller than the plate thickness. This frequency range is compatible with frequency ranges of particular interest in earthquake engineering. It is demonstrated in this paper that two seismic cloaks' configurations allow for an unprecedented flow of elastodynamic energy associated with Rayleigh surface waves. The first cloak design is inspired by some approximation of ideal cloaks' parameters within the framework of thin plate theory. The second, more accomplished but more involved, cloak design is deduced from a geometric transform in the full Navier equations that preserves the symmetry of the elasticity tensor but leads to Willis' equations, well approximated by a homogenization procedure, as corroborated by numerical simulations. The two cloaks's designs are strickingly different, and the superior efficiency of the second type of cloak emphasizes the necessity for rigour in transposition of existing cloaks's designs in thin plates to the geophysics setting. Importantly, we focus our attention on geometric transforms applied to thick plates, which is an intermediate case between thin plates and semi-infinite media, not studied previously. Cloaking efficiency (reduction of the disturbance of the wave wavefront and its amplitude behind an obstacle) and protection (reduction of the wave amplitude within the center of the cloak) are studied for ideal and approximated cloaks' parameters. These results represent a preliminary step towards designs of seismic cloaks for surface Rayleigh waves propagating in sedimentary soils structured with concrete pillars.
Source parameters of the 1989 Loma Prieta Earthquake determined from long-period Rayleigh waves
Zhang, Jiajun; Lay, Thorne
1990-07-01
The source parameters of the Loma Prieta earthquake are determined using long-period Rayleigh waves recorded by USGS/ERIS, IDA/IRIS, and GEOSCOPE stations. The source mechanism is well-constrained by the Rayleigh wave radiation pattern, with a dip = 70 (±5)°, strike = 130 (±5)°, rake = 135 (±5)°, and moment = 3.4 (±0.5) × 1019 Nm (Mw = 7.0). This mechanism is generally consistent with independent body wave determinations. The most stable long-period waves, with periods from 200 to 275 s, indicate that the source process has a centroid time of about 10 s, somewhat longer than that indicated by body waves (about 5-6 s). This discrepancy cannot be uniquely attributed to source effects because of uncertainties in the propagation corrections. The importance of using surface waves with short propagation paths for analysis of moderate size earthquakes such as the Loma Prieta event is demonstrated by the unreasonably long source durations inferred from R3 arrivals.
Coexisting Raman- and Rayleigh-Enhanced Four-Wave Mixing in Femtosecond Polarization Beats
NIE Zhi-Qiang; ZHAO Yan; ZHANG Yan-Peng; GAN Chen-Li; ZHENG Huai-Sin; LI Chang-Biao; LU Ke-Qing
2009-01-01
Based on the polarization interference of Raman- and Rayleigh-enhanced four-wave mixing processes,heterodyne detection of the Raman,Rayleigh and coexisting Raman and Rayleigh femtosecond difference-frequency polarization beats is investigated in the cw and the three Markovian stochastic models,respectively.These two processes exhibit asymmetric and symmetric spectra,respectively,and the thermal effect in them can be suppressed by a field-correlation method.Such studies of coexisting Raman- and Rayleigh-enhanced four-wave mixing processes can have important applications in coherence quantum control,and quantum information processing.
Spectral Ratios for Crack Detection Using P and Rayleigh Waves
Enrique Olivera-Villaseñor
2012-01-01
Full Text Available We obtain numerical results to help the detection and characterization of subsurface cracks in solids by the application of P and Rayleigh elastic waves. The response is obtained from boundary integral equations, which belongs to the field of elastodynamics. Once the implementation of the boundary conditions has been done, a system of Fredholm integral equations of the second kind and order zero is found. This system is solved using the method of Gaussian elimination. Resonance peaks in the frequency domain allow us to infer the presence of cracks using spectral ratios. Several models of cracked media were analyzed, where effects due to different crack orientations and locations were observed. The results obtained are in good agreement with those published in the references.
Rayleigh Wave Tomography of Mid-Continent Rift (MCR) using Earthquake and Ambient Noise Data
Aleqabi, G. I.; Wiens, D.; Wysession, M. E.; Shen, W.; van der Lee, S.; Revenaugh, J.; Frederiksen, A. W.; Darbyshire, F. A.; Stein, S. A.; Jurdy, D. M.; Wolin, E.; Bollmann, T. A.
2015-12-01
The structure of the North American Mid-Continent Rift Zone (MCRZ) is examined using Rayleigh waves from teleseismic earthquakes and ambient seismic noise recorded by the Superior Province Rifting EarthScope Experiment (SPREE). Eighty-four broadband seismometers were deployed during 2011-2013 in Minnesota and Wisconsin, USA, and Ontario, CA, along three lines; two across the rift axis and the third along the rift axis. These stations, together with the EarthScope Transportable Array, provided excellent coverage of the MCRZ. The 1.1 Ga Mesoproterozoic failed rift consists of two arms, buried under post-rifting sedimentary formations that meet at Lake Superior. We compare two array-based tomography methods using teleseismic fundamental mode Rayleigh waves phase and amplitude measurements: the two-plane wave method (TPWM, Forsyth, 1998) and the automated surface wave phase velocity measuring system (ASWMS, Jin and Gaherty, 2015). Both array methods and the ambient noise method give relatively similar results showing low velocity zones extending along the MCRZ arms. The teleseismic Rayleigh wave results from 18 - 180 s period are combined with short period phase velocity results (period 8-30 s) obtained from ambient noise by cross correlation. Phase velocities from the methods are very similar at periods of 18-30 where results overlap; in this period range we use the average of the noise and teleseismic results. Finally the combined phase velocity curve is inverted using a Monte-Carlo inversion method at each geographic point in the model. The results show low velocities at shallow depths (5-10 km) that are the result of very deep sedimentary fill within the MCRZ. Deeper-seated low velocity regions may correspond to mafic underplating of the rift zone.
A trade-off between model resolution and variance with selected Rayleigh-wave data
Xia, J.; Miller, R.D.; Xu, Y.
2008-01-01
Inversion of multimode surface-wave data is of increasing interest in the near-surface geophysics community. For a given near-surface geophysical problem, it is essential to understand how well the data, calculated according to a layered-earth model, might match the observed data. A data-resolution matrix is a function of the data kernel (determined by a geophysical model and a priori information applied to the problem), not the data. A data-resolution matrix of high-frequency (??? 2 Hz) Rayleigh-wave phase velocities, therefore, offers a quantitative tool for designing field surveys and predicting the match between calculated and observed data. First, we employed a data-resolution matrix to select data that would be well predicted and to explain advantages of incorporating higher modes in inversion. The resulting discussion using the data-resolution matrix provides insight into the process of inverting Rayleigh-wave phase velocities with higher mode data to estimate S-wave velocity structure. Discussion also suggested that each near-surface geophysical target can only be resolved using Rayleigh-wave phase velocities within specific frequency ranges, and higher mode data are normally more accurately predicted than fundamental mode data because of restrictions on the data kernel for the inversion system. Second, we obtained an optimal damping vector in a vicinity of an inverted model by the singular value decomposition of a trade-off function of model resolution and variance. In the end of the paper, we used a real-world example to demonstrate that selected data with the data-resolution matrix can provide better inversion results and to explain with the data-resolution matrix why incorporating higher mode data in inversion can provide better results. We also calculated model-resolution matrices of these examples to show the potential of increasing model resolution with selected surface-wave data. With the optimal damping vector, we can improve and assess an inverted
Effects on PP waves and Rayleigh waves of water column approximation
Zhou, Y.; Ni, S.
2015-12-01
Spectral-element method (SEM) combines the flexibility of the finite-element method and the accuracy of the pseudo-spectral method. It can handle the complexity of the 3-D earth model, such as heterogeneity of velocity and density, anisotropy, anelasticity, sharp velocity and density contrasts, topography. And with water column approximation, it can also deal with oceans. Because of its powerful ability, there are a wide range of application of SEM in studies of PP waves and Rayleigh waves. PP wave and its precursors have been used in measuring topography of 410 km or 660 km. Rayleigh waves are the most recognizable part of the seismograms and have been broadly applied in crustal and uppermost mantle tomography. In global SEM simulation, oceans are usually assumed to be incompressible, which means that the entire water column moves as a whole as a result of the normal displacement of the seafloor. It is necessary to investigate the accuracy of water column approximation when thickness of ocean approaches wavelength of the wave in the ocean water. In this paper, based on plane wave assumption, we study both the accurate form and water column approximate form of effective boundary condition. The reflection coefficient equation of PP waves with effective boundary of water was derived. Accurate and approximate PP reflection coefficient with oceans in different depth is demonstrated. The formula of Rayleigh wave phase velocity dispersion with effective water boundary is also investigated. It is shown that water column approximation in global SEM simulation is not sufficient for some parts of the ocean.
Caffagni, Enrico; Cattaneo, Marco; Bordoni, Paola
2016-04-01
Spectral ratio techniques, such as the Horizontal-to-Vertical (HV) and Standard (SSR) may exhibit different trends in specific frequency bands when conducted in alluvial basins. A possible explanation of this discrepancy can be provided by the presence of Rayleigh oscillations, that are considered responsible of an amplification of the vertical component with respect to the horizontal. We propose a new methodology for the identification of Rayleigh waves arrivals, to test on small-size basins. With this procedure, candidate Rayleigh waves are localized in time-frequency domain on an instantaneous polarization plane which is constructed by defining the instantaneous maximum vertical and horizontal spectral amplitudes. Validation of the candidate Rayleigh arrivals is performed by evaluating the instantaneous ellipticity. This step yields to a quantitative measure of the polarization, providing an indicator of the Rayleigh contribution to ground motion. We tested this methodology in the Norcia basin (central Italy) using a 18 selected earthquakes (2.0 L'Aquila sequence (2009). We demonstrate the robustness of our methodology by localizing evidences of Rayleigh wave arrivals immediately from (1 s) up to 30 s after the first S-wave group, even for low-magnitude events (Ml < 3.0). The generation of the detected Rayleigh waves analyzed in time-frequency range, appears to be magnitude-dependent and in function of the location in the basin. Our quantitative estimate of the Rayleigh polarization resulted to be comparable to the HV response value in specific frequency bands, for example in deamplification, demonstrating a plausible connection with Rayleigh oscillations. The authors encourage the usage or implementation of similar procedures conducted in basin studies, in order to determine quantitatively the Rayleigh contribution to ground motion, for a better characterization of the local seismic response.
Skeletonized wave-equation Qs tomography using surface waves
Li, Jing
2017-08-17
We present a skeletonized inversion method that inverts surface-wave data for the Qs quality factor. Similar to the inversion of dispersion curves for the S-wave velocity model, the complicated surface-wave arrivals are skeletonized as simpler data, namely the amplitude spectra of the windowed Rayleigh-wave arrivals. The optimal Qs model is then found that minimizes the difference in the peak frequencies of the predicted and observed Rayleigh wave arrivals using a gradient-based wave-equation optimization method. Solutions to the viscoelastic wave-equation are used to compute the predicted Rayleigh-wave arrivals and the misfit gradient at every iteration. This procedure, denoted as wave-equation Qs tomography (WQs), does not require the assumption of a layered model and tends to have fast and robust convergence compared to Q full waveform inversion (Q-FWI). Numerical examples with synthetic and field data demonstrate that the WQs method can accurately invert for a smoothed approximation to the subsur-face Qs distribution as long as the Vs model is known with sufficient accuracy.
Wave-equation Qs Inversion of Skeletonized Surface Waves
Li, Jing
2017-02-08
We present a skeletonized inversion method that inverts surface-wave data for the Qs quality factor. Similar to the inversion of dispersion curves for the S-wave velocity model, the complicated surface-wave arrivals are skeletonized as simpler data, namely the amplitude spectra of the windowed Rayleigh-wave arrivals. The optimal Qs model is the one that minimizes the difference in the peak frequencies of the predicted and observed Rayleigh wave arrivals using a gradient-based wave-equation optimization method. Solutions to the viscoelastic wave-equation are used to compute the predicted Rayleigh-wave arrivals and the misfit gradient at every iteration. This procedure, denoted as wave-equation Qs inversion (WQs), does not require the assumption of a layered model and tends to have fast and robust convergence compared to full waveform inversion (FWI). Numerical examples with synthetic and field data demonstrate that the WQs method can accurately invert for a smoothed approximation to the subsurface Qs distribution as long as the Vs model is known with sufficient accuracy.
Ellipticity of Rayleigh waves in basin and hard-rock sites in Northern Italy
Berbellini, Andrea; Morelli, Andrea; Ferreira, Ana M. G.
2016-07-01
We measure ellipticity of teleseismic Rayleigh waves at 95 seismic stations in Northern Italy, for wave period between 10 and 110 s, using an automatic technique and a large volume of high-quality seismic recordings from over 500 global earthquakes that occurred in 2008-2014. Northern Italy includes a wide range of crustal structures, from the wide and deep Po Plain sedimentary basin to outcropping sedimentary and crystalline rocks in the Northern Apennines and Alps. It thus provides an excellent case for studying the influence of shallow earth structure on polarization of surface waves. The ellipticity measurements show excellent spatial correlation with geological features in the region, such as high ellipticity associated with regions of low seismic velocity in the Po Plain and low ellipticity values in faster, hard rock regions in the Alps and Apennine mountains. Moreover, the observed ellipticity values also relate to the thickness of the basement, as highlighted by observed differences beneath the Alps and the Apennines. Comparison between observations and predicted ellipticity from a reference crustal model of the region show substantial fit, particularly for T ˜ 38 s data. Discrepancy for shorter wave period suggests that slight modifications of the model are needed, and that the ellipticity measurements could help to better constrain the shallow crustal structure of the region. Predictions for the Po Plain are larger than the observations by a factor of four or more and transition from retrograde to prograde Rayleigh wave motion at the surface for periods of T ˜ 10-13 s is predicted for seismic stations in the plain. Analysis of corresponding real data indicates a possible detection of teleseismic prograde particle motion, but the weak teleseismic earthquake signals are mixed with ambient noise signals at the predicted, short, transition periods. Detection of the period of polarity inversion from the joint analysis of earthquake and ambient noise
Crustal structure of northern Italy from the ellipticity of Rayleigh waves
Berbellini, Andrea; Morelli, Andrea; Ferreira, Ana M. G.
2017-04-01
Northern Italy is a diverse geological region, including the wide and thick Po Plain sedimentary basin, which is bounded by the Alps and the Apennines. The seismically slow shallow structure of the Po Plain is difficult to retrieve with classical seismic measurements such as surface wave dispersion, yet the detailed structure of the region greatly affects seismic wave propagation and hence seismic ground shaking. Here we invert Rayleigh wave ellipticity measurements in the period range 10-60 s for 95 stations in northern Italy using a fully non linear approach to constrain vertical vS,vP and density profiles of the crust beneath each station. The ellipticity of Rayleigh wave ground motion is primarily sensitive to shear-wave velocity beneath the recording station, which reduces along-path contamination effects. We use the 3D layering structure in MAMBo, a previous model based on a compilation of geological and geophysical information for the Po Plain and surrounding regions of northern Italy, and employ ellipticity data to constrain vS,vP and density within its layers. We show that ellipticity data from ballistic teleseismic wave trains alone constrain the crustal structure well. This leads to MAMBo-E, an updated seismic model of the region's crust that inherits information available from previous seismic prospection and geological studies, while fitting new seismic data well. MAMBo-E brings new insights into lateral heterogeneity in the region's subsurface. Compared to MAMBo, it shows overall faster seismic anomalies in the region's Quaternary, Pliocene and Oligo-Miocene layers and better delineates the seismic structures of the Po Plain at depth. Two low velocity regions are mapped in the Mesozoic layer in the western and eastern parts of the Plain, which seem to correspond to the Monferrato sedimentary basin and to the Ferrara-Romagna thrust system, respectively.
Orienting ocean-bottom seismometers from P-wave and Rayleigh wave polarizations
Scholz, John-Robert; Barruol, Guilhem; Fontaine, Fabrice R.; Sigloch, Karin; Crawford, Wayne C.; Deen, Martha
2017-03-01
We present two independent, automated methods for estimating the absolute horizontal misorientation of seismic sensors. We apply both methods to 44 free-fall ocean-bottom seismometers (OBSs) of the RHUM-RUM experiment (http://www.rhum-rum.net/). The techniques measure the 3-D directions of particle motion of (1) P-waves and (2) Rayleigh waves of earthquake recordings. For P-waves, we used a principal component analysis to determine the directions of particle motions (polarizations) in multiple frequency passbands. We correct for polarization deviations due to seismic anisotropy and dipping discontinuities using a simple fit equation, which yields significantly more accurate OBS orientations. For Rayleigh waves, we evaluated the degree of elliptical polarization in the vertical plane in the time and frequency domain. The results obtained for the RHUM-RUM OBS stations differed, on average, by 3.1° and 3.7° between the methods, using circular mean and median statistics, which is within the methods' estimate uncertainties. Using P-waves, we obtained orientation estimates for 31 ocean-bottom seismometers with an average uncertainty (95 per cent confidence interval) of 11° per station. For 7 of these OBS, data coverage was sufficient to correct polarization measurements for underlying seismic anisotropy and dipping discontinuities, improving their average orientation uncertainty from 11° to 6° per station. Using Rayleigh waves, we obtained misorientation estimates for 40 OBS, with an average uncertainty of 16° per station. The good agreement of results obtained using the two methods indicates that they should also be useful for detecting misorientations of terrestrial seismic stations.
Control of Rayleigh-like waves in thick plate Willis metamaterials
Diatta, Andre; Brûlé, Stéphane; Enoch, Stefan; Guenneau, Sébastien
2016-01-01
Recent advances in control of anthropic seismic sources in structured soil led us to explore interactions of elastic waves propagating in plates (with soil parameters) structured with concrete pillars buried in the soil. Pillars are $40$ m in depth and the plate is $100$ m in thickness, so that typical frequencies under study are in the frequency range 4 to 8 Hz, which is compatible with frequency ranges of particular interest in earthquake engineering. It is demonstrated in this paper that two seismic cloaks' configurations allow for an unprecedented flow of elastodynamic energy associated with Rayleigh surface waves. These designs are inspired by some ideal cloaks' parameters deduced from a geometric transform in the Navier equations that preserves the symmetry of the elasticity tensor but leads to Willis' equations as corroborated by numerical simulations. Importantly, we focus our attention on geometric transforms applied to thick plates, which is an intermediate case between thin plates and semi-infinite...
Constraints on Shear Velocity in the Cratonic Upper Mantle From Rayleigh Wave Phase Velocity
Hirsch, A. C.; Dalton, C. A.
2014-12-01
In recent years, the prevailing notion of Precambrian continental lithosphere as a thick boundary layer (200-300 km), defined by a depleted composition and a steady-state conductively cooled temperature structure, has been challenged by several lines of seismological evidence. One, profiles of shear velocity with depth beneath cratons exhibit lower wave speed at shallow depths and higher wave speed at greater depths than can be explained by temperature alone. These profiles are also characterized by positive or flat velocity gradients with depth and anomalously high attenuation in the uppermost mantle, both of which are difficult to reconcile with the low temperatures and large thermal gradient expected with a thermal boundary layer. Two, body-wave receiver-function studies have detected a mid-lithospheric discontinuity that requires a large and abrupt velocity decrease with depth in cratonic regions that cannot be achieved by thermal gradients alone. Here, we used forward-modeling to identify the suite of shear-velocity profiles that are consistent with phase-velocity observations made for Rayleigh waves that primarily traversed cratons in North America, South America, Africa, and Australia. We considered two approaches; with the first, depth profiles of shear velocity were predicted from thermal models of the cratonic upper mantle that correspond to a range of assumed values of mantle potential temperature, surface heat flow, and radiogenic heat production in the crust and upper mantle. With the second approach, depth profiles of shear velocity were randomly generated. In both cases, Rayleigh wave phase velocity was calculated from the Earth models and compared to the observed values. We show that it is very difficult to match the observations with an Earth model containing a low-velocity zone in the upper mantle; instead, the best-fit models contain a flat or positive velocity gradient with depth. We explore the implications of this result for the thermal and
Banquet Speech Some Sketches Of Rayleigh
Howard, John N.
1985-11-01
Several short sketches are presented of Lord Rayleigh, to show his method of working and his interaction with his fellow scientists. The topics discussed are: his research on the blue of the sky (Rayleigh scattering); his rescue of Waterston from near-oblivion; his research on surface acoustic waves (Rayleigh waves); his collaboration with Agnes Pockels; his research on blackbody radiation (the Rayleigh-Jeans Law).
Assessing the viscoelasticity of chicken liver by OCE and a Rayleigh wave model
Han, Zhaolong; Liu, Chih-hao; Singh, Manmohan; Aglyamov, Salavat R.; Raghunathan, Raksha; Wu, Chen; Larin, Kirill V.
2017-02-01
This study investigates the feasibility of quantifying the viscoelasticity of soft tissues with a dynamic noncontact optical coherence elastography (OCE) technique coupled with a Rayleigh wave model. Spectral analysis of an air-pulse induced elastic wave as measured by OCE provided the elastic wave dispersion curve. The dispersion curve was fitted to an analytical solution of the Rayleigh wave model to determine the Young's modulus and shear viscosity of samples. In order to validate the method, 10% gelatin phantoms with and without different concentrations of oil were prepared and tested by OCE and mechanical testing. Results demonstrated that the elasticities as assessed by the Rayleigh wave model generally agreed well with mechanical testing, and that the viscosity in the phantom with oil samples was higher than the phantoms without oil, which is in agreement with the literature. Further, this method was applied to quantify the viscoelasticity of chicken liver. The Young's modulus was E=2.04+/-0.88 kPa and the shear viscosity was η=1.20+/-0.13 Pa·s with R2=0.96+/-0.04 between the OCE-measured dispersion curve and Rayleigh wave model analytical solution. Combining OCE and the Rayleigh wave model shows promise as an effective tool for noninvasively quantifying the viscoelasticity of soft tissues.
Godfrey, Holly J.; Fry, Bill; Savage, Martha K.
2017-04-01
frequency range of 0.25-1 Hz. First-higher mode Love-waves are similarly slower than first-higher mode Rayleigh waves. This is incompatible with synthetic dispersion curves we calculate using isotropic, layered velocity models appropriate for Ruapehu and Tongariro, in which Love waves travel more quickly than Rayleigh waves of the same period. The Love-Rayleigh discrepancy is likely due to structures such as dykes or cracks in the vertical plane having increased influence on surface-wave propagation. However, several measurements at Ruapehu have Love-wave group velocities that are faster than Rayleigh-wave group velocities. The differences between the Love- and Rayleigh-wave dispersion curves also vary with the azimuth of the interstation path across Ruapehu and Tongariro Volcanoes. Significant azimuthal dependence of both Love and Rayleigh-wave velocities are also observed. This suggests azimuthal anisotropy within the volcanic structures, which coupled with radial anisotropy, makes the Vs structures of Ruapehu and Tongariro Volcanoes anisotropic with orthorhombic or lower order symmetry. We suggest that further work to determine three-dimensional volcanic structures should include provisions for such anisotropy.
Surface acoustic wave mode conversion resonator
Martin, S. J.; Gunshor, R. L.; Melloch, M. R.; Datta, S.; Pierret, R. F.
1983-08-01
The fact that a ZnO-on-Si structure supports two distinct surface waves, referred to as the Rayleigh and the Sezawa modes, if the ZnO layer is sufficiently thick is recalled. A description is given of a unique surface wave resonator that operates by efficiently converting between the two modes at the resonant frequency. Since input and output coupling is effected through different modes, the mode conversion resonator promises enhanced out-of-band signal rejection. A Rayleigh wave traversing the resonant cavity in one direction is reflected as a Sezawa wave. It is pointed out that the off-resonance rejection of the mode conversion resonator could be enhanced by designing the transducers to minimize the level of cross coupling between transducers and propagating modes.
Development of nondestructive system for detecting the cracks in KTX brake disk using Rayleigh wave
Kim, Min Soo; Lee, Ho Yong [Korea Railroad Research Institute, Uiwang (Korea, Republic of); Yeom, Yun Taek; Park, Jin Hyun; Song, Sung Jing; Kim, Hak Joon [Dept. of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Kwon, Sung Duck [Dept. of Physics, Andong National University, Andong (Korea, Republic of)
2017-02-15
Recently, KTX (Korean Train Express) train stoppage accidents were mainly caused by malfunctioning equipment, aging and cracking of railway vehicles, crack breakages of brake disks, and breakages of brake disks. Breakage of brake disk can cause large-scale casualties such as high-speed collision and concern about derailment by hitting lower axle and wheel. Therefore, in this study, a brake disk with solid and ventilation type, which is the brake disk of a KTX train was modeled, and a dynamometer system was constructed to operate the disk. A Rayleigh wave was used to inspect the surface of the brake disk. An ultrasonic inspection module was developed for the brake disk by using a local immersion method due to the difficulty involved in ultrasonic inspection using an existing immersion method. In addition, the surface defects of the brake disk were evaluated using a dynamometer mock-up system and an ultrasonic inspection module of the brake disk.
Analysis of Rayleigh waves with circular wavefront: a maximum likelihood approach
Maranò, Stefano; Hobiger, Manuel; Bergamo, Paolo; Fäh, Donat
2017-09-01
Analysis of Rayleigh waves is an important task in seismology and geotechnical investigations. In fact, properties of Rayleigh waves such as velocity and polarization are important observables that carry information about the structure of the subsoil. Applications analysing Rayleigh waves include active and passive seismic surveys. In active surveys, there is a controlled source of seismic energy and the sensors are typically placed near the source. In passive surveys, there is not a controlled source, rather, seismic waves from ambient vibrations are analysed and the sources are assumed to be far outside the array, simplifying the analysis by the assumption of plane waves. Whenever the source is in the proximity of the array of sensors or even within the array it is necessary to model the wave propagation accounting for the circular wavefront. In addition, it is also necessary to model the amplitude decay due to geometrical spreading. This is the case of active seismic surveys in which sensors are located near the seismic source. In this work, we propose a maximum likelihood (ML) approach for the analysis of Rayleigh waves generated at a near source. Our statistical model accounts for the curvature of the wavefront and amplitude decay due to geometrical spreading. Using our method, we show applications on real data of the retrieval of Rayleigh wave dispersion and ellipticity. We employ arrays with arbitrary geometry. Furthermore, we show how it is possible to combine active and passive surveys. This enables us to enlarge the analysable frequency range and therefore the depths investigated. We retrieve properties of Rayleigh waves from both active and passive surveys and show the excellent agreement of the results from the two surveys. In our approach we use the same array of sensors for both the passive and the active survey. This greatly simplifies the logistics necessary to perform a survey.
Dalton, David R.; Slawinski, Michael A.; Stachura, Piotr; Stanoev, Theodore
2016-01-01
We examine two types of guided waves: the Love and the quasi-Rayleigh waves. Both waves propagate in the same model of an elastic isotropic layer above an elastic isotropic halfspace. From their dispersion relations, we calculate their speeds as functions of the elasticity parameters, mass densities, frequency and layer thickness. We examine the sensitivity of these relations to the model and wave properties.
Harmonic excitation of mantle Rayleigh waves by the 1991 eruption of Mount Pinatubo, Philippines
Kanamori, Hiroo; MORI, Jim
1992-01-01
An unusually long (at least two hours) seismic wave train having periods of about 230 sec was recorded at many worldwide seismic stations during the major eruption of Mount Pinatubo in the Philippines on June 15, 1991. This wave train exhibits two sharp spectral peaks at 228 and 270 sec. The group velocity, phase velocity, and the particle motion of this wave train indicate that it is a Rayleigh wave. The most probable excitation mechanism is acoustic coupling of atmospheric oscillations that...
Anderson, Dale N [Los Alamos National Laboratory; Bonner, Jessie L [WESTON GEOPHYSICAL; Stroujkova, Anastasia [WESTON GEOPHYSICAL; Shumway, Robert [UC/DAVIS; Russell, David R [AFTAC
2009-01-01
Our objective is to improve seismic event screening using the properties of surface waves, We are accomplishing this through (1) the development of a Love-wave magnitude formula that is complementary to the Russell (2006) formula for Rayleigh waves and (2) quantifying differences in complexities and magnitude variances for earthquake and explosion-generated surface waves. We have applied the M{sub s} (VMAX) analysis (Bonner et al., 2006) using both Love and Rayleigh waves to events in the Middle East and Korean Peninsula, For the Middle East dataset consisting of approximately 100 events, the Love M{sub s} (VMAX) is greater than the Rayleigh M{sub s} (VMAX) estimated for individual stations for the majority of the events and azimuths, with the exception of the measurements for the smaller events from European stations to the northeast. It is unclear whether these smaller events suffer from magnitude bias for the Love waves or whether the paths, which include the Caspian and Mediterranean, have variable attenuation for Love and Rayleigh waves. For the Korean Peninsula, we have estimated Rayleigh- and Love-wave magnitudes for 31 earthquakes and two nuclear explosions, including the 25 May 2009 event. For 25 of the earthquakes, the network-averaged Love-wave magnitude is larger than the Rayleigh-wave estimate. For the 2009 nuclear explosion, the Love-wave M{sub s} (VMAX) was 3.1 while the Rayleigh-wave magnitude was 3.6. We are also utilizing the potential of observed variances in M{sub s} estimates that differ significantly in earthquake and explosion populations. We have considered two possible methods for incorporating unequal variances into the discrimination problem and compared the performance of various approaches on a population of 73 western United States earthquakes and 131 Nevada Test Site explosions. The approach proposes replacing the M{sub s} component by M{sub s} + a* {sigma}, where {sigma} denotes the interstation standard deviation obtained from the
On the reliability of direct Rayleigh-wave estimation from multicomponent cross-correlations
Xu, Zongbo; Mikesell, T. Dylan
2017-09-01
Seismic interferometry is routinely used to image and characterize underground geology. The vertical component cross-correlations (CZZ) are often analysed in this process; although one can also use radial component and multicomponent cross-correlations (CRR and CZR, respectively), which have been shown to provide a more accurate Rayleigh-wave Green's function than CZZ when sources are unevenly distributed. In this letter, we identify the relationship between the multicomponent cross-correlations (CZR and CRR) and the Rayleigh-wave Green's functions to show why CZR and CRR are less sensitive than CZZ to non-stationary phase source energy. We demonstrate the robustness of CRR with a synthetic seismic noise data example. These results provide a compelling reason as to why CRR should be used to estimate the dispersive characteristics of the direct Rayleigh wave with seismic interferometry when the signal-to-noise ratio is high.
Upper-Mantle Shear Velocities beneath Southern California Determined from Long-Period Surface Waves
Polet, J.; Kanamori, H.
1997-01-01
We used long-period surface waves from teleseismic earthquakes recorded by the TERRAscope network to determine phase velocity dispersion of Rayleigh waves up to periods of about 170 sec and of Love waves up to about 150 sec. This enabled us to investigate the upper-mantle velocity structure beneath southern California to a depth of about 250 km. Ten and five earthquakes were used for Rayleigh and Love waves, respectively. The observed surface-wave dispersion shows a clear Love/Rayleigh-wave d...
Radi, Zohir; Yelles-Chaouche, Abdelkrim; Corchete, Victor; Guettouche, Salim
2017-09-01
We resolve the crust and upper mantle structure beneath Northeast Algeria at depths of 0-400 km, using inversion of fundamental mode Rayleigh wave. Our data set consists of 490 earthquakes recorded between 2007 and 2014 by five permanent broadband seismic stations in the study area. Applying a combination of different filtering technics and inversion method shear wave velocities structure were determined as functions of depth. The resolved changes in Vs at 50 km depth are in perfect agreement with crustal thickness estimates, which reflect the study area's orogenic setting, partly overlying the collision zone between the African and Eurasian plates. The inferred Moho discontinuity depths are close to those estimated for other convergent areas. In addition, there is good agreement between our results and variations in orientations of regional seismic anisotropy. At depths of 80-180 km, negative Vs anomalies at station CBBR suggest the existence of a failed subduction slab.
Mapping buried parts of a megalithic tomb with multichannel analysis of Rayleigh-waves and GPR
Wilken, D.; Erkul, E.; Glomb, V.; Rabbel, W.
2012-04-01
The objective of the presented study was to image buried parts of a megalithic tomb in northern Germany with GPR and multichannel analysis of surface-waves (MASW). The latter method was applied with the aim of testing its feasibility when used on intermediate scale archaeological targets. As we do not expect MASW of being able to resolve archaeological objects in terms of inverted velocity structure, we look for spectral effects due to subsurface heterogeneity. Identifying and mapping these effects would give a distribution of possibly archaeological objects. The presented seismic dataset shows an amplitude shift between normal and a guided Rayleigh-wave mode. When mapped along parallel profiles the spatial distribution of this effect matches the geometry of the grave. The observed anomalies show good correlation to GPR results that included strong reflectors inside the grave border. Elastic finite difference modelling of the surface-wave propagation showed that the spectral effect can be reproduced by a compacted or bulked column above the GPR anomaly depth indicating that the observed anomalies may be caused by construction activities or load effects during multiple construction phases of the tomb. Observed GPR reflectors thus indicate the bottom of the disturbed zones and MASW effects map the distribution of disturbed subsoil columns.
Determining surface wave arrival angle anomalies
Larson, Erik W. F.; Ekström, Göran
2002-06-01
A new method for measuring arrival angles of teleseismic Love and Rayleigh waves is developed. The new method utilizes estimates of surface wave dispersion to create a phase-matched filter to isolate the Love or Rayleigh wave in three-component recordings. The polarization of the filtered wave group is determined in the time domain by application of a variation of the complex polarization method of Vidale [1986]. Orientation, linearity, and ellipticity of particle motion are estimated in several frequency bands to determine the frequency-dependent polarization. The method employs an iterative scheme, by which a predicted Love wave, based on the estimated dispersion and polarization, is subtracted from the three-component data prior to the estimation of Rayleigh wave polarization, and vice versa. The method is applied to an extensive set of Global Seismographic Network data covering the years 1989-1998. Between 4244 and 15,075 measurements are collected for fundamental mode Love and Rayleigh waves at nine different periods (37 to 150 s). Measurement uncertainties are estimated using the statistics of observations for pairwise similar paths and are generally of the order of 15-50% of the total signal, depending on the period and the wave type. Large and azimuthally invariant angle anomalies are documented for several stations and are consistent with misorientation of the horizontal seismometers. Two schemes are employed to determine the misorientations: (1) an azimuthally weighted average at each station, and (2) a joint inversion for seismometer misorientation and globally heterogeneous phase velocities. The determined corrections are robust and correlate well with those reported in earlier studies. Azimuthally varying arrival angle anomalies are shown to agree qualitatively with predictions of wave refraction calculated for recent phase velocity maps, which explain up to 30% of the variance in the new measurements.
Methods to increase the depth and precision of transient Rayleigh wave exploration
ZHANG Jian-jun(张建军); WEI Xiu-cheng(魏修成); LIU Yang(刘洋)
2004-01-01
In order to increase the exploration depth of Rayleigh wave, new idea that different from the former principles in data acquisition was applied. Suitable data acquisition parameter was given out on the basis of large amount of experiments. By reducing the group interval, the low frequency signal are enhanced instead of been attenuated. Furthermore, to solve the problem that the precision of Rayleigh wave exploration method count much to the signal-to-noise ratio, some preprocessing methods were put forward. By using zero shift rectifying, digital F-K filtering and cutting, noises can be effectively eliminated.
Engineered metabarrier as shield from seismic surface waves
2016-01-01
Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by bu...
Crustal Structure of the Pakistan Himalayas from Ambient Noise and Seismic Rayleigh Wave Inversion
Li, A.
2007-05-01
The western Himalayan syntaxi is a unique feature resulted from the India-Asia collision and its formation remains poorly understood. To image crustal structure in the western syntaxi, we analyze Rayleigh waves from ambient seismic noise and earthquake data recorded during the Pakistan Broadband Seismic Experiment. The Pakistan experiment included 9 broadband stations with an aperture of ~200 km and operated from September to December in 1992. We compute cross-correlations of ambient noise data on an hourly base and stack all the cross-correlations for 70 days to produce the estimated Green functions. Power spectrum analysis shows that the dominant energy is from 0.15 to 0.25 Hz and from 0.05 to 0.07 Hz, consistent with the well-know background seismic noise. A phase with large amplitude appears at near zero time on almost all stacked cross- correlations and its origin is not clear to us at this moment. Rayleigh waves can be clearly observed for station pairs at the distance of 80 km and larger but are contaminated by the near zero time phase at shorter station spacing. Rayleigh wave phase velocities at periods of 4 to 15 s will be produced from the ambient noise data. Using regional and teleseismic earthquakes, we expect to obtain Rayleigh wave dispersions at periods from 15 to 50 s. The phase velocities from both datasets will be inverted for crustal thickness and shear-wave structure beneath the Pakistan Himalayas.
River dykes investigation using seismic surface waves
Bitri, Adnand; Jousset, Philippe; Samyn, Kévin; Naylor, Adam
2010-05-01
Natural underground caves such as karsts are quite common in the region "Centre", France. These subsurface perturbations can be found underneath the protection dykes around "the Loire" River and the damage caused can create routes for floods. Geophysical methods such as Multi-channel Analysis of Surface Waves (MASW) can be used for locating voids or karsts systems, but its efficiency on surface with strong topography such as dykes is not certain. Three dimensional Rayleigh wave modelling was used to understand the role of topography in the propagation of surface waves and with the aim of determining the best way for MASW investigations of surfaces with strong topography such as river dykes. Numerical modelling shows that surface waves propagation is not strongly affected by topography for an array parallel to the dyke. For homogeneous models with topography, a diminution of surface waves amplitude is observed while higher propagation modes are amplified in the dispersion curves in the case of heterogeneous models with topography. For an array perpendicular to the dyke, numerical modeling shows that Rayleigh waves' velocity is lower. MASW investigations can then be applied if lateral variations of the topography are not too strong along the seismic line. Diffraction hyperbolas created by a full of water cavity were identified in numerical modelling with topography. According to these elements, a MASW survey has been performed on the dykes of "the Loire" river close to a collapsed cavity and potential karstic systems were discovered.
The acoustoelastic effect on Rayleigh waves in elastic-plastic deformed layered rocks
Liu Jin-Xia; Cui Zhi-Wen; Wang Ke-Xie
2007-01-01
On the basis of the acoustoelastic theory for elastic-plastic materials, the influence of statically deformed states including both the elastic and plastic deformations induced by applied uniaxial stresses on the Rayleigh wave in layered rocks is investigated by using a transfer matrix method. The acoustoelastic effects of elastic-plastic strains in rocks caused by static deformations, are discussed in detail. The Rayleigh-type and Sezawa modes exhibit similar trends in acoustoelastic effect: the acoustoelastic effect increasing rapidly with the frequency-thickness product and the phase velocity change approaching a constant value for thick layer and high frequency limit. Elastic-plastic deformations in the Castlegate layered rock obviously modify the phase velocity of the Rayleigh wave and the cutoff points for the Sezawa modes. The investigation may be useful for seismic exploration, geotechnical engineering and ultrasonic detection.
Elastic properties of amorphous thin films studied by Rayleigh waves
Schwarz, R.B.; Rubin, J.B.
1993-08-01
Physical vapor deposition in ultra-high vacuum was used to co-deposit nickel and zirconium onto quartz single crystals and grow amorphous Ni{sub 1-x}Zr{sub x} (0.1 < x < 0.87) thin film. A high-resolution surface acoustic wave technique was developed for in situ measurement of film shear moduli. The modulus has narrow maxima at x = 0. 17, 0.22, 0.43, 0.5, 0.63, and 0.72, reflecting short-range ordering and formation of aggregates in amorphous phase. It is proposed that the aggregates correspond to polytetrahedral atom arrangements limited in size by geometrical frustration.
Surface-wave potential for triggering tectonic (nonvolcanic) tremor
Hill, D.P.
2010-01-01
Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle is anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45?? incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia mega-thrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction, ????? 0.2). However, documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, is associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (?? ~ 0.6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.
Imaging Rayleigh Wave Attenuation and Phase Velocity beneath North America with USArray
Bao, X.; Dalton, C. A.; Jin, G.; Gaherty, J. B.
2014-12-01
The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle of United States at a novel scale. The majority of mantle models derived from USArray data contain spatial variations in velocity; however, little is known about the attenuation structure of the North American upper mantle. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity, and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. In this study, Rayleigh wave travel time and amplitude are measured using an interstation cross-correlation version of the Generalized Seismological Data Functional algorithm, which takes advantage of waveform similarity at nearby stations. Our data are from 670 large teleseismic earthquakes that occurred from 2006 to 2014 and were recorded by 1,764 Transportable Array stations. More than 4.8 million measurements at periods between 20 and 100 s are collected into our database. Isolating the signal of attenuation in the amplitude observations is challenging because amplitudes are sensitive to a number of factors in addition to attenuation, such as focusing/defocusing and local site amplification. We generate several Rayleigh wave attenuation maps at each period, using several different approaches to account for source and receiver effects on amplitude. This suite of attenuation maps allows us to distinguish between the robust features in the maps and the features that are sensitive to the treatment of source and receiver effects. We apply Helmholtz surface-wave tomography (Lin et al., 2012) to determine velocity and attenuation maps. A significant contrast in velocity and attenuation is observed in the transition between the western and central United States along the Rocky Mountain front. We find low Q values in the western US, along the eastern coast, and the Gulf plain. These areas are also
Direction dependent Love and Rayleigh wave noise characteristics using multiple arrays across Europe
Juretzek, Carina; Perleth, Magdalena; Hadziioannou, Celine
2016-04-01
Seismic noise has become an important signal source for tomography and monitoring purposes. Better understanding of the noise field characteristics is crucial to further improve noise applications. Our knowledge about common and different origins of Love and Rayleigh waves in the microseism band is still limited. This applies in particular for constraints on source locations and source mechanisms of Love waves. Here, 3-component beamforming is used to distinguish between the different polarized wave types in the primary and secondary microseism noise field recorded at several arrays across Europe. We compare characteristics of Love and Rayleigh wave noise, such as source directions and frequency content. Further, Love to Rayleigh wave ratios are measured and a dependence on direction is found, especially in the primary microseism band. Estimates of the kinetic energy density ratios propose a dominance of coherent Love waves in the primary, but not in the secondary microseism band. The seasonality of the noise field characteristics is examined by using a full year of data in 2013 and is found to be stable.
Trichandi, Rahmantara, E-mail: rachmantara.tri@gmail.com [Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, 40132, Bandung (Indonesia); Yudistira, Tedi; Nugraha, Andri Dian [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, 40132 (Indonesia); Zulhan, Zulfakriza [Earth Science Graduate Program, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Bandung, 40132 (Indonesia); Saygin, Erdinc [Research School of Earth Sciences, The Australian National University, Canberra ACT 0200 (Australia)
2015-04-24
Ambient noise tomography is relatively a new method for imaging the shallow structure of the Earth subsurface. We presents the application of this method to produce a Rayleigh wave group velocity maps around the Merapi Volcano, Central Java. Rayleigh waves group velocity maps were reconstructed from the cross-correlation of ambient noise recorded by the DOMERAPI array which consists 43 broadband seismometers. In the processing stage, we first filtered the observation data to separatethe noise from the signal that dominated by the strong volcanic activities. Next, we cross-correlate the filtered data and stack to obtain the Green’s function for all possible station pairs. Then we carefully picked the peak of each Green’s function to estimate the dispersion trend and appliedMultiple Filter Technique to obtain the dispersion curve. Inter-station group velocity curvesare inverted to produceRayleigh wave group velocity maps for periods 1 to 10 s. The resulted Rayleigh group velocity maps show the interesting features around the Merapi Volcano which generally agree with the previous studies. Merapi-Lawu Anomaly (MLA) is emerged as a relatively low anomaly in our group velocity maps.
Trichandi, Rahmantara; Yudistira, Tedi; Nugraha, Andri Dian; Zulhan, Zulfakriza; Saygin, Erdinc
2015-04-01
Ambient noise tomography is relatively a new method for imaging the shallow structure of the Earth subsurface. We presents the application of this method to produce a Rayleigh wave group velocity maps around the Merapi Volcano, Central Java. Rayleigh waves group velocity maps were reconstructed from the cross-correlation of ambient noise recorded by the DOMERAPI array which consists 43 broadband seismometers. In the processing stage, we first filtered the observation data to separatethe noise from the signal that dominated by the strong volcanic activities. Next, we cross-correlate the filtered data and stack to obtain the Green's function for all possible station pairs. Then we carefully picked the peak of each Green's function to estimate the dispersion trend and appliedMultiple Filter Technique to obtain the dispersion curve. Inter-station group velocity curvesare inverted to produceRayleigh wave group velocity maps for periods 1 to 10 s. The resulted Rayleigh group velocity maps show the interesting features around the Merapi Volcano which generally agree with the previous studies. Merapi-Lawu Anomaly (MLA) is emerged as a relatively low anomaly in our group velocity maps.
Estimating Rayleigh wave particle motion from three-component array analysis of ambient vibrations
Poggi, Valerio; Fäh, Donat
2010-01-01
Several methods have been proposed in the past years to extract the Rayleigh wave ellipticity from horizontal-to-vertical spectral ratios of single station ambient noise recordings. The disadvantage of this set of techniques is the difficulty in clearly identifying and separating the contribution of higher modes. In most cases, only the fundamental mode of ellipticity can be identified. Moreover, it is generally difficult to correct for the energy of SH and Love waves present in the horizontal components of the ambient vibration wavefield. We introduce a new methodology to retrieve Rayleigh wave ellipticity using high-resolution frequency-wavenumber array analysis. The technique is applied to the three components of motion and is based on the assumption that an amplitude maximum in the f-k cross-spectrum must represent the true power amplitude of the corresponding signal. In the case of Rayleigh waves, therefore, the ratio between maxima obtained from the horizontal (radial-polarized) and vertical components of motion will also represent the frequency-dependent ellipticity function. Consequently, if we can identify the Rayleigh dispersion curves of several modes on the f-k plane, then the corresponding modal ellipticity patterns can also be separated and extracted. To test the approach, synthetic and real data sets were processed. In all tested cases, a reliable estimation of segments of the fundamental mode ellipticity was obtained. The identification of higher modes is possible in most cases. The quality of results depends on the selected array geometry and the signal-to-noise ratio, with a major improvement achieved by increasing the number of receivers employed during the survey. An experiment conducted in the town of Visp (Switzerland) allowed the retrieval of portions of ellipticity curves up to the second Rayleigh higher mode, using two concentric circular array configurations of 14 and 11 receivers each.
Highly Sensitive Rayleigh Wave Hydrogen Sensors with WO3 Sensing Layers at Room Temperature
WANG Cheng; FAN Li; ZHANG Shu-Yi; YANG Yue-Tao; ZHOU Ding-Mao; SHUI Xiu-Ji
2011-01-01
Rayleigh wave hydrogen sensors based on 128° YX-LiNbO3 substrates with WO3 sensing layers operating at room temperature are studied.The experimental results indicate that the WO3 layers obtained by a sol-gel method have much higher sensitivities because the sensing layers produced by the sol-gel method have small grains and high roughness and porosity.It is also confirmed that in the sol-gel method,keeping WO3 solutions at low temperature and/or decreasing the viscosity of the solutions can decrease the grain sizes and increase the hydrogen-absorbability of the sensing layer.Under the optimized preparation conditions,the high sensitivity of the hydrogen sensors at room temperature is obtained,in which 1％ hydrogen in natural air induces the frequency shift of 72 kHz at the operating frequency of 124.2 MHz.Surface acoustic wave (SAW) hydrogen sensors have attracted a great deal of attention so far,in which the sensors have achieved high sensitivity as the sensors were often operated at high temperature,such as higher than 100℃.[1-4] However,in these experiments,a heater and a thermostat were required,which induced the sensors to be more complicated and unfavorable for miniaturization,and limited their application at room temperature.Furthermore,the heater can induce extra power loss and risks of fire and explosion.%Rayleigh wave hydrogen sensors based on 128° YX-LiNbO3 substrates with WO3 sensing layers operating at room temperature are studied. The experimental results indicate that the WO3 layers obtained by a sol-gel method have much higher sensitivities because the sensing layers produced by the sol-gel method have small grains and high roughness and porosity. It is also confirmed that in the sol-gel method, keeping WO3 solutions at low temperature and/or decreasing the viscosity of the solutions can decrease the grain sizes and increase the hydrogen-absorbability of the sensing layer. Under the optimized preparation conditions, the high sensitivity of the
Sun, Hong-xiang; Zhang, Shu-yi; Xia, Jian-ping
2015-06-01
The propagation characteristics of laser-generated Rayleigh waves in coating-substrate structures with anisotropic and viscoelastic properties have been investigated quantitatively. Based on the plane strain theory, finite element models for simulating laser-generated Rayleigh waves in coating-substrate structures are established, in which the carbon fiber-reinforced epoxy matrix composite and aluminum are used as the coating and/or the substrate alternately. The numerical results exhibit that the characteristics of the laser-generated Rayleigh waves, including attenuation, velocity, and dispersion, are mainly and closely related to the anisotropic and viscoelastic properties of the composite in the coating-substrate structures.
S. M. Ahmed
2012-01-01
Full Text Available The propagation of Rayleigh and Stoneley waves in a thermoelastic orthotropic granular half-space supporting a different layer under the influence of initial stress and gravity field is studied. The frequency equation of Rayleigh waves in the form of twelfth-order determinantal expression and the frequency equation of Stoneley waves in the form of eighth-order determinantal expression are obtained. The standard equation of dispersion is discussed to obtain Rayleigh and Stoneley waves that have complex roots; the real part gives the velocity of Rayleigh or Stoneley waves but the imaginary part gives the attenuation coefficient. Finally, the numerical results have been given and illustrated graphically, and their physical meaning has been explained.
Tanimoto, Toshiro; Hadziioannou, Céline; Igel, Heiner; Wassermann, Joachim; Schreiber, Ulrich; Gebauer, André; Chow, Bryant
2016-04-01
Monthly variations in the ratio of Rayleigh-to-Love waves in the secondary microseism are obtained from a colocated ring laser and an STS-2 seismograph at Wettzell, Germany. Two main conclusions are derived for the Rayleigh-to-Love wave kinetic energy ratios in the secondary microseism; first, the energy ratio is in the range 0.8-0.9 (Love wave energy is larger than Rayleigh wave energy most of the year by about 10-20%. Second, this ratio suddenly increases to 1.0-1.2 in June and July, indicating a larger fraction of Rayleigh wave energy. This change suggests that the locations and behaviors of excitation sources are different in these months.
Numerical simulation for recognition of coalfield fire areas by Rayleigh waves
Hu Mingshun; Pan Dongming; Chen Shenen; Dong Shouhua; Li Juanjuan
2013-01-01
Effective recognition of a coalfield fire area improves fire-fighting efficiency and helps avoid potential geological hazards.Coalfield fire areas are hard to detect accurately using general geophysical methods.This paper describes simulations of shallow,buried coalfield fires based on real geological conditions.Recognizing the coalfield fire by Rayleigh wave is proposed.Four representative geological models are constructed,namely; the non-burning model,the pseudo-burning model,the real-burning model,and the hidden-burning model.Numerical simulation using these models shows many markedly different characteristics between them in terms of Rayleigh wave dispersion and Eigen displacement.These characteristics,as well as the shear wave velocity obtained by inverting the fundamental dispersion,make it possible to distinguish the type of the coalfield fire area and indentify the real and serious coalfield fire area.The results are very helpful for future application of Rayleigh waves for the detection of coalfield fire area.
