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1
Chávez-García, Francisco J., Jaime Ramos-Martínez, and Evangelina Romero-Jiménez. "Surface-wave dispersion analysis in Mexico City." Bulletin of the Seismological Society of America 85, no. 4 (August 1, 1995): 1116–26. http://dx.doi.org/10.1785/bssa0850041116.
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Abstract In this article, we present an observational investigation of ground motion at Mexico City focused on surface waves. Our purpose is 2-fold; first, to understand incident ground motion during the great Michoacán earthquake of 19 September 1985, and second, to characterize surface waves propagating in the lake-bed zone. To this end we analyze the strong-motion records obtained at Mexico City for the large (MS = 8.1) earthquake of 19 September 1985. It is shown that, in the low-frequency range, we observe the Rayleigh fundamental mode in both the vertical and the radial components, and the Love fundamental mode in the transverse component at all the strong-motion stations. The vertical component also shows the first higher mode of Rayleigh waves. We use a very broadband record obtained at station CU for the smaller (MS = 6.7) earthquake of 14 May 1993 to verify that the dispersion computed from the model of Campillo et al. (1989) represents well the average surface-wave propagation between the coast and Mexico City in the 7- to 10-sec period range. We use this result to assign absolute times to the strong-motion records of the Michoacán event. This allowed us to identify additional wave trains that propagate laterally in directions other than great circle in the 3- to 5-sec period range. These wave trains are identified as Love waves. In a second analysis, we study a set of refraction data obtained during a small-scale (250 m) experiment on the virgin clay of the lake-bed zone. Phase-velocity dispersion curves for several modes of Rayleigh waves are identified in the refraction data and inverted to obtain an S-wave velocity profile. This profile is used as the uppermost layering in a 2D model of Mexico City valley. The results of numerical simulation show that surface waves generated by lateral finiteness of the clay layer suffer large dispersion and attenuation. We conclude that surface waves generated by the lateral heterogeneity of the upper-most stratigraphy very significantly affect ground motion near the edge of the valley, but their importance is negligible for distances larger than 1.5 km from the edge. Thus, locally generated surface waves propagating through the clay layer cannot explain late arrivals observed for the 1985 event. We suggest that the long duration of strong motion is due to the interaction between lateral propagation of waves guided by deep layers (1 to 4 km) and the surficial clay layer. This interaction is possible by the coincidence of the dominant frequency of the uppermost layers and the frequency of the deeply guided waves.
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Lin, Chih-Ping, and Tzong-Sheng Chang. "Multi-station analysis of surface wave dispersion." Soil Dynamics and Earthquake Engineering 24, no. 11 (December 2004): 877–86. http://dx.doi.org/10.1016/j.soildyn.2003.11.011.
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Ikeda, Tatsunori, and Takeshi Tsuji. "Two-station continuous wavelet transform cross-coherence analysis for surface-wave tomography using active-source seismic data." GEOPHYSICS 85, no. 1 (January 1, 2020): EN17—EN28. http://dx.doi.org/10.1190/geo2019-0054.1.
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ABSTRACT Surface-wave tomography has great potential to improve the lateral resolution of near-surface characterization compared to 2D surface-wave analysis with multichannel analysis of surface waves (MASW). Surface-wave tomography has been widely applied to obtain high-resolution maps of phase or group velocity from dispersion curves between pairs of stations in seismological studies. However, very few studies have done surface-wave tomography with active-source (exploration) seismic data, probably because extracting surface-wave dispersion curves between two stations is difficult due to the complex wave propagation in heterogeneous near-surface structures. Here, we describe a method to estimate reliable phase-velocity dispersion curves between two stations from exploration seismic data. In our approach, we compute cross coherences between pairs of stations to extract phase information, stacking the cross coherences from different shot gathers to improve the signal-to-noise ratio. To further distinguish surface-wave signals from noise in the time domain, we perform a time-frequency analysis using the continuous wavelet transform (CWT) on the stacked cross coherences. We used modeling of the wavelet transform between station pairs to extract phase-velocity dispersion curves from the stacked cross coherences. We apply this two-station CWT cross-coherence method to synthetic and field data sets. Both applications demonstrate that our method can extract stable phase-velocity dispersion curves between two stations better than two-station or multistation analysis without time-domain filtering. In phase-velocity distributions constructed by surface-wave tomography from the dispersion curves between two stations, the horizontal resolution is improved over MASW-based analyses. Improvement of the horizontal resolution is also achieved in S-wave velocity structures derived by inversion of the phase-velocity distributions. Our method is effective in estimating reliable phase-velocity dispersion curves and may contribute to constructing high-resolution S-wave velocity models located with a laterally heterogeneous structure, by subsequent surface-wave tomography and S-wave velocity inversion.
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Addo, K. O., and P. K. Robertson. "Shear-wave velocity measurement of soils using Rayleigh waves." Canadian Geotechnical Journal 29, no. 4 (August 1, 1992): 558–68. http://dx.doi.org/10.1139/t92-063.
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A modified version of the spectral analysis of surface waves (SASW) equipment and analysis procedure has been developed to determine in situ shear-wave velocity variation with depth from the ground surface. A microcomputer has been programmed to acquire waveform data and perform the relevant spectral analyses that were previously done by signal analyzers. Experimental dispersion for Rayleigh waves is now obtainable at a site and inverted with a fast algorithm for dispersion computation. Matching experimental and theoretical dispersion curves has been automated in an optimization routine that does not require intermittent operator intervention or experience in dispersion computation. Shear-wave velocity profiles measured by this procedure are compared with results from independent seismic cone penetration tests for selected sites in western Canada. Key words : surface wave, dispersion, inversion, optimization, shear-wave velocity.