Local Effects on Strain Seismograms at Matsushiro Seismological Observatory - 2. Rayleigh Waves
Taishi Okamoto
2007-01-01
Full Text Available We evaluate local effects on strain seismograms for a Rayleigh wave observed at Matsushiro Seismological Observatory, Japan Meteorological Agency, central Japan, by applying a method proposed in a previous report (Okamoto et al. 2007. The method involves examination of polarization angles, local phase velocity, and accuracy of velocity seismograms. The results are as follows: 1 Polarization angles of observed strain seismograms agree with expected ones from those of velocity seismograms also observed at Matsushiro; 2 Local phase velocity estimated by comparison between strain and velocity seismograms is 54% larger than the theoretical value calculated from the PREM velocity model; 3 Velocity spectra observed at Matsushiro have almost the same amplitude as an average of those at F-net observation stations near Matsushiro. These results indicate that both EW and NS component strain seismograms observed at Matsushiro have been reduced by 35% in amplitude for a Rayleigh wave due to local heterogeneity. The local effects on a Rayleigh wave are quite different from that on a Love wave obtained in the previous report.
Takayama, Osamu; Crasovan, Lucian Cornel; Johansen, Steffen Kjær;
2008-01-01
The interface of two semi-infinite media, where at least one of them is a birefringent crystal, supports a special type of surface wave that was predicted theoretically by D'yakonov in 1988. Since then, the properties of such waves, which exist in transparent media only under very special......, the existence of these surface waves in specific material examples is analyzed, discussing the challenge posed by their experimental observation....
Torello, David [GW Woodruff School of Mechanical Engineering, Georgia Tech (United States); Kim, Jin-Yeon [School of Civil and Environmental Engineering, Georgia Tech (United States); Qu, Jianmin [Department of Civil and Environmental Engineering, Northwestern University (United States); Jacobs, Laurence J. [School of Civil and Environmental Engineering, Georgia Tech and GW Woodruff School of Mechanical Engineering, Georgia Tech (United States)
2015-03-31
This research considers the effects of diffraction, attenuation, and the nonlinearity of generating sources on measurements of nonlinear ultrasonic Rayleigh wave propagation. A new theoretical framework for correcting measurements made with air-coupled and contact piezoelectric receivers for the aforementioned effects is provided based on analytical models and experimental considerations. A method for extracting the nonlinearity parameter β{sub 11} is proposed based on a nonlinear least squares curve-fitting algorithm that is tailored for Rayleigh wave measurements. Quantitative experiments are conducted to confirm the predictions for the nonlinearity of the piezoelectric source and to demonstrate the effectiveness of the curve-fitting procedure. These experiments are conducted on aluminum 2024 and 7075 specimens and a β{sub 11}{sup 7075}/β{sub 11}{sup 2024} measure of 1.363 agrees well with previous literature and earlier work.
Joint Inversion for Earthquake Depths Using Local Waveforms and Amplitude Spectra of Rayleigh Waves
Jia, Zhe; Ni, Sidao; Chu, Risheng; Zhan, Zhongwen
2017-01-01
Reliable earthquake depth is fundamental to many seismological problems. In this paper, we present a method to jointly invert for centroid depths with local (distance distance of 5°-15°) Rayleigh wave amplitude spectra on sparse networks. We use earthquake focal mechanisms and magnitudes retrieved with the Cut-and-Paste (CAP) method to compute synthetic amplitude spectra of fundamental mode Rayleigh wave for a range of depths. Then we grid search to find the optimal depth that minimizes the joint misfit of amplitude spectra and local waveforms. As case studies, we apply this method to the 2008 Wells, Nevada Mw6.0 earthquake and a Mw5.6 outer-rise earthquake to the east of Japan Trench in 2013. Uncertainties estimated with a bootstrap re-sampling approach show that this joint inversion approach constrains centroid depths well, which are also verified by independent teleseismic depth-phase data.
Elastic characterization of Au thin films utilizing laser induced acoustic Rayleigh waves
Haim, A.; Bar-Ad, S.; Azoulay, A.
2011-01-01
Wide frequency-band Rayleigh waves (~100 MHz) were utilized to characterize the elastic constants of thin Au/Cr films deposited on glass substrates. The Rayleigh waves were excited utilizing laser induced thermoelastic mechanism and detected using a knife-edge technique apparatus. The dispersion of the signals in glass substrates coated with Au/Cr was measured and fitted to theory using a non-linear regression algorithm. From the fitting, the Au films Young modulus and the film thickness were extracted. The results were analyzed with regards to AFM scans performed on the samples and independent thickness measurement done by a dektak3 profiler. Results show a good agreement between the two measurements.
Elastic characterization of Au thin films utilizing laser induced acoustic Rayleigh waves
Haim, A; Azoulay, A [Ultrasonic Section, NDT Department, Soreq - Nuclear Research Center, Yavne 81800 (Israel); Bar-Ad, S, E-mail: arbelhai@gmail.com [School of Physics and Astronomy, Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978 (Israel)
2011-01-01
Wide frequency-band Rayleigh waves ({approx}100 MHz) were utilized to characterize the elastic constants of thin Au/Cr films deposited on glass substrates. The Rayleigh waves were excited utilizing laser induced thermoelastic mechanism and detected using a knife-edge technique apparatus. The dispersion of the signals in glass substrates coated with Au/Cr was measured and fitted to theory using a non-linear regression algorithm. From the fitting, the Au films Young modulus and the film thickness were extracted. The results were analyzed with regards to AFM scans performed on the samples and independent thickness measurement done by a dektak{sup 3} profiler. Results show a good agreement between the two measurements.
Ogawa, Y., E-mail: y.ogawa@ap.titech.ac.jp [Department of Physics, Tokyo Institute of Technology, Oh-Okayama 2-12-1, Tokyo 152-8551 (Japan); Takahashi, S.; Nakajima, D.; Minami, F. [Department of Physics, Tokyo Institute of Technology, Oh-Okayama 2-12-1, Tokyo 152-8551 (Japan)
2013-01-15
Surface plasmon polariton (SPP) propagation on a Au thin film has been observed by tip-enhanced Rayleigh scattering. The interference pattern has been observed around the edge of the film. The interference is due to the near-field scattering light at the tip and SPP radiation from the edge of the film. From the interference width, we evaluated the wave number of SPP on the Au film. By changing the wavelength of the incidence light, we have obtained the dispersion relation of the SPP. The experimentally obtained dispersion relation is well corresponding to the calculated one using bulk Au parameters. - Highlights: Black-Right-Pointing-Pointer We observed surface plasmon polariton propagation on Au film by tip-enhanced Rayleigh scattering. Black-Right-Pointing-Pointer The dispersion relation was obtained by changing the wavelength of the incidence light. Black-Right-Pointing-Pointer The dispersion relation is well corresponding to the calculated one using bulk Au parameters.
S-wave velocity structure in the Nankai accretionary prism derived from Rayleigh admittance
Tonegawa, Takashi; Araki, Eiichiro; Kimura, Toshinori; Nakamura, Takeshi; Nakano, Masaru; Suzuki, Kensuke
2017-04-01
Two cabled seafloor networks with 22 and 29 stations (DONET 1 and 2: Dense Oceanfloor Network System for Earthquake and Tsunamis) have been constructed on the accretionary prism at the Nankai subduction zone of Japan since March 2010. The observation periods of DONET 1 and 2 exceed more than 5 years and 10 months, respectively. Each station contains broadband seismometers and absolute and differential pressure gauges. In this study, using Rayleigh waves of microseisms and earthquakes, we calculate the Rayleigh admittance (Ruan et al., 2014, JGR) at the seafloor for each station, i.e., an amplitude transfer function from pressure to displacement, particularly for the frequencies of 0.1-0.2 Hz (ambient noise) and 0.04-0.1 Hz (earthquake signal), and estimate S-wave velocity (Vs) structure beneath stations in DONET 1 and 2. We calculated the displacement seismogram by removing the instrument response from the velocity seismogram for each station. The pressure record observed at the differential pressure gauge was used in this study because of a high resolution of the pressure observation. In addition to Rayleigh waves of microseisms, we collected waveforms of Rayleigh waves for earthquakes with an epicentral distance of 15-90°, M>5.0, and focal depth shallower than 50 km. In the frequency domain, we smoothed the transfer function of displacement/pressure with the Parzen window of ±0.01 Hz. In order to determine one-dimensional Vs profiles, we performed a nonlinear inversion technique, i.e., simulated annealing. As a result, Vs profiles obtained at stations near the land show simple Vs structure, i.e., Vs increases with depth. However, some profiles located at the toe of the acceretionary prism have a low-velocity zone (LVZ) at a depth of 5-7 km within the accretinary sediment. The velocity reduction is approximately 5-20 %. Park et al. (2010) reported such a large reduction in P-wave velocity in the region of DONET 1 (eastern network and southeast of the Kii
Zhou, Yong; Ni, Sidao; Chu, Risheng; Yao, Huajian
2016-08-01
Numerical solvers of wave equations have been widely used to simulate global seismic waves including PP waves for modelling 410/660 km discontinuity and Rayleigh waves for imaging crustal structure. In order to avoid extra computation cost due to ocean water effects, these numerical solvers usually adopt water column approximation, whose accuracy depends on frequency and needs to be investigated quantitatively. In this paper, we describe a unified representation of accurate and approximate forms of the equivalent water column boundary condition as well as the free boundary condition. Then we derive an analytical form of the PP-wave reflection coefficient with the unified boundary condition, and quantify the effects of water column approximation on amplitude and phase shift of the PP waves. We also study the effects of water column approximation on phase velocity dispersion of the fundamental mode Rayleigh wave with a propagation matrix method. We find that with the water column approximation: (1) The error of PP amplitude and phase shift is less than 5 per cent and 9° at periods greater than 25 s for most oceanic regions. But at periods of 15 s or less, PP is inaccurate up to 10 per cent in amplitude and a few seconds in time shift for deep oceans. (2) The error in Rayleigh wave phase velocity is less than 1 per cent at periods greater than 30 s in most oceanic regions, but the error is up to 2 per cent for deep oceans at periods of 20 s or less. This study confirms that the water column approximation is only accurate at long periods and it needs to be improved at shorter periods.
Propagation of Rayleigh waves in anisotropic layer overlying a semi-infinite sandy medium
P.C. Pal
2015-06-01
Full Text Available The present investigation deals with the propagation of Rayleigh waves in anisotropic layer overlying a sandy medium. Anisotropic material is in the nature of most general case i.e. of triclinic crystal and sandy medium is of alluvial soil type. The solutions for layer and half-space are obtained analytically. The displacement components in x and z directions are obtained for both the media. The dispersion relation is obtained subjected to certain boundary conditions. The special cases are considered. The numerical results are presented in the form of wave number and phase velocity (k − c analytical curves.
Takayama, Osamu; Crasovan, Lucian Cornel; Johansen, Steffen Kjær
2008-01-01
The interface of two semi-infinite media, where at least one of them is a birefringent crystal, supports a special type of surface wave that was predicted theoretically by D'yakonov in 1988. Since then, the properties of such waves, which exist in transparent media only under very special conditi...
Jin Xing; Li Jun; Lin Shu; Zhou Zhengrong; Kang Lanchi; Ou Yiping
2008-01-01
This paper uses the 8 broad-band stations' microseism data recorded by the Seismic Monitoring Network of Fujian Province to calculate the vertical correlation coefficient between two stationsat intervals of 5 minutes. According to the time intervals technique we obtain the different coefficients and then add the correlative coefficients. Depending on this, we extract the group velocity of Rayleigh waves from the cross correlation of the ambient seismic noise between two seismic stations and figure out the group velocity' spatial distribution. The results show that the signal noise ratio (SNR) increases proportionally to the superposition times, but the results from different days are similar to one another. Synchronously, the arrival-time is also stable and there is no obvious change when coming across typhoons. It is found the velocity of the surface wave is 2.9～3. 1km/s in Fujian Province, which is close to the observationally attained value.
Gravity waves observation of wind field in stratosphere based on a Rayleigh Doppler lidar.
Zhao, Ruocan; Dou, Xiankang; Sun, Dongsong; Xue, Xianghui; Zheng, Jun; Han, Yuli; Chen, Tingdi; Wang, Guocheng; Zhou, Yingjie
2016-03-21
Simultaneous wind and temperature measurements in stratosphere with high time-spatial resolution for gravity waves study are scarce. In this paper we perform wind field gravity waves cases in the stratosphere observed by a mobile Rayleigh Doppler lidar. This lidar system with both wind and temperature measurements were implemented for atmosphere gravity waves research in the altitude region 15-60 km. Observations were carried out for two periods of time: 3 months started from November 4, 2014 in Xinzhou, China (38.425°N,112.729°E) and 2 months started from October 7, 2015 in Jiuquan, China (39.741°N, 98.495°E) . The mesoscale fluctuations of the horizontal wind velocity and the two dimensional spectra analysis of these fluctuations show the presence of dominant oscillatory modes with wavelength of 4-14 km and period of around 10 hours in several cases. The simultaneous temperature observations make it possible to identify gravity wave cases from the relationships between different variables: temperature and horizontal wind. The observed cases demonstrate the Rayleigh Doppler Lidar's capacity to study gravity waves.
Yan, Zewu; Zhao, Chunnong; Ju, Li; Gras, Slawomir; Baringa, Pablo; Blair, David G.
2005-01-01
This article describes an automatic Rayleigh scattering mapping system (ARSMS), which enables quantitative high-resolution three-dimensional mapping of inhomogeneities in optical materials. The ARSMS allows large high-grade test mass samples for gravitational wave detectors to be evaluated to ensure that an adequate low level of scattering is achieved. The ARSMS combines proprietary camera software with data analysis software and control software to achieve fully automatic operation with graphical user interfaces. This article presents the instrument concept and examples of the output. Device mapping in all degrees of freedom is shown to be better than 0.5mm, with scattering sensitivity better than 0.5ppm/cm. This system is able to scan and map the Rayleigh scattering of large samples in both of cylindrical and rectangular samples using cylindrical and Cartesian coordinates.
Degenerate RS perturbation theory. [Rayleigh-Schroedinger energies and wave functions
Hirschfelder, J. O.; Certain, P. R.
1974-01-01
A concise, systematic procedure is given for determining the Rayleigh-Schroedinger energies and wave functions of degenerate states to arbitrarily high orders even when the degeneracies of the various states are resolved in arbitrary orders. The procedure is expressed in terms of an iterative cycle in which the energy through the (2n + 1)-th order is expressed in terms of the partially determined wave function through the n-th order. Both a direct and an operator derivation are given. The two approaches are equivalent and can be transcribed into each other. The direct approach deals with the wave functions (without the use of formal operators) and has the advantage that it resembles the usual treatment of nondegenerate perturbations and maintains close contact with the basic physics. In the operator approach, the wave functions are expressed in terms of infinite-order operators which are determined by the successive resolution of the space of the zeroth-order functions.
Active micromixer using surface acoustic wave streaming
Branch; Darren W. , Meyer; Grant D. , Craighead; Harold G.
2011-05-17
An active micromixer uses a surface acoustic wave, preferably a Rayleigh wave, propagating on a piezoelectric substrate to induce acoustic streaming in a fluid in a microfluidic channel. The surface acoustic wave can be generated by applying an RF excitation signal to at least one interdigital transducer on the piezoelectric substrate. The active micromixer can rapidly mix quiescent fluids or laminar streams in low Reynolds number flows. The active micromixer has no moving parts (other than the SAW transducer) and is, therefore, more reliable, less damaging to sensitive fluids, and less susceptible to fouling and channel clogging than other types of active and passive micromixers. The active micromixer is adaptable to a wide range of geometries, can be easily fabricated, and can be integrated in a microfluidic system, reducing dead volume. Finally, the active micromixer has on-demand on/off mixing capability and can be operated at low power.
Dispersion of Rayleigh waves produced by nuclear explosions. Crustal structure of western Europe
G. PAYO
1964-06-01
Full Text Available Most of the nuclear explosion fired near Novaya-Zemlya
island from September 1961 to J a n u a r y 1963 (21 in total have been recorded
on the seismographs of Toledo Observatory. The study of these records,
mainly concerning the dispersion of Rayleigh waves, has been the purpose
of this paper.
A crust-mantle s t r u c t u r e for t h e Zemlya-Toledo p a t h has been determined
by means of group velocity curves and especially by the phase velocity
ones obtained from Rayleigh waves of explosions. This structure supposes
a crust of about 40 kms thick with an upper sedimentary layer with a
thickness of about 5,5 kms and a shear velocity of 2,3 km/sec.
The average shear velocity in the granitic and basaltic layers jointly,
is about 3,65 km/sec, permitting a small ambiguity at the position of the
Conrad discontinuity between them.
A velocity of 4,5 km/sec has been assigned for the underlying crust
material, but a better agreement with the data recorded is obtained by
taking 0.28 for the Poisson ratio value.
Dispersion of Rayleigh waves of these explosions has been compared
to the Rayleigh dispersion of some earthquakes of Eurasia, three of them
with epicentral distances similar to those of the explosions and other four
with the same azimuth in respect to that of Toledo-Zemlya, but more
distants.
The results do not show any notable difference either in dispersion
between explosion and earthquakes or in structure of the path considered.
The phase velocity between Toledo and Malaga Observatories supports
t h e same above structure for this short path.
The velocity of Lg waves, which clearly appears on the record of the
explosions, confirms this admitted structure, which serves to deduce t h e more
probable transmission mechanism for these channel waves.
Also atmospheric pressure waves have been recorded on the three
The uppermost crust structure of Ischia (southern Italy) from ambient noise Rayleigh waves
Strollo, R.; Nunziata, C.; Iannotta, A.; Iannotta, D.
2015-05-01
Ambient noise measurements were performed at the island of Ischia (southern Italy) along alignments of 2.4-7 km by using two three-component seismic stations. Synchronous noise recordings of 2-20 h were cross-correlated over 20-30 s windows, stacked and iteratively band-pass filtered to enhance the dispersive wave trains. Frequency time analysis was performed on the vertical and radial components of cross-correlations and the fundamental-mode Rayleigh wave group velocity was obtained. Validation of the dispersion data was possible with those obtained from an earthquake recording along a close path. The non-linear inversion of average Rayleigh wave group velocity dispersion curves along 13 paths (receiver inter-distances) allowed the definition of shear wave velocity models in the uppermost 1-2 km of the crust. The correlation of VS profiles vs. depth and drilling stratigraphy allowed to attribute VS lower than 1 km/s to tuffs and VS of 1.41 km/s to very fractured lavas. Higher VS are found in the central area of the island, in correspondence of the resurgent area. The top of the trachytic lava basement, with VS of 2.2-2.4 km/s and density of 2.3 g/cm3 is about 0.6-0.7 km deep b.s.l. in the centre of Ischia, below altered, very fractured lava or thermally altered tuff.
The thermal structure of cratonic lithosphere from global Rayleigh wave attenuation
Dalton, Colleen A.; Bao, Xueyang; Ma, Zhitu
2017-01-01
The resolution of and level of agreement between different attenuation models have historically been limited by complexities associated with extracting attenuation from seismic-wave amplitudes, which are also affected by the source, the receiver, and propagation through velocity heterogeneities. For intermediate- and long-period Rayleigh waves, removing the amplitude signal due to focusing and defocusing effects is the greatest challenge. In this paper, three independent data sets of fundamental-mode Rayleigh wave amplitude are analyzed to investigate how three factors contribute to discrepancies between the attenuation models: uncertainties in the amplitude measurements themselves, variable path coverage, and the treatment of focusing effects. Regionalized pure-path and fully two-dimensional attenuation models are derived and compared. The approach for determining attenuation models from real data is guided by an analysis of amplitudes measured from synthetic spectral-element waveforms, for which the input Earth model is perfectly known. The results show that differences in the amplitude measurements introduce only very minor differences between the attenuation models; path coverage and the removal of focusing effects are more important. The pure-path attenuation values exhibit a clear dependence on tectonic region at shorter periods that disappears at long periods, in agreement with pure-path phase-velocity results obtained by inverting Rayleigh wave phase delays. The 2-D attenuation maps are highly correlated with each other to spherical-harmonic degree 16 and can resolve smaller features than the previous generation of global attenuation models. Anomalously low attenuation is nearly perfectly associated with continental cratons. Variations in lithospheric thickness are determined by forward modeling the global attenuation variations as a thermal boundary layer of variable thickness. Temperature profiles that satisfy the attenuation values systematically
Gal, M.; Reading, A. M.; Ellingsen, S. P.; Koper, K. D.; Burlacu, R.
2017-06-01
In the secondary microseism band (0.1-1.0 Hz) the theoretical excitation of Rayleigh waves (Rg/LR), through oceanic wave-wave interaction, is well understood. For Love waves (LQ), the excitation mechanism in the secondary microseism band is less clear. We explore high-frequency secondary microseism excitation between 0.35 and 1 Hz by analyzing a full year (2013) of records from a three-component seismic array in Pilbara (PSAR), Australia. Our recently developed three-component waveform decomposition algorithm (CLEAN-3C) fully decomposes the beam power in slowness space into multiple point sources. This method allows for a directionally dependent power estimation for all separable wave phases. In this contribution, we compare quantitatively microseismic energy recorded on vertical and transverse components. We find the mean power representation of Rayleigh and Love waves to have differing azimuthal distributions, which are likely a result of their respective generation mechanisms. Rayleigh waves show correlation with convex coastlines, while Love waves correlate with seafloor sedimentary basins. The observations are compared to the WAVEWATCH III ocean model, implemented at the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), which describes the spatial and temporal characteristics of microseismic source excitation. We find Love wave energy to originate from raypaths coinciding with seafloor sedimentary basins where strong Rayleigh wave excitation is predicted by the ocean model. The total power of Rg waves is found to dominate at 0.35-0.6 Hz, and the Rayleigh/Love wave power ratio strongly varies with direction and frequency.
Victor M. García-Chocano
2011-12-01
Full Text Available Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in a channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.
Rayleigh and acoustic gravity waves detection on magnetograms during the Japanese Tsunami, 2011
Klausner, Virginia; Muella, Marcio T A H; Mendes, Odim; Domingues, Margarete O; Papa, Andres R R
2015-01-01
The continuous geomagnetic field survey holds an important potential in future prevention of tsunami damages, and also, it could be used in tsunami forecast. In this work, we were able to detected for the first time Rayleigh and ionospheric acoustic gravity wave propagation in the Z-component of the geomagnetic field due to the Japanese tsunami, 2011 prior to the tsunami arrival. The geomagnetic measurements were obtained in the epicentral near and far-field. Also, these waves were detected within minutes to few hours of the tsunami arrival. For these reasons, these results are very encouraging, and confirmed that the geomagnetic field monitoring could play an important role in the tsunami warning systems, and also, it could provide additional information in the induced ionospheric wave propagation models due to tsunamis.
Propagation of elastic waves in a plate with rough surfaces
DAI Shuwu; ZHANG Hailan
2003-01-01
The characteristics of Lamb wave propagating in a solid plate with rough surfacesare studied on the basis of small perturbation approximation. The Rayleigh-Lamb frequencyequation expressed with SA matrix is presented. The Rayleigh-Lamb frequency equation fora rough surface plate is different from that for a smooth surface plate, resulting in a smallperturbation Ak on Lamb wave vector k. The imaginary part of Ak gives the attenuationcaused by wave scattering. An experiment is designed to test our theoretical predications.By using wedge-shape pipes, different Lamb wave modes are excited. The signals at differentpositions are received and analyzed to get the dispersion curves and attenuations of differentmodes. The experimental results are compared with the theoretical predications.
de Lorenzo, Salvatore; Michele, Maddalena; Emolo, Antonio; Tallarico, Andrea
2017-02-01
In the present study, fundamental Rayleigh waves with varying period from 10 to 80 s are used to obtain group velocity maps in the northwest Deccan Volcanic Province of India. About 350 paths are obtained using 53 earthquakes (4.8 ≤ M ≥ 7.9) recorded by the SeisNetG (Seismic Network of Gujarat). Individual dispersion curves of group velocity of Rayleigh wave for each source-station path are estimated using multiple filter technique. These curves are used to determine lateral distribution of Rayleigh wave group velocity by tomographic inversion method. Our estimated Rayleigh group velocity at varying depths showed conspicuous corroboration with three tectonic blocks [Kachchh Rift Basin (KRB), Saurashtra Horst (SH), and Mainland Gujarat (MG)] in the region. The seismically active KRB with a thicker crust is characterized as a low velocity zone at a period varying from 10 to 30 s as indicative of mantle downwarping or sagging of the mantle beneath the KRB, while the SH and MG are found to be associated with higher group velocities, indicating the existence of the reduced crustal thickness. The trend of higher group velocity was found prevailed adjacent to the Narmada and Cambay rift basins that also correspond to the reduced crust, suggesting the processes of mantle upwarping or uplifting due to mantle upwelling. The low velocities at periods longer than 40 s beneath the KRB indicate thicker lithosphere. The known Moho depth correlates well with the observed velocities at a period of about 30 s in the Gujarat region. Our estimates of relatively lower group velocities at periods varying from 70 to 80 s may correspond to the asthenospheric flow beneath the region. It is interesting to image higher group velocity for the thinner crust beneath the Arabian Sea adjacent to the west coast of Gujarat at the period of 40 s that may correspond to the upwarped or upwelled mantle beneath the Arabian Sea. Our results have better resolution estimated by a radius of equivalent
Fletcher, Jon B.; Erdem, Jemile
2017-06-01
Rayleigh wave group velocities obtained from ambient noise tomography are inverted for an upper crustal model of the Central Valley, California, centered on the Sacramento/San Joaquin Delta. Two methods were tried; the first uses SURF96, a least squares routine. It provides a good fit to the data, but convergence is dependent on the starting model. The second uses a genetic algorithm, whose starting model is random. This method was tried at several nodes in the model and compared to the output from SURF96. The genetic code is run five times and the variance of the output of all five models can be used to obtain an estimate of error. SURF96 produces a more regular solution mostly because it is typically run with a smoothing constraint. Models from the genetic code are generally consistent with the SURF96 code sometimes producing lower velocities at depth. The full model, calculated using SURF96, employed a 2-pass strategy, which used a variable damping scheme in the first pass. The resulting model shows low velocities near the surface in the Central Valley with a broad asymmetrical sedimentary basin located close to the western edge of the Central Valley near 122°W longitude. At shallow depths, the Rio Vista Basin is found nestled between the Pittsburgh/Kirby Hills and Midland faults, but a significant basin also seems to exist to the west of the Kirby Hills fault. There are other possible correlations between fast and slow velocities in the Central Valley and geologic features such as the Stockton Arch, oil or gas producing regions and the fault-controlled western boundary of the Central Valley.
Conversion from surface wave to surface wave on reflection
Novitsky, Andrey
2010-01-01
We discuss the reflection and transmission of an incident surface wave to a pure surface wave state at another interface. This is allowed only for special media parameters: at least one of the media must be magnetic. We found such material characteristics that the obliquely incident surface wave...... can be transmitted without changing its direction (nevertheless the amplitude varies). For other media parameters, only normally incident surface waves can be converted to surface waves. We propose applications of the predicted conversion as a beam splitter and polarization filter for surface waves....
Ben Salah, Issam; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi
2012-02-01
An exact approach is used to investigate Rayleigh waves in a functionally graded piezoelectric material (FGPM) layer bonded to a semi infinite homogenous solid. The piezoelectric material is polarized when the six fold symmetry axis is put along the propagation direction x(1). The FGPM character imposes that the material properties change gradually with the thickness of the layer. Contrary to the analytical approach, the adopted numerical methods, including the ordinary differential equation (ODE) and the stiffness matrix method (SMM), treat separately the electrical and mechanical gradients. The influences of graded variations applied to FGPM film coefficients on the dispersion curves of Rayleigh waves are discussed. The effects of gradient coefficients on electromechanical coupling factor, displacement fields, stress distributions and electrical potential, are reported. The obtained deviations in comparison with the ungraded homogenous film are plotted with respect to the dimensionless wavenumber. Opposite effects are observed on the coupling factor when graded variations are applied separately. A particular attention has been devoted to the maximum of the coupling factor and it dependence on the stratification rate and the gradient coefficient. This work provides with a theoretical foundation for the design and practical applications of SAW devices with high performance.
Surface wave propagation in a ﬂuid-saturated incompressible porous medium
Rajneesh Kumar; B S Hundal
2007-06-01
A study of surface wave propagation in a ﬂuid-saturated incompressible porous half-space lying under a uniform layer of liquid is presented. The dispersion relation connecting the phase velocity with wave number is derived. The variation of phase velocity and attenuation coefﬁcients with wave number is presented graphically and discussed. As a particular case, the propagation of Rayleigh type surface waves at the free surface of an incompressible porous half-space is also deduced and discussed.
Megaquakes, prograde surface waves and urban evolution
Lomnitz, C.; Castaños, H.
2013-05-01
Cities grow according to evolutionary principles. They move away from soft-ground conditions and avoid vulnerable types of structures. A megaquake generates prograde surface waves that produce unexpected damage in modern buildings. The examples (Figs. 1 and 2) were taken from the 1985 Mexico City and the 2010 Concepción, Chile megaquakes. About 400 structures built under supervision according to modern building codes were destroyed in the Mexican earthquake. All were sited on soft ground. A Rayleigh wave will cause surface particles to move as ellipses in a vertical plane. Building codes assume that this motion will be retrograde as on a homogeneous elastic halfspace, but soft soils are intermediate materials between a solid and a liquid. When Poisson's ratio tends to ν→0.5 the particle motion turns prograde as it would on a homogeneous fluid halfspace. Building codes assume that the tilt of the ground is not in phase with the acceleration but we show that structures on soft ground tilt into the direction of the horizontal ground acceleration. The combined effect of gravity and acceleration may destabilize a structure when it is in resonance with its eigenfrequency. Castaños, H. and C. Lomnitz, 2013. Charles Darwin and the 1835 Chile earthquake. Seismol. Res. Lett., 84, 19-23. Lomnitz, C., 1990. Mexico 1985: the case for gravity waves. Geophys. J. Int., 102, 569-572. Malischewsky, P.G. et al., 2008. The domain of existence of prograde Rayleigh-wave particle motion. Wave Motion 45, 556-564.; Figure 1 1985 Mexico megaquake--overturned 15-story apartment building in Mexico City ; Figure 2 2010 Chile megaquake Overturned 15-story R-C apartment building in Concepción
Automated detection and association of surface waves
C. R. D. Woodgold
1994-06-01
Full Text Available An algorithm for the automatic detection and association of surface waves has been developed and tested over an 18 month interval on broad band data from the Yellowknife array (YKA. The detection algorithm uses a conventional STA/LTA scheme on data that have been narrow band filtered at 20 s periods and a test is then applied to identify dispersion. An average of 9 surface waves are detected daily using this technique. Beamforming is applied to determine the arrival azimuth; at a nonarray station this could be provided by poIarization analysis. The detected surface waves are associated daily with the events located by the short period array at Yellowknife, and later with the events listed in the USGS NEIC Monthly Summaries. Association requires matching both arrival time and azimuth of the Rayleigh waves. Regional calibration of group velocity and azimuth is required. . Large variations in both group velocity and azimuth corrections were found, as an example, signals from events in Fiji Tonga arrive with apparent group velocities of 2.9 3.5 krn/s and azimuths from 5 to + 40 degrees clockwise from true (great circle azimuth, whereas signals from Kuriles Kamchatka have velocities of 2.4 2.9 km/s and azimuths off by 35 to 0 degrees. After applying the regional corrections, surface waves are considered associated if the arrival time matches to within 0.25 km/s in apparent group velocity and the azimuth is within 30 degrees of the median expected. Over the 18 month period studied, 32% of the automatically detected surface waves were associated with events located by the Yellowknife short period array, and 34% (1591 with NEIC events; there is about 70% overlap between the two sets of events. Had the automatic detections been reported to the USGS, YKA would have ranked second (after LZH in terms of numbers of associated surface waves for the study period of April 1991 to September 1992.
Yang, Jiashi; Jin, Zhihe; Li, Jiangyu
2008-07-01
We show that functionally graded piezoelectric materials can be used to make modal actuators through theoretical analyses of the excitation of extensional motion in an elastic rod and Rayleigh surface waves over an elastic half-plane. The results suggest alternatives with certain advantages for the excitation of bulk and surface acoustic waves.
Dühring, Maria Bayard
of a Mach-Zehnder interferometer (MZI). This is an optical device consisting if one waveguide that is split into two waveguide arms which are assembled again later on. By applying the mechanical field from a SAW the light in the two arms can be modulated and interfere constructively and destructively......The work of this project is concerned with the simulation of surface acoustic waves (SAW) and topology optimization of SAW devices. SAWs are elastic vibrations that propagate along a material surface and are extensively used in electromechanical filters and resonators in telecommunication. A new...... application is modulation of optical waves in waveguides. This presentation elaborates on how a SAW is generated by interdigital transducers using a 2D model of a piezoelectric, inhomogeneous material implemented in the high-level programming language Comsol Multiphysics. The SAW is send through a model...
3D-ambient noise Rayleigh wave tomography of Snæfellsjökull volcano, Iceland
Obermann, Anne; Lupi, Matteo; Mordret, Aurélien; Jakobsdóttir, Steinunn S.; Miller, Stephen A.
2016-05-01
From May to September 2013, 21 seismic stations were deployed around the Snæfellsjökull volcano, Iceland. We cross-correlate the five months of seismic noise and measure the Rayleigh wave group velocity dispersion curves to gain more information about the geological structure of the Snæfellsjökull volcano. In particular, we investigate the occurrence of seismic wave anomalies in the first 6 km of crust. We regionalize the group velocity dispersion curves into 2-D velocity maps between 0.9 and 4.8 s. With a neighborhood algorithm we then locally invert the velocity maps to obtain accurate shear-velocity models down to 6 km depth. Our study highlights three seismic wave anomalies. The deepest, located between approximately 3.3 and 5.5 km depth, is a high velocity anomaly, possibly representing a solidified magma chamber. The second anomaly is also a high velocity anomaly east of the central volcano that starts at the surface and reaches approximately 2.5 km depth. It may represent a gabbroic intrusion or a dense swarm of inclined magmatic sheets (similar to the dike swarms found in the ophiolites), typical of Icelandic volcanic systems. The third anomaly is a low velocity anomaly extending up to 1.5 km depth. This anomaly, located directly below the volcanic edifice, may be interpreted either as a shallow magmatic reservoir (typical of Icelandic central volcanoes), or alternatively as a shallow hydrothermal system developed above the cooling magmatic reservoir.
Investigation into Mass Loading Sensitivity of Sezawa Wave Mode-Based Surface Acoustic Wave Sensors
N. Ramakrishnan; Parthiban, R.; Sawal Hamid Md Ali; Md. Shabiul Islam; Ajay Achath Mohanan
2013-01-01
In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW) device is investigated through finite element method (FEM) simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered SAW resonator is considered for the simulation study. Initially the occurrence of Sezawa wave mode and displacement amplitude of the Rayleigh and Sezawa wave mode is studied for lower ZnO film thickness. Further, a thin film...
Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Wu, Chen; Liu, Chih-Hao; Raghunathan, Raksha; Aglyamov, Salavat R; Vantipalli, Srilatha; Twa, Michael D; Larin, Kirill V
2017-02-01
The biomechanical properties of the cornea play a critical role in forming vision. Diseases such as keratoconus can structurally degenerate the cornea causing a pathological loss in visual acuity. UV-A/riboflavin corneal collagen crosslinking (CXL) is a clinically available treatment to stiffen the cornea and restore its healthy shape and function. However, current CXL techniques do not account for pre-existing biomechanical properties of the cornea nor the effects of the CXL treatment itself. In addition to the inherent corneal structure, the intraocular pressure (IOP) can also dramatically affect the measured biomechanical properties of the cornea. In this work, we present the details and development of a modified Rayleigh-Lamb frequency equation model for quantifying corneal biomechanical properties. After comparison with finite element modeling, the model was utilized to quantify the viscoelasticity of in situ porcine corneas in the whole eye-globe configuration before and after CXL based on noncontact optical coherence elastography measurements. Moreover, the viscoelasticity of the untreated and CXL-treated eyes was quantified at various IOPs. The results showed that the stiffness of the cornea increased after CXL and that corneal stiffness is close to linear as a function of IOP. These results show that the modified Rayleigh-Lamb wave model can provide an accurate assessment of corneal viscoelasticity, which could be used for customized CXL therapies.
Hadjoub, Zahia; Touati, Ibtissem; Doghmane, Malika; Doghmane, Abdellaziz
2008-10-01
This work concerns the investigation of loading layers/substrate structures in order to determine the critical thickness at which Rayleigh wave characteristics of layers can be completely distinguished from those of the substrates. To do so, we first calculate Rayleigh velocity dispersion curves of several thin film materials (about thirty) deposited on different slow and fast substrates (Be, Al 2O 3, AlN, Si, SiO 2, Mg, SiC, TiN, WC and Pyrex). Then, from the beginning of curve saturation (corresponding to the onset of intrinsic layer characteristics) we deduced normalized thickness transition for all layers/substrates combinations. Thus, we were able to deduce an analytical linear expression relating the critical thickness to combined effects of densities and velocities of both layers and substrates. Such a simple relation can be used, as an alternative method, to predict the transition critical thickness for any layer/substrate combination without the usual lengthy calculation of dispersion curves. To cite this article: Z. Hadjoub et al., C. R. Physique 9 (2008).
ULTRASONIC INFLUENCE OF POROSITY LEVEL ON CFRP COMPOSITE LAMINATES USING RAYLEIGH PROBE WAVES
Je-Woong Park; Do-Jung Kim; Kwang-Hee Im; Sang-Kyu Park; David K.Hsu; Adam H.Kite; Sun-Kyu Kim; Kil-Sung Lee; In-Young Yang
2008-01-01
It was found that a pitch-catch signal was more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composites (damages,fiber orientation,low level porosity,ply waviness,and cracks).Both the strength and stiffness depend on the fiber orientation and porosity volume in the composites.The porosity content of a composite structure is critical to the strength and performance of the structure in general.The depth of the sampling volume where the pitch-catch signal came from was relatively shallow with the head to-head miniature Rayleigh probes,but the depth can be increased by increasing the separation distance of the transmitting and receiving probes.Also,a method was utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate.A free software package was utilized to process micrograph images of the test sample.The results from the image processing method were compared with existing data.Beam profile was characterized in unidirectional CFRP(carbon fiber reinforced plastics) using pitch-catch Rayleigh probes and the one-sided pitch-catch technique was utilized to produce C-scan images with the aid of the automatic scanner.
Esteban Flores-Mendez
2012-01-01
Full Text Available This work is focused on studying interface waves for three canonical models, that is, interfaces formed by vacuum-solid, solid-solid, and liquid-solid. These interfaces excited by dynamic loads cause the emergence of Rayleigh's, Stoneley's, and Scholte's waves, respectively. To perform the study, the indirect boundary element method is used, which has proved to be a powerful tool for numerical modeling of problems in elastodynamics. In essence, the method expresses the diffracted wave field of stresses, pressures, and displacements by a boundary integral, also known as single-layer representation, whose shape can be regarded as a Fredholm's integral representation of second kind and zero order. This representation can be considered as an exemplification of Huygens' principle, which is equivalent to Somigliana's representation theorem. Results in frequency domain for the three types of interfaces are presented; then, using the fourier discrete transform, we derive the results in time domain, where the emergence of interface waves is highlighted.
Tataru, Dragos; Grecu, Bogdan; Zaharia, Bogdan
2014-05-01
Variations in crustal thickness in Romania where determined by joint inversion of P wave receiver functions (RFs) and Rayleigh wave group velocity dispersion. We present new models of shear wave velocity structure of the crust beneath Romanian broad band stations. The data set consist in more than 500 teleseismic earthquake with epicentral distance between 30° and 95°, magnitude greater than 6 and a signal-to-noise ratio greater than 3 for the P-wave pulse. Most epicenters are situated along the northern Pacific Rim and arrive with backazimuths (BAZs) between 0° and 135° at the Romanian seismic network. We combine receiver functions with fundamental-mode of the Rayleigh wave group velocities to further constrain the shear-wave velocity structure.To extract the group velocities we applied the Multiple Filter Technique analysis to the vertical components of the earthquakes recordings. This technique allowed us to identify the Rayleigh wave fundamental mode and to compute the dispersion curves of the group velocities at periods between 10 and 150 s allowing us to resolve shear wave velocities to a depth of 100 km. The time-domain iterative deconvolution procedure of Ligorrıa and Ammon (1999) was employed to deconvolve the vertical component of the teleseismic P waveforms from the corresponding horizontal components and obtain radial and transverse receiver functions at each broadband station. The data are inverted using a joint, linearized inversion scheme (Hermann, 2002) which accounts for the relative influence of each set of observations, and allows a trade-off between fitting the observations, constructing a smooth model, and matching a priori constraints. The results show a thin crust for stations located inside the Pannonian basin (28-30 km) and a thicker crust for those in the East European Platform (36-40 km). The stations within the Southern and Central Carpathian Orogen are characterized by crustal depths of ~35 km. For stations located in the Northern
Benoit, M H; Nyblade, A A; Pasyanos, M E
2006-01-17
The East African and Ethiopian Plateaus have long been recognized to be part of a much larger topographic anomaly on the African Plate called the African Superswell. One of the few places within the African Superswell that exhibit elevations of less than 1 km is southeastern Sudan and northern Kenya, an area containing both Mesozoic and Cenozoic rift basins. Crustal structure and uppermost mantle velocities are investigated in this area by modeling Rayleigh wave dispersion. Modeling results indicate an average crustal thickness of 25 {+-} 5 km, some 10-15 km thinner than the crust beneath the adjacent East African and Ethiopian Plateaus. The low elevations can therefore be readily attributed to an isostatic response from crustal thinning. Low Sn velocities of 4.1-4.3 km/s also characterize this region.
Metzler, Adam M; Siegmann, William L; Collins, Michael D
2012-02-01
The parabolic equation method with a single-scattering correction allows for accurate modeling of range-dependent environments in elastic layered media. For problems with large contrasts, accuracy and efficiency are gained by subdividing vertical interfaces into a series of two or more single-scattering problems. This approach generates several computational parameters, such as the number of interface slices, an iteration convergence parameter τ, and the number of iterations n for convergence. Using a narrow-angle approximation, the choices of n=1 and τ=2 give accurate solutions. Analogous results from the narrow-angle approximation extend to environments with larger variations when slices are used as needed at vertical interfaces. The approach is applied to a generic ocean waveguide that includes the generation of a Rayleigh interface wave. Results are presented in both frequency and time domains.
Crustal structure below Popocat\\'epetl Volcano (Mexico) from analysis of Rayleigh waves
De Barros, Louis; Métaxian, J -P; Valdés-Gonzales, C; Lesage, Philippe
2007-01-01
An array of ten broadband stations was installed on the Popocat\\'epetl volcano (Mexico) for five months between October 2002 and February 2003. 26 regional and teleseismic earthquakes were selected and filtered in the frequency time domain to extract the fundamental mode of the Rayleigh wave. The average dispersion curve was obtained in two steps. Firstly, phase velocities were measured in the period range [2-50] s from the phase difference between pairs of stations, using Wiener filtering. Secondly, the average dispersion curve was calculated by combining observations from all events in order to reduce diffraction effects. The inversion of the mean phase velocity yielded a crustal model for the volcano which is consistent with previous models of the Mexican Volcanic Belt. The overall crustal structure beneath Popocat\\'epetl is therefore not different from the surrounding area, and the velocities in the lower crust are confirmed to be relatively low. Lateral variations of the structure were also investigated ...
Benabid, F.; Notcutt, M.; Ju, L.; Blair, D. G.
1999-10-01
We present the level of noise induced by Rayleigh-scattered light from sapphire test mass, the limit of scattering loss on build-up power inside the interferometer and finally the tolerable absorption loss in order to meet the specification of the interferometer sensitivity. The results show that the Rayleigh scattering induced noise remains below h˜10 -25 Hz -1/2 and a higher tolerance on the absorption level in sapphire substrate compared with silica substrate.
Liu, Zhongxian; Liang, Jianwen; Wu, Chengqing
2016-06-01
Two dimensional diffraction of Rayleigh waves by a fluid-saturated poroelastic alluvial valley of arbitrary shape in a poroelastic half-space is investigated using the method of fundamental solutions (MFS). To satisfy the free surface boundary conditions exactly, Green's functions of compressional (PI and PII) and shear (SV) wave sources buried in a fluid-saturated poroelastic half-space are adopted. Next, the procedure for solving the scattering wave field is presented. It is verified that the MFS is of excellent accuracy and numerical stability. Numerical results illustrate that the dynamic response strongly depends on such factors as the incident frequency, the porosity of alluvium, the boundary drainage condition, and the valley shape. There is a significant difference between the diffraction of Rayleigh waves for the saturated soil case and for the corresponding dry soil case. The wave focusing effect both on the displacement and pore pressure can be observed inside the alluvial valley and the amplification effect seems most obvious in the case of higher porosity and lower frequency. Additionally, special attention should also be paid to the concentration of pore pressure, which is closely related to the site liquefaction in earthquakes.
Vinh, P. C.; Anh, V. T. N.; Linh, N. T. K.
2016-04-01
The secular equation of Rayleigh propagating in an orthotropic half-space coated by an orthotropic layer has been obtained by Sotiropolous [Sotiropolous, D. A. (1999), The e®ect of anisotropy on guided elastic waves in a layered half-space, Mechanics of Materials 31, 215-233] and by Sotiropolous & Tougelidis [Sotiropolous, D. A. and Tougelidis, G. (1998), Guided elastic waves in orthotropic surface layer, Ultrasonics 36, 371-374]. However, it is not totally explicit and some misprints have occurred in this secular equation in both papers. This secular equation was derived by expanding directly a six-order determinant originated from the traction-free conditions at the top surface of the layer and the continuity of displacements and stresses through the interface between the layer and the half-space. Since the expansion of this six-order determinant was not shown in both two papers, it has been difficult to readers to recognize these misprints. This paper presents a technique that provides a totally explicit secular equation of the wave. The technique makes clear the way from the traction-free and continuity conditions to the secular equation and enables us to recognize the misprints appearing in the reported secular equation. The technique can be employed to obtain explicit secular equations of Rayleigh waves for many other cases. Moreover, the paper introduces a transfer matrix in explicit form for an orthotropic layer that is much simpler in form than the one obtained previously.
Surface-wave photonic quasicrystal
Gao, Zhen; Zhang, Youming; Xu, Hongyi; Zhang, Baile
2016-01-01
In developing strategies of manipulating surface electromagnetic waves, it has been recently recognized that a complete forbidden band gap can exist in a periodic surface-wave photonic crystal, which has subsequently produced various surface-wave photonic devices. However, it is not obvious whether such a concept can be extended to a non-periodic surface-wave system that lacks translational symmetry. Here we experimentally demonstrate that a surface-wave photonic quasicrystal that lacks periodicity can also exhibit a forbidden band gap for surface electromagnetic waves. The lower cutoff of this forbidden band gap is mainly determined by the maximum separation between nearest neighboring pillars. Point defects within this band gap show distinct properties compared to a periodic photonic crystal for the absence of translational symmetry. A line-defect waveguide, which is crafted out of this surface-wave photonic quasicrystal by shortening a random row of metallic rods, is also demonstrated to guide and bend sur...
Nonlinear surface waves over topography
Janssen, T.T.
2006-01-01
As ocean surface waves radiate into shallow coastal areas and onto beaches, their lengths shorten, wave heights increase, and the wave shape transforms from nearsinusoidal to the characteristic saw-tooth shapes at the onset of breaking; in the ensuing breaking process the wave energy is cascaded to
Electromagnetic fields induced at the seafloor by Rayleigh-Stoneley waves
Webb, S.; Cobb, C.
1982-05-10
We model oceanic acoustic and seismic disturbances as Rayeigh-Stoneley waves in the layered medium consisting of ocean, sediment and rock. The waves induce electromagnetic fields because of motion of conducting materials through the geomagnetic field. Low-frequency disturbances in deep water are efficient electromagnetic generators because the motions are coherent over large volumes of highly conducting seawater. For wave frequencies below 0.1 Hz in deep water, the geomagnetic field is nearly frozen to the moving water. Consequently, the electric field measured by a voltmeter attached to the seabed is approximately ..delta..u x F, where ..delta..u is the difference between the velocity of the water and of the voltmeter itself as it is moved by the motion of the seafloor, and F is the geomagnetic field. This result applied to Love waves suggests that the electric field will result largely from the movement of the detector but detailed calculations have not been made. Although the fields are weak they should be detectable because the main interference is from ionospheric sources and the fields from, these sources are greatly attenuated at the seabed by the overlying oceanic shield. The effectiveness of the shield diminishes sharply at frequencies below 0.03 Hz. At high frequencies the principal limitation to detectability is in the inherent noise level of detectors whether electric or magnetic. At present, electric detectors are more effective than magnetic. They appear to be competitive with accelerometers for seismic detection in the deep ocean in a restricted frequency band near 0.05 Hz. A layer of unconsolidated sediment underlying the ocean profoundly affects the dispersion relation of Rayleigh-Stonely waves and thereby affects the electromagnetic induction process.
Surface-wave potential for triggering tectonic (nonvolcanic) tremor-corrected
Hill, David P.
2012-01-01
Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle are anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45° incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia megathrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction is μ* ≤ 0:2). Documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, however, are associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (μ ~ 0:6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.
Pratt, M. J.; Shen, W.; Wiens, D.; Winberry, J. P.; Anandakrishnan, S.
2016-12-01
Horizontal-to-vertical (H/V) ellipticity ratios of Rayleigh waves have been used to determine shallow (reflection imaging showing a deeper sedimentary package that extends to an unknown depth. It is also known that the frictional properties of the WIS ice-bed interface at 700 m depth are highly heterogeneous, including stick-spots of high friction, possibly as a result of compacted sediment or bedrock, and active subglacial lakes where frictional coefficients are effectively zero. Ambient noise cross-correlations are calculated between all station pairs, restricting the minimum interstation distance to 20 km, as well as constraining valid H/V ratios of radial and vertical sources between the same station pair to wave energy with good signal-to-noise between 6 s and 20 s that are sensitive to the shear velocity of the shallowest sedimentary layers beneath the ice stream and is combined with average phase and group velocity of the area to help constrain the inversion. H/V ratio modeling results suggest that ratios are highly susceptible to sedimentary layer thickness. Ratios also increase over the observed frequency band with the presence of a shallow, saturated sedimentary layer with high Vp/Vs. In preliminary results, we observe an increase in H/V ratio towards the grounding line as well as at stations where hydro-potential surface is high. These higher ratios can be attributed to higher water content within sediments, or an increase in the sedimentary layer thickness.
Xia, J.; Xu, Y.; Miller, R.D.; Chen, C.
2006-01-01
A Gibson half-space model (a non-layered Earth model) has the shear modulus varying linearly with depth in an inhomogeneous elastic half-space. In a half-space of sedimentary granular soil under a geostatic state of initial stress, the density and the Poisson's ratio do not vary considerably with depth. In such an Earth body, the dynamic shear modulus is the parameter that mainly affects the dispersion of propagating waves. We have estimated shear-wave velocities in the compressible Gibson half-space by inverting Rayleigh-wave phase velocities. An analytical dispersion law of Rayleigh-type waves in a compressible Gibson half-space is given in an algebraic form, which makes our inversion process extremely simple and fast. The convergence of the weighted damping solution is guaranteed through selection of the damping factor using the Levenberg-Marquardt method. Calculation efficiency is achieved by reconstructing a weighted damping solution using singular value decomposition techniques. The main advantage of this algorithm is that only three parameters define the compressible Gibson half-space model. Theoretically, to determine the model by the inversion, only three Rayleigh-wave phase velocities at different frequencies are required. This is useful in practice where Rayleigh-wave energy is only developed in a limited frequency range or at certain frequencies as data acquired at manmade structures such as dams and levees. Two real examples are presented and verified by borehole S-wave velocity measurements. The results of these real examples are also compared with the results of the layered-Earth model. ?? Springer 2006.
Rivet, Diane; Campillo, Michel; Sanchez-Sesma, Francisco; Shapiro, Nikolaï M.; Singh, Shri Krishna
2015-11-01
Dispersion analysis of Rayleigh waves is performed to assess the velocity of complex structures such as sedimentary basins. At short periods several modes of the Rayleigh waves are often exited. To perform a reliable inversion of the velocity structure an identification of these modes is thus required. We propose a novel method to identify the modes of surface waves. We use the spectral ratio of the ground velocity for the horizontal components over the vertical component (H/V) measured on seismic coda. We then compare the observed values with the theoretical H/V ratio for velocity models deduced from surface wave dispersion when assuming a particular mode. We first invert the Rayleigh wave measurements retrieved from ambient noise cross-correlation with the assumptions that (1) the fundamental mode and (2) the first overtone are excited. Then we use these different velocity models to predict theoretical spectral ratios of the ground velocity for the horizontal components over the vertical component (H/V). These H/V ratios are computed under the hypothesis of equipartition of a diffuse field in a layered medium. Finally we discriminate between fundamental and higher modes by comparing the theoretical H/V ratio with the H/V ratio measured on seismic coda. In an application, we reconstruct Rayleigh waves from cross-correlations of ambient seismic noise recorded at seven broad-band stations in the Valley of Mexico. For paths within the soft quaternary sediments basin, the maximum energy is observed at velocities higher than expected for the fundamental mode. We identify that the dominant mode is the first higher mode, which suggests the importance of higher modes as the main vectors of energy in such complex structures.
Huang, Y.; Yao, H.; Wu, F. T.; Liang, W.; Huang, B.; Lin, C.; Wen, K.
2013-12-01
Although orogeny seems to have stopped in western Taiwan large and small earthquakes do occur in the Taiwan Strait. Limited studies have focused on this region before and were barely within reach for comprehensive projects like TAICRUST and TAIGER for logistical reasons; thus, the overall crustal structures of the Taiwan Strait remain unknown. Time domain empirical Green's function (TDEGF) from ambient seismic noise to determine crustal velocity structure allows us to study an area using station pairs on its periphery. This research aims to resolve 1-D average crustal and upper mantle S-wave velocity (Vs) structures alone paths of several broadband station-pairs across the Taiwan Strait; 5-120 s Rayleigh wave phase velocity dispersion data derived by combining TDEGF and traditional surface wave two-station method (TS). The average Vs structures show significant differences in the upper 15 km as expected. In general, the highest Vs are observed in the coastal area of Mainland China and the lowest Vs appear along the southwest offshore of the Taiwan Island; they differ by about 0.6-1.1 km/s. For different parts of the Strait, the Vs are lower in the middle by about 0.1-0.2 km/s relative to those in the northern and southern parts. The overall crustal thickness is approximately 30 km, much thinner and less variable than under the Taiwan Island.
Jin, G.; Gaherty, J. B.; Abers, G. A.; Kim, Y.; Eilon, Z.; Buck, W. R.; Verave, R.
2012-12-01
The D'Entrecasteaux Islands and adjacent Papuan peninsula in eastern Papua New Guinea are home to the earliest stages of extension associated with the Woodlark Rift system. Very young (7-8 Ma) ultra-high pressure (coesite-eclogite facies) rocks within metamorphic core complexes (MCCs) on the D'Entrecasteaux Islands indicates exhumation from 100 km depths at plate-tectonic rates. We investigate the dynamic processes driving uplift and extension using seismic images of crustal and mantle structure derived from surface waves across the region. From March 2010 to July 2011, 31 on-shore and 8 off-shore broadband seismic stations deployed across the extensional region recorded 68 earthquakes with high signal-to-noise Rayleigh waves. We utilize a multi-channel cross-correlation technique to measure the phase delay and amplitude across the array in a period band between 20-80 sec, which images a depth range from lower crust to approximately 150 km depth. The phase difference of Rayleigh-wave arrivals between nearby stations is measured for each earthquake by fitting the narrow-band filtered cross-correlation between the observed seismograms. We then invert these intra-array phase measurements for a slowness vector map using the Eikonal equation to get the dynamic phase velocity and propagation direction. Averaging the dynamic phase velocity of all available events produces set of final phase velocity maps that can be inverted for shear-velocity structure, and the variations in phase-velocity as a function of azimuth provide constraints on anisotropy. For most of the frequency bands, the region beneath the MCCs on Goodenough Island and Fergusson Island, adjacent to the tip of the Woodlark spreading center, shows slow phase velocity, suggestive of high temperatures and/or partial melt, perhaps related to localized mantle upwelling. In contrast, the region near the Trobriand Island to the north, and the Papuan peninsula to the south, shows consistently higher phase velocity
Self-adaptive method for high frequency multi-channel analysis of surface wave method
When the high frequency multi-channel analysis of surface waves (MASW) method is conducted to explore soil properties in the vadose zone, existing rules for selecting the near offset and spread lengths cannot satisfy the requirements of planar dominant Rayleigh waves for all frequencies of interest ...
Onorato, M; Osborne, A R; Serio, M; Cavaleri, L; Brandini, C; Stansberg, C T
2004-12-01
We study random surface gravity wave fields and address the formation of large-amplitude waves in a laboratory environment. Experiments are performed in one of the largest wave tank facilities in the world. We present experimental evidence that the tail of the probability density function for wave height strongly depends on the Benjamin-Feir index (BFI)-i.e., the ratio between wave steepness and spectral bandwidth. While for a small BFI the probability density functions obtained experimentally are consistent with the Rayleigh distribution, for a large BFI the Rayleigh distribution clearly underestimates the probability of large events. These results confirm experimentally the fact that large-amplitude waves in random spectra may result from the modulational instability.
Scholz, John-Robert; Barruol, Guilhem; Fontaine, Fabrice R.; Sigloch, Karin
2016-04-01
To image the upper mantle structure beneath La Réunion hotspot, a large-scale seismic network has been deployed on land and at sea in the frame of the RHUM-RUM project (Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel). This French-German passive seismic experiment was designed to investigate and image the deep structure beneath La Réunion, from crust to core, to precise the shape and depth origin of a mantle plume, if any, and to precise the horizontal and vertical mantle flow associated to a possible plume upwelling, to its interaction with the overlying plate and with the neighboring Indian ridges. For this purpose, 57 Ocean-Bottom Seismometers (OBS) were installed around La Réunion and along the Central and Southwest Indian ridges. Broad-band instruments were deployed with the French R/V Marion Dufresne in late 2012 (cruise MD192), and recovered 13 months later by the German R/V Meteor (cruise M101). The pool of OBS was complemented by ~60 terrestrial stations, installed on different islands in the western Indian Ocean, such as La Réunion, Madagascar, Mauritius, Seychelles, Mayotte and the Îles Éparses in the Mozambique channel. The OBS installation is a free-fall down to the seafloor, where they landed in an unknown orientation. Since seismologic investigations of crustal and upper mantle structure (e.g., receiver functions) and azimuthal anisotropy (e.g., SKS-splitting and Rayleigh waves) rely on the knowledge of the correct OBS orientation with respect to the geographic reference frame, it is of importance to determine the orientations of the OBS while recording on the seafloor. In an isotropic, horizontally homogeneous and non-dipping layered globe, the misorientation of each station refers to the offset between theoretical and recorded back-azimuth angle of a passive seismic event. Using large earthquakes (MW > 5.0), it is possible to establish multiple successful measurements per station and thus to determine with good confidence the
Golenitskii, K. Â. Yu.; Koshelev, K. Â. L.; Bogdanov, A. Â. A.
2016-10-01
In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states—we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.
Golenitskii, K U; Bogdanov, A A
2016-01-01
In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states - we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.
Huajian Yao
2015-01-01
Seismic anisotropy provides important constraints on deformation patterns of Earth's material.Rayleigh wave dispersion data with azimuthal anisotropy can be used to invert for depth-dependent shear wavespeed azimuthal anisotropy,therefore reflecting depth-varying deformation patterns in the crust and upper mantle.In this study,we propose a two-step method that uses the Neighborhood Algorithm (NA) for the point-wise inversion of depth-dependent shear wavespeeds and azimuthal anisotropy from Rayleigh wave azimuthally anisotropic dispersion data.The first step employs the NA to estimate depthdependent Vsv (or the elastic parameter L) as well as their uncertainties from the isotropic part Rayleigh wave dispersion data.In the second step,we first adopt a difference scheme to compute approximate Rayleigh-wave phase velocity sensitivity kernels to azimuthally anisotropic parameters with respect to the velocity model obtained in the first step.Then we perform the NA to estimate the azi.muthally anisotropic parameters Gc/L and Gs/L at depths separately from the corresponding cosine and sine terms of the azimuthally anisotropic dispersion data.Finally,we compute the depth-dependent magnitude and fast polarization azimuth of shear wavespeed azimuthal anisotropy.The use of the global search NA and Bayesian analysis allows for more reliable estimates of depth-dependent shear wavespeeds and azimuthal anisotropy as well as their uncertainties.We illustrate the inversion method using the azimuthally anisotropic dispersion data in SE Tibet,where we find apparent changes of fast axes of shear wavespeed azimuthal anisotropy between the crust and uppermost mantle.
Duquennoy, Marc; Ouaftouh, Mohammadi; Ourak, Mohamed; Jenot, Frédéric
2002-06-01
The characterization of stress states in materials is often necessary in some industrial application. The ultrasonic methods can be potentially convenient since stress states inside materials can be obtained even if materials are opaque. Nevertheless, the knowledge of acousto-elastic coefficients is generally necessary to estimate residual stresses by ultrasonic methods, but the experimental determination of these acousto-elastic coefficients can be difficult in some cases. In this paper, Rayleigh wave (RW) acousto-elastic coefficients of an orthotropic material are theoretically determined according to its characteristics, i.e. the density and the secondand third-order elastic constants. Then, these RW acousto-elastic coefficients are directly measured during an experimental stage and a comparison between calculated and measured coefficients is realized. This study allows on the one hand to check the theoretical development and on the other hand to show that it is possible to calculate acousto-elastic coefficients theoretically from intrinsic characteristics of the material rather than measuring them directly during a calibration phase which is sometimes long and difficult to realize.
Azimuthal anisotropy of Rayleigh waves beneath the Tibetan Plateau and adjacent areas
2008-01-01
The crustal and upper mantle azimuthal anisotropy of the Tibetan Plateau and adjacent areas was studied by Rayleigh wave tomography. We collected sufficient broadband digital seismograms trav-ersing the Tibetan Plateau and adjacent areas from available stations, including especially some data from the temporary stations newly deployed in Yunnan, eastern Tibet, and western Sichuan. They made an adequate path coverage in most regions to achieve a reasonable resolution for the inversion. The model resolution tests show that the anisotropic features of scope greater than 400 km and strength greater than 2% are reliable. The azimuthal anisotropy pattern inside the Tibetan Plateau was similar to the characteristic of tectonic partition. The crustal anisotropy strength is greater than 2% in most re-gions of East Tibet, and the anisotropy shows clockwise rotation surrounding the eastern Himalayan syntaxis. Vertically, the anisotropy direction indicates a coherent pattern within the upper crust, lower crust, and lithosphere mantle of the Tibetan Plateau, which also is consistent with GPS velocity field and SKS fast polarization directions. The result supports that the crust-mantle deformation beneath the Tibetan Plateau is vertically coherent. The anisotropy strength of crust and lithospheric upper mantle in Yunnan outside the Tibetan Plateau is lower than 2%, so SKS splitting from core-mantle boundary to station should largely be attributed to the anisotropy of asthenosphere.
Azimuthal anisotropy of Rayleigh waves beneath the Tibetan Plateau and adjacent areas
SU Wei; WANG ChunYong; HUANG ZhongXian
2008-01-01
The crustal and upper mantle azimuthal anisotropy of the Tibetan Plateau and adjacent areas was studied by Rayleigh wave tomography. We collected sufficient broadband digital seismograms traversing the Tibetan Plateau and adjacent areas from available stations, including especially some data from the temporary stations newly deployed in Yunnan, eastern Tibet, and western Sichuan. They made an adequate path coverage in most regions to achieve a reasonable resolution for the inversion. The model resolution tests show that the anisotropic features of scope greater than 400 km and strength greater than 2% are reliable. The azimuthal anisotropy pattern inside the Tibetan Plateau was similar to the characteristic of tectonic partition. The crustal anisotropy strength is greater than 2% in most regions of East Tibet, and the anisotropy shows clockwise rotation surrounding the eastern Himalayan syntaxis. Vertically, the anisotropy direction indicates a coherent pattern within the upper crust, lower crust, and lithosphere mantle of the Tibetan Plateau, which also is consistent with GPS velocity field and SKS fast polarization directions. The result supports that the crust-mantle deformation beneath the Tibetan Plateau is vertically coherent. The anisotropy strength of crust and lithospheric upper mantle in Yunnan outside the Tibetan Plateau is lower than 2%, so SKS splitting from core-mantle boundary to station should largely be attributed to the anisotropy of asthenosphere.
Fang, Hongjian; Zhang, Haijiang; Yao, Huajian; Allam, Amir; Zigone, Dimitri; Ben-Zion, Yehuda; Thurber, Clifford; vanÂ derÂ Hilst, Robert D.
2016-05-01
We introduce a new algorithm for joint inversion of body wave and surface wave data to get better 3-D P wave (Vp) and S wave (Vs) velocity models by taking advantage of the complementary strengths of each data set. Our joint inversion algorithm uses a one-step inversion of surface wave traveltime measurements at different periods for 3-D Vs and Vp models without constructing the intermediate phase or group velocity maps. This allows a more straightforward modeling of surface wave traveltime data with the body wave arrival times. We take into consideration the sensitivity of surface wave data with respect to Vp in addition to its large sensitivity to Vs, which means both models are constrained by two different data types. The method is applied to determine 3-D crustal Vp and Vs models using body wave and Rayleigh wave data in the Southern California plate boundary region, which has previously been studied with both double-difference tomography method using body wave arrival times and ambient noise tomography method with Rayleigh and Love wave group velocity dispersion measurements. Our approach creates self-consistent and unique models with no prominent gaps, with Rayleigh wave data resolving shallow and large-scale features and body wave data constraining relatively deeper structures where their ray coverage is good. The velocity model from the joint inversion is consistent with local geological structures and produces better fits to observed seismic waveforms than the current Southern California Earthquake Center (SCEC) model.
Surface Waves on Metamaterials Interfaces
Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee
2016-01-01
We analyze surface electromagnetic waves supported at the interface between isotropic medium and effective anisotropic material that can be realized by alternating conductive and dielectrics layers. This configuration can host various types of surface waves and therefore can serve as a rich platf...
Surface Waves on Metamaterials Interfaces
Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee;
2016-01-01
We analyze surface electromagnetic waves supported at the interface between isotropic medium and effective anisotropic material that can be realized by alternating conductive and dielectrics layers. This configuration can host various types of surface waves and therefore can serve as a rich platf...
Surface acoustic wave microfluidics.
Ding, Xiaoyun; Li, Peng; Lin, Sz-Chin Steven; Stratton, Zackary S; Nama, Nitesh; Guo, Feng; Slotcavage, Daniel; Mao, Xiaole; Shi, Jinjie; Costanzo, Francesco; Huang, Tony Jun
2013-09-21
The recent introduction of surface acoustic wave (SAW) technology onto lab-on-a-chip platforms has opened a new frontier in microfluidics. The advantages provided by such SAW microfluidics are numerous: simple fabrication, high biocompatibility, fast fluid actuation, versatility, compact and inexpensive devices and accessories, contact-free particle manipulation, and compatibility with other microfluidic components. We believe that these advantages enable SAW microfluidics to play a significant role in a variety of applications in biology, chemistry, engineering and medicine. In this review article, we discuss the theory underpinning SAWs and their interactions with particles and the contacting fluids in which they are suspended. We then review the SAW-enabled microfluidic devices demonstrated to date, starting with devices that accomplish fluid mixing and transport through the use of travelling SAW; we follow that by reviewing the more recent innovations achieved with standing SAW that enable such actions as particle/cell focusing, sorting and patterning. Finally, we look forward and appraise where the discipline of SAW microfluidics could go next.
Knapmeyer-Endrun, Brigitte; Golombek, Matthew P.; Ohrnberger, Matthias
2016-10-01
The SEIS (Seismic Experiment for Interior Structure) instrument onboard the InSight mission will be the first seismometer directly deployed on the surface of Mars. From studies on the Earth and the Moon, it is well known that site amplification in low-velocity sediments on top of more competent rocks has a strong influence on seismic signals, but can also be used to constrain the subsurface structure. Here we simulate ambient vibration wavefields in a model of the shallow sub-surface at the InSight landing site in Elysium Planitia and demonstrate how the high-frequency Rayleigh wave ellipticity can be extracted from these data and inverted for shallow structure. We find that, depending on model parameters, higher mode ellipticity information can be extracted from single-station data, which significantly reduces uncertainties in inversion. Though the data are most sensitive to properties of the upper-most layer and show a strong trade-off between layer depth and velocity, it is possible to estimate the velocity and thickness of the sub-regolith layer by using reasonable constraints on regolith properties. Model parameters are best constrained if either higher mode data can be used or additional constraints on regolith properties from seismic analysis of the hammer strokes of InSight's heat flow probe HP3 are available. In addition, the Rayleigh wave ellipticity can distinguish between models with a constant regolith velocity and models with a velocity increase in the regolith, information which is difficult to obtain otherwise.
Investigation into Mass Loading Sensitivity of Sezawa Wave Mode-Based Surface Acoustic Wave Sensors
N. Ramakrishnan
2013-02-01
Full Text Available In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW device is investigated through finite element method (FEM simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered SAW resonator is considered for the simulation study. Initially the occurrence of Sezawa wave mode and displacement amplitude of the Rayleigh and Sezawa wave mode is studied for lower ZnO film thickness. Further, a thin film made of an arbitrary material is coated over the ZnO surface and the resonance frequency shift caused by mass loading of the film is estimated. It was observed that Sezawa wave mode shows significant sensitivity to change in mass loading and has higher sensitivity (eight times higher than Rayleigh wave mode for the same device configuration. Further, the mass loading sensitivity was observed to be greater for a low ZnO film thickness to wavelength ratio. Accordingly, highly sensitive SAW sensors can be developed by coating a sensing medium over a layered SAW device and operating at Sezawa mode resonance frequency. The sensitivity can be increased by tuning the ZnO film thickness to wavelength ratio.
Investigation into mass loading sensitivity of sezawa wave mode-based surface acoustic wave sensors.
Mohanan, Ajay Achath; Islam, Md Shabiul; Ali, Sawal Hamid; Parthiban, R; Ramakrishnan, N
2013-02-06
In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW) device is investigated through finite element method (FEM) simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered SAW resonator is considered for the simulation study. Initially the occurrence of Sezawa wave mode and displacement amplitude of the Rayleigh and Sezawa wave mode is studied for lower ZnO film thickness. Further, a thin film made of an arbitrary material is coated over the ZnO surface and the resonance frequency shift caused by mass loading of the film is estimated. It was observed that Sezawa wave mode shows significant sensitivity to change in mass loading and has higher sensitivity (eight times higher) than Rayleigh wave mode for the same device configuration. Further, the mass loading sensitivity was observed to be greater for a low ZnO film thickness to wavelength ratio. Accordingly, highly sensitive SAW sensors can be developed by coating a sensing medium over a layered SAW device and operating at Sezawa mode resonance frequency. The sensitivity can be increased by tuning the ZnO film thickness to wavelength ratio.
何正勤; 丁志峰; 叶太兰; 孙为国; 张乃铃
2002-01-01
Based on the long period digital surface wave data recorded by 11 CDSN stations and 11 IRIS stations, the dispersion curves of the group velocities of fundamental mode Rayleigh waves along 647 paths, with the periods from 10 s to 92 s, were measured by multi-filter. Their distribution at 25 central periods within the region of 18((54(N, 70(~140(E was inverted by Dimtar-Yanovskaya method. Within the period from 10 s to 15.9 s, the group velocity distribution is laterally inhomogeneous and is closely related to geotectonic units, with two low velocity zones located in the Tarim basin and the East China Sea and its north regions, respectively. From 21 s to 33 s, the framework of tectonic blocks is revealed. From 36.6 s to 40 s, the lithospheric subdivision of the Chinese mainland is obviously uncovered, with distinct boundaries among the South-North seismic belt, the Tibetan plateau, the North China, the South China and the Northeast China. Four cross-sections of group velocity distribution with period along 30(N, 38(N, 90(E and 120(E, are discussed, respectively, which display the basic features of the crust and upper mantle of the Chinese mainland and its neighboring regions. There are distinguished velocity differences among the different tectonic blocks. There are low-velocity-zones (LVZ) in the middle crust of the eastern Tibetan plateau, high velocity featured as stable platform in the Tarim basin and the Yangtze platform, shallow and thick low-velocity-zone in the upper mantle of the North China. The upper mantle LVZ in the East China Sea and the Japan Sea is related to the frictional heat from the subduction of the Philippine slab and the strong extension since the Himalayan orogenic period.
Modeling and Control Of Surface Acoustic Wave Motors
Feenstra, P.J.
2005-01-01
This thesis introduces Rayleigh waves and describes the generation of Rayleigh waves. Furthermore, the principle of operation of a SAW motor is analyzed. The analysis is based on a contact model, which describes the behavior between slider and stator. Due to the contact model, the microscopic and
Wave-equation dispersion inversion of surface waves recorded on irregular topography
Li, Jing
2017-08-17
Significant topographic variations will strongly influence the amplitudes and phases of propagating surface waves. Such effects should be taken into account, otherwise the S-velocity model inverted from the Rayleigh dispersion curves will contain significant inaccuracies. We now show that the recently developed wave-equation dispersion inversion (WD) method naturally takes into account the effects of topography to give accurate S-velocity tomograms. Application of topographic WD to demonstrates that WD can accurately invert dispersion curves from seismic data recorded over variable topography. We also apply this method to field data recorded on the crest of mountainous terrain and find with higher resolution than the standard WD tomogram.
Analysis shear wave velocity structure obtained from surface wave methods in Bornova, Izmir
Pamuk, Eren, E-mail: eren.pamuk@deu.edu.tr; Akgün, Mustafa, E-mail: mustafa.akgun@deu.edu.tr [Department of Geophysical Engineering, Dokuz Eylul University, Izmir (Turkey); Özdağ, Özkan Cevdet, E-mail: cevdet.ozdag@deu.edu.tr [Dokuz Eylul University Rectorate, Izmir (Turkey)
2016-04-18
Properties of the soil from the bedrock is necessary to describe accurately and reliably for the reduction of earthquake damage. Because seismic waves change their amplitude and frequency content owing to acoustic impedance difference between soil and bedrock. Firstly, shear wave velocity and depth information of layers on bedrock is needed to detect this changing. Shear wave velocity can be obtained using inversion of Rayleigh wave dispersion curves obtained from surface wave methods (MASW- the Multichannel Analysis of Surface Waves, ReMi-Refraction Microtremor, SPAC-Spatial Autocorrelation). While research depth is limeted in active source study, a passive source methods are utilized for deep depth which is not reached using active source methods. ReMi method is used to determine layer thickness and velocity up to 100 m using seismic refraction measurement systems.The research carried out up to desired depth depending on radius using SPAC which is utilized easily in conditions that district using of seismic studies in the city. Vs profiles which are required to calculate deformations in under static and dynamic loads can be obtained with high resolution using combining rayleigh wave dispersion curve obtained from active and passive source methods. In the this study, Surface waves data were collected using the measurements of MASW, ReMi and SPAC at the İzmir Bornova region. Dispersion curves obtained from surface wave methods were combined in wide frequency band and Vs-depth profiles were obtained using inversion. Reliability of the resulting soil profiles were provided by comparison with theoretical transfer function obtained from soil paremeters and observed soil transfer function from Nakamura technique and by examination of fitting between these functions. Vs values are changed between 200-830 m/s and engineering bedrock (Vs>760 m/s) depth is approximately 150 m.
Tanimoto, Toshiro; Lin, Chin-Jen; Hadziioannou, Céline; Igel, Heiner; Vernon, Frank
2016-11-01
Using closely located seismographs at Piñon Flat (PFO), California, for 1 year long record (2015), we estimated the Rayleigh-to-Love wave energy ratio in the secondary microseism (0.1-0.35 Hz) in four seasons. Rayleigh wave energy was estimated from a vertical component seismograph. Love wave energy was estimated from rotation seismograms that were derived from a small array at PFO. Derived ratios are 2-2.5, meaning that there is 2-2.5 times more Rayleigh wave energy than Love wave energy at PFO. In our previous study at Wettzell, Germany, this ratio was 0.9-1.0, indicating comparable energy between Rayleigh waves and Love waves. This difference suggests that the Rayleigh-to-Love wave ratios in the secondary microseism may differ greatly from region to region. It also implies that an assumption of the diffuse wavefield is not likely to be valid for this low frequency range as the equipartition of energy should make this ratio much closer.
Rayleigh-Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries
Titarchuk, Lev
2002-01-01
Accretion onto compact objects in X-ray binaries (black hole, neutron star (NS), white dwarf) is characterized by non-uniform flow density profiles. Such an effect of heterogeneity in presence of gravitational forces and pressure gradients exhibits Rayleigh-Taylor gravity waves (RTGW). They should be seen as quasiperiodic wave oscillations (QPO) of the accretion flow in the transition (boundary) layer between the Keplerian disk and the central object. In this paper the author shows that the main QPO frequency, which is very close to the Keplerian frequency, is split into separate frequencies (hybrid and low branch) under the influence of the gravitational forces in the rotational frame of reference. The RTGWs must be present and the related QPOs should be detected in any system where the gravity, buoyancy and Coriolis force effects cannot be excluded (even in the Earth and solar environments). The observed low and high QPO frequencies are an intrinsic signature of the RTGW. The author elaborates the conditions for the density profile when the RTGW oscillations are stable. A comparison of the inferred QPO frequencies with QPO observations is presented. The author finds that hectohertz frequencies detected from NS binaries can be identified as the RTGW low branch frequencies. The author also predicts that an observer can see the double NS spin frequency during the NS long (super) burst events when the pressure gradients and buoyant forces are suppressed. The Coriolis force is the only force which acts in the rotational frame of reference and its presence causes perfect coherent pulsations with a frequency twice of the NS spin. The QPO observations of neutron binaries have established that the high QPO frequencies do not go beyond of the certain upper limit. The author explains this observational effect as a result of the density profile inversions. Also the author demonstrates that a particular problem of the gravity waves in the rotational frame of reference in the
Rayleigh beacon for measuring the surface profile of a radio telescope.
Padin, S
2014-12-01
Millimeter-wavelength Rayleigh scattering from water droplets in a cloud is proposed as a means of generating a bright beacon for measuring the surface profile of a radio telescope. A λ=3 mm transmitter, with an output power of a few watts, illuminating a stratiform cloud, can generate a beacon with the same flux as Mars in 10 GHz bandwidth, but the beacon has a narrow line width, so it is extremely bright. The key advantage of the beacon is that it can be used at any time, and positioned anywhere in the sky, as long as there are clouds.
Surface Wave Velocity-Stress Relationship in Uniaxially Loaded Concrete
Shokouhi, Parisa; Zoëga, Andreas; Wiggenhauser, Herbert
2012-01-01
loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface......The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave...... velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several...
Miao, W.; Li, G.; Niu, F.
2016-12-01
Knowledge on the 3D sediment structure beneath the Gulf of Mexico passive margin is not only important to explore the oil and gas resources in the area, but also essential to decipher the deep crust and mantle structure beneath the margin with teleseismic data. In this study, we conduct a joint inversion of Rayleigh wave ellipticity and phase velocity at 6-40 s to construct a 3-D S wave velocity model in a rectangular area of 100°-87° west and 28°-37° north. We use ambient noise data from a total of 215 stations of the Transportable Array deployed under the Earthscope project. Rayleigh wave ellipticity, or Rayleigh wave Z/H (vertical to horizontal) amplitude ratio is mostly sensitive to shallow sediment structure, while the dispersion data are expected to have reasonably good resolution to uppermost mantle depths. The Z/H ratios measured from stations inside the Gulf Coastal Plain are distinctly lower in comparison with those measured from the inland stations. We also measured the phase velocity dispersion from the same ambient noise dataset. Our preliminary 3-D model is featured by strong low-velocity anomalies at shallow depth, which are spatially well correlated with Gulf Cost, East Texas, and the Lower Mississippi basins. We will discuss other features of the 3-D models once the model is finalized.
Rayleigh-wave Tomography and Seismic Anisotropic Structures in the Region of the Philippine Sea
Lee, Hsin-Yu; Legendre, Cédric P.; Chang, Emmy T. Y.
2016-04-01
The Philippine Sea Plate (PSP) is surrounded by convergent boundaries, the Pacific plate is subducting beneath the PSP along the Izu-Bonin and Mariana trenches at the east, whereas the PSP is subducting beneath the Eurasian plate along the Nankai trough, Ryukyu trench and Philippine trench at the west. The PSP can be divided by three oceanic basins: the oldest West Philippine basin developing in 35-45 Ma in the west, and the Shikoku and Parece Vela basins in 15-30 Ma in the east. Previous studies show a large variety of the seismic anisotropy structures in the region of the PSP, which correspond different scenarios of tectonic evolution for this area. In this study, we analyze both isotropic and anisotropic Rayleigh-wave velocity structures of the PSP by means of two-station method. The earthquakes of magnitude (Mw) greater than 5.0 in-between the years 1998-2014 were acquired. Totally, 7914 teleseismic events are adopted to form the measurements of Rayleigh-wave dispersion curves along 467 station-pairs over the PSP. The measured dispersion curves are then inverted into the isotropic and azimuthally anisotropic (2ψ) velocity maps at different periods with the damped, lateral smoothing LSQR inversion. The inversion is framed by the triangular grids which knots are of 200 km spacing. The consequent velocity anomalies are referenced to the average of the phase velocity at the periods between 50 and 100 seconds. The resulting velocity anomalies show a consistent pattern with the locations of the sub-basins in the PSP at the periods of 50 and 60 sec, which can be considered to be the association of lithospheric velocity structure with basin ages. The positive velocity anomalies are seen in the West Philippine basin associating the relatively old lithosphere; whereas the negative anomalies are found in the Shikoku and Parece Vela basins which the lithospheric structures are relatively young. On the other hand, the resultant azimuthal anisotropy reveals an apparent
Soomro, R. A.; Weidle, C.; Cristiano, L.; Lebedev, S.; Meier, T.; Passeq Working Group
2016-01-01
The increasingly dense coverage of Europe with broad-band seismic stations makes it possible to image its lithospheric structure in great detail, provided that structural information can be extracted effectively from the very large volumes of data. We develop an automated technique for the measurement of interstation phase velocities of (earthquake-excited) fundamental-mode surface waves in very broad period ranges. We then apply the technique to all available broad-band data from permanent and temporary networks across Europe. In a new implementation of the classical two-station method, Rayleigh and Love dispersion curves are determined by cross-correlation of seismograms from a pair of stations. An elaborate filtering and windowing scheme is employed to enhance the target signal and makes possible a significantly broader frequency band of the measurements, compared to previous implementations of the method. The selection of acceptable phase-velocity measurements for each event is performed in the frequency domain, based on a number of fine-tuned quality criteria including a smoothness requirement. Between 5 and 3000 single-event dispersion measurements are averaged per interstation path in order to obtain robust, broad-band dispersion curves with error estimates. In total, around 63,000 Rayleigh- and 27,500 Love-wave dispersion curves between 10 and 350 s have been determined, with standard deviations lower than 2 per cent and standard errors lower than 0.5 per cent. Comparisons of phase-velocity measurements using events at opposite backazimuths and the examination of the variance of the phase-velocity curves are parts of the quality control. With the automated procedure, large data sets can be consistently and repeatedly measured using varying selection parameters. Comparison of average interstation dispersion curves obtained with different degrees of smoothness shows that rough perturbations do not systematically bias the average dispersion measurement. They
Petrescu, Laura; Darbyshire, Fiona; Bastow, Ian; Totten, Eoghan; Gilligan, Amy
2017-05-01
The thick, seismically fast lithospheric keels underlying continental cores (cratons) are thought to have formed in the Precambrian and resisted subsequent tectonic destruction. A consensus is emerging from a variety of disciplines that keels are vertically stratified, but the processes that led to their development remain uncertain. Eastern Canada is a natural laboratory to study Precambrian lithospheric formation and evolution. It comprises the largest Archean craton in the world, the Superior Craton, surrounded by multiple Proterozoic orogenic belts. To investigate its lithospheric structure, we construct a frequency-dependent anisotropic seismic model of the region using Rayleigh waves from teleseismic earthquakes recorded at broadband seismic stations across eastern Canada. The joint interpretation of phase velocity heterogeneity and azimuthal anisotropy patterns reveals a seismically fast and anisotropically complex Superior Craton. The upper lithosphere records fossilized Archean tectonic deformation: anisotropic patterns align with the orientation of the main tectonic boundaries at periods ≤110 s. This implies that cratonic blocks were strong enough to sustain plate-scale deformation during collision at 2.5 Ga. Cratonic lithosphere with fossil anisotropy partially extends beneath adjacent Proterozoic belts. At periods sensitive to the lower lithosphere, we detect fast, more homogenous, and weakly anisotropic material, documenting postassembly lithospheric growth, possibly in a slow or stagnant convection regime. A heterogeneous, anisotropic transitional zone may also be present at the base of the keel. The detection of multiple lithospheric fabrics at different periods with distinct tectonic origins supports growing evidence that cratonization processes may be episodic and are not exclusively an Archean phenomenon.
Lateral Variations of Rayleigh-Wave Dispersions in the Philippine Sea Region
Wen-Yen Chang
2007-01-01
Full Text Available Fresh two-dimensional group and phase-velocity distribution maps of the Philippine Sea and surrounding areas are constructed using the tomographic inversion of more than 2500 Rayleigh-wave dispersion curves in the 20- to 120-sec period range. The results show that, for the periods used, both the group and phase-velocity variation patterns are very close to the geological and topographic features and are also consistent with previous studies of magnetic anomalies and evolutionary history of the Philippine Basin. On average, the periods of the peak group-velocity for the West Philippine Basin and the Oki-Daito ridge are about 40 and 32 sec for the Parece Vela and Shikoku basins. This implies that the lithosphere of the western Philippine Sea Basin is thicker, which is related to plate cooling and seafloor age. For most of the examined periods, the high velocity symmetry of the two sides of the Central Basin Ridge in the West Philippine Basin coincides well with the evolutionary history of the Philippine Sea Basin, and may be taken as additional evidence confirming the existence of the ridge. The group and phase-velocity distributions for periods longer than 80 sec are smooth throughout the whole Philippine Sea Basin, which implies that the upper mantle beneath the Philippine Sea Basin is nearly homogeneous at depths of 100 - 200 km. Moreover, the group and phase velocities in the region of the East Volcano Belt and Active Marginal Basin remain almost constant in the 36- to 80-sec period range, which indicates that the boundary between the lithosphere and asthenosphere is probably not obvious in this area.
Rayleigh Wave Phase Velocity in the Upper Mantle Beneath the Indian Ocean
Godfrey, K. E.; Dalton, C. A.; Ritsema, J.
2016-12-01
Most of what is currently understood about the seismic properties of oceanic upper mantle is based on either global studies or regional studies of the upper mantle beneath the Pacific Ocean. However, global seismic models and geochemical studies of mid-ocean ridge basalts indicate differences in the properties of the upper mantle beneath the Pacific, Atlantic, and Indian oceans. Though the Indian Ocean is not as well studied seismically, it is host to a number of geologically interesting features including 16,000 km of mid-ocean ridge with a range of spreading rates from 14 mm/yr along the Southwest Indian Ridge to 55-75 mm/yr along the Southeast Indian Ridge. The Indian Ocean also contains multiple volcanic hotspots, the Australian-Antarctic Discordance, and a low geoid anomaly south of India, and it overlies a portion of a large low-shear-velocity province. We are using Rayleigh waves to construct a high-resolution seismic velocity model of the Indian Ocean upper mantle. We utilize a global dataset of phase delays measured at 20 periods, between 37 and 375 seconds; the dataset includes between 700 and 20,000 that traverse our study region exclusively, with a larger number of paths at shorter periods. We explore variations in phase velocity using two separate approaches. One, we allow phase velocity to vary only as a function of seafloor age. Two, we perform a damped least-squares inversion to solve for 2-D phase velocity maps at each period. Preliminary results indicate low velocities along the Southeast Indian Ridge and Central Indian Ridge, but the expected low velocities are less apparent along the slow-spreading Southwest Indian Ridge. We observe a region of fast velocities extending from Antarctica northward between the Kerguelen and Crozet hotspots, and lower than expected velocities beneath the Reunion hotspot. Additionally, we find low velocities associated with a region of extinct seafloor spreading in the Wharton basin.
Workman, Eli; Lin, Fan-Chi; Koper, Keith D.
2017-01-01
We present a single station method for the determination of Rayleigh wave ellipticity, or Rayleigh wave horizontal to vertical amplitude ratio (H/V) using Frequency Dependent Polarization Analysis (FDPA). This procedure uses singular value decomposition of 3-by-3 spectral covariance matrices over 1-hr time windows to determine properties of the ambient seismic noise field such as particle motion and dominant wave-type. In FPDA, if the noise is mostly dominated by a primary singular value and the phase difference is roughly 90° between the major horizontal axis and the vertical axis of the corresponding singular vector, we infer that Rayleigh waves are dominant and measure an H/V ratio for that hour and frequency bin. We perform this analysis for all available data from the Earthscope Transportable Array between 2004 and 2014. We compare the observed Rayleigh wave H/V ratios with those previously measured by multicomponent, multistation noise cross-correlation (NCC), as well as classical noise spectrum H/V ratio analysis (NSHV). At 8 s the results from all three methods agree, suggesting that the ambient seismic noise field is Rayleigh wave dominated. Between 10 and 30 s, while the general pattern agrees well, the results from FDPA and NSHV are persistently slightly higher (˜2 per cent) and significantly higher (>20 per cent), respectively, than results from the array-based NCC. This is likely caused by contamination from other wave types (i.e. Love waves, body waves, and tilt noise) in the single station methods, but it could also reflect a small, persistent error in NCC. Additionally, we find that the single station method has difficulty retrieving robust Rayleigh wave H/V ratios within major sedimentary basins, such as the Williston Basin and Mississippi Embayment, where the noise field is likely dominated by reverberating Love waves and tilt noise.
Sridharan, S. [National Atmospheric Research Lab., Chittoor (India); Sathishkumar, S.; Gurubaran, S. [Indian Inst. of Geomagnetism, Tirunelveli (India). Equatorial Geophysical Research Lab.
2008-07-01
Three nights of simultaneous Rayleigh lidar temperature measurements over Gadanki (13.5 N,79.2 E) and medium frequency (MF) radar wind measurements over Tirunelveli (8.7 N,77.8 E) have been analyzed to illustrate the possible effects due to tidal-gravity wave interactions on upper mesospheric inversion layers. The occurrence of tidal gravity wave interaction is investigated using MF radar wind measurements in the altitude region 86-90 km. Of the three nights, it is found that tidal gravity wave interaction occurred in two nights. In the third night, diurnal tidal amplitude is found to be significantly larger. As suggested in Sica et al. (2007), mesospheric temperature inversion seems to be a signature of wave saturation in the mesosphere, since the temperature inversion occurs at heights, when the lapse rate is less than half the dry adiabatic lapse rate. (orig.)
Sridharan, S.; Sathishkumar, S.; Gurubaran, S.
2008-11-01
Three nights of simultaneous Rayleigh lidar temperature measurements over Gadanki (13.5° N, 79.2° E) and medium frequency (MF) radar wind measurements over Tirunelveli (8.7° N, 77.8° E) have been analyzed to illustrate the possible effects due to tidal-gravity wave interactions on upper mesospheric inversion layers. The occurrence of tidal gravity wave interaction is investigated using MF radar wind measurements in the altitude region 86 90 km. Of the three nights, it is found that tidal gravity wave interaction occurred in two nights. In the third night, diurnal tidal amplitude is found to be significantly larger. As suggested in Sica et al. (2007), mesospheric temperature inversion seems to be a signature of wave saturation in the mesosphere, since the temperature inversion occurs at heights, when the lapse rate is less than half the dry adiabatic lapse rate.
Rayleigh-Lamb wave propagation on a fractional order viscoelastic plate.
Meral, F Can; Royston, Thomas J; Magin, Richard L
2011-02-01
A previous study of the authors published in this journal focused on mechanical wave motion in a viscoelastic material representative of biological tissue [Meral et al., J. Acoust. Soc. Am. 126, 3278-3285 (2009)]. Compression, shear and surface wave motion in and on a viscoelastic halfspace excited by surface and sub-surface sources were considered. It was shown that a fractional order Voigt model, where the rate-dependent damping component that is dependent on the first derivative of time is replaced with a component that is dependent on a fractional derivative of time, resulted in closer agreement with experiment as compared with conventional (integer order) models, such as those of Voigt and Zener. In the present study, this analysis is extended to another configuration and wave type: out-of-plane response of a viscoelastic plate to harmonic anti-symmetric Lamb wave excitation. Theoretical solutions are compared with experimental measurements for a polymeric tissue mimicking phantom material. As in the previous configurations the fractional order modeling assumption improves the match between theory and experiment over a wider frequency range. Experimental complexities in the present study and the reliability of the different approaches for quantifying the shear viscoelastic properties of the material are discussed.
Corchete, V.; Chourak, M.
2011-10-01
In this study, we present the lithospheric structure of the south-eastern part of the Iberian Peninsula by means of a set of 2D images of shear velocity, for depths ranging from 0 to 50 km. This goal will be attained by means of the inversion of the Rayleigh wave dispersion. For it, the traces of 25 earthquakes occurred on the neighbouring of the study area, from 2001 to 2003, will be considered. These earthquakes have been registered by 11 broadband stations located on Iberia. All seismic events have been grouped in source zones to get an average dispersion curve for each source-station path. The dispersion curves have been measured for periods between 2 and 45 s, by combination of two digital filtering techniques: Multiple Filter Technique and Time Variable Filtering. The resulting set of source-station averaged dispersion curves has been inverted according to the generalized inversion theory, to get S-wave velocity models for each source-station path. Later, these models have been interpolated using the method of kriging, to obtain a 2D mapping of the S-wave velocity structure for the south-eastern part of Iberia. The results presented in this paper show that the techniques used here are a powerful tool to investigate the crust and upper mantle structure, through the dispersion analysis and its inversion to obtain shear velocity distributions with depth. By means of this analysis, principal structural features of the south-eastern part of Iberia, such as the existence of lateral and vertical heterogeneity in the whole study area, or the location of the Moho discontinuity at 30 km of depth (with an average S-velocity of uppermost mantle of 4.7 km/s), have been revealed. Other important structural features revealed by this analysis have been that the uppermost of Iberian massif shows higher velocity values than the uppermost of the Alpine domain, indicating that the massif is old and tectonically stable. The average velocity of the crust in Betic cordillera is of
Study of Magnetohydrodynamic Surface Waves on Liquid Gallium
Hantao Ji; William Fox; David Pace; H.L. Rappaport
2004-05-13
Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak, waves are weakly damped and the real part of the dispersion is unaffected, while in the opposite limit waves are strongly damped with shortened wavelengths. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A non-invasive diagnostic accurately measures surface waves at multiple locations by reflecting an array of lasers off the surface onto a screen, which is recorded by an Intensified-CCD camera. The measured dispersion relation is consistent with the linear theory with a reduced surface tension likely due to surface oxidation. In excellent agreement with linear theory, it is observed that surface waves are damped only when a horizontal magnetic field is imposed parallel to the propagation direction. No damping is observed under a perpendicular magnetic field. The existence of strong wave damping even without magnetic field suggests the importance of the surface oxide layer. Implications to the liquid metal wall concept in fusion reactors, especially on the wave damping and a Rayleigh-Taylor instability when the Lorentz force is used to support liquid metal layer against gravity, are discussed.
Drops subjected to surface acoustic waves: flow dynamics
Brunet, Philippe; Baudoin, Michael; Bou Matar, Olivier; Dynamique Des Systèmes Hors Equilibre Team; Aiman-Films Team
2012-11-01
Ultrasonic acoustic waves of frequency beyond the MHz are known to induce streaming flow in fluids that can be suitable to perform elementary operations in microfluidics systems. One of the currently appealing geometry is that of a sessile drop subjected to surface acoustic waves (SAW). Such Rayleigh waves produce non-trival actuation in the drop leading to internal flow, drop displacement, free-surface oscillations and atomization. We recently carried out experiments and numerical simulations that allowed to better understand the underlying physical mechanisms that couple acoustic propagation and fluid actuation. We varied the frequency and amplitude of actuation, as well as the properties of the fluid, and we measured the effects of these parameters on the dynamics of the flow. We compared these results to finite-elements numerical simulations.
Petrescu, L.; Darbyshire, F. A.; Gilligan, A.; Bastow, I. D.; Totten, E. J.
2015-12-01
Cratons are Precambrian continental nuclei that are geologically distinct from modern continental regions and are typically underlain by seismically fast lithospheric roots (keels) to at least 200 km depth. Both plate and non-plate tectonic origin theories such as stacking of subducted slabs or multiple mantle plume underplating have been proposed to explain keel growth.Eastern Canada is an ideal continental region to investigate cratonization processes and the onset of plate tectonics. It comprises part of the largest Archean craton in the world, the Superior Province, flanked by a ~1.1 Ga Himalayan-scale orogenic belt, the Grenville Province, and the 500-300 Ma old Appalachian orogenic province, following the same general SW-NE axial trend. The region is also cross-cut by the Great Meteor Hotspot track, providing an excellent opportunity to study the interaction of hotspot tectonism with progressively younger lithospheric domains.We investigate the lithospheric structure of Precambrian Eastern Canada using teleseismic earthquake data recorded at permanent and temporary networks. We measure interstation dispersion curves of Rayleigh wave phase velocities between ~15 and 220 s, and compare the results to standard continental and cratonic reference models. We combine the dispersion curves via a tomographic inversion which solves for isotropic phase velocity heterogeneity and azimuthal anisotropy across the region at a range of periods. The phase velocity maps indicate variations in lithospheric properties from the heart of the Superior craton to the SE Canadian coast.The new regional-scale models will help to understand the processes that generated, stabilized and reworked the cratonic roots through their billion-year tectonic history. We investigate how surface tectonic boundaries relate to deeper lithospheric structural changes, and consider the effects of the multiple Wilson cycles that affected Laurentia.
Ultrasonic phased array with surface acoustic wave for imaging cracks
Ohara, Yoshikazu; Oshiumi, Taro; Nakajima, Hiromichi; Yamanaka, Kazushi; Wu, Xiaoyang; Uchimoto, Tetsuya; Takagi, Toshiyuki; Tsuji, Toshihiro; Mihara, Tsuyoshi
2017-06-01
To accurately measure crack lengths, we developed a real-time surface imaging method (SAW PA) combining an ultrasonic phased array (PA) with a surface acoustic wave (SAW). SAW PA using a Rayleigh wave with a high sensitivity to surface defects was implemented for contact testing using a wedge with the third critical angle that allows the Rayleigh wave to be generated. Here, to realize high sensitivity imaging, SAW PA was optimized in terms of the wedge and the imaging area. The improved SAW PA was experimentally demonstrated using a fatigue crack specimen made of an aluminum alloy. For further verification in more realistic specimens, SAW PA was applied to stainless-steel specimens with a fatigue crack and stress corrosion cracks (SCCs). The fatigue crack was visualized with a high signal-to-noise ratio (SNR) and its length was measured with a high accuracy of better than 1 mm. The SCCs generated in the heat-affected zones (HAZs) of a weld were successfully visualized with a satisfactory SNR, although responses at coarse grains appeared throughout the imaging area. The SCC lengths were accurately measured. The imaging results also precisely showed complicated distributions of SCCs, which were in excellent agreement with the optically observed distributions.
M Subbiah; V Ganesh
2010-06-01
We consider the extended Rayleigh problem of hydrodynamic stability dealing with the stability of inviscid homogeneous shear flows in sea straits of arbitrary cross section. We prove a short wave stability result, namely, if $k>0$ is the wave number of a normal mode then $k>k_c$ (for some critical wave number $k_c$) implies the stability of the mode for a class of basic flows. Furthermore, if $K(z)=\\frac{-({U''}_0-T_0{U'}_0)}{U_0-U_{0s}}$, where $U_0$ is the basic velocity, $T_0$ (a constant) the topography and prime denotes differentiation with respect to vertical coordinate then we prove that a sufficient condition for the stability of basic flow is $0 < K(z)≤\\left(\\frac{^2}{D^2}+\\frac{T^2_0}{4}\\right)$, where the flow domain is $0≤ z≤ D$.
Ang, Kar M; Yeo, Leslie Y; Hung, Yew M; Tan, Ming K
2016-09-21
The deposition of a thin graphene film atop a chip scale piezoelectric substrate on which surface acoustic waves are excited is observed to enhance its performance for fluid transport and manipulation considerably, which can be exploited to achieve further efficiency gains in these devices. Such gains can then enable complete integration and miniaturization for true portability for a variety of microfluidic applications across drug delivery, biosensing and point-of-care diagnostics, among others, where field-use, point-of-collection or point-of-care functionality is desired. In addition to a first demonstration of vibration-induced molecular transport in graphene films, we show that the coupling of the surface acoustic wave gives rise to antisymmetric Lamb waves in the film which enhance molecular diffusion and hence the flow through the interstitial layers that make up the film. Above a critical input power, the strong substrate vibration displacement can also force the molecules out of the graphene film to form a thin fluid layer, which subsequently destabilizes and breaks up to form a mist of micron dimension aerosol droplets. We provide physical insight into this coupling through a simple numerical model, verified through experiments, and show several-fold improvement in the rate of fluid transport through the film, and up to 55% enhancement in the rate of fluid atomization from the film using this simple method.
Low power sessile droplet actuation via modulated surface acoustic waves
Baudoin, Michael; Matar, Olivier Bou; Herth, Etienne
2012-01-01
Low power actuation of sessile droplets is of primary interest for portable or hybrid lab-on-a-chip and harmless manipulation of biofluids. In this paper, we show that the acoustic power required to move or deform droplets via surface acoustic waves can be substantially reduced through the forcing of the drops inertio-capillary modes of vibrations. Indeed, harmonic, superharmonic and subharmonic (parametric) excitation of these modes are observed when the high frequency acoustic signal (19.5 MHz) is modulated around Rayleigh-Lamb inertio-capillary frequencies. This resonant behavior results in larger oscillations and quicker motion of the drops than in the non-modulated case.
A study of body-to-surface wave conversion associated with deep earthquakes
Shen, Z.; Ni, S.
2015-12-01
Understanding converted surface waves is helpful because they could improve the accuracy of earthquake location if the exacted scattered point is known as well as serve to image shallow structures with dispersion features. Previous studies have reported a few observations of body-to-surface-wave conversion associated with deep earthquakes. For example, Wagner and Langston used coda intensity analysis and f-k analysis to confirm a P-to-Rg wave and performed forward modeling with T-matrix method demonstrating that a 1km relief was responsible for the observed body-to-surface wave scattering. Moreover, Furumura et al. observed unusual Rayleigh waves converted from S wave observed at Australia with deep earthquakes occurred along Kermadec-Tonga trench and a 2D Pseudospetral method is adopted to illustrate that the Rayleigh waves could be explained by ridge structures. Both T-matrix and pseudospetral algorithms are based on numerical methods. However, we lack a theory to study the mechanism of those surface waves quantitatively. For instance, the relationship between the topography with the dominate frequency of converted surface waves could be resolved thoroughly with a theoretical approach. From this perspective, we carried out a theoretical method to calculate the converted Rayleigh wave with surface topography. During the calculation, a homogeneous half space medium is assumed and the path of the converted phase is divided into two segments. Firstly, we will introduce our theoretical method in detail and a comparison of our results and SEM results will be presented to verify our methods. Secondly, the topography effect and the transfer efficiency of P and S wave will be examined quantitatively with different source mechanisms. Then, we will report an observation of unusual large amplitude surface waves transferred from body waves at local stations. Our preliminary result shows that those anomalous waves are identified as Rayleigh wave and are probably generated by
Laser Generation of Surface Waves on Cylinder with a Slow Coating
ZHANG Shi-Gong; HU Wen-Xiang
2008-01-01
@@ An analytical model of acoustic field excited by a pulsed-laser line source on a coated cylinder is presented.Surface wave dispersive behaviours for a cylinder with a slow coating are analysed and compared with that of a bare cylinder.Based on this analysis, the laser-generated transient response of the perturbed Rayleigh wave and the higher modes of steel cylinder with a zinc coating are calculated from the model using residue theory and FFT technique.The theoretical result from the superposed waveform of the perturbed Rayleigh wave and higher modes agree well with the waveform obtained in experiment.The results show that the model and numerical method provide a useful technique for quantitatively characterizing coating parameters of coated cylinder by the laser generated surface waves.
Bagheri, Amirhossein; Greenhalgh, Stewart; Khojasteh, Ali; Rahimian, Mohammad
2015-10-01
The dispersion of interface waves is studied theoretically in a model consisting of a liquid layer of finite thickness overlying a transversely isotropic solid layer which is itself underlain by a transversely isotropic solid of dissimilar elastic properties. The method of potential functions and Hankel transformation was utilized to solve the equations of motion. Two frequency equations were developed: one for Love waves and the other for the remaining surface and interface waves. Numerical group and phase velocity dispersion curves were computed for four different classes of model, in which the substratum is stiffer or weaker than the overlying layer, and for various thickness combinations of the layers. Dispersion curves are presented for generalized Rayleigh, Scholte, Stoneley and Love waves, each of which are possible in all proposed models. They show the dependence of the velocity on layer thicknesses and material properties (elastic constants). Special cases involving zero thickness for the water layer or the solid layer, and/or isotropic material properties for the solid exhibit interesting features and agree favourably with previously published results for these simpler cases, thus validating the new formulation.
Krylov, V. V.
1995-09-01
A general phenomenological approach is given for the description of mechanical surface properties of solids and their influence on surface acoustic wave propogation. Surface properties under consideration may be changes of the stress distribution in subsurface atomic layers, the presence of adsorbed gas molecules, surface degradation as a result of impacts from an aggressive environment, damage due to mechanical manufacturing or polishing, deposition of thin films or liquid layers, surface corrugations, etc. If the characteristic thickness of the affected layers is much less than the wavelengths of the propagating surface waves, then the effects of all these irregularities can be described by means of non-classical boundary conditions incorporating the integral surface parameters such as surface tension, surface moduli of elasticity and surface mass density. The effect of surface properties on the propagation of Rayleigh surface waves is analysed in comparison with the results of traditional approaches, in particular with Auld's energy perturbation method. One of the important implications of the above-mentioned boudnary conditions is that they are adequate for the description of the effect of rarely distributed adsorbed atoms or molecules. This allows, in particular, to obtain a rigorous theoretical description of chemical sensors using surface acoustic waves and to derive analytical expressions for their sensitivity.
Ground Boundary Conditions for Thermal Convection Over Horizontal Surfaces at High Rayleigh Numbers
Hanjalić, K.; Hrebtov, M.
2016-07-01
We present "wall functions" for treating the ground boundary conditions in the computation of thermal convection over horizontal surfaces at high Rayleigh numbers using coarse numerical grids. The functions are formulated for an algebraic-flux model closed by transport equations for the turbulence kinetic energy, its dissipation rate and scalar variance, but could also be applied to other turbulence models. The three-equation algebraic-flux model, solved in a T-RANS mode ("Transient" Reynolds-averaged Navier-Stokes, based on triple decomposition), was shown earlier to reproduce well a number of generic buoyancy-driven flows over heated surfaces, albeit by integrating equations up to the wall. Here we show that by using a set of wall functions satisfactory results are found for the ensemble-averaged properties even on a very coarse computational grid. This is illustrated by the computations of the time evolution of a penetrative mixed layer and Rayleigh-Bénard (open-ended, 4:4:1 domain) convection, using 10 × 10 × 100 and 10 × 10 × 20 grids, compared also with finer grids (e.g. 60 × 60 × 100), as well as with one-dimensional treatment using 1 × 1 × 100 and 1 × 1 × 20 nodes. The approach is deemed functional for simulations of a convective boundary layer and mesoscale atmospheric flows, and pollutant transport over realistic complex hilly terrain with heat islands, urban and natural canopies, for diurnal cycles, or subjected to other time and space variations in ground conditions and stratification.
Prajapati, Ramprasad
2016-07-01
The Rayleigh-Taylor (R-T) instability is recently investigated is strongly coupled plasma looking to its importance in dense stellar systems and Inertial Confinement Fusion [1-3]. In the present work, the effect of quantum corrections are studied on Rayleigh-Taylor (R-T) instability and internal wave propagation in a strongly coupled, magnetized, viscoelastic fluid. The modified generalized hydrodynamic model is used to derive the analytical dispersion relation. The internal wave mode and dispersion relation are modified due to the presence of quantum corrections and viscoelastic effects. We observe that strong coupling effects and quantum corrections significantly modifies the dispersion characteristics. The dispersion relation is also discussed in weakly coupled (hydrodynamic) and strongly coupled (kinetic) limits. The explicit expression of R-T instability criterion is derived which is influenced by shear velocity and quantum corrections. Numerical calculations are performed in astrophysical and experimental relevance and it is examined that both the shear and quantum effects suppresses the growth rate of R-T instability. The possible application of the work is discussed in Inertial Confinement Fusion (ICF) to discuss the suppression of R-T instability under considered situation. References: [1] R. P. Prajapati, Phys. Plasmas 23, 022106 (2016). [2] K. Avinash and A. Sen, Phys. Plasmas 22, 083707 (2015). [3] A. Das and P. Kaw, Phys. Plasmas 21 (2014) 062102.
Menke, William
2017-02-01
We prove that the problem of inverting Rayleigh wave phase velocity functions c( k ) , where k is wavenumber, for density ρ ( z ) , rigidity μ ( z ) and Lamé parameter λ ( z ) , where z is depth, is fully non-unique, at least in the highly-idealized case where the base Earth model is an isotropic half space. The model functions completely trade off. This is one special case of a common inversion scenario in which one seeks to determine several model functions from a single data function. We explore the circumstances under which this broad class of problems is unique, starting with very simple scenarios, building up to the somewhat more complicated (and common) case where data and model functions are related by convolutions, and then finally, to scale-independent problems (which include the Rayleigh wave problem). The idealized cases that we examine analytically provide insight into the kinds of nonuniqueness that are inherent in the much more complicated problems encountered in modern geophysical imaging (though they do not necessarily provide methods for solving those problems). We also define what is meant by a Backus and Gilbert resolution kernel in this kind of inversion and show under what circumstances a unique localized average of a single model function can be constructed.
Menke, William
2017-04-01
We prove that the problem of inverting Rayleigh wave phase velocity functions c( k ), where k is wavenumber, for density ρ ( z ), rigidity μ ( z ) and Lamé parameter λ ( z ), where z is depth, is fully non-unique, at least in the highly-idealized case where the base Earth model is an isotropic half space. The model functions completely trade off. This is one special case of a common inversion scenario in which one seeks to determine several model functions from a single data function. We explore the circumstances under which this broad class of problems is unique, starting with very simple scenarios, building up to the somewhat more complicated (and common) case where data and model functions are related by convolutions, and then finally, to scale-independent problems (which include the Rayleigh wave problem). The idealized cases that we examine analytically provide insight into the kinds of nonuniqueness that are inherent in the much more complicated problems encountered in modern geophysical imaging (though they do not necessarily provide methods for solving those problems). We also define what is meant by a Backus and Gilbert resolution kernel in this kind of inversion and show under what circumstances a unique localized average of a single model function can be constructed.
Persaud, Patricia; Di Luccio, Francesca; Clayton, Robert W.
2015-03-01
Rayleigh wave tomography provides images of the shallow mantle shear wave velocity structure beneath the Gulf of California. Low-velocity zones (LVZs) are found on axis between 26 and 50 km depth beneath the Guaymas Basin but mostly off axis under the other rift basins, with the largest feature underlying the Ballenas Transform Fault. We interpret the broadly distributed LVZs as regions of partial melting in a solid mantle matrix. The pathway for melt migration and focusing is more complex than an axis-centered source aligned above a deeper region of mantle melt and likely reflects the magmatic evolution of rift segments. We also consider the existence of solid lower continental crust in the Gulf north of the Guaymas Basin, where the association of the LVZs with asthenospheric upwelling suggests lateral flow assisted by a heat source. These results provide key constraints for numerical models of mantle upwelling and melt focusing in this young oblique rift.
Wagner, L. S.; Forsyth, D. W.; Fouch, M. J.; James, D. E.
2009-12-01
The High Lava Plains (HLP) of eastern Oregon represent an unusual track of bimodal volcanism extending from the southeastern-most corner of the state to its current position beneath the Newberry Volcano on the eastern margin of the Cascades. The silicic volcanism is time progressive along this track, beginning some 15 Ma near the Owyhee plateau and then trending to the north east. The timing and location of the start of the HLP coincides with that of the initial volcanism associated with the Yellowstone/Snake River Plain track (YSRP). While the YSRP has often been interpreted as the classic intra-continental hot spot track, the HLP, which trends almost normal to absolute plate motion, is harder to explain. This study uses the 100+ stations associated with the HLP seismic deployment together with another ~100 Earthscope Transportable Array stations (TA) to perform a high resolution inversion for Rayleigh wave phase velocities using the 2-plane-wave methodology of Forsyth and Li (2004). Because of the comparatively small grid spacing of this study, we are able to discern much finer scale structures than studies looking at the entire western U.S. with only TA stations. Preliminary results indicate very low velocities across the study area, especially at upper mantle depths. Especially low velocities are seen beneath the Owyhee plateau and along both the HLP and YSRP tracks. Final details about the exact geometries of these features will help constrain possible scenarios for the formation of the HLP volcanic sequence.
2012-03-22
Seismology Data Management Center (DMC), corrected for the instrument response to displacement in nanometers, and rotated to transverse, radial, and...estimated in the a) Middle East, b) Korean Peninsula region, and in c) central Italy . Figure 3. Ms(VMAX)-Love versus Ms (VMAX)- Rayleigh for...earthquakes in the a) Middle East, b) Korean Peninsula region, and in c) central Italy . The third dataset focused on the damaging L’Aquila earthquake (6
Engineered metabarrier as shield from seismic surface waves
Palermo, Antonio; Krödel, Sebastian; Marzani, Alessandro; Daraio, Chiara
2016-12-01
Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by burying sub-wavelength resonant structures under the soil surface. Each resonant structure consists of a cylindrical mass suspended by elastomeric springs within a concrete case and can be tuned to the resonance frequency of interest. The design allows controlling seismic waves with wavelengths from 10-to-100 m with meter-sized resonant structures. We develop an analytical model based on effective medium theory able to capture the mode conversion mechanism. The model is used to guide the design of metabarriers for varying soil conditions and validated using finite-element simulations. We investigate the shielding performance of a metabarrier in a scaled experimental model and demonstrate that surface ground motion can be reduced up to 50% in frequency regions below 10 Hz, relevant for the protection of buildings and civil infrastructures.
Engineered metabarrier as shield from seismic surface waves.
Palermo, Antonio; Krödel, Sebastian; Marzani, Alessandro; Daraio, Chiara
2016-12-20
Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by burying sub-wavelength resonant structures under the soil surface. Each resonant structure consists of a cylindrical mass suspended by elastomeric springs within a concrete case and can be tuned to the resonance frequency of interest. The design allows controlling seismic waves with wavelengths from 10-to-100 m with meter-sized resonant structures. We develop an analytical model based on effective medium theory able to capture the mode conversion mechanism. The model is used to guide the design of metabarriers for varying soil conditions and validated using finite-element simulations. We investigate the shielding performance of a metabarrier in a scaled experimental model and demonstrate that surface ground motion can be reduced up to 50% in frequency regions below 10 Hz, relevant for the protection of buildings and civil infrastructures.
Fletcher, Jon Peter B.; Erdem, Jemile; Seats, Kevin; Lawrence, Jesse
2016-01-01
If shaking from a local or regional earthquake in the San Francisco Bay region were to rupture levees in the Sacramento/San Joaquin Delta then brackish water from San Francisco Bay would contaminate the water in the Delta: the source of fresh water for about half of California. As a prelude to a full shear-wave velocity model that can be used in computer simulations and further seismic hazard analysis, we report on the use of ambient noise tomography to build a fundamental-mode, Rayleigh-wave group velocity model for the region around the Sacramento/San Joaquin Delta in the western Central Valley, California. Recordings from the vertical component of about 31 stations were processed to compute the spatial distribution of Rayleigh wave group velocities. Complex coherency between pairs of stations were stacked over 8 months to more than a year. Dispersion curves were determined from 4 to about 18 seconds. We calculated average group velocities for each period and inverted for deviations from the average for a matrix of cells that covered the study area. Smoothing using the first difference is applied. Cells of the model were about 5.6 km in either dimension. Checkerboard tests of resolution, which is dependent on station density, suggest that the resolving ability of the array is reasonably good within the middle of the array with resolution between 0.2 and 0.4 degrees. Overall, low velocities in the middle of each image reflect the deeper sedimentary syncline in the Central Valley. In detail, the model shows several centers of low velocity that may be associated with gross geologic features such as faulting along the western margin of the Central Valley, oil and gas reservoirs, and large cross cutting features like the Stockton arch. At shorter periods around 5.5s, the model’s western boundary between low and high velocities closely follows regional fault geometry and the edge of a residual isostatic gravity low. In the eastern part of the valley, the boundaries
Surface wave chemical detector using optical radiation
Thundat, Thomas G.; Warmack, Robert J.
2007-07-17
A surface wave chemical detector comprising at least one surface wave substrate, each of said substrates having a surface wave and at least one measurable surface wave parameter; means for exposing said surface wave substrate to an unknown sample of at least one chemical to be analyzed, said substrate adsorbing said at least one chemical to be sensed if present in said sample; a source of radiation for radiating said surface wave substrate with different wavelengths of said radiation, said surface wave parameter being changed by said adsorbing; and means for recording signals representative of said surface wave parameter of each of said surface wave substrates responsive to said radiation of said different wavelengths, measurable changes of said parameter due to adsorbing said chemical defining a unique signature of a detected chemical.
Gupta R.R.
2014-02-01
Full Text Available The present investigation deals with the propagation of waves in a micropolar transversely isotropic half space with an overlying inviscid fluid layer. Effects of fluid loading and anisotropy on the phase velocity, attenuation coefficient, specific loss and relative frequency shift. Finally, a numerical solution was carried out for aluminium epoxy material and the computer simulated results for the phase velocity, attenuation coefficient, specific loss and relative frequency shift are presented graphically. A particular case for the propagation of Rayleigh waves in a micropolar transversely isotropic half-space is deduced and dispersion curves are plotted for the same as functions of the wave number. An amplitude of displacements and microrotation together with the path of surface particles are also calculated for the propagation of Rayleigh waves in the latter case
Seismic Tomography Around the Eastern Edge of the Alps From Ambient-Noise-Based Rayleigh Waves
Zigone, Dimitri; Fuchs, Florian; Kolinsky, Petr; Gröschl, Gidera; Apoloner, Maria-Theresia; Qorbani, Ehsan; Schippkus, Sven; Löberich, Eric; Bokelmann, Götz; AlpArray Working Group
2016-04-01
Inspecting ambient noise Green's functions is an excellent tool for monitoring the quality of seismic data, and for swiftly detecting changes in the configuration of a seismological station. Those Green's functions readily provide stable information about structural variations near the Earth's surface. We apply the technique to a network consisting of about 40 broadband stations in the area of the Easternmost Alps, in particular those operated by the University of Vienna (AlpArrayAustria) and the Vienna University of Technology. Those data are used to estimate Green's functions between station pairs; the Green's function consist mainly of surface waves, and we use them to investigate crustal structure near the Eastern edge of the Alps. To obtain better signal-to-noise ratios in the noise correlation functions, we adopt a procedure using short time windows (2 hr). Energy tests are performed on the data to remove effects of transient sources and instrumental problems. The resulting 9-component correlation tensor is used to make travel time measurements on the vertical, radial and transverse components. Those measurements can be used to evaluate dispersion using frequency-time analysis for periods between 5-30 seconds. After rejecting paths without sufficient signal-to-noise ratio, we invert the velocity measurements using the Barmin et al. (2001) approach on a 10 km grid size. The obtained group velocity maps reveal complex structures with clear velocity contrasts between sedimentary basins and crystalline rocks. The Bohemian Massif and the Northern Calcareous Alps are associated with fast-velocity bodies. By contrast, the Vienna Basin presents clear low-velocity zones with group velocities down to 2 km/s at period of 7 s. The group velocities are then inverted to 3D images of shear wave speeds using the linear inversion method of Herrmann (2013). The results highlight the complex crustal structure and complement earthquake tomography studies in the region. Updated
Broadband transverse electric surface wave in silicene
Ukhtary, M. Shoufie; Nugraha, Ahmad R. T.; Hasdeo, Eddwi H.; Saito, Riichiro
2016-08-01
Transverse electric (TE) surface wave in silicine is theoretically investigated. The TE surface wave in silicene is found to exhibit better characteristics compared with that in graphene, in terms of a broader frequency range and more confinement to the surface which originate from the buckled structure of silicene. We found that even undoped silicene can support the TE surface wave. We expect the similar characteristics of the TE surface wave in other two-dimensional materials that have a slightly buckled honeycomb lattice.
On the generation of internal wave modes by surface waves
Harlander, Uwe; Kirschner, Ian; Maas, Christian; Zaussinger, Florian
2016-04-01
Internal gravity waves play an important role in the ocean since they transport energy and momentum and the can lead to mixing when they break. Surface waves and internal gravity waves can interact. On the one hand, long internal waves imply a slow varying shear current that modifies the propagation of surface waves. Surface waves generated by the atmosphere can, on the other hand, excite internal waves by nonlinear interaction. Thereby a surface wave packet consisting of two close frequencies can resonate with a low frequency internal wave (Phillips, 1966). From a theoretical point of view, the latter has been studied intensively by using a 2-layer model, i.e. a surface layer with a strong density contrast and an internal layer with a comparable weak density contrast (Ball, 1964; Craig et al., 2010). In the present work we analyse the wave coupling for a continuously stratified fluid using a fully non-linear 2D numerical model (OpenFoam) and compare this with laboratory experiments (see Lewis et al. 1974). Surface wave modes are used as initial condition and the time development of the dominant surface and internal waves are studied by spectral and harmonic analysis. For the simple geometry of a box, the results are compared with analytical spectra of surface and gravity waves. Ball, F.K. 1964: Energy transfer between external and internal gravity waves. J. Fluid Mech. 19, 465. Craig, W., Guyenne, P., Sulem, C. 2010: Coupling between internal and surface waves. Natural Hazards 57, 617-642. Lewis, J.E., Lake, B.M., Ko, D.R.S 1974: On the interaction of internal waves and surfacr gravity waves, J. Fluid Mech. 63, 773-800. Phillips, O.M. 1966: The dynamics of the upper ocean, Cambridge University Press, 336pp.
Surface Wave Amplitude Anomalies in the Western United States
Eddy, C.; Ekstrom, G.
2011-12-01
We determine maps of local surface wave amplitude factors across the Western United States for Rayleigh and Love waves at discrete periods between 25 and 125s. Measurements of raw amplitude anomalies are made from data recorded at 1161 USArray stations for minor arc arrivals of earthquakes with Mw>5.5 occurring between 2006 and 2010. We take the difference between high-quality amplitude anomaly measurements for events recorded on station pairs less than 2 degrees apart. The mean of these differences for each station pair is taken as the datum. Surface wave amplitudes are controlled by four separate mechanisms: focusing due to elastic structure, attenuation due to anelastic structure, source effects, and receiver effects. By taking the mean of the differences of amplitude anomalies for neighboring stations, we reduce the effects of focusing, attenuation, and the seismic source, thus isolating amplitude anomalies due to near-receiver amplitude effects. We determine local amplitude factors for each USArray station by standard linear inversion of the differential data set. The individual station amplitude factors explain the majority of the variance of the data. For example, derived station amplitude factors for 50s Rayleigh waves explain 92% of the variance of the data. We explore correlations between derived station amplitude factors and local amplitude factors predicted by crust and upper mantle models. Maps of local amplitude factors show spatial correlation with topography and geologic structures in the Western United States, particularly for maps derived from Rayleigh wave amplitude anomalies. A NW-SE trending high in amplitude factors in Eastern California is evident in the 50s map, corresponding to the location of the Sierra Nevada Mountains. High amplitude factors are observed in Colorado and New Mexico in the 50s-125s maps in the location of the highest peaks of the Rocky Mountains. High amplitude factors are also seen in Southern Idaho and Eastern Wyoming in
Databases of surface wave dispersion
L. Boschi
2005-06-01
Full Text Available Observations of seismic surface waves provide the most important constraint on the elastic properties of the Earths lithosphere and upper mantle. Two databases of fundamental mode surface wave dispersion were recently compiled and published by groups at Harvard (Ekström et al., 1997 and Utrecht/Oxford (Trampert and Woodhouse, 1995, 2001, and later employed in 3-d global tomographic studies. Although based on similar sets of seismic records, the two databases show some significant discrepancies. We derive phase velocity maps from both, and compare them to quantify the discrepancies and assess the relative quality of the data; in this endeavour, we take careful account of the effects of regularization and parametrization. At short periods, where Love waves are mostly sensitive to crustal structure and thickness, we refer our comparison to a map of the Earths crust derived from independent data. On the assumption that second-order effects like seismic anisotropy and scattering can be neglected, we find the measurements of Ekström et al. (1997 of better quality; those of Trampert and Woodhouse (2001 result in phase velocity maps of much higher spatial frequency and, accordingly, more difficult to explain and justify geophysically. The discrepancy is partly explained by the more conservative a priori selection of data implemented by Ekström et al. (1997. Nevertheless, it becomes more significant with decreasing period, which indicates that it could also be traced to the different measurement techniques employed by the authors.
Wang, H.; Currie, C. A.
2013-12-01
For many continental plates, significant vertical motion of Earth's surface has occurred within the plate interior which can not be clearly linked to plate tectonic processes. For example, several craton areas exhibit anomalous basins, e.g., the Williston basin, Illinois basin and Michigan basin in North America. In orogenic belts, there are examples of local areas (~100 km wide) where the surface has undergone subsidence and then uplift of >1 km, such as the Arizaro basin (central Andes) and Wallowa Mountains (northeast Oregon). Given the near-circular shape of the surface deflection, it has been suggested that they may be related to gravitational foundering of dense lower lithosphere, i.e., Rayleigh-Taylor instability (or 'RT drip'). In order to investigate the surface effects of an RT drip, we use two methods: (1) 2D thermal-mechanical numerical models to study links between drip dynamics and crustal deformation and (2) a theoretical analysis of the crustal deformation induced by stresses from the RT drip. The numerical models consist of a continental lithosphere overlying a sublithospheric mantle. A high-density material is placed in the mantle lithosphere or lower crust to initiate a drip event, and a stress-free boundary condition allows the development of surface topography during model evolution. A reasonable range of crustal viscosity and thickness is tested to study the RT drip in different tectonic settings, from a cold craton to a hot orogen with thick crust. Four types of surface deflection are observed: (1) subsidence; (2) subsidence followed by uplift; (3) uplift; and (4) little deflection. When the crust is relatively strong or thin, the surface has a negative elevation, forming a basin. For a weak or thick crust, the RT drip induces crustal flow, leading to crustal thickening that can uplift the surface; an extremely weak crust decouples the surface and RT drip and the surface is unperturbed. Our theoretical analysis considers the surface
Surface Acoustic Wave Frequency Comb
Savchenkov, A A; Ilchenko, V S; Seidel, D; Maleki, L
2011-01-01
We report on realization of an efficient triply-resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyper-parametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb observing the modulation of the modulated light escaping the resonator.
Haney, Matthew M.; Mikesell, T. Dylan; van Wijk, Kasper; Nakahara, Hisashi
2012-01-01
Using ambient seismic noise for imaging subsurface structure dates back to the development of the spatial autocorrelation (SPAC) method in the 1950s. We present a theoretical analysis of the SPAC method for multicomponent recordings of surface waves to determine the complete 3 × 3 matrix of correlations between all pairs of three-component motions, called the correlation matrix. In the case of isotropic incidence, when either Rayleigh or Love waves arrive from all directions with equal power, the only non-zero off-diagonal terms in the matrix are the vertical–radial (ZR) and radial–vertical (RZ) correlations in the presence of Rayleigh waves. Such combinations were not considered in the development of the SPAC method. The method originally addressed the vertical–vertical (ZZ), RR and TT correlations, hence the name spatial autocorrelation. The theoretical expressions we derive for the ZR and RZ correlations offer additional ways to measure Rayleigh wave dispersion within the SPAC framework. Expanding on the results for isotropic incidence, we derive the complete correlation matrix in the case of generally anisotropic incidence. We show that the ZR and RZ correlations have advantageous properties in the presence of an out-of-plane directional wavefield compared to ZZ and RR correlations. We apply the results for mixed-component correlations to a data set from Akutan Volcano, Alaska and find consistent estimates of Rayleigh wave phase velocity from ZR compared to ZZ correlations. This work together with the recently discovered connections between the SPAC method and time-domain correlations of ambient noise provide further insights into the retrieval of surface wave Green’s functions from seismic noise.
Tanimoto, T.; Anderson, D. L.
1983-01-01
The lateral heterogeneity and apparent anisotropy of the upper mantle are studied by measuring Rayleigh and Love wave phase velocities in the period range 100-250 sec. Spherical harmonic descriptions of the lateral heterogeneity are obtained for order and degree up to 1=m=10. Slow regions are evident at the East Pacific rise, northeast Africa, Tibet, Tasman sea, southwestern North America and triple junctions in the Northern Atlantic and Indian oceans. Fast regions occur in Australia, western Pacific and the eastern Atlantic. Details which are not evident in previous studies include two fast regions in the central Pacific and the subduction zone in the Scotia Arc region. Inversion for azimuthal dependence showed (1) little correlation between the fast phase velocity directions and the plate motion vector in plate interiors, but (2) correlation of the fast direction with the perpendicular direction to trenches and ridges. Phase velocity is high when waves propagate perpendicular to these structures. Severe tradeoffs exist between heterogeneity and azimuthal dependence because of the yet unsatisfactory path coverage.
Tanimoto, T.; Anderson, D. L.
1985-01-01
The lateral heterogeneity and apparent anisotropy of the upper mantle are studied by measuring Rayleigh and Love wave phase velocities in the period range 100-250 sec. Spherical harmonic descriptions of the lateral heterogeneity are obtained for order and degree up to 1=m=10. Slow regions are evident at the East Pacific rise, northeast Africa, Tibet, Tasman sea, southwestern North America and triple junctions in the Northern Atlantic and Indian oceans. Fast regions occur in Australia, western Pacific and the eastern Atlantic. Details which are not evident in previous studies include two fast regions in the central Pacific and the subduction zone in the Scotia Arc region. Inversion for azimuthal dependence showed (1) little correlation between the fast phase velocity directions and the plate motion vector in plate interiors, but (2) correlation of the fast direction with the perpendicular direction to trenches and ridges. Phase velocity is high when waves propagate perpendicular to these structures. Severe tradeoffs exist between heterogeneity and azimuthal dependence because of the yet unsatisfactory path coverage.
Ardhuin, Fabrice
2012-01-01
Oceanic observations, even in very deep water, and atmospheric pressure or seismic records, from anywhere on Earth, contain noise with dominant periods between 3 and 10 seconds, that can be related to surface gravity waves in the oceans. This noise is consistent with a dominant source explained by a nonlinear wave-wave interaction mechanism, and takes the form of surface gravity waves, acoustic or seismic waves. Previous theoretical works on seismic noise focused on surface (Rayleigh) waves, and did not consider finite depth effects on the generating wave kinematics. These finite depth effects are introduced here, which requires the consideration of the direct wave-induced pressure at the ocean bottom, a contribution previously overlooked in the context of seismic noise. That contribution can lead to a considerable reduction of the seismic noise source, which is particularly relevant for noise periods larger than 10 s. The theory is applied to acoustic waves in the atmosphere, extending previous theories that...
On the propagation of elasto-thermodiffusive surface waves in heat-conducting materials
Sharma, J. N.; Sharma, Y. D.; Sharma, P. K.
2008-09-01
The present paper deals with the study of the propagation of Rayleigh surface waves in homogeneous isotropic, thermodiffusive elastic half-space. After developing the formal solution of the model, the secular equations for stress free, thermally insulated or isothermal, and isoconcentrated boundary conditions of the half-space have been obtained. The secular equations have been solved by using irreducible Cardano's method with the help of DeMoivre's theorem in order to obtain phase velocity and attenuation coefficient of waves under consideration. The motion of the surface particles during the Rayleigh surface wave propagation is also discussed and found to be elliptical in general. The inclinations of wave normal with the major axis of the elliptical path of a typical particle have also been computed. Finally, the numerically simulated results regarding phase velocity, attenuation coefficient, specific loss and thermo-mechanical coupling factors of thermoelastic diffusive waves have been obtained and presented graphically. Some very interesting and useful characteristics of surface acoustic waves have been obtained, which may help in improving the fabrication quality of optical and electronic devices in addition to construction and design of materials such as semiconductors and composite structures. Therefore, this work finds applications in the geophysics and electronics industry.
Wenchang Hao; Jiuling Liu; Minghua Liu; Yong Liang; Shitang He
2016-01-01
The effect of the sensitive area of the two-port resonator configuration on the mass sensitivity of a Rayleigh surface acoustic wave (R-SAW) sensor was investigated theoretically, and verified in experiments. A theoretical model utilizing a 3-dimensional finite element method (FEM) approach was established to extract the coupling-of-modes (COM) parameters in the absence and presence of mass loading covering the electrode structures. The COM model was used to simulate the frequency response of...
Parabolic Wave Equation for Surface Water Waves.
1986-11-01
extended to wave propagation problems in other fields of physical sciences, such as nonlinear optics ( Svelto , 1974), plasma physics (Karpman, 1975...34 Journal of Fluid Mechanics, Vol. 72, pp. 373-384. Svelto , 0., 1974, Progress in Optics, North-Holland Pub., Chapter 1, pp. 1-51. Tappert, F.D., 1977, "The
Simple equations guide high-frequency surface-wave investigation techniques
Xia, J.; Xu, Y.; Chen, C.; Kaufmann, R.D.; Luo, Y.
2006-01-01
We discuss five useful equations related to high-frequency surface-wave techniques and their implications in practice. These equations are theoretical results from published literature regarding source selection, data-acquisition parameters, resolution of a dispersion curve image in the frequency-velocity domain, and the cut-off frequency of high modes. The first equation suggests Rayleigh waves appear in the shortest offset when a source is located on the ground surface, which supports our observations that surface impact sources are the best source for surface-wave techniques. The second and third equations, based on the layered earth model, reveal a relationship between the optimal nearest offset in Rayleigh-wave data acquisition and seismic setting - the observed maximum and minimum phase velocities, and the maximum wavelength. Comparison among data acquired with different offsets at one test site confirms the better data were acquired with the suggested optimal nearest offset. The fourth equation illustrates that resolution of a dispersion curve image at a given frequency is directly proportional to the product of a length of a geophone array and the frequency. We used real-world data to verify the fourth equation. The last equation shows that the cut-off frequency of high modes of Love waves for a two-layer model is determined by shear-wave velocities and the thickness of the top layer. We applied this equation to Rayleigh waves and multi-layer models with the average velocity and obtained encouraging results. This equation not only endows with a criterion to distinguish high modes from numerical artifacts but also provides a straightforward means to resolve the depth to the half space of a layered earth model. ?? 2005 Elsevier Ltd. All rights reserved.
Surface waves on metal-dielectric metamaterials
Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee;
2016-01-01
of surface waves and, therefore, can serve as a platform allowing many applications for surface photonics. Most of these surface waves are directional and their propagation direction is sensitive to permittivities of the media forming the interface. Hence, their propagation can be effectively controlled...... by changing a wavelength or material parameters. We discover that two new types of surface waves with complex dispersion exist for a uniaxial medium with both negative ordinary and extraordinary permittivities. Such new surface wave solutions originate from the anisotropic permittivities of the uniaxial media......, resulting in unique hyperbolic–like wavevector dependencies....
Broadband wave manipulation in surface-wave photonic crystal
Gao, Zhen
2016-01-01
The ability to perfectly guide surface electromagnetic waves around ultra-sharp corners without back-scattering and radiation is in great demand for various photonic and plasmonic applications. This is fundamentally difficult to realize because of the dramatic momentum mismatch and wave nature of radiation at the sharp corners. Here we experimentally demonstrate that a simple photonic structure, a periodic square array of metallic cylinders standing on a metal surface, can behaves as a surface-wave photonic crystal with complete photonic band gap to overcome this bottleneck simply. A line-defect waveguide can support and guide surface waves around ultra-sharp corners without perceptible radiation and reflection, achieving almost perfect transmission efficiency in a broad frequency range. We also demonstrate an ideal T-shaped splitter to split input surface waves equally into two arms and a square radiation-suppressed plasmonic open resonator with high quality factors by simply inducing line-defects in this fu...
Abo-Dahab, S. M. [Taif University, Taif (Saudi Arabia); Abd-Alla, A. M. [SVU, Qena (Egypt); Khan, Aftab [Sohag University, Sohag (Egypt)
2015-08-15
The aim of this paper is to study the propagation of surface waves in a rotating fibre-reinforced viscoelastic media of higher order under the influence of magnetic field. The general surface wave speeds derived to study the effects of rotation and magnetic field on surface waves. Particular cases for Stoneley, Love and Rayleigh waves are also discussed and dispersion relation for the waves has been deduced. The results obtained in this investigation are more general in the sense that some earlier published results are obtained from our result as special cases. For order zero our results are well agreement to fibre-reinforced materials. Also by neglecting the reinforced elastic parameters, the results reduce to well known isotropic medium. It is observed that in a rotating medium the surface waves are dispersive. Also magnetic effects play a significant roll. It is observed that Love wave remain unaffected in a rotating medium but remain under the influence of magnetic field. Rayleigh waves are affected by rotation and magnetic field whereas Stoneley waves are independent of Maxwell stresses. It is also observed that, surface waves cannot propagate in a fast rotating medium or in the presence of magnetic field of high intensity. Numerical results for particular materials are given and illustrated graphically. The results indicate that the effect of rotation and magnetic field are very pronounced.
Dyakonov surface waves in lossy metamaterials
Sorni, A J; Zapata-Rodríguez, C J; Miret, J J
2015-01-01
We analyze the existence of localized waves in the vicinities of the interface between two dielectrics, provided one of them is uniaxial and lossy. We found two families of surface waves, one of them approaching the well-known Dyakonov surface waves (DSWs). In addition, a new family of wave fields exists which are tightly bound to the interface. Although its appearance is clearly associated with the dissipative character of the anisotropic material, the characteristic propagation length of such surface waves might surpasses the working wavelength by nearly two orders of magnitude.
Deshpande, A. A.; Mohan, G.
2016-10-01
The northwestern Deccan volcanic province (NWDVP) of India, encompassing the Saurashtra peninsula and the adjoining Gulf of Cambay, is investigated through joint inversion of surface wave dispersion measurements and teleseismic P receiver functions, to estimate the crustal and shallow upper mantle shear wave velocity (Vs) structure. The Mw ∼ 7.7 Bhuj earthquake and the post Bhuj regional events, recorded during the period 2001-2010 at 7 stations along 37 source-receiver paths were used along with 35 teleseismic events. A joint curve fitting inversion technique is applied to obtain a best fit for the fundamental mode Rayleigh wave group velocity dispersion curves for time periods 5-50 s and high quality crustal P wave receiver functions obtained at each station. Significant crustal heterogeneity is observed within the study region with the average crustal Vs ranging from 3.5 km/s to 3.8 km/s with the paths cutting across the Gulf of Cambay exhibiting large reduction in shear wave velocities. Utilizing the average crustal Vs ≈ 3.66 km/s estimated for Saurashtra, together with the average crustal P wave velocity (Vp) ≈ 6.54 km/s derived independently through deep seismic sounding studies, yields a bulk Vp/Vs ratio of 1.786 or an equivalent crustal Poisson's ratio of 0.271. A major contribution to the high Poisson's ratio comes from the 12 to 16 km thick lower crustal layers with shear velocities ranging from 3.8 km/s to 4.19 km/s suggesting widespread magmatic underplating due to emplacement of mafic cumulates in the lower crust. The shallow uppermost mantle shear velocities are in the range 4.2-4.5 km/s averaging 4.36 km/s, which is less than that observed for the Indian shield, indicating the effects of residual thermal anomaly. The variation in the crustal Vs, high Poisson's ratios and low upper mantle shear velocities reflect the thermal and compositional effects of the Deccan volcanism which are manifested in terms of pervasive presence of mafic dykes
Generation of long subharmonic internal waves by surface waves
Tahvildari, Navid; Kaihatu, James M.; Saric, William S.
2016-10-01
A new set of Boussinesq equations is derived to study the nonlinear interactions between long waves in a two-layer fluid. The fluid layers are assumed to be homogeneous, inviscid, incompressible, and immiscible. Based on the Boussinesq equations, an analytical model is developed using a second-order perturbation theory and applied to examine the transient evolution of a resonant triad composed of a surface wave and two oblique subharmonic internal waves. Wave damping due to weak viscosity in both layers is considered. The Boussinesq equations and the analytical model are verified. In contrast to previous studies which focus on short internal waves, we examine long waves and investigate some previously unexplored characteristics of this class of triad interaction. In viscous fluids, surface wave amplitudes must be larger than a threshold to overcome viscous damping and trigger internal waves. The dependency of this critical amplitude as well as the growth and damping rates of internal waves on important parameters in a two-fluid system, namely the directional angle of the internal waves, depth, density, and viscosity ratio of the fluid layers, and surface wave amplitude and frequency is investigated.
Calculation of surface acoustic waves in a multilayered piezoelectric structure
Zhang Zuwei; Wen Zhiyu; Hu Jing
2013-01-01
The propagation properties of the surface acoustic waves (SAWs) in a ZnO-SiO2-Si multilayered piezoelectric structure are calculated by using the recursive asymptotic method.The phase velocities and the electromechanical coupling coefficients for the Rayleigh wave and the Love wave in the different ZnO-SiO2-Si structures are calculated and analyzed.The Love mode wave is found to be predominantly generated since the c-axis of the ZnO film is generally perpendicular to the substrate.In order to prove the calculated results,a Love mode SAW device based on the ZnO-SiO2-Si multilayered structure is fabricated by micromachining,and its frequency responses are detected.The experimental results are found to be mainly consistent with the calculated ones,except for the slightly larger velocities induced by the residual stresses produced in the fabrication process of the films.The deviation of the experimental results from the calculated ones is reduced by thermal annealing.
Geyer, Anna
2016-01-01
Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.
Geyer, Anna
2016-01-01
Following a general principle introduced by Ehrnstr\\"{o}m et.al. we prove that for an equation modeling the free surface evolution of moderate amplitude waves in shallow water, all symmetric waves are traveling waves.
Bell, Samuel; Ruan, Youyi; Forsyth, Donald W.
2016-10-01
Using Rayleigh wave tomography of noise-removed ocean bottom seismometer data from the Cascadia Initiative, we illuminate the structure of the upper mantle beneath the Juan de Fuca plate. Beneath the Juan de Fuca ridge, there is strong asymmetry, with a pronounced low-velocity zone in the 25-65 km depth range. Extending to the west from the spreading axis, this anomaly has velocities low enough to indicate the presence of melt. The asymmetry in velocity structure and the much greater abundance of seamounts on the west flank of the ridge suggest that dynamic, buoyant upwelling is important, perhaps triggered by thermal or compositional anomalies beneath Axial Seamount. In contrast, there is no evidence for asymmetry in the axial zone or lower than expected velocities beneath the Gorda ridge. On the eastern flank of the Juan de Fuca ridge, the shear velocity in the 25-65 depth range is higher than expected; the lithosphere appears to be colder and thicker than predicted by standard plate cooling models, perhaps caused by the downwelling counterpart of the upwelling on the west side of the ridge. Close to the trench, there is a sharp decrease in shear velocity. We interpret this as aqueous alteration caused by hydrothermal circulation through deep normal faults associated with bending of the plate. Beneath the Astoria and Nitinat fans, where abyssal plain sediment is thickest, the velocity decrease is much smaller, which is consistent with a thick sediment cap that prevents hydrothermal alteration of the plate.
Surface Shear, Persistent Wave Groups and Rogue Waves
Chafin, Clifford
2014-01-01
We investigate the interaction of waves with surface flows by considering the full set of conserved quantities, subtle but important surface elevations induced by wave packets and by directly considering the necessary forces to prevent packet spreading in the deep water limit. Narrow surface shear flows are shown to exert strong localizing and stabilizing forces on wavepackets to maintain their strength and amplify their intensity even in the linear regime. Necessary criticisms of some earlier notions of stress and angular momentum of waves are included and we argue that nonlinearity enters the system in a way that makes the formation of rogue waves nonperturbative. Quantitative bounds on the surface shear flow necessary to stabilize packets of any wave amplitude are given.
S SAHA; A CHATTOPADHYAY; K C MISTRI; A K SINGH
2017-09-01
The present study aims to study the propagation of Rayleigh-type wave in a layer, composed of isotropic viscoelastic material of Voigt type, with the effect of yielding base and rigid base in two distinct cases.With the aid of an analytical treatment, closed-form expressions of phase velocity and damped velocity for both the cases are deduced. As a special case of the problem it is found that obtained results are in good agreement with the established standard results existing in the literature. It is established through the study that volume viscoelastic and shear-viscoelastic material parameter and yielding parameter have significant effect on phaseand damped velocities of Rayleigh-type wave in both the cases. Numerical calculations and graphical illustration have been carried out for both the considered cases in the presence and the absence of viscoelasticity. Acomparative study has been performed to analyse the effect of layer with yielding base, traction-free base and rigid base on the phase and damped velocities of Rayleigh-type wave.
Improvements on Mean Free Wave Surface Modeling
董国海; 滕斌; 程亮
2002-01-01
Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream function wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave breaker index in the calculation of wave breaking dissipation. The model is based on Roelvink (1993), but the numerical techniques used in the solution are based on the Weighted-Average Flux (WAF) method (Watson et al., 1992), with Time-Operator-Splitting (TOS) used for the treatment of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modeling wave set-up. The short wave (or incident primary wave) energy equation issolved by use of a traditional Lax-Wendroff technique. The present model is found to be satisfactory compared with the measurements conducted by Stive (1983).
Harmon, Nicholas; Rychert, Catherine A.
2016-08-01
We present a method for joint inversion of teleseismic and ambient noise Rayleigh wave data for phase velocity maps from 18 to 50 s period. We adapt the two-plane wave method for teleseismic data to include ambient noise phase data. We apply the method to data from Iceland's ICEMELT and HOTSPOT arrays. Checkerboard tests show that the joint inversion improves phase velocity model recovery over methods that use the data sets independently, particularly at 18 s period. The addition of ambient noise data also extends resolution to shallower depths and shorter periods in comparison to previous teleseismic results beneath Iceland. We show there are significant differences in the phase velocity maps from the joint approach in comparison to other approaches, for instance, using only teleseismic data, only ambient noise data, or the mean of the two. The difference in phase velocities in turn affects the resulting shear velocity models. The advantage of the joint inversion is that it produces a single phase velocity map that satisfies both data sets simultaneously. Our phase velocity maps show a transition from low velocities centered beneath the main volcanic centers in Iceland at 18-25 s period, primarily crustal depths, to a low-velocity region that traces the rift zones from the Reykjanes Ridge in the south to the Kolbeinsey Ridge in the north at 29-50 s period, greater depths. These results are consistent with previous studies, although with an extended and improved region of resolution, which extends further into the Atlantic and Arctic Ocean.
Ultrasonic Approach of Rayleigh Pitch-Catch Contact Ultrasound Waves on CFRP Laminated Composites
In-Young Yang; Kwang-Hee Im; Uk Heo; David K Hsu; Je-Woong Park; Hak-Joon Kim; Sung-Jin Song
2008-01-01
CFRP (carbon fiber reinforced plastics) composite materials have wide applicability because of their inherent design flexibility and improved material properties. However, impacted composite structures have 50%-75% less strength than undamaged structures. In this work, a CFRP composite material was nondestructively characterized in order to ensure product quality and structural integrity of CFRP and one-sided pitch-catch technique was developed to measure impacted-damaged area by using an automated-data acquisition system in an immersion tank. A pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave under defect conditions in the composite.
Sensitivity of surface acoustic wave devices
Filipiak, Jerzy; Zubko, Konrad
2001-08-01
The SAW devices are widely used as filters, delay lines, resonators and gas sensors. It is possible to use it as mechanical force. The paper describes sensitivity of acceleration sensor based on SAW using the Rayleigh wave propagation. Since characteristic of acceleration SAW sensors are largely determined by piezoelectric materials, it is very important to select substrate with required characteristics. Researches and numerical modeling based on simply sensor model include piezoelectric beam with unilateral free end. An aggregated mass is connected to the one. The dimension and aggregated mass are various. In this case a buckling stress and sensitivity are changed. Sensitivity in main and perpendicular axis are compare for three sensor based on SiO2, LiNbO3, Li2B4O7. Influences of phase velocity, electro-mechanical coupling constant and density on sensitivity are investigated. Some mechanical parameters of the substrates in dynamic work mode are researched using sensor model and Rayleigh model of vibrations without vibration damping. The model is useful because it simply determines dependencies between sensor parameters and substrate parameters. Differences between measured and evaluated quantities are less than 5 percent. Researches based on sensor modes, which fulfilled mechanical specifications similarly to aircraft navigation.
A Wave Modulation Model of Ripples over Long Surface Waves
CONG Peixiu; ZHENG Guizhen
2011-01-01
A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modulation model is proposed. In this model, the wind surface stress modulation is related to the modulation of tipple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the tipple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves.
Wave scattering from statistically rough surfaces
Bass, F G; ter Haar, D
2013-01-01
Wave Scattering from Statistically Rough Surfaces discusses the complications in radio physics and hydro-acoustics in relation to wave transmission under settings seen in nature. Some of the topics that are covered include radar and sonar, the effect of variations in topographic relief or ocean waves on the transmission of radio and sound waves, the reproduction of radio waves from the lower layers of the ionosphere, and the oscillations of signals within the earth-ionosphere waveguide. The book begins with some fundamental idea of wave transmission theory and the theory of random processes a
An implementation of differential search algorithm (DSA) for inversion of surface wave data
Song, Xianhai; Li, Lei; Zhang, Xueqiang; Shi, Xinchun; Huang, Jianquan; Cai, Jianchao; Jin, Si; Ding, Jianping
2014-12-01
Surface wave dispersion analysis is widely used in geophysics to infer near-surface shear (S)-wave velocity profiles for a wide variety of applications. However, inversion of surface wave data is challenging for most local-search methods due to its high nonlinearity and to its multimodality. In this work, we proposed and implemented a new Rayleigh wave dispersion curve inversion scheme based on differential search algorithm (DSA), one of recently developed swarm intelligence-based algorithms. DSA is inspired from seasonal migration behavior of species of the living beings throughout the year for solving highly nonlinear, multivariable, and multimodal optimization problems. The proposed inverse procedure is applied to nonlinear inversion of fundamental-mode Rayleigh wave dispersion curves for near-surface S-wave velocity profiles. To evaluate calculation efficiency and stability of DSA, four noise-free and four noisy synthetic data sets are firstly inverted. Then, the performance of DSA is compared with that of genetic algorithms (GA) by two noise-free synthetic data sets. Finally, a real-world example from a waste disposal site in NE Italy is inverted to examine the applicability and robustness of the proposed approach on surface wave data. Furthermore, the performance of DSA is compared against that of GA by real data to further evaluate scores of the inverse procedure described here. Simulation results from both synthetic and actual field data demonstrate that differential search algorithm (DSA) applied to nonlinear inversion of surface wave data should be considered good not only in terms of the accuracy but also in terms of the convergence speed. The great advantages of DSA are that the algorithm is simple, robust and easy to implement. Also there are fewer control parameters to tune.
Seismic interferometry of railroad induced ground motions: body and surface wave imaging
Quiros, Diego A.; Brown, Larry D.; Kim, Doyeon
2016-04-01
Seismic interferometry applied to 120 hr of railroad traffic recorded by an array of vertical component seismographs along a railway within the Rio Grande rift has recovered surface and body waves characteristic of the geology beneath the railway. Linear and hyperbolic arrivals are retrieved that agree with surface (Rayleigh), direct and reflected P waves observed by nearby conventional seismic surveys. Train-generated Rayleigh waves span a range of frequencies significantly higher than those recovered from typical ambient noise interferometry studies. Direct P-wave arrivals have apparent velocities appropriate for the shallow geology of the survey area. Significant reflected P-wave energy is also present at relatively large offsets. A common midpoint stack produces a reflection image consistent with nearby conventional reflection data. We suggest that for sources at the free surface (e.g. trains) increasing the aperture of the array to record wide angle reflections, in addition to longer recording intervals, might allow the recovery of deeper geological structure from railroad traffic. Frequency-wavenumber analyses of these recordings indicate that the train source is symmetrical (i.e. approaching and receding) and that deeper refracted energy is present although not evident in the time-offset domain. These results confirm that train-generated vibrations represent a practical source of high-resolution subsurface information, with particular relevance to geotechnical and environmental applications.
Unidirectional propagation of designer surface acoustic waves
Lu, Jiuyang; Ke, Manzhu; Liu, Zhengyou
2014-01-01
We propose an efficient design route to generate unidirectional propagation of the designer surface acoustic waves. The whole system consists of a periodically corrugated rigid plate combining with a pair of asymmetric narrow slits. The directionality of the structure-induced surface waves stems from the destructive interference between the evanescent waves emitted from the double slits. The theoretical prediction is validated well by simulations and experiments. Promising applications can be anticipated, such as in designing compact acoustic circuits.
High frequency surface acoustic wave resonator-based sensor for particulate matter detection
Thomas, Sanju; Cole, Marina; Villa-López, Farah Helue; Gardner, J. W.
2016-01-01
This paper describes the characterization of high frequency Surface Acoustic Wave Resonator-based (SAWR) sensors, for the detection of micron and sub-micron sized particles. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh wave SAWRs where one is used for particle detection and the other as a reference. Electro-acoustic detection of different sized particles shows a strong relationship between mass sensitivity (Δf/Δm) and particle diameter (Dp). This enables frequency-dependent S...
Tokam, A K; Tabod, C T; Nyblade, A A; Julia, J; Wiens, D A; Pasyanos, M E
2010-02-18
Cameroon using 1-D shear wave velocity models obtained from the joint inversion of Rayleigh wave group velocities and P-receiver functions for 32 broadband seismic stations. From the 1-D shear wave velocity models, we obtain new insights into the composition and structure of the crust and upper mantle across Cameroon. After briefly reviewing the geological framework of Cameroon, we describe the data and the joint inversion method, and then interpret variations in crustal structure found beneath Cameroon in terms of the tectonic history of the region.
Observation of sagittal X-ray diffraction by surface acoustic waves in Bragg geometry.
Vadilonga, Simone; Zizak, Ivo; Roshchupkin, Dmitry; Evgenii, Emelin; Petsiuk, Andrei; Leitenberger, Wolfram; Erko, Alexei
2017-04-01
X-ray Bragg diffraction in sagittal geometry on a Y-cut langasite crystal (La3Ga5SiO14) modulated by Λ = 3 µm Rayleigh surface acoustic waves was studied at the BESSY II synchrotron radiation facility. Owing to the crystal lattice modulation by the surface acoustic wave diffraction, satellites appear. Their intensity and angular separation depend on the amplitude and wavelength of the ultrasonic superlattice. Experimental results are compared with the corresponding theoretical model that exploits the kinematical diffraction theory. This experiment shows that the propagation of the surface acoustic waves creates a dynamical diffraction grating on the crystal surface, and this can be used for space-time modulation of an X-ray beam.
A proper methodology aimed at surface wave tomography
J. Badal
1997-06-01
Full Text Available When applying a methodology for obtaining the 3D shear-wave velocity structure of a medium from surface wave dispersion data, the problem must be considered with caution since one inverts path-averaged velocities and the use of any inversion method entails some drawbacks such as lack of uniqueness, unwarranted stability and constraints affecting the data. In order to avoid the application of consecutive inversions and to overcome these drawbacks, we propose alternative mapping methods, for example spatial prediction methods, or else the use of an algorithm that, from a mathematical viewpoint, can be understood through the application of the orthogonal projection theorem onto convex sets (POCS. Among the first ones, we try inverse weighted distance interpolation. The POCS algorithm we have used discretises a second order differential equation for the velocity field with boundary conditions. All these imaging techniques aimed at volumetric modelling and the visualisation of data are discussed, and finally we show some results based on ray path velocities obtained previously by inversion of phase and group velocities of Rayleigh waves propagating across the Iberian peninsula.
Gaddale Suresh
2015-06-01
Full Text Available We measure the inter-station Rayleigh and Love wave phase velocities across the northwestern Indian Peninsular shield (NW-IP through cross-correlation and invert these velocities to evaluate the underneath crust and upper mantle velocity structure down to 400 km. We consider a cluster of three stations in the northern tip of the Peninsula and another cluster of eight stations in the south. We measure phase velocities along 28 paths for Rayleigh waves and 17 paths for Love waves joining two stations with one from each cluster and using broadband records of earthquakes which lie nearly on the great circle joining the pair of stations. The phase velocities are in the period range of 10 to 275 s for Rayleigh waves and of 10 to 120 s for Love waves. The isotropic model obtained through inversion of the phase velocities indicates 199.1 km thick lithosphere with 3-layered crust of thickness 36.3 km; the top two layers have nearly same velocities and both constitute the upper crust with thickness of 12.6 km. The upper crust is mafic, whereas the lower crust is felsic. In the mantle lid, velocities increase with depth. The velocities of mantle lid beneath NW-IP is lower than those beneath south Indian Peninsula showing the former is hotter than the later perhaps due to large Phanerozoic impact on NW-IP. The significant upper mantle low velocity zone beneath NW-IP indicates high temperature which could be attributed to the past existence of a broad plume head at the west-central part of the Peninsula.
Parisi, Laura
2016-02-10
The surface wave full ray theory (FRT) is an efficient tool to calculate synthetic waveforms of surface waves. It combines the concept of local modes with exact ray tracing as a function of frequency, providing a more complete description of surface wave propagation than the widely used great circle approximation (GCA). The purpose of this study is to evaluate the ability of the FRT approach to model teleseismic long-period surface waveforms (T ∼ 45–150 s) in the context of current 3-D Earth models to empirically assess its validity domain and its scope for future studies in seismic tomography. To achieve this goal, we compute vertical and horizontal component fundamental mode synthetic Rayleigh waveforms using the FRT, which are compared with calculations using the highly accurate spectral element method. We use 13 global earth models including 3-D crustal and mantle structure, which are derived by successively varying the strength and lengthscale of heterogeneity in current tomographic models. For completeness, GCA waveforms are also compared with the spectral element method. We find that the FRT accurately predicts the phase and amplitude of long-period Rayleigh waves (T ∼ 45–150 s) for almost all the models considered, with errors in the modelling of the phase (amplitude) of Rayleigh waves being smaller than 5 per cent (10 per cent) in most cases. The largest errors in phase and amplitude are observed for T ∼ 45 s and for the three roughest earth models considered that exhibit shear wave anomalies of up to ∼20 per cent, which is much larger than in current global tomographic models. In addition, we find that overall the GCA does not predict Rayleigh wave amplitudes well, except for the longest wave periods (T ∼ 150 s) and the smoothest models considered. Although the GCA accurately predicts Rayleigh wave phase for current earth models such as S20RTS and S40RTS, FRT\\'s phase errors are smaller, notably for the shortest wave periods considered (T
Parisi, Laura; Ferreira, Ana M. G.
2016-04-01
The surface wave full ray theory (FRT) is an efficient tool to calculate synthetic waveforms of surface waves. It combines the concept of local modes with exact ray tracing as a function of frequency, providing a more complete description of surface wave propagation than the widely used great circle approximation (GCA). The purpose of this study is to evaluate the ability of the FRT approach to model teleseismic long-period surface waveforms (T ˜ 45-150 s) in the context of current 3-D Earth models to empirically assess its validity domain and its scope for future studies in seismic tomography. To achieve this goal, we compute vertical and horizontal component fundamental mode synthetic Rayleigh waveforms using the FRT, which are compared with calculations using the highly accurate spectral element method. We use 13 global earth models including 3-D crustal and mantle structure, which are derived by successively varying the strength and lengthscale of heterogeneity in current tomographic models. For completeness, GCA waveforms are also compared with the spectral element method. We find that the FRT accurately predicts the phase and amplitude of long-period Rayleigh waves (T ˜ 45-150 s) for almost all the models considered, with errors in the modelling of the phase (amplitude) of Rayleigh waves being smaller than 5 per cent (10 per cent) in most cases. The largest errors in phase and amplitude are observed for T ˜ 45 s and for the three roughest earth models considered that exhibit shear wave anomalies of up to ˜20 per cent, which is much larger than in current global tomographic models. In addition, we find that overall the GCA does not predict Rayleigh wave amplitudes well, except for the longest wave periods (T ˜ 150 s) and the smoothest models considered. Although the GCA accurately predicts Rayleigh wave phase for current earth models such as S20RTS and S40RTS, FRT's phase errors are smaller, notably for the shortest wave periods considered (T ˜ 45 s and
Size Effects on Surface Elastic Waves in a Semi-Infinite Medium with Atomic Defect Generation
F. Mirzade
2013-01-01
Full Text Available The paper investigates small-scale effects on the Rayleigh-type surface wave propagation in an isotopic elastic half-space upon laser irradiation. Based on Eringen’s theory of nonlocal continuum mechanics, the basic equations of wave motion and laser-induced atomic defect dynamics are derived. Dispersion equation that governs the Rayleigh surface waves in the considered medium is derived and analyzed. Explicit expressions for phase velocity and attenuation (amplification coefficients which characterize surface waves are obtained. It is shown that if the generation rate is above the critical value, due to concentration-elastic instability, nanometer sized ordered concentration-strain structures on the surface or volume of solids arise. The spatial scale of these structures is proportional to the characteristic length of defect-atom interaction and increases with the increase of the temperature of the medium. The critical value of the pump parameter is directly proportional to recombination rate and inversely proportional to deformational potentials of defects.
Xi Shao
2016-03-01
Full Text Available The Visible Infrared Imaging Radiometer Suite (VIIRS onboard Suomi National Polar Orbiting Partnership (SNPP uses a solar diffuser (SD as its radiometric calibrator for the reflective solar band calibration. The SD is made of Spectralon™ (one type of fluoropolymer and was chosen because of its controlled reflectance in the Visible/Near-Infrared/Shortwave-Infrared region and its near-Lambertian reflectance property. On-orbit changes in VIIRS SD reflectance as monitored by the Solar Diffuser Stability Monitor showed faster degradation of SD reflectance for 0.4 to 0.6 µm channels than the longer wavelength channels. Analysis of VIIRS SD reflectance data show that the spectral dependent degradation of SD reflectance in short wavelength can be explained with a SD Surface Roughness (length scale << wavelength based Rayleigh Scattering (SRRS model due to exposure to solar UV radiation and energetic particles. The characteristic length parameter of the SD surface roughness is derived from the long term reflectance data of the VIIRS SD and it changes at approximately the tens of nanometers level over the operational period of VIIRS. This estimated roughness length scale is consistent with the experimental result from radiation exposure of a fluoropolymer sample and validates the applicability of the Rayleigh scattering-based model. The model is also applicable to explaining the spectral dependent degradation of the SDs on other satellites. This novel approach allows us to better understand the physical processes of the SD degradation, and is complementary to previous mathematics based models.
Tian, Zhen; Huo, Linsheng; Gao, Weihang; Li, Hongnan; Song, Gangbing
2017-10-01
Wave-based concrete structural health monitoring has attracted much attention. A stress wave experiences significant attenuation in concrete, however there is a lack of a unified method for predicting the attenuation coefficient of the stress wave. In this paper, a simple and effective absorption attenuation model of stress waves in concrete is developed based on the Rayleigh damping model, which indicates that the absorption attenuation coefficient of stress waves in concrete is directly proportional to the square of the stress wave frequency when the damping ratio is small. In order to verify the theoretical model, related experiments were carried out. During the experiments, a concrete beam was designed in which the d33-model piezoelectric smart aggregates were embedded to detect the propagation of stress waves. It is difficult to distinguish direct stress waves due to the complex propagation paths and the reflection and scattering of stress waves in concrete. Hence, as another innovation of this paper, a new method for computing the absorption attenuation coefficient based on the time-reversal method is developed. Due to the self-adaptive focusing properties of the time-reversal method, the time-reversed stress wave focuses and generates a peak value. The time-reversal method eliminates the adverse effects of multipaths, reflection, and scattering. The absorption attenuation coefficient is computed by analyzing the peak value changes of the time-reversal focused signal. Finally, the experimental results are found to be in good agreement with the theoretical model.
Skeletonized wave equation of surface wave dispersion inversion
Li, Jing
2016-09-06
We present the theory for wave equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. Similar to wave-equation travel-time inversion, the complicated surface-wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the (kx,ω) domain. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2D or 3D velocity models. This procedure, denoted as wave equation dispersion inversion (WD), does not require the assumption of a layered model and is less prone to the cycle skipping problems of full waveform inversion (FWI). The synthetic and field data examples demonstrate that WD can accurately reconstruct the S-wave velocity distribution in laterally heterogeneous media.
Xu, Zongbo; Xia, Jianghai; Luo, Yinhe; Cheng, Feng; Pan, Yudi
2016-04-01
People have calculated Rayleigh-wave phase velocities from vertical component of ambient seismic noise for several years. Recently, researchers started to extract Love waves from transverse component recordings of ambient noise, where "transverse" is defined as the direction perpendicular to a great-circle path or a line in small scale through observation sensors. Most researches assumed Rayleigh waves could be negligible, but Rayleigh waves can exist in the transverse component when Rayleigh waves propagate in other directions besides radial direction. In study of data acquired in western Junggar Basin near Karamay city, China, after processing the transverse component recordings of ambient noise, we obtain two energy trends, which are distinguished with Rayleigh-wave and Love-wave phase velocities, in the frequency-velocity domain using multichannel analysis of surface waves (MASW). Rayleigh waves could be also extracted from the transverse component data. Because Rayleigh-wave and Love-wave phase velocities are close in high frequencies (>0.1 Hz), two kinds of surface waves might be merged in the frequency-velocity domain. Rayleigh-wave phase velocities may be misidentified as Love-wave phase velocities. To get accurate surface-wave phase velocities from the transverse component data using seismic interferometry in investigating the shallow geology, our results suggest using MASW to calculate real Love-wave phase velocities.
Tapping of Love waves in an isotropic surface waveguide by surface-to-bulk wave transduction.
Tuan, H.-S.; Chang, C.-P.
1972-01-01
A theoretical study of tapping a Love wave in an isotropic microacoustic surface waveguide is given. The surface Love wave is tapped by partial transduction into a bulk wave at a discontinuity. It is shown that, by careful design of the discontinuity, the converted bulk wave power and the radiation pattern may be controlled. General formulas are derived for the calculation of these important characteristics from a relatively general surface contour deformation.
de Lucena, Rodrigo F.; Taioli, Fabio
2014-09-01
This paper presents a study on Rayleigh wave modeling. After model implementation using Matlab software, unpublished studies were conducted of dispersion curve sensitivity to percentage changes in parameter values, including S- and P-wave velocities, substrate density, and layer thickness. The study of the sensitivity of dispersion curves demonstrated that parameters such as S-wave velocity and layer thickness cannot be ignored as inversion parameters, while P-wave velocity and density can be considered as known parameters since their influence is minimal. However, the results showed limitations that should be considered and overcome when choosing the known and unknown parameters through determining a good initial model or/and by gathering a priori information. A methodology considering the sensitivity study of dispersion curves was developed and evaluated to generate initial values (initial model) to be included in the local search inversion algorithm, clearly establishing initial favorable conditions for data inversion.
Long-wave analysis and control of the viscous Rayleigh-Taylor instability with electric fields
Cimpeanu, Radu; Anderson, Thomas; Petropoulos, Peter; Papageorgiou, Demetrios
2016-11-01
We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a solid surface in the presence of a horizontally acting electric field. The competition between gravity, surface tension and the nonlocal effect of the applied electric field is captured analytically in the form of a nonlinear evolution equation. A semi-spectral solution strategy is employed to resolve the dynamics of the resulting partial differential equation. Furthermore, we conduct direct numerical simulations (DNS) of the Navier-Stokes equations and assess the accuracy of the obtained solutions when varying the electric field strength from zero up to the point when complete stabilization at the target finite wavelengths occurs. We employ DNS to examine the limitations of the asymptotically derived behavior in the context of increasing liquid film heights, with agreement found to be excellent even beyond the target lengthscales. Regimes in which the thin film assumption is no longer valid and droplet pinch-off occurs are then analyzed. Finally, the asymptotic and computational approaches are used in conjunction to identify efficient active control mechanisms allowing the manipulation of the fluid interface in light of engineering applications at small scales, such as mixing.
Superdirected Beam of the Surface Spin Wave
Annenkov, Alexander Yu; Lock, Edwin H
2016-01-01
Visualized diffraction patterns of the surface spin wave excited by arbitrarily oriented linear transducer in tangentially magnetized ferrite film are investigated experimentally in the plane of ferrite film for the case where the transducer length D is much larger than the wavelength L. Superdirected (nonexpanding) beam of the surface spin wave with noncollinear wave vector k and group velocity vector V was observed experimentally: the angular width of this beam was about zero, the smearing of the beam energy along the film plane was minimal and the length of the beam trajectory was maximal (50 mm). Thus it was shown that such phenomenon as superdirected propagation of the wave exists in the nature.
Joint body and surface wave tomography applied to the Toba caldera complex (Indonesia)
Jaxybulatov, Kairly; Koulakov, Ivan; Shapiro, Nikolai
2016-04-01
We developed a new algorithm for a joint body and surface wave tomography. The algorithm is a modification of the existing LOTOS code (Koulakov, 2009) developed for local earthquake tomography. The input data for the new method are travel times of P and S waves and dispersion curves of Rayleigh and Love waves. The main idea is that the two data types have complementary sensitivities. The body-wave data have good resolution at depth, where we have enough crossing rays between sources and receivers, whereas the surface waves have very good near-surface resolution. The surface wave dispersion curves can be retrieved from the correlations of the ambient seismic noise and in this case the sampled path distribution does not depend on the earthquake sources. The contributions of the two data types to the inversion are controlled by the weighting of the respective equations. One of the clearest cases where such approach may be useful are volcanic systems in subduction zones with their complex magmatic feeding systems that have deep roots in the mantle and intermediate magma chambers in the crust. In these areas, the joint inversion of different types of data helps us to build a comprehensive understanding of the entire system. We apply our algorithm to data collected in the region surrounding the Toba caldera complex (north Sumatra, Indonesia) during two temporary seismic experiments (IRIS, PASSCAL, 1995, GFZ, LAKE TOBA, 2008). We invert 6644 P and 5240 S wave arrivals and ~500 group velocity dispersion curves of Rayleigh and Love waves. We present a series of synthetic tests and real data inversions which show that joint inversion approach gives more reliable results than the separate inversion of two data types. Koulakov, I., LOTOS code for local earthquake tomographic inversion. Benchmarks for testing tomographic algorithms, Bull. seism. Soc. Am., 99(1), 194-214, 2009, doi:10.1785/0120080013
Time-Domain Pure-state Polarization Analysis of Surface Waves Traversing California
Zhang, J; Walter, W R; Lay, T; Wu, R
2003-11-04
A time-domain pure-state polarization analysis method is used to characterize surface waves traversing California parallel to the plate boundary. The method is applied to data recorded at four broadband stations in California from twenty-six large, shallow earthquakes which occurred since 1988, yielding polarization parameters such as the ellipticity, Euler angles, instantaneous periods, and wave incident azimuths. The earthquakes are located along the circum-Pacific margin and the ray paths cluster into two groups, with great-circle paths connecting stations MHC and PAS or CMB and GSC. The first path (MHC-PAS) is in the vicinity of the San Andreas Fault System (SAFS), and the second (CMB-GSC) traverses the Sierra Nevada Batholith parallel to and east of the SAFS. Both Rayleigh and Love wave data show refractions due to lateral velocity heterogeneities under the path, indicating that accurate phase velocity and attenuation analysis requires array measurements. The Rayleigh waves are strongly affected by low velocity anomalies beneath Central California, with ray paths bending eastward as waves travel toward the south, while Love waves are less affected, providing observables to constrain the depth extent of the anomalies. Strong lateral gradients in the lithospheric structure between the continent and the ocean are the likely cause of the path deflections.
Pilz, Marco; Parolai, Stefano; Woith, Heiko
2017-01-01
SUMMARYIn recent years there has been increasing interest in the study of seismic noise interferometry as it can provide a complementary approach to active source or earthquake based methods for imaging and continuous monitoring the shallow structure of the Earth. This meaningful information is extracted from wavefields propagating between those receiver positions at which seismic noise was recorded. Until recently, noise-based imaging relied mostly on Rayleigh waves. However, considering similar wavelengths, a combined use of Rayleigh and Love wave tomography can succeed in retrieving velocity heterogeneities at depth due to their different sensitivity kernels. Here we present a novel one-step algorithm for simultaneously inverting Rayleigh and Love wave dispersion data aiming at identifying and describing complex 3D velocity structures. The algorithm may help to accurately and efficiently map the shear-wave velocities and the Poisson ratio of the surficial soil layers. In the high-frequency range, the scattered part of the correlation functions stabilizes sufficiently fast to provide a reliable estimate of the velocity structure not only for imaging purposes but also allows for changes in the medium properties to be monitored. Such monitoring can be achieved with a high spatial resolution in 3D and with a time resolution as small as a few hours. In this article, we describe a recent array experiment in a volcanic environment in Solfatara (Italy) and we show that this novel approach has identified strong velocity variations at the interface between liquids and gas-dominated reservoirs, allowing localizing a region which is highly dynamic due to the interaction between the deep convection and its surroundings.
Nonlinear surface waves in photonic hypercrystals
Ali, Munazza Zulfiqar
2017-08-01
Photonic crystals and hyperbolic metamaterials are merged to give the concept of photonic hypercrystals. It combines the properties of its two constituents to give rise to novel phenomena. Here the propagation of Transverse Magnetic waves at the interface between a nonlinear dielectric material and a photonic hypercrystal is studied and the corresponding dispersion relation is derived using the uniaxial parallel approximation. Both dielectric and metallic photonic hypercrystals are studied and it is found that nonlinearity limits the infinite divergence of wave vectors of the surface waves. These states exist in the frequency region where the linear surface waves do not exist. It is also shown that the nonlinearity can be used to engineer the group velocity of the resulting surface wave.
Ruts and waves in the road surface.
Tromp, J.P.M.
1989-01-01
The characteristics of a road and a road surface should not unexpectedly change, if the traffic process is to be kept safe and under control. Knowledge on accidents, in which ruts and waves played a part does not seem to exist. Knowledge on driver behaviour due to the occurrence of waves or ruts is
2009-09-30
formulation of the teleseismic explosion identification problem with multiple discriminants, Bull. Seism . Soc.Am.9T. 1730-1741. Bonner, J.L., D...Application at Regional and Teleseismic Distances, Part II: Application and Ms-mh Performance. Bull. Seism . Soc. Am. 96: 678-696 Bonner, J. L., R. B...Herrmann, D. Harkrider, and M. Pasyanos (2008). The surface wave magnitude for the 9 October 2006 North Korean nuclear explosion. Bull. Seism . Soc
On the Amplitude Equations for Weakly Nonlinear Surface Waves
Benzoni-Gavage, Sylvie; Coulombel, Jean-François
2012-09-01
Nonlocal generalizations of Burgers' equation were derived in earlier work by Hunter (Contemp Math, vol 100, pp 185-202. AMS, 1989), and more recently by Benzoni-Gavage and Rosini (Comput Math Appl 57(3-4):1463-1484, 2009), as weakly nonlinear amplitude equations for hyperbolic boundary value problems admitting linear surface waves. The local-in-time well-posedness of such equations in Sobolev spaces was proved by Benzoni-Gavage (Differ Integr Equ 22(3-4):303-320, 2009) under an appropriate stability condition originally pointed out by Hunter. The same stability condition has also been shown to be necessary for well-posedness in Sobolev spaces in a previous work of the authors in collaboration with Tzvetkov (Benzoni-Gavage et al. in Adv Math 227(6):2220-2240, 2011). In this article, we show how the verification of Hunter's stability condition follows from natural stability assumptions on the original hyperbolic boundary value problem, thus avoiding lengthy computations in each particular situation. We also show that the resulting amplitude equation has a Hamiltonian structure when the original boundary value problem has a variational origin. Our analysis encompasses previous equations derived for nonlinear Rayleigh waves in elasticity.
Regional Body-Wave Corrections and Surface-Wave Tomography Models to Improve Discrimination
Walter, W R; Pasyanos, M E; Rodgers, A J; Meyeda, K M; Sicherman, A
2003-07-18
multivariate combinations of ratios for their discrimination power. We also make use of the MDAC2 spectra and the noise spectra to determine the expected signal-to-noise value of each phase and use that to optimize the multivariate discriminants as a function of location. We quantify the discrimination power using the misidentified event trade-off curves and an equi-probable measure. In addition to the traditional phases, we are also exploring the application of coda amplitudes in discrimination. Coda-derived spectra can be peaked due to Rg-to-coda scattering, which can indicate an unusually shallow source. For surface waves we have a new high-resolution regional Rayleigh-Wave tomography for the Yellow Sea and Korean Peninsula Region, based on measuring thousands of seismograms. We also continue to make new measurements for our regional Rayleigh and Love wave group velocity tomography models of Western Eurasia and North Africa. These tomography models provide high-resolution maps of group velocity from 10- to 100-s period. The maps also provide estimates of the expected phase spectra of new events that can be used in phase-match filters to compress the expected signals and improve the signal-to-noise ratio on surface wave magnitude (Ms) estimates. Phase match filters in combination with regional Ms formulas can significantly lower the threshold at which Ms can be measured, extending the Ms-mb discriminant. We have measured Ms in western Eurasia for thousands of events at tens of stations, with and without phase match filtering, and found a marked improvement in discrimination. Here we start to quantify the improvement to both discrimination performance and the Ms threshold reduction. The group velocity models also provide constraints on velocity structure, particularly in low seismicity regions. For example we are working with Dr. Bob Henmann and Dr. Charles Ammon to combine tomography derived group velocity curves with station based receiver functions in joint inversions to
Palomeras, Imma; Villasenor, Antonio; Thurner, Sally; Levander, Alan; Gallart, Josep; Harnafi, Mimoun
2016-04-01
The Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin, constitute the westernmost Mediterranean. From north to south this region consists of the Pyrenees, the result of interaction between the Iberian and Eurasian plates; the Iberian Massif, a region that has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes) and the Atlas Mountains, resulting from post-Oligocene subduction roll-back and Eurasian-Nubian plate convergence. In this study we analyze data from recent broad-band array deployments and permanent stations on the Iberian Peninsula and in Morocco (Spanish IberArray and Siberia arrays, the US PICASSO array, the University of Munster array, and the Spanish, Portuguese, and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km, comparable to USArray. We have calculated the Rayleigh waves phase velocities from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). We inverted the phase velocities to obtain a shear velocity model for the lithosphere to ~200 km depth. The model shows differences in the crust for the different areas, where the highest shear velocities are mapped in the Iberian Massif crust. The crustal thickness is highly variable ranging from ~25 km beneath the eastern Betics to ~55km beneath the Gibraltar Strait, Internal Betics and Internal Rif. Beneath this region a unique arc shaped anomaly with high upper mantle velocities (>4.6 km/s) at shallow depths (Gibraltar arc to ~55 km depth. Low upper mantle velocities (<4.2 km/s) are observed beneath the Atlas, the northeastern end of the Betic Mountains and the Late Cenozoic volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths
Photonics surface waves on metamaterials interfaces.
Takayama, Osamu; Bogdanov, Andrey; Lavrinenko, Andrei V
2017-09-12
A surface wave (SW) in optics is a light wave, which is supported at an interface of two dissimilar media and propagates along the interface with its field amplitude exponentially decaying away from the boundary. The research on surface waves has been flourishing in last few decades thanks to their unique properties of surface sensitivity and field localization. These features have resulted in applications in nano-guiding, sensing, light-trapping and imaging based on the near-field techniques, contributing to the establishment of the nanophotonics as a field of research. Up to present, a wide variety of surface waves has been investigated in numerous material and structure settings. This paper reviews the recent progress and development in the physics of SWs localized at metamaterial interfaces, as well as bulk media in order to provide broader perspectives on optical surface waves in general. For each type of the surface waves, we discuss material and structural platforms. We mainly focus on experimental realizations in the visible and near-infrared wavelength ranges. We also address existing and potential application of SWs in chemical and biological sensing, and experimental excitation and characterization methods. © 2017 IOP Publishing Ltd.
The Detection of Vertical Cracks in Asphalt Using Seismic Surface Wave Methods
Iodice, M.; Muggleton, J.; Rustighi, E.
2016-09-01
Assessment of the location and of the extension of cracking in road surfaces is important for determining the potential level of deterioration in the road overall and the infrastructure buried beneath it. Damage in a pavement structure is usually initiated in the tarmac layers, making the Rayleigh wave ideally suited for the detection of shallow surface defects. This paper presents an investigation of two surface wave methods to detect and locate top-down cracks in asphalt layers. The aim of the study is to compare the results from the well- established Multichannel Analysis of Surface Waves (MASW) and the more recent Multiple Impact of Surface Waves (MISW) in the presence of a discontinuity and to suggest the best surface wave technique for evaluating the presence and the extension of vertical cracks in roads. The study is conducted through numerical simulations alongside experimental investigations and it considers the cases for which the cracking is internal and external to the deployment of sensors. MISW is found to enhance the visibility of the reflected waves in the frequency wavenumber (f-k) spectrum, helping with the detection of the discontinuity. In some cases, by looking at the f-k spectrum obtained with MISW it is possible to extract information regarding the location and the depth of the cracking.
Assessment of a geological model by surface wave analyses
Martorana, R.; Capizzi, P.; Avellone, G.; D'Alessandro, A.; Siragusa, R.; Luzio, D.
2017-02-01
A set of horizontal to vertical spectral ratio (HVSR) and multichannel analysis of surface waves (MASW) measurements, carried out in the Altavilla Milicia (Sicily) area, is analyzed to test a geological model of the area. Statistical techniques have been used in different stages of the data analysis, to optimize the reliability of the information extracted from geophysical measurements. In particular, cluster analysis algorithms have been implemented to select the time windows of the microseismic signal to be used for calculating the spectral ratio H/V and to identify sets of spectral ratio peaks likely caused by the same underground structures. Using results of reflection seismic lines, typical values of P-wave and S-wave velocity were estimated for each geological formation present in the area. These were used to narrow down the research space of parameters for the HVSR interpretation. MASW profiles have been carried out close to each HVSR measuring point, provided the parameters of the shallower layers for the HVSR models. MASW inversion has been constrained by extrapolating thicknesses from a known stratigraphic sequence. Preliminary 1D seismic models were obtained by adding deeper layers to models that resulted from MASW inversion. These justify the peaks of the HVSR curves due to layers deeper than MASW investigation depth. Furthermore, much deeper layers were included in the HVSR model, as suggested by geological setting and stratigraphic sequence. This choice was made considering that these latter layers do not generate other HVSR peaks and do not significantly affect the misfit. The starting models have been used to limit the starting research space for a more accurate interpretation, made considering the noise as a superposition of Rayleigh and Love waves. Results allowed to recognize four main seismic layers and to associate them to the main stratigraphic successions. The lateral correlation of seismic velocity models, joined with tectonic evidences
Fischer-Friedrich, Elisabeth; Nguyen van yen, Romain; Kruse, Karsten
2007-03-01
In the bacterium Escherichia coli, the Min-proteins show pronounced pole-to-pole oscillations. They are functional for suppressing cell division at the cell ends, leaving the center as the only possible site for division. Analyzing different models of Min-protein dynamics in a bacterial geometry, we find waves on the cytoplasmic membrane. Interestingly, the surface wave solutions of different models belong to different symmetry classes. We suggest that experiments on Min-protein surface waves in vitro are helpful in distinguishing between different classes of models of Min-protein dynamics.
Rajneesh Kumar
2014-01-01
Full Text Available The present investigation deals with the propagation of Rayleigh type surface waves in an isotropic microstretch thermoelastic diffusion solid half space under a layer of inviscid liquid. The secular equation for surface waves in compact form is derived after developing the mathematical model. The dispersion curves giving the phase velocity and attenuation coefficients with wave number are plotted graphically to depict the effect of an imperfect boundary alongwith the relaxation times in a microstretch thermoelastic diffusion solid half space under a homogeneous inviscid liquid layer for thermally insulated, impermeable boundaries and isothermal, isoconcentrated boundaries, respectively. In addition, normal velocity component is also plotted in the liquid layer. Several cases of interest under different conditions are also deduced and discussed.
Accardo, N. J.; Gaherty, J. B.; Shillington, D. J.; Nyblade, A.; Ebinger, C. J.; Mbogoni, G. J.; Chindandali, P. R. N.; Mulibo, G. D.; Ferdinand-Wambura, R.; Kamihanda, G.
2015-12-01
The Malawi Rift (MR) is an immature rift located at the southern tip of the Western branch of the East African Rift System (EARS). Pronounced border faults and tectonic segmentation are seen within the upper crust. Surface volcanism in the region is limited to the Rungwe volcanic province located north of Lake Malawi (Nyasa). However, the distribution of extension and magma at depth in the crust and mantle lithosphere is unknown. As the Western Rift of the EARS is largely magma-poor except for discrete volcanic provinces, the MR presents the ideal location to elucidate the role of magmatism in early-stage rifting and the manifestation of segmentation at depth. This study investigates the shear velocity of the crust and mantle lithosphere beneath the MR to constrain the thermal structure, the amount of total crustal and lithospheric thinning, and the presence and distribution of magmatism beneath the rift. Utilizing 55 stations from the SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) passive-source seismic experiment operating in Malawi and Tanzania, we employed a multi-channel cross-correlation algorithm to obtain inter-station phase and amplitude information from Rayleigh wave observations between 20 and 80 s period. We retrieve estimates of phase velocity between 9-20 s period from ambient noise cross-correlograms in the frequency domain via Aki's formula. We invert phase velocity measurements to obtain estimates of shear velocity (Vs) between 50-200 km depth. Preliminary results reveal a striking low-velocity zone (LVZ) beneath the Rungwe volcanic province with Vs ~4.2-4.3 km/s in the uppermost mantle. Low velocities extend along the entire strike of Lake Malawi and to the west where a faster velocity lid (~4.5 km/s) is imaged. These preliminary results will be extended by incorporating broadband data from seven "lake"-bottom seismometers (LBS) to be retrieved from Lake Malawi in October of this year. The crust and mantle modeling will be
Structure of the airflow above surface waves
Buckley, Marc; Veron, Fabrice
2016-04-01
Weather, climate and upper ocean patterns are controlled by the exchanges of momentum, heat, mass, and energy across the ocean surface. These fluxes are, in turn, influenced by the small-scale physics at the wavy air-sea interface. We present laboratory measurements of the fine-scale airflow structure above waves, achieved in over 15 different wind-wave conditions, with wave ages Cp/u* ranging from 1.4 to 66.7 (where Cp is the peak phase speed of the waves, and u* the air friction velocity). The experiments were performed in the large (42-m long) wind-wave-current tank at University of Delaware's Air-Sea Interaction laboratory (USA). A combined Particle Image Velocimetry and Laser Induced Fluorescence system was specifically developed for this study, and provided two-dimensional airflow velocity measurement as low as 100 um above the air-water interface. Starting at very low wind speeds (U10~2m/s), we directly observe coherent turbulent structures within the buffer and logarithmic layers of the airflow above the air-water interface, whereby low horizontal velocity air is ejected away from the surface, and higher velocity fluid is swept downward. Wave phase coherent quadrant analysis shows that such turbulent momentum flux events are wave-phase dependent. Airflow separation events are directly observed over young wind waves (Cp/u*wind waves (Cp/u*=3.7). Over slightly older wind waves (Cp/u* = 6.5), the measured wave-induced airflow perturbations are qualitatively consistent with linear critical layer theory.
Surface-Wave Tomography of Yucca Flat, Nevada
Toney, L. D.; Abbott, R. E.; Knox, H. A.; Preston, L. A.; Hoots, C. R.
2016-12-01
In 2015, Sandia National Laboratories conducted an active-source seismic survey of Yucca Flat, Nevada, on the Nevada National Security Site. The Yucca Flat basin hosted over 900 nuclear tests between 1951 and 1992. Data from this survey will help characterize seismic propagation effects of the area, informing models for the next phase of the Source Physics Experiments. The survey source was a 13,000-kg weight-drop at 91 locations along a 19-km N-S transect and 56 locations along an 11-km E-W transect. Over 350 three-component 2-Hz geophones were variably spaced at 10, 20, and 100 m along each line. We employed roll-along survey geometry to ensure 10-m receiver spacing within 2 km of the source. Phase velocity surface-wave analysis via the refraction-microtremor (ReMi) method was previously performed on this data in order to obtain an S-wave velocity model of the subsurface. However, the results of this approach were significantly impacted in areas where ray paths were proximate to underground nuclear tests, resulting in a spatially incomplete model. We have processed the same data utilizing group velocities and the multiple filter technique (MFT), with the hope that the propagation of wave groups is less impacted by the disrupted media surrounding former tests. We created a set of 30 Gaussian band-pass filters with scaled relative passbands and central frequencies ranging from 1 to 50 Hz. We picked fundamental Rayleigh wave arrivals from the filtered data; these picks were then inverted for 2D S-wave velocity along the transects. The new S-wave velocity model will be integrated with previous P-wave tomographic results to yield a more complete model of the subsurface structure of Yucca Flat. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Bidirectional surface wave splitter at visible frequencies.
Gan, Qiaoqiang; Bartoli, Filbert J
2010-12-15
We experimentally demonstrate a metal-film bidirectional surface wave splitter for guiding light at two visible wavelengths in opposite directions. Two nanoscale gratings were patterned on opposite sides of a subwavelength slit. The metallic surface grating structures were tailored geometrically to have different plasmonic bandgaps, enabling each grating to guide light of one wavelength and prohibit propagation at the other wavelength. The locations of the bandgaps were experimentally confirmed by interferometric measurements. Based on these design principles, a green-red bidirectional surface wave splitter is demonstrated, and the observed optical properties are shown to agree with theoretical predictions.
Mrg: A Magnitude Scale for 1 s Rayleigh Waves at Local Distances with Focus on Yield Estimation
2016-08-23
Bache, T. (1982), Estimating the yield of underground nuclear explosions, Bull. Seism . Soc. Am., 72, pp. S131-S168. Cho, K. H., R. B. Herrmann, C. J...Ammon, and K. Lee (2007), Imaging the upper crust of the Korean peninsula by surface-wave tomography, Bull. Seism . Soc. Am., 97, pp. 198-207. Denny...Monitoring the earthquake source process in North America, Bull. Seism . Soc. Am., 101, pp. 2609-2625. Kennett, B.L.N., E. R. Engdahl, and R. Buland
Photonic crystal surface waves for optical biosensors.
Konopsky, Valery N; Alieva, Elena V
2007-06-15
We present a new optical biosensor technique based on registration of dual optical s-polarized modes on a photonic crystal surface. The simultaneous registration of two optical surface waves with different evanescent depths from the same surface spot permits the segregation of the volume and the surface contributions from an analyte, while the absence of metal damping permits an increase in the propagation length of the optical surface waves and the sensitivity of the biosensor. Our technique was tested with the binding of biotin molecules to a streptavidin monolayer that has been detected with signal/noise ratio of approximately 15 at 1-s signal accumulation time. The detection limit is approximately 20 fg of the analyte on the probed spot of the surface.
Laser photoacoustic technique for ultrasonic surface acoustic wave velocity evaluation on porcelain
Qian, K.; Tu, S. J.; Gao, L.; Xu, J.; Li, S. D.; Yu, W. C.; Liao, H. H.
2016-10-01
A laser photoacoustic technique has been developed to evaluate the surface acoustic wave (SAW) velocity of porcelain. A Q-switched Nd:YAG laser at 1064 nm was focused by a cylindrical lens to initiate broadband SAW impulses, which were detected by an optical fiber interferometer with high spatial resolution. Multiple near-field surface acoustic waves were observed on the sample surface at various locations along the axis perpendicular to the laser line source as the detector moved away from the source in the same increments. The frequency spectrum and dispersion curves were obtained by operating on the recorded waveforms with cross-correlation and FFT. The SAW phase velocities of the porcelain of the same source are similar while they are different from those of different sources. The marked differences of Rayleigh phase velocities in our experiment suggest that this technique has the potential for porcelain identification.
Graphene-coated rayleigh SAW resonators for NO2 detection
Thomas, Stephen M.; Cole, Marina; De Luca, A; Torrisi, F.; Ferrari, A. C.; Udrea, Florin; Gardner, J. W.
2014-01-01
This paper describes the development of a novel low-cost Rayleigh Surface Acoustic Wave Resonator (SAWR) device coated with a graphene layer that is capable of detecting PPM levels of NO2 in air. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh SAWRs arranged in a dual oscillator configuration; where one resonator is coated with gas-sensitive graphene, and the other left uncoated to act as a reference. An array of NMP-dispersed exfoliated reduced graphene oxide dots was deposited...
Pasyanos, M E
2005-03-21
This paper presents the results of a large-scale study of surface wave dispersion performed across Eurasia and North Africa. Improvements were made to previous surface wave work by enlarging the study region, increasing path density, improving spatial resolution, and expanding the period range. This study expands the coverage area northwards and eastwards relative to a previous dispersion analysis, which covered only North Africa and the Middle East. We have significantly increased the number of seismograms examined and group velocity measurements made. We have now made good quality dispersion measurements for about 30,000 Rayleigh wave and 20,000 Love wave paths, and have incorporated measurements from several other researchers into the study. A conjugate gradient method was employed for the group velocity tomography, which improved the inversion from the previous study by adopting a variable smoothness. This technique allows us to go to higher resolution where the data allow without producing artifacts. The current results include both Love and Rayleigh wave inversions across the region for periods from 7 to 100 seconds at 1{sup o} resolution. Short period group velocities are sensitive to slow velocities associated with large sedimentary features such as the Caspian Sea, West Siberian Platform, Mediterranean Sea, Bay of Bengal, Tarim Basin, and Persian Gulf. Intermediate periods are sensitive to differences in crustal thickness, such as those between oceanic and continental crust or along orogenic zones and continental plateaus. At longer periods, fast velocities are consistently found beneath cratons while slow upper mantle velocities occur along rift systems, subduction zones, and collision zones such as the Tethys Belt. We have compared the group velocities at various periods with features such as sediment thickness, topographic height, crustal thickness, proximity to plate boundaries, lithospheric age and lithospheric thickness, and find significant
Park, Y; Nyblade, A; Rodgers, A; Al-Amri, A
2007-11-09
The shear velocity structure of the shallow upper mantle beneath the Arabian Shield has been modeled by inverting new Rayleigh wave phase velocity measurements between 45 and 140 s together with previously published Rayleigh wave group velocity measurement between 10 and 45 s. For measuring phase velocities, we applied a modified array method that minimizes the distortion of raypaths by lateral heterogeneity. The new shear velocity model shows a broad low velocity region in the lithospheric mantle across the Shield and a low velocity region at depths {ge} 150 km localized along the Red Sea coast and Makkah-Madinah-Nafud (MMN) volcanic line. The velocity reduction in the upper mantle corresponds to a temperature anomaly of {approx}250-330 K. These finding, in particular the region of continuous low velocities along the Red Sea and MMN volcanic line, do not support interpretations for the origin of the Cenozoic plateau uplift and volcanism on the Shield invoking two separate plumes. When combined with images of the 410 and 660 km discontinuities beneath the southern part of the Arabian Shield, body wave tomographic models, a S-wave polarization analysis, and SKS splitting results, our new model supports an interpretation invoking a thermal upwelling of warm mantle rock originating in the lower mantle under Africa that crosses through the transition zone beneath Ethiopia and moves to the north and northwest under the eastern margin of the Red Sea and the Arabian Shield. In this interpretation, the difference in mean elevation between the Platform and Shield can be attributed to isostatic uplift caused by heating of the lithospheric mantle under the Shield, with significantly higher region along the Red Sea possibly resulting from a combination of lithosphere thinning and dynamic uplift.
Kolínský, Petr; Fuchs, Florian; Gröschl, Gidera; Bokelmann, Götz; AlpArray Working Group
2016-04-01
We utilize array beamforming techniques to investigate deterministic surface waves from regional and teleseismic earthquakes. Because the signal is well recognized and the fundamental mode for both Love and Rayleigh waves is separated before the beamforming, instead of searching for energy of all possible signals, we identify the frequency dependence of surface wave phase velocity and the true backazimuths of propagation. Using the dense AlpArray seismic broadband network distributed in the greater Alpine region across Europe with interstation distances around 40 km, we consider each station as a centre of an array of neighboring 5 to 6 stations. This allows us to calculate the local phase velocity dispersion curves for individual regions with diameter of approximately 80 - 100 km. By the beamforming, phase velocities are corrected for the true propagation backazimuth, which is slightly frequency dependent for each event. We invert the dispersion curves for S and P wave velocity distribution with depth. Measuring the phase velocity from different events distributed around the world, azimuthal dependence of the phase velocity is estimated and thus anisotropy constrained for particular depths. Beamforming of the signals in the time window sliding along the coda after the fundamental mode allows us to detect deterministic late surface-wave signals coming from certain directions dissimilar from the direct fundamental mode backazimuths for some of the events - these can be considered as surface wave reflections from lateral heterogeneities and vertical boundaries.
Blackfolds, plane waves and minimal surfaces
Armas, Jay; Blau, Matthias
2015-01-01
Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and comp...
Surface tension effects in breaking wave noise.
Deane, Grant B
2012-08-01
The role of surface active materials in the sea surface microlayer on the production of underwater noise by breaking waves is considered. Wave noise is assumed to be generated by bubbles formed within actively breaking whitecaps, driven into breathing mode oscillation at the moment of their formation by non-equilibrium, surface tension forces. Two significant effects associated with surface tension are identified-a reduction in low frequency noise (bubbles by fluid turbulence within the whitecap and a reduction in overall noise level due to a decrease in the excitation amplitude of bubbles associated with reduced surface tension. The impact of the latter effect on the accuracy of Weather Observations Through Ambient Noise estimates of wind speed is assessed and generally found to be less than ±1 m s(-1) for wind speeds less than 10 m s(-1) and typical values of surfactant film pressure within sea slicks.
Ridouane, El Hassan; Hasnaoui, Mohammed; Campo, Antonio
2006-01-01
Coupled laminar natural convection with radiation in air-filled square enclosure heated from below and cooled from above is studied numerically for a wide variety of radiative boundary conditions at the sidewalls. A numerical model based on the finite difference method was used for the solution of mass, momentum and energy equations. The surface-to-surface method was used to calculate the radiative heat transfer. Simulations were performed for two values of the emissivities of the active and insulated walls (ɛ1=0.05 or 0.85, ɛ2=0.05 or 0.85) and Rayleigh numbers ranging from 103 to 2.3×106 . The influence of those parameters on the flow and temperature patterns and heat transfer rates are analyzed and discussed for different steady-state solutions. The existing ranges of these solutions are reported for the four different cases considered. It is founded that, for a fixed Ra, the global heat transfer across the enclosure depends only on the magnitude of the emissivity of the active walls. The oscillatory behavior, characterizing the unsteady-state solutions during the transitions from bicellular flows to the unicellular flow are observed and discussed.
Kulesh, M.; Holschneider, M.; Shardakov, I.
2005-12-01
The problem of the surface elastic wave propagation in the half-space within the framework of the Cosserat continuum has been considered. Medium deformation in this model is described not only by the displacement vector, but also by kinematically independent rotation vector. This model can be used for the description of the media with microstructure, for example concrete, sand, sandy-gravel mixture etc. At the same time the applications of these models almost do not exist in praxis, since there are no reliable data about the material properties in nonsymmetrical elasticity theory and in fact there are no experiments which can demonstrate the effects of couple-stress behavior in solid under deformation. The main result of presented work consist in fact, that within the framework of the Cosserat continuum in half-space besides elliptical Rayleigh wave can be in existence the surface shear wave with only transversal component. Geometrically such wave is equal to Love wave, but in classical elasticity theory existence of the Love wave as surface elastic wave is defined by presence of a layer on a half-space, and while a layer thickness vanishing the Love wave proceeds to a plane wave. Thus, in Cosserat medium the new wave mode is found out, and there is no analogue of it in classical elasticity theory. As a second result of presented work the method of the displacement seismogram inversion has been proposed. This method is based on continues wavelet transform and allows to restore the wave number, phase and group velocities. These results can be effectively used in possible experiments which are aimed at the detection of couple-stress effects in medium and further at the identification of material constants of nonsymmetrical elasticity theory. This work was supported by Russian Foundation of Fundamental Research under project 03-01-00561 and by the Deutsche Forschungsgemeinschaft (DFG) within the framework of the priority program SPP 1114, Mathematical methods for time
Viscoelastic love-type surface waves
Borcherdt, Roger D.
2008-01-01
The general theoretical solution for Love-Type surface waves in viscoelastic media provides theoreticalexpressions for the physical characteristics of the waves in elastic as well as anelastic media with arbitraryamounts of intrinsic damping. The general solution yields dispersion and absorption-coefficient curves for the waves as a function of frequency and theamount of intrinsic damping for any chosen viscoelastic model.Numerical results valid for a variety of viscoelastic models provide quantitative estimates of the physicalcharacteristics of the waves pertinent to models of Earth materials ranging from small amounts of damping in the Earth’s crust to moderate and large amounts of damping in soft soils and water-saturated sediments. Numerical results, presented herein, are valid for a wide range of solids and applications.
Chiral Surface Waves for Enhanced Circular Dichroism
Pellegrini, Giovanni; Celebrano, Michele; Duò, Lamberto; Biagioni, Paolo
2016-01-01
We present a novel chiral sensing platform that combines a one-dimensional photonic crystal design with a birefringent surface defect. The platform sustains simultaneous transverse electric and transverse magnetic surface modes, which are exploited to generate chiral surface waves. The present design provides homogeneous and superchiral fields of both handednesses over arbitrarily large areas in a wide spectral range, resulting in the enhancement of the circular dichroism signal by two orders of magnitude, thus paving the road toward the successful combination of surface-enhanced spectroscopies and electromagnetic superchirality.
Surface acoustic wave propagation in graphene film
Roshchupkin, Dmitry, E-mail: rochtch@iptm.ru; Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Irzhak, Dmitry [Institute of Microelectronics Technology and High-Purity Materials Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Ortega, Luc [Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS, UMR 8502, 91405 Orsay Cedex (France); Zizak, Ivo; Erko, Alexei [Institute for Nanometre Optics and Technology, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein Strasse 15, 12489 Berlin (Germany); Tynyshtykbayev, Kurbangali; Insepov, Zinetula [Nazarbayev University Research and Innovation System, 53 Kabanbay Batyr St., Astana 010000 (Kazakhstan)
2015-09-14
Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals.
Chiral surface waves for enhanced circular dichroism
Pellegrini, Giovanni; Finazzi, Marco; Celebrano, Michele; Duò, Lamberto; Biagioni, Paolo
2017-06-01
We present a novel chiral sensing platform that combines a one-dimensional photonic crystal design with a birefringent surface defect. The platform sustains simultaneous transverse electric and transverse magnetic surface modes, which are exploited to generate chiral surface waves. The present design provides homogeneous and superchiral fields of both handednesses over arbitrarily large areas in a wide spectral range, resulting in the enhancement of the circular dichroism signal by more than two orders of magnitude, thus paving the road toward the successful combination of surface-enhanced spectroscopies and electromagnetic superchirality.
Surface acoustic wave propagation in graphene film
Roshchupkin, Dmitry; Ortega, Luc; Zizak, Ivo; Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Erko, Alexei; Tynyshtykbayev, Kurbangali; Irzhak, Dmitry; Insepov, Zinetula
2015-09-01
Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals.
Gas sensing with surface acoustic wave devices
Martin, S. J.; Schweizer, K. S.; Ricco, A. J.; Zipperian, T. E.
1985-03-01
The use of a ZnO-on-Si surface acoustic wave (SAW) resonator as a gas sensor is discussed. In particular, the sensitivity of the device to organic vapors is examined. The planar nature of the SAW device, in which the acoustic energy is confined to within roughly one acoustic wavelength of the surface, makes the device extremely sensitive to surface perturbations. This characteristic has been exploited in the construction of SAW gas sensors in which the surface wave propagation characteristics are altered by species adsorbed from the ambient gas. The porous nature of the sputtered ZnO film, in conjunction with the microbalance capability of the SAW device, gives the sensor the ability to distinguish molecules on the basis of both size and mass.
Surface waves on metal-dielectric metamaterials
Takayama, Osamu; Shkondin, Evgeniy; Panah, Mohammad Esmail Aryaee;
2016-01-01
In this paper we analyze surface electromagnetic waves supported at an interface between an isotropic medium and an effective anisotropic material that can be realized by alternating conductive and dielectric layers with deep subwavelength thicknesses. This configuration can host various types of...
Some Applications of Surface Acoustic Wave Sensors
2000-01-01
The paper describes the evaluation of thin amorphous magnetic film by using of surface acoustic waves on piezo electric substrate. The obtained experimental data show strong dependence of material parameters on the annealing temperature. The mixed ferromagnetic/SAW devices for electronic applications will be also discussed.
Sankar N. Bhattacharya
2015-11-01
Full Text Available Sensitivity kernels or partial derivatives of phase velocity (c and group velocity (U with respect to medium parameters are useful to interpret a given set of observed surface wave velocity data. In addition to phase velocities, group velocities are also being observed to find the radial anisotropy of the crust and mantle. However, sensitivities of group velocity for a radially anisotropic Earth have rarely been studied. Here we show sensitivities of group velocity along with those of phase velocity to the medium parameters VSV, VSH , VPV, VPH , h and density in a radially anisotropic spherical Earth. The peak sensitivities for U are generally twice of those for c; thus U is more efficient than c to explore anisotropic nature of the medium. Love waves mainly depends on VSH while Rayleigh waves is nearly independent of VSH . The sensitivities show that there are trade-offs among these parameters during inversion and there is a need to reduce the number of parameters to be evaluated independently. It is suggested to use a nonlinear inversion jointly for Rayleigh and Love waves; in such a nonlinear inversion best solutions are obtained among the model parameters within prescribed limits for each parameter. We first choose VSH, VSV and VPH within their corresponding limits; VPV and h can be evaluated from empirical relations among the parameters. The density has small effect on surface wave velocities and it can be considered from other studies or from empirical relation of density to average P-wave velocity.
Chiu, Chi-Shun; Gwo, Shangjr
2008-05-01
The immobilization scheme of monodispersed gold nanoparticles (10-nm diameter) on piezoelectric substrate surfaces using organosilane molecules as cross-linkers has been developed for lithium niobate (LiNbO3) and silicon oxide (SiO2)/gold-covered lithium tantalate (LiTaO3) of Rayleigh and guided shear horizontal- (guided SH) surface acoustic wave (SAW) sensors. In this study, comparative measurements of gold nanoparticle adsorption kinetics using high-resolution field-emission scanning electron microscopy and SAW sensors allow the frequency responses of SAW sensors to be quantitatively correlated with surface densities of adsorbed nanoparticles. Using this approach, gold nanoparticles are used as the "nanosized mass standards" to scale the mass loading in a wide dynamical range. Rayleigh-SAW and guided SH-SAW sensors are employed here to monitor the surface mass changes on the device surfaces in gas and liquid phases, respectively. The mass sensitivity ( approximately 20 Hz.cm2/ng) of Rayleigh-SAW device (fundamental oscillation frequency of 113.3 MHz in air) is more than 2 orders of magnitude higher than that of conventional 9-MHz quartz crystal microbalance sensors. Furthermore, in situ (aqueous solutions), real-time measurements of adsorption kinetics for both citrate-stabilized gold nanoparticles and DNA-gold nanoparticle conjugates are also demonstrated by guided SH-SAW (fundamental oscillation frequency of 121.3 MHz). By comparing frequency shifts between the adsorption cases of gold nanoparticles and DNA-gold nanoparticle conjugates, the average number of bound oligonucleotides per gold nanoparticle can also be determined. The high mass sensitivity ( approximately 6 Hz.cm2/ng) of guided SH-SAW sensors and successful detection of DNA-gold nanoparticle conjugates paves the way for real-time biosensing in liquids using nanoparticle-enhanced SAW devices.
Linear and Nonlinear Surface Waves in Electrohydrodynamics
Hunt, Matthew; Vanden-broeck, Jean-Marc; Papageorgiou, Demetrios
2015-01-01
The problem of interest in this article are waves on a layer of finite depth governed by the Euler equations in the presence of gravity, surface tension, and vertical electric fields. Perturbation theory is used to identify canonical scalings and to derive a Kadomtsev-Petviashvili equation withan additional non-local term arising in interfacial electrohydrodynamics.When the Bond number is equal to 1/3, dispersion disappears and shock waves could potentially form. In the additional limit of vanishing electric fields, a new evolution equation is obtained which contains third and fifth-order dispersion as well as a non-local electric field term.
Blackfolds, plane waves and minimal surfaces
Armas, Jay; Blau, Matthias
2015-07-01
Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.
Senveli, Sukru U.; Tigli, Onur
2013-12-01
This paper introduces the use of finite element method analysis tools to investigate the use of a Rayleigh type surface acoustic wave (SAW) sensor to interrogate minute amounts of liquids trapped in microcavities placed on the delay line. Launched surface waves in the ST-X quartz substrate couple to the liquid and emit compressional waves. These waves form a resonant cavity condition and interfere with the surface waves in the substrate. Simulations show that the platform operates in a different mechanism than the conventional mass loading of SAW devices. Based on the proposed detection mechanism, it is able to distinguish between variations of 40% and 90% glycerin based on phase relations while using liquid volumes smaller than 10 pl. Results from shallow microcavities show high correlation with sound velocity parameter of the liquid whereas deeper microcavities display high sensitivities with respect to glycerin concentration. Simulated devices yield a maximum sensitivity of -0.77°/(% glycerin) for 16 μm wavelength operation with 8 μm deep, 24 μm wide, and 24 μm long microcavities.
NUMERICAL STUDY ON EFFECT OF WAVING BED ON THE SURFACE WAVE
WU Zheng-ren; CHENG You-liang; WANG Song-ling
2006-01-01
The effect of the waving bed on the surface wave was investigated. The wave equation was reduced from the potential flow theory with the perturbation technique, and then was solved by using the pseudo-spectral method. The waterfall of the surface wave was simulated with the Matlab. It is shown that for the waving bed, an additional harmonic wave appears on the surface together with the solitary wave existing for the non-waving bed, and two kinds of waves do not interfere with each other. With the development of time, the waveform for the waving bed is kept invariable, and just the amplitude is reduced gradually. Wave-breaking phenomenon for the non-waving bed does not appear, so the waving bed seems useful to prevent the breaking of the wave.
Surface wave velocity structure of the western Himalayan syntaxis
Hanna, A. C.; Weeraratne, D. S.
2013-09-01
The Nanga Parbat Haramosh massif (NPHM) is located in the western syntaxis of the India-Eurasia collision zone and is subject to erosion rates that are so extreme as to impact the isostatic equilibrium of the massif. In order to investigate the interaction between large scale tectonic forces and local isostatic processes, we employ a Rayleigh wave tomography method to measure phase velocities within the massif and surrounding region at crust and mantle depths. Our inversion solves for phase velocity anomalies by representing perturbations in the wavefield as the interference of two plane waves. Our data set was obtained from a temporary seismic array deployed in 1996 and includes 53 teleseismic events with Mw ≥ 5.0, at periods from 20 to 79 s. Phase velocities at short periods are low, ranging from 3.2 km s-1 at 20 s, and increasing gradually to 3.5 km s-1 at 40 s. These velocities are 11 per cent lower than velocities observed in the Indian continental Plate at periods below 45 s. Above 50 s, phase velocities in the Nanga Parbat region are significantly higher, ranging from 3.7 km s-1 at 45 s to 4.0 km s-1 at 79 s. These high phase velocities above 60 s are consistent with average velocities measured within the Indian Plate. Comparison of these results with surface wave studies in other regions of the Tibetan plateau including the eastern syntaxis and central Tibet show a similar low velocity anomaly below 45 s. Phase velocities above 55 s, however, are significantly higher in the Nanga Parbat region compared to velocities reported for all other regions of the plateau. Shear wave inversions produce significantly low velocities in the upper crust of the NPHM but exceed average lithospheric velocities below the Moho. We suggest the combination of anomalously low velocities in the upper crust and high velocities at lithospheric depths is due to rapid exhumation of deep crustal material causing elevated geothermal gradients. Azimuthal anisotropy shows a NNW-SSE fast
Pavlis, Gary L.; Mahdi, Hanan
1996-04-01
We studied the propagation of Rayleigh waves at regional distances in central Asia using a combination of array processing techniques and surface wave analysis. We present results from the detailed analysis of three representative events recorded by a 10-station, broadband network that has been running in the central Asian country of Kyrgyzstan since 1991: an Ms = 5.1 event near Ashkhabad, Turkmenistan; an Ms = 5.8 event in south central Tibet; and the October 7, 1994, nuclear explosion at Lop Nor. We find there is a remarkable difference in the propagation characteristics of surface waves along these three paths. The path from the event in Turkmenistan is simple and is well approximated by propagation through a laterally homogeneous medium. Array processing shows the entire Rayleigh wave train stacks coherently and arrives from an azimuth close to that predicted by a great circle path. Furthermore, estimates of dispersion curves and fundamental mode signals determined for individual stations show little variation across the array. The Tibet and Lop Nor paths are completely different. We find strong evidence for complicated multipathing and scattering effects along both of these paths. We observe a three-stage pattern in the Tibet case: (1) the early, lowest-frequency part of the Rayleigh wave packet arrives as a coherent signal from close to the great circle path azimuth; (2) this is overpowered in the period range around 20 s by a strong multipath signal that propagates across the array from a much more southerly azimuth; and (3) periods below 20 s rapidly become incoherent, and the signal does not have a well-defined direction of propagation. The Lop Nor path shows similar complexity. On this path there is little dispersion for measurable periods greater than 10 s, so the low-frequency energy arrives in an Airy phase. The Airy phase stacks somewhat coherently (it stacks, but significant power is lost in the best beam), and slowness analysis shows it arrives from
Kogure, Masaru; Nakamura, Takuji; Ejiri, Mitsumu K.; Nishiyama, Takanori; Tomikawa, Yoshihiro; Tsutsumi, Masaki; Suzuki, Hidehiko; Tsuda, Takuo T.; Kawahara, Takuya D.; Abo, Makoto
2017-08-01
The potential energy of gravity waves (GWs) per unit mass (Ep), at altitudes of 15-70 km, has been examined from temperature profiles obtained by a Rayleigh/Raman lidar at Syowa Station (69°S, 40°E) from May 2011 to October 2013, with the exception of the summer months. The GWs with ground-based wave periods longer than 2 h and vertical wavelengths between 1.8 and 16 km were extracted from the temperature profiles. Ep was larger in winter than in spring and fall, although in 2012, at altitudes below 30 km, Ep was larger in spring than in winter and fall. Ep increased with a mean scale height of 11.3 km. Ep profiles showed a local maximum at an altitude of 20 km and a minimum at 25 km in almost every month, which has not been reported by previous studies observed by radiosondes. The values of Ep in October of 2012 were smaller at 35-60 km and larger at 20-35 km than those in October of 2011 and 2013. This difference in the Ep profile is most probably caused by different seasonal variations of zonal winds. The larger and smaller Ep values seem to be observed both below and above the altitude at which the zonal wind speed reached 0 m s-1. This result suggests that wind filtering of gravity waves with small phase speeds is significantly important in early spring.
Blackfolds, Plane Waves and Minimal Surfaces
Armas, Jay
2015-01-01
Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid...
Watching surface waves in phononic crystals.
Wright, Oliver B; Matsuda, Osamu
2015-08-28
In this paper, we review results obtained by ultrafast imaging of gigahertz surface acoustic waves in surface phononic crystals with one- and two-dimensional periodicities. By use of quasi-point-source optical excitation, we show how, from a series of images that form a movie of the travelling waves, the dispersion relation of the acoustic modes, their corresponding mode patterns and the position and widths of phonon stop bands can be obtained by temporal and spatio-temporal Fourier analysis. We further demonstrate how one can follow the temporal evolution of phononic eigenstates in k-space using data from phononic-crystal waveguides as an example. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Renaudin, Alan; Chabot, Vincent; Grondin, Etienne; Aimez, Vincent; Charette, Paul G
2010-01-07
This article presents a device incorporating surface plasmon resonance (SPR) sensing and surface acoustic wave (SAW) actuation integrated onto a common LiNbO(3) piezoelectric substrate. The device uses Rayleigh-type SAW to provide active microfluidic mixing in the fluid above the SPR sensor. Validation experiments show that SAW-induced microfluidic mixing results in accelerated binding kinetics of an avidin-biotin assay. Results also show that, though SAW action causes a parasitic SPR response due to heat injection into the fluid, a relatively brief relaxation time following the SAW pulses allows the effect to dissipate, without affecting the overall assay response. Since both SPR sensors and SAW transducers can be fabricated simultaneously using low-cost microfabrication methods on a single substrate, the proposed design is well-suited to lab-on-chip applications.
Wireless Multiplexed Surface Acoustic Wave Sensors Project
Youngquist, Robert C.
2014-01-01
Wireless Surface Acoustic Wave (SAW) Sensor is a new technology for obtaining multiple, real-time measurements under extreme environmental conditions. This project plans to develop a wireless multiplexed sensor system that uses SAW sensors, with no batteries or semiconductors, that are passive and rugged, can operate down to cryogenic temperatures and up to hundreds of degrees C, and can be used to sense a wide variety of parameters over reasonable distances (meters).
Wave groups in uni-directional surface-wave models
Groesen, van E.
1998-01-01
Uni-directional wave models are used to study wave groups that appear in wave tanks of hydrodynamic laboratories; characteristic for waves in such tanks is that the wave length is rather small, comparable to the depth of the layer. In second-order theory, the resulting Nonlinear Schrödinger (NLS) eq
Broadband surface-wave transformation cloak
Xu, Su; Xu, Hongyi; Gao, Hanhong; Jiang, Yuyu; Yu, Faxin; Joannopoulos, John D.; Soljačić, Marin; Chen, Hongsheng; Sun, Handong; Zhang, Baile
2015-01-01
Guiding surface electromagnetic waves around disorder without disturbing the wave amplitude or phase is in great demand for modern photonic and plasmonic devices, but is fundamentally difficult to realize because light momentum must be conserved in a scattering event. A partial realization has been achieved by exploiting topological electromagnetic surface states, but this approach is limited to narrow-band light transmission and subject to phase disturbances in the presence of disorder. Recent advances in transformation optics apply principles of general relativity to curve the space for light, allowing one to match the momentum and phase of light around any disorder as if that disorder were not there. This feature has been exploited in the development of invisibility cloaks. An ideal invisibility cloak, however, would require the phase velocity of light being guided around the cloaked object to exceed the vacuum speed of light—a feat potentially achievable only over an extremely narrow band. In this work, we theoretically and experimentally show that the bottlenecks encountered in previous studies can be overcome. We introduce a class of cloaks capable of remarkable broadband surface electromagnetic waves guidance around ultrasharp corners and bumps with no perceptible changes in amplitude and phase. These cloaks consist of specifically designed nonmagnetic metamaterials and achieve nearly ideal transmission efficiency over a broadband frequency range from 0+ to 6 GHz. This work provides strong support for the application of transformation optics to plasmonic circuits and could pave the way toward high-performance, large-scale integrated photonic circuits. PMID:26056299
Parallel Algorithm in Surface Wave Waveform Inversion
无
2001-01-01
In Surface wave waveform inversion, we want to reconstruct 3Dshear wav e velocity structure, which calculation beyond the capability of the powerful pr esent day personal computer or even workstation. So we designed a high parallele d algorithm and carried out the inversion on Parallel computer based on the part itioned waveform inversion (PWI). It partitions the large scale optimization pro blem into a number of independent small scale problems and reduces the computati onal effort by several orders of magnitude. We adopted surface waveform inversio n with a equal block(2°×2°) discretization.
Levshin, Anatoli L.; Barmin, Mikhail P.; Moschetti, Morgan P.; Mendoza, Carlos; Ritzwoller, Michael H.
2012-01-01
The purpose of this study is to develop and test a modiﬁcation to a previous method of regional seismic event location based on Empirical Green’s Functions (EGFs) produced from ambient seismic noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long ambient noise time-series recorded at the two stations. The EGFs principally contain Rayleigh- and Love-wave energy on the vertical and transverse components, respectively, and we utilize these signals between about 5 and 12 s period. The previous method, based exclusively on Rayleigh waves, may yield biased epicentral locations for certain event types with hypocentral depths between 2 and 5 km. Here we present theoretical arguments that show how Love waves can be introduced to reduce or potentially eliminate the bias. We also present applications of Rayleigh- and Love-wave EGFs to locate 10 reference events in the western United States. The separate Rayleigh and Love epicentral locations and the joint locations using a combination of the two waves agree to within 1 km distance, on average, but conﬁdence ellipses are smallest when both types of waves are used.
Illusions and Cloaks for Surface Waves
McManus, T. M.; Valiente-Kroon, J. A.; Horsley, S. A. R.; Hao, Y.
2014-08-01
Ever since the inception of Transformation Optics (TO), new and exciting ideas have been proposed in the field of electromagnetics and the theory has been modified to work in such fields as acoustics and thermodynamics. The most well-known application of this theory is to cloaking, but another equally intriguing application of TO is the idea of an illusion device. Here, we propose a general method to transform electromagnetic waves between two arbitrary surfaces. This allows a flat surface to reproduce the scattering behaviour of a curved surface and vice versa, thereby giving rise to perfect optical illusion and cloaking devices, respectively. The performance of the proposed devices is simulated using thin effective media with engineered material properties. The scattering of the curved surface is shown to be reproduced by its flat analogue (for illusions) and vice versa for cloaks.
Importance of a 3D forward modeling tool for surface wave analysis methods
Pageot, Damien; Le Feuvre, Mathieu; Donatienne, Leparoux; Philippe, Côte; Yann, Capdeville
2016-04-01
Since a few years, seismic surface waves analysis methods (SWM) have been widely developed and tested in the context of subsurface characterization and have demonstrated their effectiveness for sounding and monitoring purposes, e.g., high-resolution tomography of the principal geological units of California or real time monitoring of the Piton de la Fournaise volcano. Historically, these methods are mostly developed under the assumption of semi-infinite 1D layered medium without topography. The forward modeling is generally based on Thomson-Haskell matrix based modeling algorithm and the inversion is driven by Monte-Carlo sampling. Given their efficiency, SWM have been transfered to several scale of which civil engineering structures in order to, e.g., determine the so-called V s30 parameter or assess other critical constructional parameters in pavement engineering. However, at this scale, many structures may often exhibit 3D surface variations which drastically limit the efficiency of SWM application. Indeed, even in the case of an homogeneous structure, 3D geometry can bias the dispersion diagram of Rayleigh waves up to obtain discontinuous phase velocity curves which drastically impact the 1D mean velocity model obtained from dispersion inversion. Taking advantages of high-performance computing center accessibility and wave propagation modeling algorithm development, it is now possible to consider the use of a 3D elastic forward modeling algorithm instead of Thomson-Haskell method in the SWM inversion process. We use a parallelized 3D elastic modeling code based on the spectral element method which allows to obtain accurate synthetic data with very low numerical dispersion and a reasonable numerical cost. In this study, we choose dike embankments as an illustrative example. We first show that their longitudinal geometry may have a significant effect on dispersion diagrams of Rayleigh waves. Then, we demonstrate the necessity of 3D elastic modeling as a forward
Shear wave velocity structure in North America from large-scale waveform inversions of surface waves
Alsina, D.; Woodward, R. L.; Snieder, R. K.
1996-07-01
A two-step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath North America using surface wave data. The lateral resolution for most areas of the model is of the order of several hundred kilometers. The most obvious feature in the tomographic images is the rapid transition between low velocities in the tectonically active region west of the Rocky Mountains and high velocities in the stable central and eastern shield of North America. The model also reveals smaller-scale heterogeneous velocity structures. A high-velocity anomaly is imaged beneath the state of Washington that could be explained as the subducting Juan de Fuca plate beneath the Cascades. A large low-velocity structure extends along the coast from the Mendocino to the Rivera triple junction and to the continental interior across the southwestern United States and northwestern Mexico. Its shape changes notably with depth. This anomaly largely coincides with the part of the margin where no lithosphere is consumed since the subduction has been replaced by a transform fault. Evidence for a discontinuous subduction of the Cocos plate along the Middle American Trench is found. In central Mexico a transition is visible from low velocities across the Trans-Mexican Volcanic Belt (TMVB) to high velocities beneath the Yucatan Peninsula. Two elongated low-velocity anomalies beneath the Yellowstone Plateau and the eastern Snake River Plain volcanic system and beneath central Mexico and the TMVB seem to be associated with magmatism and partial melting. Another low-velocity feature is seen at depths of approximately 200 km beneath Florida and the Atlantic Coastal Plain. The inversion technique used is based on a linear surface wave scattering theory, which gives tomographic images of the relative phase velocity perturbations in four period bands ranging from 40 to 150 s. In order to find a smooth reference model a nonlinear inversion based on ray theory is first performed. After
Shear wave velocity structure in North America from large-scale waveform inversions of surface waves
Alsina, D.; Woodward, R.L.; Snieder, R.K.
1996-01-01
A two-step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath North America using surface wave data. The lateral resolution for most areas of the model is of the order of several hundred kilometers. The most obvious feature in the tomographic images is the rapid transition between low velocities in the technically active region west of the Rocky Mountains and high velocities in the stable central and eastern shield of North America. The model also reveals smaller-scale heterogeneous velocity structures. A high-velocity anomaly is imaged beneath the state of Washington that could be explained as the subducting Juan de Fuca plate beneath the Cascades. A large low-velocity structure extends along the coast from the Mendocino to the Rivera triple junction and to the continental interior across the southwestern United States and northwestern Mexico. Its shape changes notably with depth. This anomaly largely coincides with the part of the margin where no lithosphere is consumed since the subduction has been replaced by a transform fault. Evidence for a discontinuous subduction of the Cocos plate along the Middle American Trench is found. In central Mexico a transition is visible from low velocities across the Trans-Mexican Volcanic Belt (TMVB) to high velocities beneath the Yucatan Peninsula. Two elongated low-velocity anomalies beneath the Yellowstone Plateau and the eastern Snake River Plain volcanic system and beneath central Mexico and the TMVB seem to be associated with magmatism and partial melting. Another low-velocity feature is seen at depths of approximately 200 km beneath Florida and the Atlantic Coastal Plain. The inversion technique used is based on a linear surface wave scattering theory, which gives tomographic images of the relative phase velocity perturbations in four period bands ranging from 40 to 150 s. In order to find a smooth reference model a nonlinear inversion based on ray theory is first performed. After
Zulhan, Zulfakriza; Saygin, Erdinc; Cummins, Phil; Widiyantoro, Sri; Nugraha, Andri Dian; Luehr, Birger-G.; Bodin, Thomas
2015-04-01
Our previous study on MERAMEX data (Zulfakriza et al., 2014) obtained features of the tomographic images which correlate well with the surface geology of central Java in periods between 1 to 12 sec. Kendeng Basin and active volcanoes in the central part of this region are clearly imaged with low group velocities with values around 0.8 km/sec, while the carbonate structures in the southern part of the region correspond to higher group velocities in the range of 1.8 to 2.0 km/sec. In this current study, we invert dispersion curves obtained from seismic noise tomography to estimate shear wave-depth profiles of the region. The results are used to discuss the spatial variation of shear wave velocities for a depth range down from the surface to upper crust. Most of the shear wave velocity anomalies, including the upper crustal areas of the Kendeng basin and active volcanoes, are consistent with our previous study of Rayleigh wave group velocities and fit to the regional geology. Keywords: Dispersion Inversion; shear wave velocity; Central Java, Indonesia. Reference: Zulfakriza, Z., Saygin, E., Cummins, P., Widiyantoro, S., Nugraha, A., Luehr, B.-G., Bodin, T., 2014. Upper crustal structure of central Java, Indonesia, from transdimensional seismic ambient noise tomography. Geophys. J. Int. 197.
A global shear velocity model of the mantle from normal modes and surface waves
durand, S.; Debayle, E.; Ricard, Y. R.; Lambotte, S.
2013-12-01
We present a new global shear wave velocity model of the mantle based on the inversion of all published normal mode splitting functions and the large surface wave dataset measured by Debayle & Ricard (2012). Normal mode splitting functions and surface wave phase velocity maps are sensitive to lateral heterogeneities of elastic parameters (Vs, Vp, xi, phi, eta) and density. We first only consider spheroidal modes and Rayleigh waves and restrict the inversion to Vs, Vp and the density. Although it is well known that Vs is the best resolved parameter, we also investigate whether our dataset allows to extract additional information on density and/or Vp. We check whether the determination of the shear wave velocity is affected by the a priori choice of the crustal model (CRUST2.0 or 3SMAC) or by neglecting/coupling poorly resolved parameters. We include the major discontinuities, at 400 and 670 km. Vertical smoothing is imposed through an a priori gaussian covariance matrix on the model and we discuss the effect of coupling/decoupling the inverted structure above and below the discontinuities. We finally discuss the large scale structure of our model and its geodynamical implications regarding the amount of mass exchange between the upper and lower mantle.
Computer simulation study of surface wave dynamics at the crystal--melt interface
Benet, Jorge; Sanz, Eduardo
2014-01-01
We study, by means of computer simulations, the crystal-melt interface of three different systems: hard-spheres, Lennard Jones and the TIP4P/2005 water model. In particular, we focus on the dynamics of surface waves. We observe that the processes involved in the relaxation of surface waves are characterized by distinct time scales: a slow one related to the continuous recrystallization and melting, that is governed by capillary forces; and a fast one which we suggest to be due to a combination of processes that quickly cause small perturbations to the shape of the interface (like e. g. Rayleigh waves, subdiffusion, or attachment/detachment of particles to/from the crystal). The relaxation of surface waves becomes dominated by the slow process as the wavelength increases. Moreover, we see that the slow relaxation is not influenced by the details of the microscopic dynamics. In a time scale characteristic for the diffusion of the liquid phase, the relaxation dynamics of the crystal-melt interface of water is ar...
Extraordinary transmission of gigahertz surface acoustic waves
Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H.; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H.; Wright, Oliver B.
2016-09-01
Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.
Extraordinary transmission of gigahertz surface acoustic waves.
Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H; Wright, Oliver B
2016-09-19
Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3-50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.
Extraordinary transmission of gigahertz surface acoustic waves
Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H.; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H.; Wright, Oliver B.
2016-01-01
Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging. PMID:27640998
Interaction of Vortices with a progressive Surface Wave
LinlinWANG; HuiyangMA
1996-01-01
Interaction of submerged vortices with a progressive surface wave is investigated by the finite-difference numerical solution of Navier-Stokes equations.The progressive wave is the surface gravity water wave in a finite depth.The initial vortex model is Oseen vortex.The numerical computations show that a special pattern of the wave surface may be observed by the interaction from the submerged vortices.The influences of Froude number,the initial geometric configuration of vortices,and the amplitude,inital phase of surface wave on the wave pattern are discussed.
Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal
Gao, Zhen; Zhang, Baile
2016-01-01
We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices.
Steady periodic gravity waves with surface tension
Walsh, Samuel
2009-01-01
In this paper we consider two-dimensional, stratified, steady water waves propagating over an impermeable flat bed and with a free surface. The motion is assumed to be driven by capillarity (that is, surface tension) on the surface and a gravitational force acting on the body of the fluid. We prove the existence of global continua of classical solutions that are periodic and traveling. This is accomplished by first constructing a 1-parameter family of laminar flow solutions, $\\mathcal{T}$, then applying bifurcation theory methods to obtain local curves of small amplitude solutions branching from $\\mathcal{T}$ at an eigenvalue of the linearized problem. Each solution curve is then continued globally by means of a degree theoretic theorem in the spirit of Rabinowitz. Finally, we complement the degree theoretic picture by proving an alternate global bifurcation theorem via the analytic continuation method of Dancer.
A. M. Abd-Alla
2013-01-01
Full Text Available Estimation is done to investigate the gravitational and rotational parameters effects on surface waves in fibre-reinforced thermoelastic media. The theory of generalized surface waves has been firstly developed and then it has been employed to investigate particular cases of waves, namely, Stoneley waves, Rayleigh waves, and Love waves. The analytical expressions for surface waves velocity and attenuation coefficient are obtained in the physical domain by using the harmonic vibrations and four thermoelastic theories. The wave velocity equations have been obtained in different cases. The numerical results are given for equation of coupled thermoelastic theory (C-T, Lord-Shulman theory (L-S, Green-Lindsay theory (G-L, and the linearized (G-N theory of type II. Comparison was made with the results obtained in the presence and absence of gravity, rotation, and parameters for fibre-reinforced of the material media. The results obtained are displayed by graphs to clear the phenomena physical meaning. The results indicate that the effect of gravity, rotation, relaxation times, and parameters of fibre-reinforced of the material medium is very pronounced.
Scattered surface wave energy in the seismic coda
Zeng, Y.
2006-01-01
One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.
Piezoelectric Film Waveguides for Surface Acoustic Waves
M.F. Zhovnir
2016-11-01
Full Text Available The paper presents results of mathematical modeling of piezoelectric film waveguide structures for surface acoustic waves (SAW. Piezoelectric ZnO film is supposed to be placed on a fused quartz substrate. The analytical ratios and numerical results allow to determine the design parameters of the waveguide structures to provide a single-mode SAW propagation mode. The results of amplitude and phase experimental studies of the SAW in the waveguide structures that were carried out on the laser optical sensing set up confirm the theoretical calculations.
Surface Acoustic Wave Atomizer and Electrostatic Deposition
Yamagata, Yutaka
A new methodology for fabricating thin film or micro patters of organic/bio material using surface acoustic wave (SAW) atomizer and electrostatic deposition is proposed and characteristics of atomization techniques are discussed in terms of drop size and atomization speed. Various types of SAW atomizer are compared with electrospray and conventional ultrasonic atomizers. It has been proved that SAW atomizers generate drops as small as electrospray and have very fast atomization speed. This technique is applied to fabrication of micro patterns of proteins. According to the result of immunoassay, the specific activity of immunoglobulin was preserved after deposition process.
Absorption of surface acoustic waves by graphene
S. H. Zhang
2011-06-01
Full Text Available We present a theoretical study on interactions of electrons in graphene with surface acoustic waves (SAWs. We find that owing to momentum and energy conservation laws, the electronic transition accompanied by the SAW absorption cannot be achieved via inter-band transition channels in graphene. For graphene, strong absorption of SAWs can be observed in a wide frequency range up to terahertz at room temperature. The intensity of SAW absorption by graphene depends strongly on temperature and can be adjusted by changing the carrier density. This study is relevant to the exploration of the acoustic properties of graphene and to the application of graphene as frequency-tunable SAW devices.
Tremblay, Simon-Pierre; Karray, Mourad; Chekired, Mohamed; Bessette, Carole; Jinga, Livius
2017-01-01
The inspection of underground concrete utility structures can be a challenging task due to their inaccessibility. This article presents a nondestructive inspection technique for the lids of such structures based on the propagation of elastic waves where the variation in soil vertical acceleration following an impact is recorded along a given line at the surface of the soil. The structures investigated are made of reinforced concrete and are located below a shallow homogeneous soil layer which is covered by a pavement. It is shown through finite difference numerical modeling that elastic waves are affected by the state of degradation of the underground concrete structure. It is also shown that the difference in dynamic properties between the soil and the concrete structure causes the latter to act as a waveguide that affects the variation of the vertical acceleration measured at the surface of the model. The propagation of elastic waves within different underground profiles is studied in terms of the variation of their energy and of their group and phase velocity. Theoretical models, computed using the propagator matrix technique, are presented in the appendix to demonstrate the importance of the waveguide effects, caused by the presence of the concrete structure, on the group and phase velocity dispersion curves of Rayleigh waves. Finally, some of the results obtained from the inspection of two different real underground structures are also presented. These results show that the proposed inspection technique, developed based on 1D and 2D numerical testing, is also effective for real structures.
Resonant surface acoustic wave chemical detector
Brocato, Robert W.; Brocato, Terisse; Stotts, Larry G.
2017-08-08
Apparatus for chemical detection includes a pair of interdigitated transducers (IDTs) formed on a piezoelectric substrate. The apparatus includes a layer of adsorptive material deposited on a surface of the piezoelectric substrate between the IDTs, where each IDT is conformed, and is dimensioned in relation to an operating frequency and an acoustic velocity of the piezoelectric substrate, so as to function as a single-phase uni-directional transducer (SPUDT) at the operating frequency. Additionally, the apparatus includes the pair of IDTs is spaced apart along a propagation axis and mutually aligned relative to said propagation axis so as to define an acoustic cavity that is resonant to surface acoustic waves (SAWs) at the operating frequency, where a distance between each IDT of the pair of IDTs ranges from 100 wavelength of the operating frequency to 400 wavelength of the operating frequency.
Surface Plasmon Wave Adapter Designed with Transformation Optics
Zhang, Jingjing; Xiao, Sanshui; Wubs, Martijn
2011-01-01
On the basis of transformation optics, we propose the design of a surface plasmon wave adapter which confines surface plasmon waves on non-uniform metal surfaces and enables adiabatic mode transformation of surface plasmon polaritons with very short tapers. This adapter can be simply achieved...... with homogeneous anisotropic naturally occurring materials or subwavelength grating-structured dielectric materials. Full wave simulations based on a finite-element method have been performed to validate our proposal....
Surface Plasmon Wave Adapter Designed with Transformation Optics
Zhang, Jingjing; Xiao, Sanshui; Wubs, Martijn;
2011-01-01
On the basis of transformation optics, we propose the design of a surface plasmon wave adapter which confines surface plasmon waves on non-uniform metal surfaces and enables adiabatic mode transformation of surface plasmon polaritons with very short tapers. This adapter can be simply achieved...... with homogeneous anisotropic naturally occurring materials or subwavelength grating-structured dielectric materials. Full wave simulations based on a finite-element method have been performed to validate our proposal....
Surface Wave Tomography of South China Sea from Ambient Seismic Noise and Two-station Measurements
Liang, W.-T.; Gung, Y.-C.
2012-04-01
We have taken the cross-correlation of seismic ambient noise technique as well as the two-station method to analyze the velocity structure in the South China Sea region. The dataset used in this study includes broadband waveforms recorded at the Taiwan BATS (Broadband Array in Taiwan for Seismology), Japan OHP (Ocean Hemisphere Project), Malaysia and Vietnam seismic networks. We remove the instrument response from daily data and filter the waveform with various frequency bands according to the length of each station-pair. Then we apply the commonly used 1-bit normalization to minimize the effect of earthquakes, instrumental irregularities, and non-stationary noise sources near to the stations. With the derived daily cross correlation function (CCF), we are able to examine the timing quality for each station-pair. We then obtain the surface Rayleigh wave dispersion curves from the stacked CCF for each station-pair. To cover the longer period band in the dispersion curves, we adopt the two-station method to compute both the group and phase velocities of surface waves. A new surface wave tomography based on ambient seismic noise study and traditional two-station technique has been achieved in this study. Raypaths that travel through the Central basin present higher velocity, which is in agreement with the idea of thin crust. On the other hand, the slower velocity between Taiwan and Northern Luzon, Philippine is mainly due to a thick accretionary prism above the Manila trench.
谷音; 于志敏
2011-01-01
A 2D finite element model for a semi-infinite space with layered media and Rayleigh wave input was built by using equivalent viscous-elastic artificial boundary elements. The responses in free-field of even and layered media were computed. The results indicated that the finite element method has excellent estimation precision compared with the theore tical solutions. The dynamic response of a pile-soil-bridge structure with dynamic interaction under Rayleigh waves was analyzed. A typical rigid frame bridge was included in this case study. The influence of different site conditions, changes of location of soft interlayer, different Rayleigh wave input and pile length on Rayleigh wave propagation and the seismic response were considered. The influencing factors of the rigid frame bridge structure were also discussed.%基于等效粘弹性人工边界单元建立了可考虑成层介质及Rayleigh波输入的二维有限元时域模型,计算了Sayleih波作用下成层介质与均匀介质的自由场反应,与理论解比较表明有限元计算结果具有较好的工程精度.针对Rayleigh波作用下桩-土-典型刚构桥梁结构动力反应进行了分析,考虑了场地条件的不同、软夹层位置的改变、不同频率Rayleigh波的输入以及桩长对Rayleigh波传播与场地地震反应的影响,对影响因素进行了讨论.
Spica, Z. J.; Perton, M.; Calo, M.; Cordoba-Montiel, F.; Legrand, D.; Iglesias, A.
2015-12-01
Standard application of the seismic ambient noise tomography considers the existence of synchronous records at stations for green's functions retrieval. More recent theoretical and experimental observations showed the possibility to apply correlation of coda of noise correlation (C3) to obtain green's functions between stations of asynchronous seismic networks making possible to dramatically increase databases for imagining the Earth's interior. However, this possibility has not been fully exploited yet, and right now the data C3 are not included into tomographic inversions to refine seismic structures. Here we show for the first time how to incorporate the data of C1 and C3 to calculate dispersion maps of Rayleigh waves in the range period of 10-120s, and how the merging of these datasets improves the resolution of the structures imaged. Tomographic images are obtained for an area covering Mexico, the Gulf of Mexico and the southern U.S. We show dispersion maps calculated using both data of C1 and the complete dataset (C1+C3). The latter provide new details of the seismic structure of the region allowing a better understanding of their role on the geodynamics of the study area. The resolving power obtained in our study is several times higher than in previous studies based on ambient noise. This demonstrates the new possibilities for imaging the Earth's crust and upper mantle using this enlarged database.
Surface-wave tomography of Ireland and surroundings using ambient noise and teleseismic data
Bonadio, Raffaele; Arroucau, Pierre; Lebedev, Sergei; Meier, Thomas; Schaeffer, Andrew; Licciardi, Andrea; Piana Agostinetti, Nicola
2016-04-01
Ireland's geology is dominated by northeast-southwest structural trends and suture zones, mostly inferred from geological mapping and a few active source seismic experiments. However, their geometry and extent at depth and their continuity across the Irish Sea are still poorly known. Important questions also remain unanswered regarding the thickness and bulk properties of the sedimentary cover at the regional scale, the deformation and flow of the deep crust during the formation of Ireland, the thickness of Ireland's lithosphere today, and the thermal structure and dynamics of the asthenosphere beneath Ireland. In this work, we take advantage of abundant, newly available broadband data from temporary array deployments and permanent seismic networks in Ireland and Great Britain to produce high-resolution models of seismic velocity structure and anisotropy of the lithosphere. We combine Rayleigh and Love phase velocity measurements from waveform cross-correlation using both ambient noise and teleseismic data in order to produce high-quality dispersion curves for periods ranging from 1 to 300 s. The phase velocity measurement procedures are adapted from Meier et al.[2], Lebedev et al.[1] and Soomro et al.[3] and are automated in order to deal with the large amount of data and ensure consistency and reproducibility. For the nearly 200 stations used in this study, we obtain a very large number of dispersion curves from both ambient noise and teleseimic data. Dispersion measurements are then inverted in a tomographic procedure for surface-wave phase velocity maps in a very broad period range. The maps constrain the 3D seismic-velocity structure of the crust and upper mantle underlying Ireland and the Irish Sea. {9} Lebedev, S., T. Meier, R. D. van der Hilst. Asthenospheric flow and origin of volcanism in the Baikal Rift area, Earth Planet. Sci. Lett., 249, 415-424, 2006. Meier, T., K. Dietrich, B. Stockhert, H.P. Harjes, One-dimensional models of shear wave velocity for
On elliptic cylindrical Kadomtsev-Petviashvili equation for surface waves
Khusnutdinova, K R; Matveev, V B; Smirnov, A O
2012-01-01
The `elliptic cylindrical Kadomtsev-Petviashvili equation' is derived for surface gravity waves with nearly-elliptic front, generalising the cylindrical KP equation for nearly-concentric waves. We discuss transformations between the derived equation and two existing versions of the KP equation, for nearly-plane and nearly-concentric waves. The transformations are used to construct important classes of exact solutions of the derived equation and corresponding approximate solutions for surface waves.
Surface wave inversion for a p-wave velocity profile: Estimation of the squared slowness gradient
Ponomarenko, A.V.; Kashtan, B.M.; Troyan, V.N.; Mulder, W.A.
2013-01-01
Surface waves can be used to obtain a near-surface shear wave profile. The inverse problem is usually solved for the locally 1-D problem of a set of homogeneous horizontal elastic layers. The output is a set of shear velocity values for each layer in the profile. P-wave velocity profile can be estim
Surface-wave mode coupling : modelling and inverting waveforms including body-wave phases
Marquering, H.A.
1996-01-01
This thesis is concerned with a similar problem as addressed by Li & Tanimoto (1993) in the surfacewave mode approach. In this thesis it is shown that surface-wave mode coupling is required when body-wave phases in laterally heterogeneous media are modelled by surface-wave mode summation. An efficie
An Internal Wave as a Frequency Filter for Surface Gravity Waves on Water
Lossow, K
2010-01-01
We consider one-dimensional model of the interaction between surface and the internal gravity water waves. The internal wave is modeled by its basic form: a non-dispersive field with a horizontal current that is uniform over all depth, insignificantly affected by the surface waves, while ignoring surface tension and wind growth/decay effects. The depth is infinite. Approximation for the height of the surface wave on the flow by the "elementary quasi stationary" solutions was found. It was shown that the flow acts as a frequency filter for gravitational waves on water.
Surface-acoustic-wave (SAW) flow sensor
Joshi, Shrinivas G.
1991-03-01
The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 deg rotated Y-cut lithium niobate substrate and heated to 55 C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cu cm/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.
Huang, Liang; Lyu, Qingqing; Wen, Dandan; Zhong, Zhiyong; Zhang, Huaiwu; Bai, Feiming
2016-01-01
The surface acoustic wave properties of piezoelectric/magnetostrictive layered structures consisting of insulating ZnO and metallic Metglas with giant Δ E effect were studied based on a stable scattering matrix method. Only the first Rayleigh mode was found with phase velocity between 2200 m/s and 2650 m/s, and the maximum electro-mechanical coupling coefficient about 1%. It was found that the center frequency of ZnO/Metglas is highly sensitive on the change of magnetic field, up to 440 MHz/Oe. However, there is a cutoff Young's modulus of Metglas for different designs of SAW, below which the Rayleigh mode will disappear. For a magnetoelectric SAW design with the center frequency of 335 MHz and covering a full magnetic field range from -1.4 to +1.4 Oe, the frequency sensitivity is 212 MHz/Oe, equivalent to a magnetic field sensitivity of 5 × 10-12 Tesla. Unlike conventional magnetoelectric bulk laminates or film stacks, the detection of frequency shift instead of electrical charge allows not only shrinkage of device volume but also a broad frequency band detection of weak magnetic field.
Short-period surface-wave phase velocities across the conterminous United States
Ekström, G.
2017-09-01
Surface-wave phase-velocity maps for the full footprint of the USArray Transportable Array (TA) across the conterminous United States are developed and tested. Three-component, long-period continuous seismograms recorded on more than 1800 seismometers, most of which were deployed for 18 months or longer, are processed using a noise cross-correlation technique to derive inter-station Love and Rayleigh dispersion curves at periods between 5 and 40 s. The phase-velocity measurements are quality controlled using an automated algorithm and then used in inversions for Love and Rayleigh phase-velocity models at discrete periods on a 0.25°-by-0.25° pixel grid. The robustness of the results is examined using comparisons of maps derived from subsets of the data. A winter-summer division of the cross-correlation data results in small model differences, indicating relatively minor sensitivity of the results to seasonal variations in the distribution of noise sources. Division of the dispersion data based on inter-station azimuth does not result in geographically coherent model differences, suggesting that azimuthal anisotropy at the regional scale is weak compared with variations in isotropic velocities and does not substantially influence the results for isotropic velocities. The phase-velocity maps and dispersion measurements are documented and made available as data products of the 10-year-long USArray TA deployment.
Surface Waves in Almost Incompressible Elastic Materials
Virta, Kristoffer
2013-01-01
A recent study shows that the classical theory concerning accuracy and points per wavelength is not valid for surface waves in almost incompressible elastic materials. The grid size must instead be proportional to $(\\frac{\\mu}{\\lambda})^{(1/p)}$ to achieve a certain accuracy. Here $p$ is the order of accuracy the scheme and $\\mu$ and $\\lambda$ are the Lame parameters. This accuracy requirement becomes very restrictive close to the incompressible limit where $\\frac{\\mu}{\\lambda} \\ll 1$, especially for low order methods. We present results concerning how to choose the number of grid points for 4th, 6th and 8th order summation-by-parts finite difference schemes. The result is applied to Lambs problem in an almost incompressible material.
The radiation of surface wave energy: Implications for volcanic tremor
Haney, M. M.; Denolle, M.; Lyons, J. J.; Nakahara, H.
2015-12-01
The seismic energy radiated by active volcanism is one common measurement of eruption size. For example, the magnitudes of individual earthquakes in volcano-tectonic (VT) swarms can be summed and expressed in terms of cumulative magnitude, energy, or moment release. However, discrepancies exist in current practice when treating the radiated energy of volcano seismicity dominated by surface waves. This has implications for volcanic tremor, since eruption tremor typically originates at shallow depth and is made up of surface waves. In the absence of a method to compute surface wave energy, estimates of eruption energy partitioning between acoustic and seismic waves typically assume seismic energy is composed of body waves. Furthermore, without the proper treatment of surface wave energy, it is unclear how much volcanic tremor contributes to the overall seismic energy budget during volcanic unrest. To address this issue, we derive, from first principles, the expression of surface wave radiated energy. In contrast with body waves, the surface wave energy equation is naturally expressed in the frequency domain instead of the time domain. We validate our result by reproducing an analytical solution for the radiated power of a vertical force source acting on a free surface. We further show that the surface wave energy equation leads to an explicit relationship between energy and the imaginary part of the surface wave Green's tensor at the source location, a fundamental property recognized within the field of seismic interferometry. With the new surface wave energy equation, we make clear connections to reduced displacement and propose an improved formula for the calculation of surface wave reduced displacement involving integration over the frequency band of tremor. As an alternative to reduced displacement, we show that reduced particle velocity squared is also a valid physical measure of tremor size, one based on seismic energy rate instead of seismic moment rate. These
Site effects in Mexico City: Constraints from surface wave inversion of shallow refraction data
Ramos-Martínez, J.; Chávez-García, F. J.; Romero-Jiménez, E.; Rodríguez-Zúñiga, J. L.; Gómez-González, J. M.
1997-03-01
In order to understand and simulate site effects on strong ground motion records of recent earthquakes in Mexico City, it is fundamental to determine the in situ elastic and anelastic properties of the shallow stratigraphy of the basin. The main properties of interest are the shear wave velocities and Q-quality factors and their correlation with similar parameters in zones of the city. Despite population density and paved surfaces, it is feasible to gather shallow refraction data to obtain laterally homogeneous subsoil structures at some locations. We focused our analysis in the Texcoco Lake region of the northeastern Mexico City basin. This area consists of unconsolidated clay sediments, similar to those of the lake bed zone in Mexico City, where ground motion amplification and long duration disturbances are commonly observed. We recorded Rayleigh and Love waves using explosive and sledgehammer sources and 4.5 Hz vertical and horizontal geophones, respectively. Additionally, for the explosive source, we recorded three-component seismograms using 1 Hz seismometers. We obtained phase velocity dispersion curves from ray parameter-frequency domain analyses and inverted them for vertical distribution of S wave velocity. The initial model was obtained from a standard first-break refraction analysis. We also obtained an estimation of the QS shear wave quality factor for the uppermost stratigraphy. Results compare well with tilt and cone penetrometer resistance measurements at the same test site, emphasizing the importance of these studies for engineering purposes.
Impacts of tropical cyclone inflow angle on ocean surface waves
ZHAO Wei; HONG Xin
2011-01-01
The inflow angle of tropical cyclones (TC) is generally neglected in numerical studies of ocean surface waves induced by TC. In this study, the impacts of TC inflow angle on ocean surface waves were investigated using a high-resolution wave model. Six numerical experiments were conducted to examine, in detail, the effects of inflow angle on mean wave parameters and the spectrum of wave directions. A comparison of the waves simulated in these experiments shows that inflow angle significantly modifies TC-induced ocean surface waves. As the inflow angle increases, the asymmetric axis of the significant wave height (SWH) field shifts 30° clockwise, and the maximum SWH moves from the front-right to the rear-right quadrant. Inflow angle also affects other mean wave parameters, especially in the rear-left quadrant, such as the mean wave direction, the mean wavelength, and the peak direction. Inflow angle is a key factor in wave models for the reproduction of double-peak or multi-peak patterns in the spectrum of wave directions. Sensitivity experiments also show that the simulation with a 40° inflow angle is the closest to that of the NOAA statistical SLOSH inflow angle. This suggests that 40° can be used as the inflow angle in future TC-induced ocean surface wave simulations when SLOSH or observed inflow angles are not available.
Anisotropic tomography of the European lithospheric structure from surface wave studies
Nita, Blanka; Maurya, Satish; Montagner, Jean-Paul
2016-06-01
We present continental-scale seismic isotropic and anisotropic imaging of shear wave upper-mantle structure of tectonically diversified terranes creating the European continent. Taking into account the 36-200 s period range of surface waves enables us to model the deep subcontinental structure at different vertical scale-lengths down to 300 km. After very strict quality selection criteria, we have obtained phase wave speeds at different periods for fundamental Rayleigh and Love modes from about 9000 three-component seismograms. Dispersion measurements are performed by using Fourier-domain waveform inversion technique named "roller-coaster-type" algorithm. We used the reference model with a varying average crustal structure for each source-station path. That procedure led to significant improvement of the quality and number of phase wave speed dispersion measurements compared to the common approach of using a reference model with one average crustal structure. Surface wave dispersion data are inverted at depth for retrieving isotropy and anisotropy parameters. The fast axis directions related to azimuthal anisotropy at different depths constitute a rich database for geodynamical interpretations. Shear wave anomalies of the horizontal dimension larger than 200 km are imaged in our models. They correlate with tectonic provinces of varying age-provenance. Different anisotropy patterns are observed along the most distinctive feature on our maps-the bordering zone between the Palaeozoic and Precambrian Europe. We discuss the depth changes of the lithosphere-asthenosphere boundary along the profiles crossing the chosen tectonic units of different origin and age: Fennoscandia, East European Craton, Anatolia, Mediterranean subduction zones. Within the flat and stable cratonic lithosphere, we find traces of the midlithospheric discontinuity.
Simulation and Optimization of Surface Acoustic Wave Devises
Dühring, Maria Bayard
2007-01-01
In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model of a piezoele......In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model...
Ravenna, Matteo; Lebedev, Sergei
2016-04-01
We develop a Markov Chain Monte Carlo method for joint inversion of Rayleigh- and Love-wave dispersion curves that is able to yield robust radially and azimuthally anisotropic shear velocity profiles, with resolution to depths down to the transition zone. The probabilistic feature of the algorithm is a powerful tool that is able to provide error assessment of the shear velocity models, quantify non-uniqueness and address the issue of data noise estimation by treating it as an unknown parameter in the inversion. In a fixed dimensional Bayesian formulation, we choose to set the number of parameters relatively high, with a more dense parametrization in the uppermost mantle in order to have a good resolution of the Litosphere-Astenosphere Boundary region. We apply the MCMC algorithm to the inversion of surface-wave phase velocities accurately determined in broad period ranges in a few test regions. In the Baikal-Mongolia region we invert Rayleigh- and Love- wave dispersion curves for radially anisotropic structure (Vsv,Vsh) of the crust and upper mantle. In the Tuscany region, where we have phase velocity data with good azimuthal coverage, a different implementation of the algorithm is applied that is able to resolve azimuthal anisotropy; the Rayleigh wave dispersion curves measured at different azimuths have been inverted for the Vsv structure and the depth distribution of the 2-psi azimuthal anisotropy of the region, with good resolution down to asthenospheric depths.
Yamamoto, Hidekazu; Saito, Tokumi; Ohashi, Hiromasa [Iwate University, Iwate (Japan)
1999-02-01
In conventional microtremor prospecting methods, underground structure is estimated using the phase velocity of Rayleigh-wave only. However, it is considered that the underground structure can be estimated at a higher accuracy by using two phase velocities of Rayleigh-wave and Love-wave that directly reflects S-wave velocity structure. Therefore, three-component microtremor array observation of a circle (equilateral triangle) with the maximum radius of 40 to 250 m was carried out at the center of Morioka city. Analysis was carried out by means of extended space with autocorrelation to obtain phase velocities of Love- and Rayleigh-waves. The frequency zone of the obtained Rayleigh-wave phase velocity is 1.5 Hz to 8.6 Hz, and the phase velocity is 2670 m/s to 733 m/s. The frequency zone of the obtained Love-wave phase velocity is 3 Hz to 8.6 Hz, and the phase velocity is 2100 m/s to 412 m/s. The underground structure obtained by using two observed phase velocities is clarified under a depth of 116 m. A stratum deemed to be the basement exists from a depth of 21 m (Vs=1100 m). As a result, the underground structure can be estimated at a higher accuracy if two phase velocities of Love-and Rayleigh-waves are used. (translated by NEDO)
Surface acoustic wave (SAW) vibration sensors.
Filipiak, Jerzy; Solarz, Lech; Steczko, Grzegorz
2011-01-01
In the paper a feasibility study on the use of surface acoustic wave (SAW) vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.
Surface Acoustic Wave (SAW Vibration Sensors
Jerzy Filipiak
2011-12-01
Full Text Available In the paper a feasibility study on the use of surface acoustic wave (SAW vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.
An Efficient Hydrodynamic Model for Surface Waves
WANG Kun; JIN Sheng; LU Gang
2009-01-01
In the present study,a semi-implicit finite difference model for non-bydrostatic,free-surface flows is analyzed and discussed.The governing equations are the three-dimensional free-surface Reynolds-averaged Navier-Stokes equations defined on a general,irregular domain of arbitrary scale.At outflow,a combination of a sponge layer technique and a radiation boundary condition is applied to minimize wave reflection.The equations are solved with the fractional step method where the hydrostatic pressure component is determined first,while the non-hydrostatic component of the pressure is computed from the pressure Poisson equation in which the coefficient matrix is positive definite and symmetric.The advectiou and horizontal viscosity terms are discretized by use of a semi-Lagrangian approach.The resulting model is computationally efficient and unrestricted to the CFL condition.The developed model is verified against analytical solutions and experimental data,with excellent agreement.
Statistical model on the surface elevation of waves with breaking
2008-01-01
In the surface wind drift layer with constant momentum flux, two sets of the consistent surface eleva- tion expressions with breaking and occurrence conditions for breaking are deduced from the first in- tegrals of the energy and vortex variations and the kinetic and mathematic breaking criterions, then the expression of the surface elevation with wave breaking is established by using the Heaviside function. On the basis of the form of the sea surface elevation with wave breaking and the understanding of small slope sea waves, a triple composite function of real sea waves is presented including the func- tions for the breaking, weak-nonlinear and basic waves. The expression of the triple composite func- tion and the normal distribution of basic waves are the expected theoretical model for surface elevation statistics.
Spoof surface plasmon Fabry-Perot open resonators in a surface-wave photonic crystal
Gao, Zhen; Xu, Hongyi; Zhang, Youming; Zhang, Baile
2016-01-01
We report on the proposal and experimental realization of a spoof surface plasmon Fabry-Perot (FP) open resonator in a surface-wave photonic crystal. This surface-wave FP open resonator is formed by introducing a finite line defect in a surface-wave photonic crystal. The resonance frequencies of the surface-wave FP open resonator lie exactly within the forbidden band gap of the surface-wave photonic crystal and the FP open resonator uses this complete forbidden band gap to concentrate surface waves within a subwavelength cavity. Due to the complete forbidden band gap of the surface-wave photonic crystal, a new FP plasmonic resonance mode that exhibits monopolar features which is missing in traditional FP resonators and plasmonic resonators is demonstrated. Near-field response spectra and mode profiles are presented in the microwave regime to characterize properties of the proposed FP open resonator for spoof surface plasmons.
Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves
Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh
2017-08-01
The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.
Surface wave group velocity tomography of East Asia, part 1
Wu, Francis T.
1993-07-01
Group velocities of both Rayleigh and Love waves are used in a tomographic inversion to obtain group velocity maps of East Asia (60 deg E-140 deg E and 20 deg N-50 deg N). The period range studied is 30-70 seconds. For periods longer than 40 seconds, a high group velocity gradient clearly exists along longitude 105 deg E; the velocities are noticeably higher east of this longitude than west of this longitude. The Tibetan Plateau appears as a prominent low velocity (about 15%) structure in this area; central Tibet appears as the area with the lowest velocity. The North China Plain is an area of high velocities, probably as a result of thin crust. The variability of deep crustal and upper mantle structures underneath the different tectonic provinces in the study can clearly be seen. In a separate study, using the dataset above and that from the former Soviet Union, we have derived the Rayleigh tomographic images of a larger area (40 deg E-160 deg E and 20 deg N-70 deg N). While the Tibetan plateau still remains to be the most prominent low velocity features, two other features are also clear, a very high velocity Siberian platform and a high velocity ridge extending from Lake Baikal to Central Mongolia. These studies are useful in delineating tectonics.
Surface spin-electron acoustic waves in magnetically ordered metals
Andreev, Pavel A
2015-01-01
Degenerate plasmas with motionless ions show existence of three surface waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound. Applying the separated spin evolution quantum hydrodynamics to half-space plasma we demonstrate the existence of the surface spin-electron acoustic wave (SSEAW). We study dispersion of the SSEAW. We show that there is hybridization between the surface Langmuir wave and the SSEAW at rather small spin polarization. In the hybridization area the dispersion branches are located close to each other. In this area there is a strong interaction between these waves leading to the energy exchange. Consequently, generating the Langmuir waves with the frequencies close to hybridization area we can generate the SSEAWs. Thus, we report a method of creation of the SEAWs.
Observation of resonant interactions among surface gravity waves
Bonnefoy, F; Michel, G; Semin, B; Humbert, T; Aumaître, S; Berhanu, M; Falcon, E
2016-01-01
We experimentally study resonant interactions of oblique surface gravity waves in a large basin. Our results strongly extend previous experimental results performed mainly for perpendicular or collinear wave trains. We generate two oblique waves crossing at an acute angle, while we control their frequency ratio, steepnesses and directions. These mother waves mutually interact and give birth to a resonant wave whose properties (growth rate, resonant response curve and phase locking) are fully characterized. All our experimental results are found in good quantitative agreement with four-wave interaction theory with no fitting parameter. Off-resonance experiments are also reported and the relevant theoretical analysis is conducted and validated.
Opportunities and pitfalls in surface-wave interpretation
Schuster, Gerard T.
2017-01-21
Many explorationists think of surface waves as the most damaging noise in land seismic data. Thus, much effort is spent in designing geophone arrays and filtering methods that attenuate these noisy events. It is now becoming apparent that surface waves can be a valuable ally in characterizing the near-surface geology. This review aims to find out how the interpreter can exploit some of the many opportunities available in surface waves recorded in land seismic data. For example, the dispersion curves associated with surface waves can be inverted to give the S-wave velocity tomogram, the common-offset gathers can reveal the presence of near-surface faults or velocity anomalies, and back-scattered surface waves can be migrated to detect the location of near-surface faults. However, the main limitation of surface waves is that they are typically sensitive to S-wave velocity variations no deeper than approximately half to one-third the dominant wavelength. For many exploration surveys, this limits the depth of investigation to be no deeper than approximately 0.5-1.0 km.
Determination of ocean surface wave shape from forward scattered sound.
Walstead, Sean P; Deane, Grant B
2016-08-01
Forward scattered sound from the ocean surface is inverted for wave shape during three periods: low wind, mix of wind and swell, and stormy. Derived wave profiles are spatially limited to a Fresnel region at or near the nominal surface specular reflection point. In some cases, the surface wave profiles exhibit unrealistic temporal and spatial properties. To remedy this, the spatial gradient of inverted waves is constrained to a maximum slope of 0.88. Under this global constraint, only surface waves during low wind conditions result in a modeled surface multipath that accurately matches data. The power spectral density of the inverted surface wave field saturates around a frequency of 8 Hz while upward looking SONAR saturates at 1 Hz. Each shows a high frequency spectral slope of -4 that is in agreement with various empirical ocean wave spectra. The improved high frequency resolution provided by the scattering inversion indicates that it is possible to remotely gain information about high frequency components of ocean waves. The inability of the inversion algorithm to determine physically realistic surface waves in periods of high wind indicates that bubbles and out of plane scattering become important in those operating scenarios.
1979-01-31
Mohorovicic discontinuity is 28 , 4 km, and a low velocity zone ranges in depth from about 108 km to about 213 km. In the Aleutian Basin, the...features of the structure worth noticing from Fig. 9 are the depth to the Mohorovicic discontinuity and the pre- sence of the low velocity zone (LVZ). The
Freely decaying weak turbulence for sea surface gravity waves.
Onorato, M; Osborne, A R; Serio, M; Resio, D; Pushkarev, A; Zakharov, V E; Brandini, C
2002-09-30
We study the long-time evolution of deep-water ocean surface waves in order to better understand the behavior of the nonlinear interaction processes that need to be accurately predicted in numerical models of wind-generated ocean surface waves. Of particular interest are those nonlinear interactions which are predicted by weak turbulence theory to result in a wave energy spectrum of the form of [k](-2.5). We numerically implement the primitive Euler equations for surface waves and demonstrate agreement between weak turbulence theory and the numerical results.
Luo, Y.; Xia, J.; Xu, Y.; Zeng, C.; Liu, J.
2010-01-01
Love-wave propagation has been a topic of interest to crustal, earthquake, and engineering seismologists for many years because it is independent of Poisson's ratio and more sensitive to shear (S)-wave velocity changes and layer thickness changes than are Rayleigh waves. It is well known that Love-wave generation requires the existence of a low S-wave velocity layer in a multilayered earth model. In order to study numerically the propagation of Love waves in a layered earth model and dispersion characteristics for near-surface applications, we simulate high-frequency (>5 Hz) Love waves by the staggered-grid finite-difference (FD) method. The air-earth boundary (the shear stress above the free surface) is treated using the stress-imaging technique. We use a two-layer model to demonstrate the accuracy of the staggered-grid modeling scheme. We also simulate four-layer models including a low-velocity layer (LVL) or a high-velocity layer (HVL) to analyze dispersive energy characteristics for near-surface applications. Results demonstrate that: (1) the staggered-grid FD code and stress-imaging technique are suitable for treating the free-surface boundary conditions for Love-wave modeling, (2) Love-wave inversion should be treated with extra care when a LVL exists because of a lack of LVL information in dispersions aggravating uncertainties in the inversion procedure, and (3) energy of high modes in a low-frequency range is very weak, so that it is difficult to estimate the cutoff frequency accurately, and "mode-crossing" occurs between the second higher and third higher modes when a HVL exists. ?? 2010 Birkh??user / Springer Basel AG.
Surface characters of internal waves generated by Rankine ovoid
Zhaoting Xu; Xu Chen; Izolda V. Sturova
2006-01-01
A linear theory on the internal waves generated in the stratified fluid with a pycnocline is presented in this paper. The internal wave fields such as the velocity fields in the stratified fluid and velocity gradient fields at the free surface are also investigated by means of the theoretical and numerical method. From the numerical results, it is shown that the internal wave generated by horizontally moving Rankine ovoid is a sort of trapped wave which propagates in a wave guide, and its waveform is a kind of Mach front-type internal wave in the pycnocline. Influence of the internal wave on the flow fields at the free surface is represented by the velocity gradient fields resulted from the internal waves generated by motion of the Rankine ovoid. At the same time, it is also shown that under the hypothesis of inviscid fluid, the synchronism between the surface velocity gradient fields at the free surface and the internal wave fields in the fluid is retained. This theory opens a possibility to study further the modulated spectrum of the Bragg waves at the free surface.
Evaluation of ground stiffness parameters using continuous surface wave geophysics
Gordon, Anne; Foged, Niels
2000-01-01
-small-strain stiffness of the ground Gmax. Continuous surface wave geophysics offers a quick, non-intrusive and economical way of making such measurements. This paper reviews the continuous surface wave techniques and evaluates, in engineering terms, the applicability of the method to the site investigation industry....
Evaluation of ground stiffness parameters using continuous surface wave geophysics
Gordon, Anne; Foged, Niels
2000-01-01
-small-strain stiffness of the ground Gmax. Continuous surface wave geophysics offers a quick, non-intrusive and economical way of making such measurements. This paper reviews the continuous surface wave techniques and evaluates, in engineering terms, the applicability of the method to the site investigation industry....
Surface acoustic wave devices for sensor applications
Bo, Liu; Xiao, Chen; Hualin, Cai; Mohammad, Mohammad Ali; Xiangguang, Tian; Luqi, Tao; Yi, Yang; Tianling, Ren
2016-02-01
Surface acoustic wave (SAW) devices have been widely used in different fields and will continue to be of great importance in the foreseeable future. These devices are compact, cost efficient, easy to fabricate, and have a high performance, among other advantages. SAW devices can work as filters, signal processing units, sensors and actuators. They can even work without batteries and operate under harsh environments. In this review, the operating principles of SAW sensors, including temperature sensors, pressure sensors, humidity sensors and biosensors, will be discussed. Several examples and related issues will be presented. Technological trends and future developments will also be discussed. Project supported by the National Natural Science Foundation of China (Nos. 60936002, 61025021, 61434001, 61574083), the State Key Development Program for Basic Research of China (No. 2015CB352100), the National Key Project of Science and Technology (No. 2011ZX02403-002) and the Special Fund for Agroscientific Research in the Public Interest of China (No. 201303107). M.A.M is additionally supported by the Postdoctoral Fellowship (PDF) program of the Natural Sciences and Engineering Research Council (NSERC) of Canada and the China Postdoctoral Science Foundation (CPSF).
Surface Acoustic Waves to Drive Plant Transpiration
Gomez, Eliot F.; Berggren, Magnus; Simon, Daniel T.
2017-03-01
Emerging fields of research in electronic plants (e-plants) and agro-nanotechnology seek to create more advanced control of plants and their products. Electronic/nanotechnology plant systems strive to seamlessly monitor, harvest, or deliver chemical signals to sense or regulate plant physiology in a controlled manner. Since the plant vascular system (xylem/phloem) is the primary pathway used to transport water, nutrients, and chemical signals—as well as the primary vehicle for current e-plant and phtyo-nanotechnology work—we seek to directly control fluid transport in plants using external energy. Surface acoustic waves generated from piezoelectric substrates were directly coupled into rose leaves, thereby causing water to rapidly evaporate in a highly localized manner only at the site in contact with the actuator. From fluorescent imaging, we find that the technique reliably delivers up to 6x more water/solute to the site actuated by acoustic energy as compared to normal plant transpiration rates and 2x more than heat-assisted evaporation. The technique of increasing natural plant transpiration through acoustic energy could be used to deliver biomolecules, agrochemicals, or future electronic materials at high spatiotemporal resolution to targeted areas in the plant; providing better interaction with plant physiology or to realize more sophisticated cyborg systems.
Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal
Gao, Zhen; Gao, Fei [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Zhang, Baile, E-mail: blzhang@ntu.edu.sg [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore 637371 (Singapore); Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore, Singapore 637371 (Singapore)
2016-01-25
We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices. Wave patterns associated with the high transmission of coupled defect surface modes are directly mapped with a near-field microwave scanning probe for various structures including a straight waveguide, a sharp corner, and a T-shaped splitter. These results may find use in the design of integrated surface-wave devices with suppressed crosstalk.
Anomalous wave as a result of the collision of two wave groups on sea surface
Ruban, V P
2016-01-01
The numerical simulation of the nonlinear dynamics of the sea surface has shown that the collision of two groups of relatively low waves with close but noncollinear wave vectors (two or three waves in each group with a steepness of about 0.2) can result in the appearance of an individual anomalous wave whose height is noticeably larger than that in the linear theory. Since such collisions quite often occur on the ocean surface, this scenario of the formation of rogue waves is apparently most typical under natural conditions.
Bivariate Rayleigh Distribution and its Properties
Ahmad Saeed Akhter
2007-01-01
Full Text Available Rayleigh (1880 observed that the sea waves follow no law because of the complexities of the sea, but it has been seen that the probability distributions of wave heights, wave length, wave induce pitch, wave and heave motions of the ships follow the Rayleigh distribution. At present, several different quantities are in use for describing the state of the sea; for example, the mean height of the waves, the root mean square height, the height of the “significant waves” (the mean height of the highest one-third of all the waves the maximum height over a given interval of the time, and so on. At present, the ship building industry knows less than any other construction industry about the service conditions under which it must operate. Only small efforts have been made to establish the stresses and motions and to incorporate the result of such studies in to design. This is due to the complexity of the problem caused by the extensive variability of the sea and the corresponding response of the ships. Although the problem appears feasible, yet it is possible to predict service conditions for ships in an orderly and relatively simple manner Rayleigh (1980 derived it from the amplitude of sound resulting from many independent sources. This distribution is also connected with one or two dimensions and is sometimes referred to as “random walk” frequency distribution. The Rayleigh distribution can be derived from the bivariate normal distribution when the variate are independent and random with equal variances. We try to construct bivariate Rayleigh distribution with marginal Rayleigh distribution function and discuss its fundamental properties.
2015-09-30
Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves Lian Shen St. Anthony Falls Laboratory and Department of Mechanical...on studying surface gravity wave evolution and spectrum in the presence of surface currents caused by strongly nonlinear internal solitary waves...interaction of surface and internal gravity waves in the South China Sea. We will seek answers to the following questions: 1) How does the wind-wave
Bawadi Nor Faizah
2016-01-01
Full Text Available Research in the important parameters for modeling the dynamic behavior of soils has led to rapid development of the small strain stiffness and damping ratio for use in the seismic method. It is because, the experimental determination of the damping ratio is problematic, especially for hard soils sample. Many researchers have proved that the surface wave method is a reliable tool to determine shear wave velocity and damping ratio profiles at a site with very small strains level. Surface wave methods based on Rayleigh waves propagation and the resulting attenuation curve can become erroneous when higher modes contribute to the soil’s response. In this study, two approaches has been used to determine the shear strain amplitude and damping ratio of residual soils at small strain level using Spectral Analysis of Surface Wave (SASW method. One is to derive shear strain amplitude from the frequency-response curve and the other is to derive damping ratio from travel-time data. Then, the results are compared to the conventional method.
袁伟; 周洪生; 刘成东; 李江鹏; 张薇
2013-01-01
Rayleigh wave exploration as a non-destructive in situ detection method has been increasingly used in geotechnical engineering testing and environmental engineering. Extraction of dispersion curves is an important step in the surface wave velocity. This will be short-time Fourier transform and the generalized S transform two linear time - frequency analysis method for Rayleigh wave dispersion curve extraction. According to the analysis of the theoretical model and real seismic data, it is concluded that; ①Short-time Fourier transform only for shallow high-frequency part of the energy of strong Rayleigh wave dispersion curve extraction is better, while the low-frequency energy extraction is the weaker part of the poor.②Generalized S transform X and p by the introduction of two parameters to the signal frequency according to the level of automatic mediation shape and size of the window function, with multi-resolution features, so while the high and low frequency of the Rayleigh wave signal better treatment effect, and thus help to improve the exploration depth of the Rayleigh wave.%瑞雷面波勘探作为一种无损原位检测方法,已越来越多的应用于岩土工程测试与环境工程中,其中频散曲线的提取则是得到面波速度的重要一步.这里将短时傅里叶变换与广义S变换两种线性时～频分析方法用于瑞雷面波的频散曲线提取,并加以对比分析它们的应用效果.通过理论模型与实际地震记录分析得出:①短时傅里叶变换只能对浅部能量较强的高频部份的瑞雷面波的频散曲线提取效果较好,而对低频能量较弱的部份提取效果则不佳；②广义S变换通过λ和ρ两个参数的引入,使其能根据信号频率的高低自动调解窗函数的形态与大小,具有多分辨的特性,使其同时对高频、低频的瑞雷面波信号有更好的处理效果,从而有利于提高瑞雷波的勘探深度.
Splitting the surface wave in metal/dielectric nanostructures
Zhu Song; Wu Jian
2011-01-01
We investigate a modified surface wave splitter with a double-layer structure, which consists of symmetrical metallic grating and an asymmetrical dielectric, using the finite-difference time-domain (FDTD) simulation method.The metal/dielectric interface structure at this two-side aperture can support bound waves of different wavelengths,thus guiding waves in opposite directions. The covered dielectric films play an important role in the enhancement and confinement of the diffraction wave by the waveguide modes. The simulation result shows that the optical intensities of the guided surface wave at wavelengths of 760-nm and 1000-nm are about 100 times and 4～5 times those of the weaker side, respectively, which means that the surface wave is split by the proposed device.
Direct detection of near-surface faults by migration of back-scattered surface waves
Yu, Han
2014-08-05
We show that diffraction stack migration can be used to estimate the distribution of near-surface faults. The assumption is that near-surface faults generate detectable back-scattered surface waves from impinging surface waves. The processing steps are to isolate the back-scattered surface waves, and then migrate them by diffraction migration using the surface wave velocity as the migration velocity. Instead of summing events along trial quasi-hyperbolas, surface wave migration sums events along trial quasi-linear trajectories that correspond to the moveout of back-scattered surface waves. A deconvolution filter derived from the data can be used to collapse a dispersive arrival into a non-dispersive event. Results with synthetic data and field records validate the feasibility of this method. Applying this method to USArray data or passively recorded exploration data might open new opportunities in mapping tectonic features over the extent of the array.
Wave-current interaction near the Gulf Stream during the surface wave dynamics experiment
Wang, David W.; Liu, Antony K.; Peng, Chih Y.; Meindl, Eric A.
1994-01-01
This paper presents a case study on the wave-current interaction near the local curvature of a Gulf Stream meander. The wave data were obtained from in situ measurements by a pitch-roll discus buoy during the Surface Wave Dynamics Experiment (SWADE) conducted off Wallops Island, Virginia, from October 1990 to March 1991. Owing to the advection of the Gulf Stream by the semidiurnal tide, the discus buoy was alternately located outside and inside the Gulf Stream. The directional wave measurements from the buoy show the changes in wave direction, wave energy, and directional spreading when waves encountered the current in the Gulf Stream meanders. A wave refraction model, using the ray-tracing method with an estimated Gulf Stream velocity field and meandering condition, was used to simulate wave refraction patterns and to estimate wave parameters at relative locations corresponding to buoy measurements. The numerical simulation shows that a focusing zone of wave rays was formed near the boundary and behind the crest of a simulated Gulf Stream meander. The focusing of wave rays causes changes in wave direction, increases in wave energy, and decreases in wave directional spreading, which are in good agreement with the results from the buoy measurements.
CORRIGENDUM: Atoms riding Rayleigh waves Atoms riding Rayleigh waves
Benedek, G.; Echenique, P. M.; Toennies, J. P.; Traeger, F.
2010-09-01
In the original paper the affiliation list is incorrect. The correct address list is as follows: G Benedek1, 5, P M Echenique1, 2, J P Toennies3 and F Traeger4 1 Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 Donostia—San Sebastián, Spain 2 Departamento de Física de Materiales and CFM (CSIC-UPV/EHU), Universidad del País Vasco/Euskal Herriko Unibertsitatea, E-20018 San Sebastián/Donostia, Spain 3 Max Planck-Institut für Dynamik und Selbstorganisation, Bunsenstraße 10 D-37073 Göttingen, Germany 4 Fakultät für Chemie und Biochemie, Ruhr-Universität Bochum Universitätsstraße 150, 44801 Bochum, Germany 5 Permanent address: Dipartimento di Scienza dei Materiali, Universitá di Milano-Bicocca, Via Cozzi 53, 20125 Milano, Italy
Surface acoustic wave characterization of optical sol-gel thin layers.
Fall, Dame; Compoint, François; Duquennoy, Marc; Piombini, Hervé; Ouaftouh, Mohammadi; Jenot, Frédéric; Piwakowski, Bogdan; Belleville, Philippe; Ambard, Chrystel
2016-05-01
Controlling the thin film deposition and mechanical properties of materials is a major challenge in several fields of application. We are more particularly interested in the characterization of optical thin layers produced using sol-gel processes to reduce laser-induced damage. The mechanical properties of these coatings must be known to control and maintain optimal performance under various solicitations during their lifetime. It is therefore necessary to have means of characterization adapted to the scale and nature of the deposited materials. In this context, the dispersion of ultrasonic surface waves induced by a micrometric layer was studied on an amorphous substrate (fused silica) coated with a layer of ormosil using a sol-gel process. Our ormosil material is a silica-PDMS mixture with a variable polydimethylsiloxane (PDMS) content. The design and implementation of Surface Acoustic Wave InterDigital Transducers (SAW-IDT) have enabled quasi-monochromatic Rayleigh-type SAW to be generated and the dispersion phenomenon to be studied over a wide frequency range. Young's modulus and Poisson's ratio of coatings were estimated using an inverse method.
Development of Surface Acoustic Wave Electronic Nose
S.K. Jha
2010-07-01
Full Text Available The paper proposes an effective method to design and develop surface acoustic wave (SAW sensor array-based electronic nose systems for specific target applications. The paper suggests that before undertaking full hardware development empirically through hit and trial for sensor selection, it is prudent to develop accurate sensor array simulator for generating synthetic data and optimising sensor array design and pattern recognition system. The latter aspects are most time-consuming and cost-intensive parts in the development of an electronic nose system. This is because most of the electronic sensor platforms, circuit components, and electromechanical parts are available commercially-off-the-shelve (COTS, whereas knowledge about specific polymers and data analysis software are often guarded due to commercial or strategic interests. In this study, an 11-element SAW sensor array is modelled to detect and identify trinitrotoluene (TNT and dinitrotoluene (DNT explosive vapours in the presence of toluene, benzene, di-methyl methyl phosphonate (DMMP and humidity as interferents. Additive noise sources and outliers were included in the model for data generation. The pattern recognition system consists of: (i a preprocessor based on logarithmic data scaling, dimensional autoscaling, and singular value decomposition-based denoising, (ii principal component analysis (PCA-based feature extractor, and (iii an artificial neural network (ANN classifier. The efficacy of this approach is illustrated by presenting detailed PCA analysis and classification results under varied conditions of noise and outlier, and by analysing comparative performance of four classifiers (neural network, k-nearest neighbour, naïve Bayes, and support vector machine.Defence Science Journal, 2010, 60(4, pp.364-376, DOI:http://dx.doi.org/10.14429/dsj.60.493
Observation of Zenneck-Like Waves over a Metasurface Designed for Launching HF Radar Surface Wave
Florent Jangal
2016-01-01
Full Text Available Since the beginning of the 20th century a controversy has been continuously revived about the existence of the Zenneck Wave. This wave is a theoretical solution of Maxwell’s equations and might be propagated along the interface between the air and a dielectric medium. The expected weak attenuation at large distance explains the constant interest for this wave. Notably in the High Frequency band such a wave had been thought as a key point to reduce the high attenuation observed in High Frequency Surface Wave Radar. Despite many works on that topic and various experiments attempted during one century, there is still an alternation of statements between its existence and its nonexistence. We report here an experiment done during the optimisation of the transmitting antennas for Surface Wave Radars. Using an infrared method, we visualize a wave having the structure described by Zenneck above a metasurface located on a dielectric slab.
An experimental study of wave coupling in gravity surface wave turbulence
Aubourg, Quentin; Sommeria, Joel; Viboud, Samuel; Mordant, Nicolas
2016-11-01
Weak turbulence is a theoretical framework aimed at describing wave turbulence (in the weakly nonlinear limit) i.e. a statistical state involving a large number of nonlinearly coupled waves. For gravity waves at the surface of water, it provides a phenomenology that may describe the formation of the spectrum of the ocean surface. Analytical predictions of the spectra are made based on the fact that energy transfer occurs through 4-wave coupling. By using an advanced stereoscopic imaging technique, we measure in time the deformation of the water surface. We obtain a state of wave turbulence by using two small wedge wavemakers in a 13-m diameter wavetank. We then use high order correlator (bi- and tri-coherence) in order to get evidence of the active wave coupling present in our system as used successfully for gravity-capillary wave turbulence. At odds with the weak turbulence theory we observe 3-wave interaction involving 2 quasi linear wave and a bound wave whose frequency lies on the first harmonics of the linear dispersion relation. We do not observe 4-wave coupling within the accuracy of our measurement. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement No 647018-WATU).
Surface Wave Cloak from Graded Refractive Index Nanocomposites
La Spada, L.; McManus, T. M.; Dyke, A.; Haq, S.; Zhang, L.; Cheng, Q.; Hao, Y.
2016-07-01
Recently, a great deal of interest has been re-emerged on the possibility to manipulate surface waves, in particular, towards the THz and optical regime. Both concepts of Transformation Optics (TO) and metamaterials have been regarded as one of key enablers for such applications in applied electromagnetics. In this paper, we experimentally demonstrate for the first time a dielectric surface wave cloak from engineered gradient index materials to illustrate the possibility of using nanocomposites to control surface wave propagation through advanced additive manufacturing. The device is designed analytically and validated through numerical simulations and measurements, showing good agreement and performance as an effective surface wave cloak. The underlying design approach has much wider applications, which span from microwave to optics for the control of surface plasmon polaritons (SPPs) and radiation of nanoantennas.
Surface waves in a vertically excited circular cylindrical container
Jian Yong-Jun; E Xue-Quan; Zhang Jie; Meng Jun-Min
2004-01-01
The nonlinear free surface amplitude equation, which has been derived from the inviscid fluid by solving the potential equation of water waves with a singular perturbation theory in a vertically oscillating rigid circular cylinder,is investigated successively in the fourth-order Runge-Kutta approach with an equivalent time-step. Computational results include the evolution of the amplitude with time, the characteristics of phase plane determined by the real and imaginary parts of the amplitude, the single-mode selection rules of the surface waves in different forced frequencies,contours of free surface displacement and corresponding three-dimensional evolution of surface waves, etc. In addition,the comparison of the surface wave modes is made between theoretical calculations and experimental measurements,and the results are reasonable although there are some differences in the forced frequency.
Spatial characteristics of ocean surface waves
Gemmrich, Johannes; Thomson, Jim; Rogers, W. Erick; Pleskachevsky, Andrey; Lehner, Susanne
2016-08-01
The spatial variability of open ocean wave fields on scales of O (10km) is assessed from four different data sources: TerraSAR-X SAR imagery, four drifting SWIFT buoys, a moored waverider buoy, and WAVEWATCH III Ⓡ model runs. Two examples from the open north-east Pacific, comprising of a pure wind sea and a mixed sea with swell, are given. Wave parameters attained from observations have a natural variability, which decreases with increasing record length or acquisition area. The retrieval of dominant wave scales from point observations and model output are inherently different to dominant scales retrieved from spatial observations. This can lead to significant differences in the dominant steepness associated with a given wave field. These uncertainties have to be taken into account when models are assessed against observations or when new wave retrieval algorithms from spatial or temporal data are tested. However, there is evidence of abrupt changes in wave field characteristics that are larger than the expected methodological uncertainties.
Surface Waves in the paritally ionized solar plasma slab
Pandey, B P
2013-01-01
The properties of surface waves in the partially ionized, incompressible magnetized plasma slab are investigated in the present work. The waves are affected by the non ideal MHD effects which causes the finite drift of the magnetic field in the medium. When the finite drift of the magnetic field is ignored, the characteristics of the wave propagation in the partially ionized plasma fluid is similar to the ideal MHD except now the propagation properties depend on the fractional ionization of the medium. In the presence of Hall diffusion, the propagation of the sausage and kink surface waves depends on the level of fractional ionization of the medium. When both the Hall and Pedersen diffusion are present in the medium, the waves undergoes damping. For typical solar parameters, waves may damp over few minutes.
Experimental study of three-wave interactions among capillary-gravity surface waves
Haudin, Florence; Deike, Luc; Jamin, Timothée; Falcon, Eric; Berhanu, Michael
2016-01-01
In propagating wave systems, three or four-wave resonant interactions constitute a classical non-linear mechanism exchanging energy between the different scales. Here we investigate three-wave interactions for gravity-capillary surface waves in a closed laboratory tank. We generate two crossing wave-trains and we study their interaction. Using two optical methods, a local one (Laser Doppler Vibrometry) and a spatio-temporal one (Diffusive Light Photography), a third wave of smaller amplitude is detected, verifying the three-wave resonance conditions in frequency and in wavenumber. Furthermore, by focusing on the stationary regime and by taking into account viscous dissipation, we directly estimate the growth rate of the resonant mode. The latter is then compared to the predictions of the weakly non-linear triadic resonance interaction theory. The obtained results confirm qualitatively and extend previous experimental results obtained only for collinear wave-trains. Finally, we discuss the relevance of three-w...
Stroh formalism and Rayleigh waves
Tanuma, Kazumi
2008-01-01
Introduces a powerful and elegant mathematical method for the analysis of anisotropic elasticity equationsThe reader can grasp the essentials as quickly as possibleCan be used as a textbook, which presents compactly introduction and applications of the Stroh formalismAppeals to the people not only in mathematics but also in mechanics and engineering sciencePrerequisites are only basic linear algebra, calculus and fundamentals of differential equations
Ray-map migration of transmitted surface waves
Li, Jing
2016-08-25
Near-surface normal faults can sometimes separate two distinct zones of velocity heterogeneity, where the medium on one side of the fault has a faster velocity than on the other side. Therefore, the slope of surface-wave arrivals in a common-shot gather should abruptly change near the surface projection of the fault. We present ray-map imaging method that migrates transmitted surface waves to the fault plane, and therefore it roughly estimates the orientation, depth, and location of the near-surface fault. The main benefits of this method are that it is computationally inexpensive and robust in the presence of noise.
Elastic contact conditions to optimize friction drive of surface acoustic wave motor.
Kuribayashi Kurosawa, M; Takahashi, M; Higuchi, T
1998-01-01
The optimum pressing force, namely the preload, for a slider to obtain superior operation conditions in a surface acoustic wave motor have been examined. We used steel balls as sliders. The preload was controlled using a permanent magnet. The steel balls were 0.5, 1, and 2 mm diameter, with the differences in diameter making it possible to change contact conditions, such as the contact pressure, contact area, and deformation of the stator and the slider. The stator transducer was lithium niobate, 128 degrees rotated, y-cut x-propagation substrate. The driving frequency of the Rayleigh wave was about 10 MHz. Hence, the particle vibration amplitude at the surface is as small as 10 nm. For superior friction drive conditions, a high contact pressure was required. For example, in the case of the 1 mm diameter steel ball at the sinusoidal driving voltage of 180 V(peak), the slider speed was 43 cm/sec, the thrust output force was 1 mN, and the acceleration was 23 times as large as the gravitational acceleration at a contact pressure of 390 MPa. From the Hertz theory of contact stress, the contact area radius was only 3 microm. The estimation of the friction drive performance was carried out from the transient traveling distance of the slider in a 3 msec burst drive. As a result, the deformation of the stator and the slider by the preload should be half of the vibration amplitude. This condition was independent of the ball diameter and the vibration amplitude. The output thrust per square millimeter was 50 N, and the maximum speed was 0.7 m/sec. From these results, we conclude that it is possible for the surface acoustic wave motor to have a large output force, high speed, quick response, long traveling distance, and a thin micro linear actuator.
Josse, F; Bender, F; Cernose, R W
2001-12-15
The design and performance of guided shear horizontal surface acoustic wave (guided SH-SAW) devices on LiTaO3 substrates are investigated for high-sensitivity chemical and biochemical sensors in liquids. Despite their structural similarity to Rayleigh SAW, SH-SAWs often propagate slightly deeper within the substrate, hence preventing the implementation of high-sensitivity detectors. The device sensitivity to mass and viscoelastic loading is increased using a thin guiding layer on the device surface. Because of their relatively low shear wave velocity, various polymers including poly(methyl methacrylate) (PMMA) and cyanoethyl cellulose (cured or cross-linked) are investigated as the guiding layers to trap the acoustic energy near the sensing surface. The devices have been tested in biosensing and chemical sensing experiments. Suitable design principles for these applications are discussed with regard to wave guidance, electrical passivation of the interdigital transducers from the liquid environments, acoustic loss, and sensor signal distortion. In biosensing experiments, using near-optimal PMMA thickness of approximately 2 microm, mass sensitivity greater than 1500 Hz/(ng/mm2) is demonstrated, resulting in a minimum detection limit less than 20 pg/mm2. For chemical sensor experiments, it is found that optimal waveguide thickness must be modified to account for the chemically sensitive layer which also acts to guide the SH-SAW. A detection limit of 780 (3 x peak-to-peak noise) or 180 ppb (3 x rms noise) is estimated from the present measurements for some organic compounds in water.
Enhanced Sensitive Love Wave Surface Acoustic Wave Sensor Designed for Immunoassay Formats
Mihaela Puiu; Ana-Maria Gurban; Lucian Rotariu; Simona Brajnicov; Cristian Viespe; Camelia Bala
2015-01-01
We report a Love wave surface acoustic wave (LW-SAW) immunosensor designed for the detection of high molecular weight targets in liquid samples, amenable also for low molecular targets in surface competition assays. We implemented a label-free interaction protocol similar to other surface plasmon resonance bioassays having the advantage of requiring reduced time analysis. The fabricated LW-SAW sensor supports the detection of the target in the nanomolar range, and can be ultimately incorporat...
Horizon effects with surface waves on moving water
Rousseaux, Germain; Mathis, Christian; Coullet, Pierre; Philbin, Thomas G; Leonhardt, Ulf
2010-01-01
Surface waves on a stationary flow of water are considered, in a linear model that includes the surface tension of the fluid. The resulting gravity-capillary waves experience a rich array of horizon effects when propagating against the flow. In some cases three horizons (points where the group velocity of the wave reverses) exist for waves with a single laboratory frequency. Some of these effects are familiar in fluid mechanics under the name of wave blocking, but other aspects, in particular waves with negative co-moving frequency and the Hawking effect, were overlooked until surface waves were investigated as examples of analogue gravity [R. Schuetzhold and W. G. Unruh W G, Phys. Rev. D 66 (2002) 044019]. A comprehensive presentation of the various horizon effects for gravity-capillary waves is given, with emphasis on the deep water/long wavelength case kh>>1 where many analytical results can be derived. A similarity of the state space of the waves to that of a thermodynamic system is pointed out.
Numerical simulation of floating bodies in extreme free surface waves
Z. Z. Hu
2011-02-01
Full Text Available In this paper, we use the in-house Computational Fluid Dynamics (CFD flow code AMAZON-SC as a numerical wave tank (NWT to study wave loading on a wave energy converter (WEC device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water. The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.
Numerical simulation of floating bodies in extreme free surface waves
Hu, Z. Z.; Causon, D. M.; Mingham, C. G.; Qian, L.
2011-02-01
In this paper, we use the in-house Computational Fluid Dynamics (CFD) flow code AMAZON-SC as a numerical wave tank (NWT) to study wave loading on a wave energy converter (WEC) device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water). The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.
Interpretation of nonlinearity in wind generated ocean surface waves
Varkey, M.J.
This study attempts to resolve a mix-up between a physical process and its mathematical interpretation in the context of wind waves on ocean surface. Wind generated wave systems, are conventionally interpreted as a result of interaction of a number...
Palladium nanoparticle-based surface acoustic wave hydrogen sensor.
Sil, Devika; Hines, Jacqueline; Udeoyo, Uduak; Borguet, Eric
2015-03-18
Palladium (Pd) nanoparticles (5-20 nm) are used as the sensing layer on surface acoustic wave (SAW) devices for detecting H2. The interaction with hydrogen modifies the conductivity of the Pd nanoparticle film, producing measurable changes in acoustic wave propagation, which allows for the detection of this explosive gas. The nanoparticle-based SAW sensor responds rapidly and reversibly at room temperature.
Stokesian swimming of a sphere by radial helical surface wave
Felderhof, B U
2016-01-01
The swimming of a sphere by means of radial helical surface waves is studied on the basis of the Stokes equations. Explicit expressions are derived for the matrices characterizing the mean translational and rotational swimming velocities and the mean rate of dissipation to second order in the wave amplitude.
Scattering of mid-IR-range surface electromagnetic waves by optically smooth metal surfaces
Bonch-Bruevich, A.M.; Libenson, M.N.; Makin, V.S.; Pudkov, S.D.; Trubaev, V.V.
1985-09-01
The paper reports the experimental observation of the intense scattering of surface electromagnetic waves with a wavelength of 10.6 microns excited on an optically smooth metal surface with a residual roughness having a mean square height of less than 25 A. A method for determining the attenuation of surface electromagnetic waves is proposed, and a test of the method is reported which involves the measurement of the relative intensity of the local scattering of the waves along their path. 9 references.
Calculating wave-generated bottom orbital velocities from surface-wave parameters
Wiberg, P.L.; Sherwood, C.R.
2008-01-01
Near-bed wave orbital velocities and shear stresses are important parameters in many sediment-transport and hydrodynamic models of the coastal ocean, estuaries, and lakes. Simple methods for estimating bottom orbital velocities from surface-wave statistics such as significant wave height and peak period often are inaccurate except in very shallow water. This paper briefly reviews approaches for estimating wave-generated bottom orbital velocities from near-bed velocity data, surface-wave spectra, and surface-wave parameters; MATLAB code for each approach is provided. Aspects of this problem have been discussed elsewhere. We add to this work by providing a method for using a general form of the parametric surface-wave spectrum to estimate bottom orbital velocity from significant wave height and peak period, investigating effects of spectral shape on bottom orbital velocity, comparing methods for calculating bottom orbital velocity against values determined from near-bed velocity measurements at two sites on the US east and west coasts, and considering the optimal representation of bottom orbital velocity for calculations of near-bed processes. Bottom orbital velocities calculated using near-bed velocity data, measured wave spectra, and parametric spectra for a site on the northern California shelf and one in the mid-Atlantic Bight compare quite well and are relatively insensitive to spectral shape except when bimodal waves are present with maximum energy at the higher-frequency peak. These conditions, which are most likely to occur at times when bottom orbital velocities are small, can be identified with our method as cases where the measured wave statistics are inconsistent with Donelan's modified form of the Joint North Sea Wave Project (JONSWAP) spectrum. We define the 'effective' forcing for wave-driven, near-bed processes as the product of the magnitude of forcing times its probability of occurrence, and conclude that different bottom orbital velocity statistics
Peralta, J.; López-Valverde, M. A. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Imamura, T. [Institute of Space and Astronautical Science-Japan Aerospace Exploration Agency 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Read, P. L. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford (United Kingdom); Luz, D. [Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Piccialli, A., E-mail: peralta@iaa.es [LATMOS, UVSQ, 11 bd dAlembert, 78280 Guyancourt (France)
2014-07-01
This paper is the second in a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases where the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this second part, we study the waves' solutions when several atmospheric approximations are applied: Lamb, surface, and centrifugal waves. Lamb and surface waves are found to be quite similar to those in a geostrophic regime. By contrast, centrifugal waves turn out to be a special case of Rossby waves that arise in atmospheres in cyclostrophic balance. Finally, we use our results to identify the nature of the waves behind atmospheric periodicities found in polar and lower latitudes of Venus's atmosphere.
Scaling observations of surface waves in the Beaufort Sea
Madison Smith
2016-04-01
Full Text Available Abstract The rapidly changing Arctic sea ice cover affects surface wave growth across all scales. Here, in situ measurements of waves, observed from freely-drifting buoys during the 2014 open water season, are interpreted using open water distances determined from satellite ice products and wind forcing time series measured in situ with the buoys. A significant portion of the wave observations were found to be limited by open water distance (fetch when the wind duration was sufficient for the conditions to be considered stationary. The scaling of wave energy and frequency with open water distance demonstrated the indirect effects of ice cover on regional wave evolution. Waves in partial ice cover could be similarly categorized as distance-limited by applying the same open water scaling to determine an ‘effective fetch’. The process of local wave generation in ice appeared to be a strong function of the ice concentration, wherein the ice cover severely reduces the effective fetch. The wave field in the Beaufort Sea is thus a function of the sea ice both locally, where wave growth primarily occurs in the open water between floes, and regionally, where the ice edge may provide a more classic fetch limitation. Observations of waves in recent years may be indicative of an emerging trend in the Arctic Ocean, where we will observe increasing wave energy with decreasing sea ice extent.
Seismic tomography of Yunnan region using short-period surface wave phase velocity
何正勤; 苏伟; 叶太兰
2004-01-01
The data of short-period (1～18 s) surface waves recorded by 23 stations belonging to the digital seismic network of Yunnan Province of China are used in this paper. From these data, the dispersion curves of phase velocities of the fundamental mode Rayleigh wave along 209 paths are determined by using the two-station narrowband filtering cross-correlation method.Adopting tomography method, the distribution maps of phase velocities at various periods in Yunnan region are inverted. The maps of phase velocities on profiles along 24°N, 25°N, 26°N, 27°N and 100.5°E and the distribution maps of phase velocities at 3 periods in the study region are given. The results show that the phase velocity distribution in Yunnan region has strong variations in horizontal direction, and the phase velocity distribution in short-period range is closely related to the thickness of sedimentary layers in the shallow crust. The phase velocity in southern part of the Sichuan-Yunnan rhombic block encircled by the Honghe fault and Xiaojiang fault is obviously lower than that in surrounding areas. The epicentral locations of strong earthquakes in Yunnan region are mainly distributed in transitional zones between low and high phase velocities.
Rupture features of the 2010 Mw 8.8 Chile earthquake extracted from surface waves
Huang, Yi-Ling; Hwang, Ruey-Der; Jhuang, Yi-Shan; Lin, Cai-Yi
2017-03-01
This study used the rupture directivity theory to derive the fault parameters of the 2010 Mw 8.8 Chile earthquake on the basis of the azimuth-dependent source duration obtained from the Rayleigh-wave phase velocity. Results revealed that the 2010 Chile earthquake featured asymmetric bilateral faulting. The two rupture directions were N171°E (northward) and N17°E (southward), with rupture lengths of approximately 313 and 118 km, respectively, and were related to the locking degree in the source region. The entire source duration was approximately 187 s. After excluding the rise time from the source duration, the northward rupture velocity was approximately 2.02 km/s, faster than the southward rupture velocity (1.74 km/s). On average, the rupture velocity derived from this study was slower than that estimated from finite-fault inversion; however, several historical earthquakes in the Chile region also showed slow rupture velocity when using low-frequency signals, as surface waves do. Two earlier studies through global-positioning-system data analysis showed that the static stress drop of 50-70 bars for the 2010 Chile earthquake was higher than that for subduction-zone earthquakes. Hence, a remarkable feature was that the 2010 Chile earthquake had a slow rupture velocity and a high static stress drop, which suggested an inverse relationship between rupture velocity and static stress drop.[Figure not available: see fulltext.
Source mechanism of the May 18, 1980, Mount St. Helens eruption from regional surface waves
Burger, Roy W.; Langston, Charles A.
1985-08-01
A reference source equalization method using regional surface waves from the Mount St. Helens eruption of May 18, 1980, and the Elk Lake event of February 14, 1981, was used to determine the St. Helens eruption source time history. The time domain deconvolution signals display a complex series of pulses lasting 250 s. An initial pulse was isolated and was found to have a smoothly varying two-lobed radiation pattern for both Love and Rayleigh waves, suggesting a near-horizontal point force directed south consistent with previous results. The initial southward force corresponds to the acceleration of the landslide in a northern direction about 5-10 s after the triggering earthquake. Lateral forces were isolated 70-140 s later, consistent with the occurrence of the large lateral blast and the slide changing its direction down the Toutle River Valley. There also appears to be significant source activity between 140 and 250 s after the initial pulse. This later activity exhibits forces in the northwest-southeast azimuth and may correspond to the final deceleration of the landslide. Several vertical pulses were located between 10-60 and 100-120 s after the eruption began. Much of the vertical force represents the two sets of explosions which occurred during the eruption.
Wave Generated by the NACA4412 Hydrofoil near Free Surface
Hassan Ghassemi
2013-01-01
Full Text Available The generation of wave due to moving hydrofoil in steady streams close to a free surface is presented. The potential-based boundary element method is employed to the NACA4412 hydrofoil with linearized dynamic and kinematic boundary conditions on the free surface. The perturbation velocity potential is calculated using the Green formulation and Kutta condition. The numerical results of waves generated by the hydrofoil are presented and discussed at various Froude numbers and immersion depths.
Anomalous Surface Wave Launching by Handedness Phase Control
Zhang, Xueqian
2015-10-09
Anomalous launch of a surface wave with different handedness phase control is achieved in a terahertz metasurface based on phase discontinuities. The polarity of the phase profile of the surface waves is found to be strongly correlated to the polarization handedness, promising polarization-controllable wavefront shaping, polarization sensing, and environmental refractive-index sensing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Estimating propagation velocity through a surface acoustic wave sensor
Xu, Wenyuan (Oakdale, MN); Huizinga, John S. (Dellwood, MN)
2010-03-16
Techniques are described for estimating the propagation velocity through a surface acoustic wave sensor. In particular, techniques which measure and exploit a proper segment of phase frequency response of the surface acoustic wave sensor are described for use as a basis of bacterial detection by the sensor. As described, use of velocity estimation based on a proper segment of phase frequency response has advantages over conventional techniques that use phase shift as the basis for detection.
Estimation of Sea Surface Wave Spectra Using Acoustic Tomography.
1987-09-01
Holister Dis speciael Dean of Graduate Studiesj ESTIMATION OF SEA SURFACE WAVE SPECTRA USING ACOUSTIC TOMOGRAPHY by James Henry Miller B.S. Electrical...James Henry Miller 1987 The author hereby prants to MIT permission to reproduce and distribute copies of this thesis in whole or in part. Signature of...ESTIMATION OF SEA SURFACE WAVE SPECTRA USING ACOUSTIC TOMOGRAPHY by James Henry Miller Submitted in partial fulfillment of the requirements for the
Modulation of cavity-polaritons by surface acoustic waves
de Lima, M. M.; Poel, Mike van der; Hey, R.;
2006-01-01
We modulate cavity-polaritons using surface acoustic waves. The corresponding formation of a mini-Brillouin zone and band folding of the polariton dispersion is demonstrated for the first time. Results are in good agreement with model calculations.......We modulate cavity-polaritons using surface acoustic waves. The corresponding formation of a mini-Brillouin zone and band folding of the polariton dispersion is demonstrated for the first time. Results are in good agreement with model calculations....
Visualization of Surface Acoustic Waves in Thin Liquid Films
Rambach, R. W.; Taiber, J.; Scheck, C. M. L.; Meyer, C.; Reboud, J.; Cooper, Jonathan M.; Franke, T.
2016-01-01
We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with anWe demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfl...
Estimating propagation velocity through a surface acoustic wave sensor
Xu, Wenyuan; Huizinga, John S.
2010-03-16
Techniques are described for estimating the propagation velocity through a surface acoustic wave sensor. In particular, techniques which measure and exploit a proper segment of phase frequency response of the surface acoustic wave sensor are described for use as a basis of bacterial detection by the sensor. As described, use of velocity estimation based on a proper segment of phase frequency response has advantages over conventional techniques that use phase shift as the basis for detection.
Wave turbulence in a two-layer fluid: coupling between free surface and interface waves
Issenmann, Bruno; Falcon, Eric
2016-01-01
We experimentally study gravity-capillary wave turbulence on the interface between two immiscible fluids of close density with free upper surface. We locally measure the wave height at the interface between both fluids by means of a highly sensitive laser Doppler vibrometer. We show that the inertial range of the capillary wave turbulence regime is significantly extended when the upper fluid depth is increased: The crossover frequency between the gravity and capillary wave turbulence regimes is found to decrease whereas the dissipative cut-off frequency of the spectrum is found to increase. We explain most of these observations by the progressive decoupling between waves propagating at the interface and the ones at the free surface, using the full dispersion relation of gravity-capillary waves in a two-layer fluid of finite depths.s.
Beam interactions with surface waves and higher-order modes in oversized backward wave oscillators
Ogura, Kazuo; Kojima, Akihiko; Kawabe, Fumiaki; Yambe, Kiyoyuki [Niigata University, Niigata (Japan); Amin, Ruhul [Islamic University of Technology, Gazipur (Bangladesh)
2014-10-15
Beam interactions with surface waves and higher-order modes in an oversized backward wave oscillator (BWO) are studied. In addition to the well-known Cherenkov interaction, the slow cyclotron interaction occurs due to transverse perturbations of the electron beam. The Cherenkov interaction dominates the slow cyclotron interaction. Growth rates of both the interactions for the higher order modes are small compared with those for the surface-wave modes in an oversized BWO. The coaxial slow-wave structure exhibits a reduced number of higher-order modes, which consequently reduces the mode competition problem and improves beam interactions with higher order modes. For higher values of beam currents, the slow cyclotron wave grows at a faster rate than the Cherenkov waves.
Rayleigh reflections and nonlinear acoustics of solids
Breazeale, M. A.
1980-10-01
Schlierken studies of ultrasonic waves, and nonlinear acoustics of solids are addressed. A goniometer for use in a Schlieren system for visualization of ultrasonic waves in liquids is described. The goniometer is used to obtain Schlieren photographs of leaky Rayleigh waves excited on an Al2O3 layer on a stainless steel reflector immersed in water, showing that the Rayleigh wave velocity in this case is less than that of either a water Al203 layer or a water stainless steel layer. Also investigated are: (1) nonlinearity parameters and third order elastic constants of copper between 300 and 3 K; (2) measurement of nonlinearity parameters in small solid samples by the harmonic generation technique; (3) relationship between solid nonlinearity parameters and thermodynamic Gruneisen parameters; and (4) quantum mechanical theory of nonlinear interaction of ultrasonic waves.
Karakostas, F. G.; Rakoto, V.; Lognonne, P. H.
2015-12-01
Meteor impacts are a very important seismic source for planetary seismology, since their locations and, in some cases, their occurence times can be accurately known from orbiters, tracking or optical observations. Their importance becomes greater in the case of a seismic experiment with one seismometer, as the SEIS (Seismic Experiment of Interior Structure) of the future Martian mission "InSight", as the known location allows a direct inversion of differential travel times and wave forms in terms of structure. Meteor impacts generate body and surface seismic waves when they reach the surface of a planet. But when they explode into the atmosphere, due to ablation, they generate shock waves, which are converted into linear, seismic waves in the solid part and acoustic waves in the atmosphere. This effect can be modeled when the amplitude of Rayleigh and other Spheroidal normal modes is made with the atmospheric/ground coupling effects. In this study, meteor impacts are modeled as seismic sources in a comparative analysis for the cases of Earth and Mars. Using the computed seismograms, calculated by the summation of the normal modes of the full planet (e.g. with atmosphere) the properties of the seismic source can be obtained. Its duration is typically associated to the radiation duration of shock waves until they reach the linear regime of propagation. These transition times are comparatively analyzed, for providing constraints on the seismic source duration on Earth and Mars. In the case of Earth, we test our approach with the Chelyabinsk superbolide. The computed seismograms are used in order to perform the inversion of the source, by comparison with the data of the Global Seismographic Network. The results are interpreted and compared with other observations. In the case of Mars, equivalent sources are similarly modeled in different atmospheric, impact size and lithospheric conditions.
Energy budget of surface waves in the global ocean
TENG Yong; YANG Yongzeng; QIAO Fangli; LU Jing; YIN Xunqiang
2009-01-01
Mechanical energy input from atmosphere and losses from wave-breaking dissipation of sea surface waves are estimated by a direct scheme. This scheme is based on the integration in the wavenumber space of the wind input and breaking dissipation source functions of the MASNUM wave model.The global amount of wind energy input, averaged in 2005, is about 57 TW, and the wave-breaking dissipation summed in deep-water is about 33 TW, over a half of the wind energy input. The residual may be dissipated by beach processes. Global distributions of the energy input and breaking dissipation concentrate in the westerlies of the Southern Hemisphere.
The Surface Wave Scattering-Microwave Scanner (SWS-MS)
Geffrin, Jean-Michel; Chamtouri, Maha; Merchiers, Olivier; Tortel, Hervé; Litman, Amélie; Bailly, Jean-Sébastien; Lacroix, Bernard; Francoeur, Mathieu; Vaillon, Rodolphe
2016-01-01
The Surface Wave Scattering-Microwave Scanner (SWS-MS) is a device that allows the measurement of the electromagnetic fields scattered by objects totally or partially submerged in surface waves. No probe is used to illuminate the sample, nor to guide or scatter the local evanescent waves. Surface waves are generated by total internal reflection and the amplitude and phase of the fields scattered by the samples are measured directly, both in the far-field and the near-field regions. The device's principles and their practical implementation are described in details. The surface wave generator is assessed by measuring the spatial distribution of the electric field above the surface. Drift correction and the calibration method for far-field measurements are explained. Comparison of both far-field and near-field measurements against simulation data shows that the device provides accurate results. This work suggests that the SWS-MS can be used for producing experimental reference data, for supporting a better understanding of surface wave scattering, for assisting in the design of near-field optical or infrared systems thanks to the scale invariance rule in electrodynamics, and for performing nondestructive control of defects in materials.
Rotational components of earthquake ground motions derived from surface waves%地震面波产生的地震动转动分量研究
李宏男; 孙立晔
2001-01-01
In this paper, the rotational components ot earthquake groundmotions are derived from the surface waves, the Rayleigh and Love waves by using the theory of elastic wave motion. The relevant calculational formula and approach are given. Especially, the dispersion of surface waves is introduced to the rotational components, whihc may be more suitable for engineering practice. Finally, numerical examples of the rotational components from the earthquake records are presented by using the given methods.%本文利用弹性波动理论对地面转动分量，即瑞利(Rayleigh)波和乐夫(Love)波产生的转动分量进行了研究，给出了相应的计算公式和计算方法。特别注意到面波的频散效应对转动分量的影响，并将这一特性引入到转动分量的求取中，使问题的解决更切合于实际。最后选取实际地震记录，利用得到的公式计算出地震面波产生的转动分量。
Polarization controlled directional propagation of Bloch surface wave.
Kovalevich, Tatiana; Boyer, Philippe; Suarez, Miguel; Salut, Roland; Kim, Myun-Sik; Herzig, Hans Peter; Bernal, Maria-Pilar; Grosjean, Thierry
2017-03-06
Bloch surface waves (BSWs) are recently developing alternative to surface plasmon polaritons (SPPs). Due to dramatically enhanced propagation distance and strong field confinement these surface states can be successfully used in on-chip all-optical integrated devices of increased complexity. In this work we propose a highly miniaturized grating based BSW coupler which is gathering launching and directional switching functionalities in a single element. This device allows to control with polarization the propagation direction of Bloch surface waves at subwavelength scale, thus impacting a large panel of domains such as optical circuitry, function design, quantum optics, etc.
Acoustomicrofluidic application of quasi-shear surface waves.
Darinskii, A N; Weihnacht, M; Schmidt, H
2017-02-20
The paper analyzes the possibility of using predominantly boundary polarized surface acoustic waves for actuating fluidic effects in microchannels fabricated inside containers made of PDMS. The aim is to remove a shortcoming peculiar to conventionally utilized predominantly vertically polarized waves. Such waves strongly attenuate while they propagate under container side walls because of the leakage into them. Due to a specific feature of PDMS - extremely small shear elastic modulus - losses of boundary polarized modes should be far smaller. The amplitude of vertical mechanical displacements can be increased right inside the channel owing to the scattering of acoustic fields. As an example, the predominantly vertically polarized surface wave on 128YX LiNbO3 is compared with the quasi-shear leaky wave on 64YX LiNbO3. Our computations predict that, given the electric power supplied to the launching transducer, the quasi-shear wave will drive the fluid more efficiently than the surface wave on 128YX LiNbO3 when the container wall thickness is larger than 25-30 wavelengths, if there are no additional scatterers inside the channel. In the presence of a scatterer, such as a thin gold strip, the quasi-shear wave can be more efficient when the wall thickness exceeds 10-15 wavelengths.
Steep waves in free-surface flow past narrow topography
Wade, Stephen L.; Binder, Benjamin J.; Mattner, Trent W.; Denier, James P.
2017-06-01
In this work, we compute steep forced solitary wave solutions for the problem of free-surface flow over a localised topographic disturbance in an otherwise flat horizontal channel bottom. A single forced solitary wave and a double-crested forced solitary wave solution are shown to exist, both of which approach the Stokes limiting configuration of an included angle of 12 0° and a stagnation point at the wave crests. The solution space for the topographically forced problem is compared to that found in Wade et al. ["On the free-surface flow of very steep forced solitary waves," J. Fluid Mech. 739, 1-21 (2014)], who considered forcing due to a localised distribution of pressure applied to the free surface. The main feature that differentiates the two types of forcing is an additional solution that exists in the pressure-forced problem, a steep wave with a cusp at a single wave crest. Our numerical results suggest that this cusped-wave solution does not exist in the topographically forced problem.
Surface plasma waves over bismuth–vacuum interface
Ashim P Jain; J Parashar
2003-09-01
A surface plasma wave (SPW) over bismuth–vacuum interface has a signature of mass anisotropy of free electrons. For SPW propagation along the trigonal axis there is no birefringence. The frequency cutoff of SPW cutoff=$_{p}/\\sqrt{2(_{L}+)}$ lies in the far infrared region and can be accessed using free electron laser. The damping rate of waves at low temperatures is low. The surface plasma wave may be excited by an electron beam of current ∼ 100 mA propagating parallel to the interface in its close proximity.
Some aspects of dispersive horizons: lessons from surface waves
Chaline, J; Maïssa, P; Rousseaux, G
2012-01-01
Hydrodynamic surface waves propagating on a moving background flow experience an effective curved space-time. We discuss experiments with gravity waves and capillary-gravity waves in which we study hydrodynamic black/white-hole horizons and the possibility of penetrating across them. Such possibility of penetration is due to the interaction with an additional "blue" horizon, which results from the inclusion of surface tension in the low-frequency gravity-wave theory. This interaction leads to a dispersive cusp beyond which both horizons completely disappear. We speculate the appearance of high-frequency "superluminal" corrections to be a universal characteristic of analogue gravity systems, and discuss their relevance for the trans-Planckian problem. We also discuss the role of Airy interference in hybridising the incoming waves with the flowing background (the effective spacetime) and blurring the position of the black/white-hole horizon.
High-frequency shear-horizontal surface acoustic wave sensor
Branch, Darren W
2013-05-07
A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.
Yamanaka, Hiroaki; Kato, Kei; Chimoto, Kosuke; Tsuno, Seiji
2015-09-01
A procedure for estimation of Rayleigh wave phase velocities from microtremor observations, using an array with a reference station, is investigated in this study. Simultaneous observation of microtremors at a reference station and at a strong motion observation array in the Kanto Basin, Japan, was carried out. We first calculated cross correlations between records at the reference station and those at stations in the array using a seismic interferometric processing method on a 4300-h data series. After identifying dispersive Rayleigh waves from results of multiple filtering analysis of the cross correlations, semblance analysis of the cross correlations for different segments was carried out to estimate phase velocities for fundamental and higher-mode Rayleigh waves. The phase velocities from the proposed method are more appropriate than those from conventional methods at long periods as they avoid contamination by higher mode Rayleigh waves. The fundamental Rayleigh wave phase velocities were inverted to an S-wave velocity profile for deep sedimentary layers. We also examined the variations in the phase velocity with decreasing data duration. The phase velocities at periods less than 3 s from 6-h records are similar to those from 4300-h records, suggesting that our method is possibly applicable in microtremor exploration.
Elastic Softening of Surface Acoustic Wave Caused by Vacancy Orbital in Silicon Wafer
Mitsumoto, Keisuke; Akatsu, Mitsuhiro; Baba, Shotaro; Takasu, Rie; Nemoto, Yuichi; Goto, Terutaka; Yamada-Kaneta, Hiroshi; Furumura, Yuji; Saito, Hiroyuki; Kashima, Kazuhiko; Saito, Yoshihiko
2014-03-01
We have performed surface acoustic wave (SAW) measurements to examine vacancies in a surface layer of a boron-doped silicon wafer currently used in semiconductor industry. A SAW with a frequency of fs = 517 MHz was optimally generated by an interdigital transducer with a comb gap of w=2.5 µm on a piezoelectric ZnO film deposited on the (001) silicon surface. The SAW propagating along the [100] axis with a velocity of vs=4.967 km/s is in agreement with the Rayleigh wave, which shows an ellipsoidal trajectory motion in the displacement components ux and uz within a penetration depth of λp = 3.5 µm. The elastic constant Cs of the SAW revealed the softening of ΔCs/Cs = 1.9 × 10-4 below 2 K down to 23 mK. Applied magnetic fields of up to 2 T completely suppress the softening. The quadrupole susceptibilities based on the coupling between the electric quadrupoles Ou, Ov, and Ozx of the vacancy orbital consisting of Γ8-Γ7 states and the symmetry strains ɛu, ɛv, and ɛzx associated with the SAW account for the softening and its field dependence on Cs. We deduced a low vacancy concentration N = 3.1 × 1012/cm3 in the surface layer within λp = 3.5 µm of the silicon wafer. This result promises an innovative technology for vacancy evaluation in the fabrication of high-density semiconductor devices in industry.
Terahertz-wave generation by surface-emitted four-wave mixing in optical fiber
Ping Zhou; Dianyuan Fan
2011-01-01
We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional singlemode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range.Surface-emitted geometry is employed to decrease absorption loss.A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory.This is a promising way for realizing a reasonable narrow-band terahert-wave source.%@@ We propose a novel terahertz-wave source through the four-wave mixing effect in a conventional singlemode optical fiber pumped by a dual-wavelength laser whose difference frequency lies in the terahertz range.Surface-emitted geometry is employed to decrease absorption loss.A detailed derivation of the terahertz-wave power expression is presented using the coupled-wave theory.This is a promising way for realizing a reasonable narrow-band terahertz-wave source.
Rayleigh-Taylor mixing in supernova experiments
Swisher, N. C.; Abarzhi, S. I., E-mail: snezhana.abarzhi@gmail.com [Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Kuranz, C. C. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Arnett, D. [University of Arizona, Tucson, Arizona 85721 (United States); Hurricane, O.; Remington, B. A.; Robey, H. F. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2015-10-15
We report a scrupulous analysis of data in supernova experiments that are conducted at high power laser facilities in order to study core-collapse supernova SN1987A. Parameters of the experimental system are properly scaled to investigate the interaction of a blast-wave with helium-hydrogen interface, and the induced Rayleigh-Taylor instability and Rayleigh-Taylor mixing of the denser and lighter fluids with time-dependent acceleration. We analyze all available experimental images of the Rayleigh-Taylor flow in supernova experiments and measure delicate features of the interfacial dynamics. A new scaling is identified for calibration of experimental data to enable their accurate analysis and comparisons. By properly accounting for the imprint of the experimental conditions, the data set size and statistics are substantially increased. New theoretical solutions are reported to describe asymptotic dynamics of Rayleigh-Taylor flow with time-dependent acceleration by applying theoretical analysis that considers symmetries and momentum transport. Good qualitative and quantitative agreement is achieved of the experimental data with the theory and simulations. Our study indicates that in supernova experiments Rayleigh-Taylor flow is in the mixing regime, the interface amplitude contributes substantially to the characteristic length scale for energy dissipation; Rayleigh-Taylor mixing keeps order.
Linking Rayleigh-Rice theory with near linear shift invariance in light scattering phenomena
Stover, John C.; Schroeder, Sven; Staats, Chris; Lopushenko, Vladimir; Church, Eugene
2016-09-01
Understanding topographic scatter has been the subject of many publications. For optically smooth surfaces that scatter only from roughness (and not from contamination, films or bulk defects) the Rayleigh-Rice relationship resulting from a rigorous electromagnetic treatment has been successfully used for over three decades and experimentally proven at wavelengths ranging from the X-Ray to the far infrared (even to radar waves). The "holy grail" of roughness-induced scatter would be a relationship that is not limited to just optically smooth surfaces, but could be used for any surface where the material optical constants and the surface power spectral density function (PSD) are known. Just input these quantities and calculate the BRDF associated with any source incident angle, wavelength and polarization. This is an extremely challenging problem, but that has not stopped a number of attempts. An intuitive requirement on such general relationships is that they must reduce to the simple Rayleigh-Rice formula for sufficiently smooth surfaces. Unfortunately that does not always happen. Because most optically smooth surfaces also scatter from non-topographic features, doubt creeps in about the accuracy of Rayleigh-Rice. This paper investigates these issues and explains some of the confusion generated in recent years. The authors believe there are measurement issues, scatter source issues and rough surface derivation issues, but that Rayleigh- Rice is accurate as formulated and should not be "corrected." Moreover, it will be shown that the empirically observed near shift invariance of surface scatter phenomena is a direct consequence of the Rayleigh-Rice theory.
Omnidirectional surface wave cloak using an isotropic homogeneous dielectric coating
Mitchell-Thomas, R. C.; Quevedo-Teruel, O.; Sambles, J. R.; Hibbins, A. P.
2016-08-01
The field of transformation optics owes a lot of its fame to the concept of cloaking. While some experimental progress has been made towards free-space cloaking in three dimensions, the material properties required are inherently extremely difficult to achieve. The approximations that then have to be made to allow fabrication produce unsatisfactory device performance. In contrast, when surface wave systems are the focus, it has been shown that a route distinct from those used to design free-space cloaks can be taken. This results in very simple solutions that take advantage of the ability to incorporate surface curvature. Here, we provide a demonstration in the microwave regime of cloaking a bump in a surface. The distortion of the shape of the surface wave fronts due to the curvature is corrected with a suitable refractive index profile. The surface wave cloak is fabricated from a metallic backed homogeneous dielectric waveguide of varying thickness, and exhibits omnidirectional operation.
Experimental study of breaking and energy dissipation in surface waves
Ruiz Chavarria, Gerardo; Le Gal, Patrice; Le Bars, Michael
2014-11-01
We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as ɛ = H/ λ (where H is the wave height and λ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when ɛ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry. G. Ruiz Chavarria acknowledges DGAPA-UNAM by support under Project IN 116312 (Vorticidad y ondas no lineales en fluidos).
Research into surface wave phenomena in sedimentary basins
Wojcik, G. L.; Isenberg, J.; Ma, F.; Richardson, E.
1981-12-01
This study is a continuation of an engineering seismology research effort prompted by the sensitivity of guidance sets in Minuteman Wing V to distant earthquakes. An earlier report considers the probable cause of anomalous patterns of seismic alarms triggered by two North American earthquakes. This report extends the previous study by examining the propagation of surface waves from the 1975 Pocatello Valley, Idaho earthquake sequence across Wyoming to Wing V. In addition, the more general question of surface wave phenomena in sedimentary basins is addressed, particularly the effect of laterally inhomogeneous (dipping) basin-bedrock interfaces. Findings indicate that fundamental and first overtone surface waves are significantly modified by the travel path. In contrast, higher modes are relatively unchanged by the travel path, and affect Wing V in much the same way as body waves considered in the previous study.
Xia, J.; Miller, R.D.; Park, C.B.; Hunter, J.A.; Harris, J.B.; Ivanov, J.
2002-01-01
Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated Vs and borehole measured Vs in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived Vs values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis. ?? 2002 Elsevier Science Ltd. All rights reserved.
Surface wave tomography of Europe from ambient seismic noise
Lu, Yang; Stehly, Laurent; Paul, Anne
2017-04-01
We present a European scale high-resolution 3-D shear wave velocity model derived from ambient seismic noise tomography. In this study, we collect 4 years of continuous seismic recordings from 1293 stations across much of the European region (10˚W-35˚E, 30˚N-75˚N), which yields more than 0.8 million virtual station pairs. This data set compiles records from 67 seismic networks, both permanent and temporary from the EIDA (European Integrated Data Archive). Rayleigh wave group velocity are measured at each station pair using the multiple-filter analysis technique. Group velocity maps are estimated through a linearized tomographic inversion algorithm at period from 5s to 100s. Adaptive parameterization is used to accommodate heterogeneity in data coverage. We then apply a two-step data-driven inversion method to obtain the shear wave velocity model. The two steps refer to a Monte Carlo inversion to build the starting model, followed by a linearized inversion for further improvement. Finally, Moho depth (and its uncertainty) are determined over most of our study region by identifying and analysing sharp velocity discontinuities (and sharpness). The resulting velocity model shows good agreement with main geological features and previous geophyical studies. Moho depth coincides well with that obtained from active seismic experiments. A focus on the Greater Alpine region (covered by the AlpArray seismic network) displays a clear crustal thinning that follows the arcuate shape of the Alps from the southern French Massif Central to southern Germany.
Pillet, R.; Rouland, D.; Roult, G.; Wiens, D. A.
1999-02-01
Direct earthquake-to-station Rayleigh and Love wave data observed on high gain broadband records are analyzed in order to improve the lateral resolution of the uppermost mantle in the southwest Pacific region. We used data of nine permanent Geoscope and Iris stations located in the southern hemisphere and nine other stations as part of two temporary networks, the first one installed in New Caledonia and Vanuatu (hereafter named Cavascope network) by ORSTOM and the EOST from Louis Pasteur University in Strasbourg (France) and the second one installed in the Fiji, Tonga and Niue islands (hereafter named Spase network) by Washington University in St. Louis (USA). In order to collect more significant details on the surficial structures, we included the analysis of short period waves down to 8 s. A multiple frequency filtering technique has been used to recover phase velocities of Rayleigh and Love waves for selected earthquakes with magnitude greater than 5.5 and with known centroid moment tensor (CMT). About 1100 well-distributed seismograms have been processed in the period range 8-100 s and corrections for topography and water depth have been applied to the observed phase velocities. The geographical distribution of phase velocity anomalies have then been computed using the tomographic method developed by Montagner [Montagner, J.P., 1986a. Regional three-dimensional structures using long-period surface waves. Ann. Geophys. 4 (B3), 283-294]. Due to a poor knowledge of dense, well-distributed, crustal thickness values and corresponding velocity models, we did not perform or speculate on the construction of an S-wave 3D velocity model; therefore, we limited this study to the interpretation of the phase velocity distribution. The location of phase velocity anomalies are well determined and the deviations are discussed within the framework of the geological context and compared with other tomographic models. At long periods, from 40 s to 100 s, our results agree well
Asymptotic Rayleigh instantaneous unit hydrograph
Troutman, B.M.; Karlinger, M.R.
1988-01-01
The instantaneous unit hydrograph for a channel network under general linear routing and conditioned on the network magnitude, N, tends asymptotically, as N grows large, to a Rayleigh probability density function. This behavior is identical to that of the width function of the network, and is proven under the assumption that the network link configuration is topologically random and the link hydraulic and geometric properties are independent and identically distributed random variables. The asymptotic distribution depends only on a scale factor, {Mathematical expression}, where ?? is a mean link wave travel time. ?? 1988 Springer-Verlag.
Excitation of surface plasma waves over corrugated slow-wave structure
Ashim P Jain; Jetendra Parashar
2005-08-01
A microwave propagating along vacuum–dielectric–plasma interface excites surface plasma wave (SPW). A periodic slow-wave structure placed over dielectric slows down the SPW. The phase velocity of slow SPW is sensitive to height, periodicity, number of periods, thickness and the separation between dielectric and slow-wave structure. These slow SPW can couple the microwave energy to the plasma and can sustain the discharge. The efficiency of the power coupling is few per cent and is sensitive to separation between dielectric and slow-wave structure.
Horizon effects for surface waves in wave channels and circular jumps
Jannes, Gil; Chaline, Jennifer; Maïssa, Philippe; Mathis, Christian; Rousseaux, Germain
2011-01-01
Surface waves in classical fluids experience a rich array of black/white hole horizon effects. The dispersion relation depends on the characteristics of the fluid (in our case, water and silicon oil) as well as on the fluid depth and the wavelength regime. In some cases, it can be tuned to obtain a relativistic regime plus high-frequency dispersive effects. We discuss two types of ongoing analogue white-hole experiments: deep water waves propagating against a counter-current in a wave channel and shallow waves on a circular hydraulic jump.
A surface wave elastography technique for measuring tissue viscoelastic properties.
Zhang, Xiaoming
2017-04-01
A surface wave elastography method is proposed to study the viscoelastic properties of skin by measuring the surface wave speed and attenuation on the skin. Experiments were carried out on porcine skin tissues. The surface wave speed is measured by the change of phase with distance. The wave attenuation is measured by the decay of wave amplitude with distance. The change of viscoelastic properties with temperature was studied at room and body temperatures. The wave speed was 1.83m/s at 22°C but reduced to 1.52m/s at 33°C. The viscoelastic ratio was almost constant from 22°C to 33°C. Fresh and decayed tissues were studied. The wave speed of the decayed tissue increased from 1.83m/s of fresh state to 2.73m/s. The viscoelastic ratio was 0.412/mm at the decayed state compared to 0.215/mm at the fresh state. More tissue samples are needed to study these viscoelastic parameters according to specific applications.
Temperature Compensation of Surface Acoustic Waves on Berlinite
Searle, David Michael Marshall
The surface acoustic wave properties of Berlinite (a-AlPO4) have been investigated theoretically and experimentally, for a variety of crystallographic orientations, to evaluate its possible use as a substrate material for temperature compensated surface acoustic wave devices. A computer program has been developed to calculate the surface wave properties of a material from its elastic, piezoelectric, dielectric and lattice constants and their temperature derivatives. The program calculates the temperature coefficient of delay, the velocity of the surface wave, the direction of power flow and a measure of the electro-mechanical coupling. These calculations have been performed for a large number of orientations using a modified form of the data given by Chang and Barsch for Berlinite and predict several new temperature compensated directions. Experimental measurements have been made of the frequency-temperature response of a surface acoustic wave oscillator on an 80° X axis boule cut which show it to be temperature compensated in qualitative agreement with the theoretical predictions. This orientation shows a cubic frequency-temperature dependence instead of the expected parabolic response. Measurements of the electro-mechanical coupling coefficient k gave a value lower than predicted. Similar measurements on a Y cut plate gave a value which is approximately twice that of ST cut quartz, but again lower than predicted. The surface wave velocity on both these cuts was measured to be slightly higher than predicted by the computer program. Experimental measurements of the lattice parameters a and c are also presented for a range of temperatures from 25°C to just above the alpha-beta transition at 584°C. These results are compared with the values obtained by Chang and Barsch. The results of this work indicate that Berlinite should become a useful substrate material for the construction of temperature compensated surface acoustic wave devices.
Magnetoacoustic surface gravity waves at a spherical interface
Ballai, I.; Forgács-Dajka, E.; Douglas, M.
2011-03-01
Aims: The plasma structured by magnetic fields in the solar atmosphere is a perfect medium for the propagation of guided magnetic and magnetoacoustic waves. Geometrical restriction of wave propagation is known to confer a dispersive character for waves. In addition, waves propagating along discontinuities in the medium are known to remain localized. As an extension to theories of guided waves in magnetic slabs and cylinders under solar and stellar conditions, we aim to study the propagation of magnetoacoustic-gravity waves at a spherical interface in the low solar corona (considered here as a density discontinuity), modelling global waves recently observed in the corona in EUV wavelengths. Methods: Using conservation laws at the interface we derive the dispersion relation in spherical geometry with a radially expanding magnetic field in the presence of gravitational stratification. The obtained dispersion relation describing fast magnetoacoustic-gravity surface waves is derived using an approximative method taking into account that propagation takes place near the solar surface. Results: Theoretical results obtained in the present study are applied to investigate the propagation of EIT waves in the low corona. The frequency of waves is shown to increase with decreasing density contrast at the interface. We also show that, for a given azimuthal wavenumber, the magnetic field has a very small effect on the value of the frequency of waves. When plotted against the location of the interface (in the radial direction) the frequency varies inversely proportional to the distance, while for a fixed density ratio and location of the interface the frequency is obtained to be defined in a very narrow region.
Characters of surface deformation and surface wave in thermal capillary convection
DUAN; Li; KANG; Qi; HU; Wenrei
2006-01-01
In the field of fluid mechanics, free surface phenomena is one of the most important physical processes. In the present research work, the surface deformation and surface wave caused by temperature difference of sidewalls in a rectangular cavity have been investigated. The horizontal cross-section of the container is 52 mm×42 mm, and there is a silicon oil layer of height 3.5 mm in the experimental cavity. Temperature difference between the two side walls of the cavity is increased gradually, and the flow on the liquid layer will develop from stable convection to un-stable convection. An optical diagnostic system consisting of a modified Michelson interferometer and image processor has been developed for study of the surface deformation and surface wave of thermal capillary convection. The Fourier transformation method is used to interferometer fringe analysis. The quantitative results of surface deformation and surface wave have been calculated from a serial of the interference fringe patterns. The characters of surface deformation and surface wave have been obtained. They are related with temperature gradient and surface tension. Surface deformation is fluctuant with time, which shows the character of surface wave. The cycle period of the wave is 4.8 s, and the amplitudes are from 0 to 0.55 μm. The phase of the wave near the cool side of the cavity is opposite and correlative to that near the hot side. The present experiment proves that the surface wave of thermal capillary convection exists on liquid free surface, and it is wrapped in surface deformation.
Generation of 1D interference patterns of Bloch surface waves
Kadomina, E. A.; Bezus, E. A.; Doskolovich, L. L.
2016-09-01
Interference patterns of Bloch surface waves with a period that is significantly less than the wavelength of incident radiation are formed using dielectric diffraction gratings located on the surface of photonic crystal. The simulation based on electromagnetic diffraction theory is used to demonstrate the possibility of high-quality interference patterns due to resonant enhancement of higher evanescent diffraction orders related to the excitation of the Bloch surface waves. The contrast of the interference patterns is close to unity, and the period is less than the period of the diffraction structure by an order of magnitude.
吴腾飞; 吴荣新; 张平松; 程刚
2013-01-01
Advanced?detection?is?an?essential?technology?for?preventing?geology?hazards?in?the?construction?of?underground?engineering.?At?first,?this?paper?summarized?the?domestic?and?foreign?tunnel?detection?method,?and?focuses?on?analysis?of?the?Rayleigh?wave?detection?technology?in?tunnel?advanced?detection?advantages.?Introduces?the?detection?principle?and?the?field?construction?method?of?Rayleigh?wave,?and?uses?He-Fu?High?Speed?Rail?examples?to?prove?that?compared?to?traditional?tunnel?detection?methods,?Rayleigh?wave?has?advantages?of?simple?construction,?economical,?shallow?detection?higher?resolution?etc,?to?a?great?extent?can?find?out?tunnel?spread?range?of?geological?anomalies,?providing?a?reliable?basis?for?driving?security.?In?the?end,?the?future?research?direction?of?Rayleigh?wave?in?tunnel?advanced?detection?is?proposed?according?to?engineering?experiment.%超前探测是预防地下工程施工环节发生灾害的重要技术方法。此文先对国内外隧道超前探测技术方法进行了总结，并着重分析了瑞雷波探测技术在隧道超前探测中的优势。介绍了多道瞬态瑞雷波探测的技术原理和现场施工方法，通过合福高铁安徽段7标某隧道超前预报的应用实例，说明瑞雷波探测技术与其他隧道超前探测方法相比，具有施工简便、经济、浅层探测分辨率高等优点，可大限度地查明隧道掘进波及范围内地质异常情况，为掘进安全提供可靠技术依据。最后，笔者根据工程试验，提出了瑞雷波在隧道超前探测中今后的研究方向。
Solar energy converter using surface plasma waves
Anderson, L. M. (Inventor)
1984-01-01
Sunlight is dispersed over a diffraction grating formed on the surface of a conducting film on a substrate. The angular dispersion controls the effective grating period so that a matching spectrum of surface plasmons is excited for parallel processing on the conducting film. The resulting surface plasmons carry energy to an array of inelastic tunnel diodes. This solar energy converter does not require different materials for each frequency band, and sunlight is directly converted to electricity in an efficient manner by extracting more energy from the more energetic photons.
The Dynamics of Flat Surface Internal Geophysical Waves with Currents
Compelli, Alan; Ivanov, Rossen I.
2016-08-01
A two-dimensional water wave system is examined consisting of two discrete incompressible fluid domains separated by a free common interface. In a geophysical context this is a model of an internal wave, formed at a pycnocline or thermocline in the ocean. The system is considered as being bounded at the bottom and top by a flatbed and wave-free surface respectively. A current profile with depth-dependent currents in each domain is considered. The Hamiltonian of the system is determined and expressed in terms of canonical wave-related variables. Limiting behaviour is examined and compared to that of other known models. The linearised equations as well as long-wave approximations are presented.
The Dynamics of Flat Surface Internal Geophysical Waves with Currents
Compelli, Alan
2016-01-01
A two-dimensional water wave system is examined consisting of two discrete incompressible fluid domains separated by a free common interface. In a geophysical context this is a model of an internal wave, formed at a pycnocline or thermocline in the ocean. The system is considered as being bounded at the bottom and top by a flatbed and wave-free surface respectively. A current profile with depth-dependent currents in each domain is considered. The Hamiltonian of the system is determined and expressed in terms of canonical wave-related variables. Limiting behaviour is examined and compared to that of other known models. The linearised equations as well as long-wave approximations are presented.
On the cascade mechanism of short surface wave modulation
M. Charnotskii
2002-01-01
Full Text Available Modulation of short surface ripples by long surface or internal waves by a cascade mechanism is considered. At the first stage, the orbital velocity of the long wave (LW adiabatically modulates an intermediate length nonlinear gravity wave (GW, which generates a bound (parasitic capillary wave (CW near its crest in a wide spatial frequency band. Due to strong dependence of the CW amplitude on that of the GW, the resulting ripple modulation by LW can be strong. Adiabatic modulation at the first stage is calculated for an arbitrarily strong LW current. The CWs are calculated based on the Lonquet-Higgins theory, in the framework of a steady periodic solution, which proves to be sufficient for the cases considered. Theoretical results are compared with data from laboratory experiments. A discussion of related sea clutter data is given in the conclusion.
The Whitham Equation as a Model for Surface Water Waves
Moldabayev, Daulet; Dutykh, Denys
2014-01-01
The Whitham equation was proposed as an alternate model equation for the simplified description of uni-directional wave motion at the surface of an inviscid fluid. As the Whitham equation incorporates the full linear dispersion relation of the water wave problem, it is thought to provide a more faithful description of shorter waves of small amplitude than traditional long wave models such as the KdV equation. In this work, we identify a scaling regime in which the Whitham equation can be derived from the Hamiltonian theory of surface water waves. The Whitham equation is integrated numerically, and it is shown that the equation gives a close approximation of inviscid free surface dynamics as described by the Euler equations. The performance of the Whitham equation as a model for free surface dynamics is also compared to two standard free surface models: the KdV and the BBM equation. It is found that in a wide parameter range of amplitudes and wavelengths, the Whitham equation performs on par with or better tha...
Artificial ocean upwelling utilizing the energy of surface waves
Soloviev, Alexander
2016-04-01
Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10 oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.
无
2007-01-01
Surface waves comprise an important aspect of the interaction between the atmosphere and the ocean, so a dynamically consistent framework for modelling atmosphere-ocean interaction must take account of surface waves, either implicitly or explicitly. In order to calculate the effect of wind forcing on waves and currents, and vice versa, it is necessary to employ a consistent formulation of the energy and momentum balance within the airflow, wave field, and water column. It is very advantageous to apply surface-following coordinate systems, whereby the steep gradients in mean flow properties near the air-water interface in the cross-interface direction may be resolved over distances which are much smaller than the height of the waves themselves. We may account for the waves explicitly by employing a numerical spectral wave model, and applying a suitable theory of wave-mean flow interaction. If the mean flow is small compared with the wave phase speed, perturbation expansions of the hydrodynamic equations in a Lagrangian or generalized Lagrangian mean framework are useful: for stronger flows, such as for wind blowing over waves, the presence of critical levels where the mean flow velocity is equal to the wave phase speed necessitates the application of more general types of surface-following coordinate system. The interaction of the flow of air and water and associated differences in temperature and the concentration of various substances (such as gas species) gives rise to a complex boundary-layer structure at a wide range of vertical scales, from the sub-millimetre scales of gaseous diffusion, to several tens of metres for the turbulent Ekman layer. The balance of momentum, heat, and mass is also affected significantly by breaking waves, which act to increase the effective area of the surface for mass transfer, and increase turbulent diffusive fluxes via the conversion of wave energy to turbulent kinetic energy.
Modeling anomalous surface - wave propagation across the Southern Caspian basin
Priestly, K.F.; Patton, H.J.; Schultz, C.A.
1998-01-09
The crust of the south Caspian basin consists of 15-25 km of low velocity, highly attenuating sediment overlying high velocity crystalline crust. The Moho depth beneath the basin is about 30 km as compared to about 50 km in the surrounding region. Preliminary modeling of the phase velocity curves shows that this thick sediments of the south Caspian basin are also under-lain by a 30-35 km thick crystalline crust and not by typical oceanic crust. This analysis also suggest that if the effect of the over-pressuring of the sediments is to reduce Poissons` ratio, the over-pressured sediments observed to approximately 5 km do not persist to great depths. It has been shown since 1960`s that the south Caspian basin blocks the regional phase Lg. Intermediate frequency (0.02-0.04 Hz) fundamental mode Raleigh waves propagating across the basin are also severely attenuated, but the low frequency surface waves are largely unaffected. This attenuation is observed along the both east-to-west and west-to-east great circle paths across the basin, and therefore it cannot be related to a seismograph site effect. We have modeled the response of surface waves in an idealized rendition of the south Caspian basin model using a hybrid normal mode / 2-D finite difference approach. To gain insight into the features of the basin which cause the anomalous surface wave propagation, we have varied parameters of the basin model and computed synthetic record sections to compare with the observed seismograms. We varied the amount of mantel up-warp, the shape of the boundaries, the thickness and shear wave Q of the sediments and mantle, and the depth of the water layer. Of these parameters, the intermediate frequency surface waves are most severely affected by the sediments thickness and shear wave attenuation. fundamental mode Raleigh wave phase velocities measure for paths crossing the basin are extremely low.
Gravitational waves from surface inhomogeneities of neutron stars
Konar, Sushan; Mukherjee, Dipanjan; Bhattacharya, Dipankar; Sarkar, Prakash
2016-11-01
Surface asymmetries of accreting neutron stars are investigated for their mass quadrupole moment content. Though the amplitude of the gravitational waves from such asymmetries seems to be beyond the limit of detectability of the present generation of detectors, it appears that rapidly rotating neutron stars with strong magnetic fields residing in high-mass x-ray binaries would be worth considering for a targeted search for continuous gravitational waves with the next generation of instruments.
Gosselin, Jeremy M.; Dosso, Stan E.; Cassidy, John F.; Quijano, Jorge E.; Molnar, Sheri; Dettmer, Jan
2017-10-01
This paper develops and applies a Bernstein-polynomial parametrization to efficiently represent general, gradient-based profiles in nonlinear geophysical inversion, with application to ambient-noise Rayleigh-wave dispersion data. Bernstein polynomials provide a stable parametrization in that small perturbations to the model parameters (basis-function coefficients) result in only small perturbations to the geophysical parameter profile. A fully nonlinear Bayesian inversion methodology is applied to estimate shear wave velocity (VS) profiles and uncertainties from surface wave dispersion data extracted from ambient seismic noise. The Bayesian information criterion is used to determine the appropriate polynomial order consistent with the resolving power of the data. Data error correlations are accounted for in the inversion using a parametric autoregressive model. The inversion solution is defined in terms of marginal posterior probability profiles for VS as a function of depth, estimated using Metropolis-Hastings sampling with parallel tempering. This methodology is applied to synthetic dispersion data as well as data processed from passive array recordings collected on the Fraser River Delta in British Columbia, Canada. Results from this work are in good agreement with previous studies, as well as with co-located invasive measurements. The approach considered here is better suited than `layered' modelling approaches in applications where smooth gradients in geophysical parameters are expected, such as soil/sediment profiles. Further, the Bernstein polynomial representation is more general than smooth models based on a fixed choice of gradient type (e.g. power-law gradient) because the form of the gradient is determined objectively by the data, rather than by a subjective parametrization choice.
High-Temperature Surface-Acoustic-Wave Transducer
Zhao, Xiaoliang; Tittmann, Bernhard R.
2010-01-01
Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection. An efficient, high-temperature, low-profile surface acoustic wave transducer design has been identified and tested for nondestructive evaluation of structures or materials. The development is a Sol-Gel bismuth titanate-based surface-acoustic-wave (SAW) sensor that can generate efficient surface acoustic waves for crack inspection. The produced sensor is very thin (submillimeter), and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. One major uniqueness of the Sol-Gel bismuth titanate SAW sensor is that it is easy to implement to structures of various shapes. With a spray coating process, the sensor can be applied to surfaces of large curvatures. Second, the sensor is very thin (as a coating) and has very minimal effect on airflow or rotating equipment imbalance. Third, it can withstand temperatures up to 530 C, which is very useful for engine applications where high temperature is an issue.
Lateral Flooding Associated to Wave Flood Generation on River Surface
Ramírez-Núñez, C.; Parrot, J.-F.
2016-06-01
This research provides a wave flood simulation using a high resolution LiDAR Digital Terrain Model. The simulation is based on the generation of waves of different amplitudes that modify the river level in such a way that water invades the adjacent areas. The proposed algorithm firstly reconstitutes the original river surface of the studied river section and then defines the percentage of water loss when the wave floods move downstream. This procedure was applied to a gently slope area in the lower basin of Coatzacoalcos river, Veracruz (Mexico) defining the successive areas where lateral flooding occurs on its downstream movement.
Yang, Si-Tong; Wei, Jiu-Chuan; Cheng, Jiu-Long; Shi, Long-Qing; Wen, Zhi-Jie
2016-12-01
Currently, numerical simulations of seismic channel waves for the advance detection of geological structures in coal mine roadways focus mainly on modeling twodimensional wave fields and therefore cannot accurately simulate three-dimensional (3-D) full-wave fields or seismic records in a full-space observation system. In this study, we use the first-order velocity-stress staggered-grid finite difference algorithm to simulate 3-D full-wave fields with P-wave sources in front of coal mine roadways. We determine the three components of velocity V x, V y, and V z for the same node in 3-D staggered-grid finite difference models by calculating the average value of V y, and V z of the nodes around the same node. We ascertain the wave patterns and their propagation characteristics in both symmetrical and asymmetric coal mine roadway models. Our simulation results indicate that the Rayleigh channel wave is stronger than the Love channel wave in front of the roadway face. The reflected Rayleigh waves from the roadway face are concentrated in the coal seam, release less energy to the roof and floor, and propagate for a longer distance. There are surface waves and refraction head waves around the roadway. In the seismic records, the Rayleigh wave energy is stronger than that of the Love channel wave along coal walls of the roadway, and the interference of the head waves and surface waves with the Rayleigh channel wave is weaker than with the Love channel wave. It is thus difficult to identify the Love channel wave in the seismic records. Increasing the depth of the receivers in the coal walls can effectively weaken the interference of surface waves with the Rayleigh channel wave, but cannot weaken the interference of surface waves with the Love channel wave. Our research results also suggest that the Love channel wave, which is often used to detect geological structures in coal mine stopes, is not suitable for detecting geological structures in front of coal mine roadways
Surface waves propagation on a turbulent flow forced electromagnetically
Gutiérrez, Pablo
2015-01-01
We study the propagation of monochromatic surface waves on a turbulent flow. The flow is generated in a layer of liquid metal by an electromagnetic forcing. This forcing creates a quasi two-dimensional (2D) turbulence with strong vertical vorticity. The turbulent flow contains much more energy than the surface waves. In order to focus on the surface wave, the deformations induced by the turbulent flow are removed. This is done by performing a coherent phase averaging. For wavelengths smaller than the forcing lengthscale, we observe a significant increase of the wavelength of the propagating wave that has not been reported before. We suggest that it can be explained by the random deflection of the wave induced by the velocity gradient of the turbulent flow. Under this assumption, the wavelength shift is an estimate of the fluctuations of deflection angle. The local measurements of the wave frequency far from the wavemaker do not reveal such systematic behavior, although a small shift is measured. Finally we qu...
Enhanced Sensitive Love Wave Surface Acoustic Wave Sensor Designed for Immunoassay Formats
Mihaela Puiu
2015-05-01
Full Text Available We report a Love wave surface acoustic wave (LW-SAW immunosensor designed for the detection of high molecular weight targets in liquid samples, amenable also for low molecular targets in surface competition assays. We implemented a label-free interaction protocol similar to other surface plasmon resonance bioassays having the advantage of requiring reduced time analysis. The fabricated LW-SAW sensor supports the detection of the target in the nanomolar range, and can be ultimately incorporated in portable devices, suitable for point-of-care testing (POCT applications.
Enhanced sensitive love wave surface acoustic wave sensor designed for immunoassay formats.
Puiu, Mihaela; Gurban, Ana-Maria; Rotariu, Lucian; Brajnicov, Simona; Viespe, Cristian; Bala, Camelia
2015-05-05
We report a Love wave surface acoustic wave (LW-SAW) immunosensor designed for the detection of high molecular weight targets in liquid samples, amenable also for low molecular targets in surface competition assays. We implemented a label-free interaction protocol similar to other surface plasmon resonance bioassays having the advantage of requiring reduced time analysis. The fabricated LW-SAW sensor supports the detection of the target in the nanomolar range, and can be ultimately incorporated in portable devices, suitable for point-of-care testing (POCT) applications.
Caliendo, Cinzia
2012-01-01
The operation of electroacoustic devices based on surface acoustic waves (SAW) propagation along β-SiC/AlN and amorphous-SiC/AlN substrates is theoretically studied with respect to the AlN film thickness, the SAW propagation direction, temperature and electric boundary conditions. GHz-range, enhanced electroacoustic coupling coefficient, temperature compensated around 20 °C electroacoustic devices are the advantages of SiC/AlN composite structures. These structures are also suitable for the implementation of sensors with improved performances with respect to SAW devices based on bulk single crystal piezoelectric substrates. The structures feasibility was confirmed by structural investigation and quantitative analysis of sputtered amorphous-SiC and AlN films on Si substrates.
Langasite Surface Acoustic Wave Sensors: Fabrication and Testing
Zheng, Peng; Greve, David W.; Oppenheim, Irving J.; Chin, Tao-Lun; Malone, Vanessa
2012-02-01
We report on the development of harsh-environment surface acoustic wave sensors for wired and wireless operation. Surface acoustic wave devices with an interdigitated transducer emitter and multiple reflectors were fabricated on langasite substrates. Both wired and wireless temperature sensing was demonstrated using radar-mode (pulse) detection. Temperature resolution of better than ±0.5°C was achieved between 200°C and 600°C. Oxygen sensing was achieved by depositing a layer of ZnO on the propagation path. Although the ZnO layer caused additional attenuation of the surface wave, oxygen sensing was accomplished at temperatures up to 700°C. The results indicate that langasite SAW devices are a potential solution for harsh-environment gas and temperature sensing.
Multichannel analysis of surface wave method with the autojuggie
Tian, G.; Steeples, D.W.; Xia, J.; Miller, R.D.; Spikes, K.T.; Ralston, M.D.
2003-01-01
The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the 'autojuggie') is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys. ?? 2003 Elsevier Science Ltd. All rights reserved.
Bussonière, Adrien; Brunet, Philippe; Matar, Olivier Bou
2016-01-01
When sessile droplets are excited by ultrasonic traveling surface acoustic waves (SAWs), they undergo complex dynamics with both oscillations and translational motion. While the nature of the Rayleigh-Lamb quadrupolar drop oscillations has been identified, their origin and their influence on the drop mobility remains unexplained. Indeed the physics behind this peculiar dynamics is complex with nonlinearities involved both at the excitation level (acoustic streaming and radiation pressure) and in the droplet response (nonlinear oscillations and contact line dynamics). In this paper, we investigate the dynamics of sessile and pendant drops excited by SAWs. For pendant drops, so-far unreported dynamics are observed close to the drop detachment threshold with the suppression of the translational motion. Away from this threshold, the comparison between pendant and sessile drop dynamics allows us to identify the role played by gravity or more generally by an initial or dynamically induced stretching of the drop. In...
Andersen, Kurt Munk
1997-01-01
Rayleigh's principle expresses that the smallest eigenvalue of a regular Sturm-Liouville problem with regular boundary conditions is the minimum value of a certain functional, the so called Rayleigh's quotient, and that this value is attained at the corresponding eigenfunctions only. This can...... be proved by means of more advanced methods. However, it turns out that there is an elementary proof, which is presented in the report....
Characteristics of surface waves in anisotropic left-handed materials
Jiang Yong-Yuan; Shi Hong-Yan; Zhang Yong-Qiang; Hou Chun-Feng; Sun Xiu-Dong
2007-01-01
We report the coexistence of TE and TM surface modes in certain same frequency domain at the interface between one isotropic regular medium and another biaxially anistotropic left-handed medium. The conditions for the existence of TE and TM polarized surface waves in biaxially anisotropic left-handed materials are identified, respectively.The Poynting vector and the energy density associated with surface modes are calculated. Depending on the system parameters, either TE or TM surface modes can have the time averaged Poynting vector directed to or opposite to the mode phase velocity. It is seen that the characteristics of surface waves in biaxially anisotropic left-handed media are significantly different from that in isotropic left-handed media.
Berngardt, O I; Podlesnyi, A V; Kurkin, V I; Zherebtsov, G A
2016-01-01
Based on the Irkutsk fast monostatic chirp ionosonde data we made a statistical analysis of ionospheric effects for 28 earthquakes which appeared in 2011-2016 years. These effects are related with surface (Rayleigh) seismic waves far from epicenter. The analysis has shown that nine of these earthquakes were accompanied by vertical midscale ionospheric irregularities (multicusp). To estimate the ionospheric efficiency of the seismic waves we proposed new index $K_{W}$. The index estimates the maximal amplitude of the acoustic shock wave generated by given spatial distribution of seismic vibrations and related with maximal spectral power of seismic oscillations. Based on the analysis of experimental data we have shown that earthquake-related multicusp is observed mostly at daytime [07:00-17:00]LST for $K_{W}\\ge4.7$. The observations of intrinsic gravity waves by GPS technique in the epicenter vicinity do not show such a daytime dependence. Based on 24/05/2013 Okhotsk Sea earthquake example, we demonstrated that...