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Lin, Chih-Ping, Chun-Hung Lin, and Chih-Jung Chien. "Dispersion analysis of surface wave testing – SASW vs. MASW." Journal of Applied Geophysics 143 (August 2017): 223–30. http://dx.doi.org/10.1016/j.jappgeo.2017.05.008.
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Boiero, Daniele, Paolo Bergamo, Roberto Bruno Rege, and Laura Valentina Socco. "Estimating surface-wave dispersion curves from 3D seismic acquisition schemes: Part 1 — 1D models." GEOPHYSICS 76, no. 6 (November 2011): G85—G93. http://dx.doi.org/10.1190/geo2011-0124.1.
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Surface-wave analysis is based on the estimation of surface-wave dispersion curves, which are then inverted to provide 1D S-wave velocity profiles. Surface-wave dispersion curves can be extracted from P-wave records obtained in seismic exploration and used to characterize the ground structure at a shallow depth. Dispersion curve estimation using 2D wavefield transforms is well-established for 2D acquisition schemes (in-line source and receiver spread). It is possible to extract surface-wave dispersion curves using 2D wavefield transforms from 3D seismic data acquired with any acquisition scheme. In particular, we focus on areal geometry and orthogonal geometry, and we provide a method based on the analysis in the offset domain and the [Formula: see text] multiple signal classification (MUSIC) transform. We assess the performance of the method on synthetic and field data concerning 1D sites.
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Park, Choon B., Richard D. Miller, and Jianghai Xia. "Multichannel analysis of surface waves." GEOPHYSICS 64, no. 3 (May 1999): 800–808. http://dx.doi.org/10.1190/1.1444590.
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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 redundancy with a single field configuration, and the ability to adjust the offset, effectively reducing random or nonlinear noise introduced during recording. A multichannel shot gather decomposed into a swept‐frequency record allows the fast generation of an accurate dispersion curve. The accuracy of dispersion curves determined using this method is proven through field comparisons of the inverted shear‐wave velocity ([Formula: see text]) profile with a downhole [Formula: see text] profile.
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Xi, Chaoqiang, Jianghai Xia, Binbin Mi, Tianyu Dai, Ya Liu, and Ling Ning. "Modified frequency–Bessel transform method for dispersion imaging of Rayleigh waves from ambient seismic noise." Geophysical Journal International 225, no. 2 (January 11, 2021): 1271–80. http://dx.doi.org/10.1093/gji/ggab008.
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SUMMARY Ambient noise surface wave methods have gained much attention among geophysical and civil engineering communities because of their capability of determining near-surface shear wave velocities in highly populated urban areas. Higher mode information of surface waves is important in dispersion curve inversion for shear wave velocity structure. The frequency–Bessel (F-J) transform method is an effective tool for multimode surface wave extraction, which has been applied to multiscale investigations of the Earth structure. The measured dispersion energy with the F-J method, however, would usually be contaminated by a type of ‘crossed’ artefacts at high frequencies, which are caused by spatial aliasing and bidirectional velocity scan of dispersion analysis methods. The ‘crossed’ artefacts usually cross and smear the true dispersion energy in the frequency–velocity domain. We propose a modified F-J (MFJ) transform method in which the Bessel function is replaced by the Hankel function for dispersion analysis of empirical Green's function. The MFJ method performs a unidirectional velocity scanning on the outgoing wave to avoid the ‘crossed’ artefacts. Synthetic and real-world examples demonstrate the effectiveness of the proposed MFJ method in improving the accuracy of Rayleigh wave multimode dispersion measurements.
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Wu, T. T., and Y. Y. Chen. "Wavelet Analysis of Laser-Generated Surface Waves in a Layered Structure With Unbond Regions." Journal of Applied Mechanics 66, no. 2 (June 1, 1999): 507–13. http://dx.doi.org/10.1115/1.2791076.
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This paper presents the results on the utilization of a wavelet transform to study the dispersion of laser-generated surface waves in an epoxy-bonded copper-aluminum layered specimen with and without unbond areas. Laser ultrasonic experiments based on the point-source/point-receiver (PS/PR) technique were undertaken to measure surface wave signals in a layered specimen. The wavelet transform with a Morlet wavelet function was adopted to analyze the group velocity dispersion of the surface wave signals. A novel hybrid formula for group velocity dispersion is proposed for measurements across unbond regions. Results and data obtained are in good agreement with calculated and experimental dispersion curves. The general behavior of the group velocity dispersion for different measurement, configurations can be utilized to differentiate the unbond regions in a layered structure.
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Hu, Shufan, Yonghui Zhao, Laura Valentina Socco, and Shuangcheng Ge. "Retrieving 2-D laterally varying structures from multistation surface wave dispersion curves using multiscale window analysis." Geophysical Journal International 227, no. 2 (July 20, 2021): 1418–38. http://dx.doi.org/10.1093/gji/ggab282.
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SUMMARY The analysis of multistation surface wave records is of increasing popularity in imaging the structure of the Earth due to its robustness on dispersion measurement. Since the representation of multistation surface wave dispersion curves (DCs) is uncertain in laterally varying media, average information beneath the receiver array is assumed to be obtained by inverting the dispersion curves with a horizontally layered model. To retrieve a more realistic 2-D laterally varying structure, we present a multiscale window analysis of surface waves (MWASW) method for analysing 2-D active-source surface wave data. The MWASW method is based on the use of a forward algorithm for calculating the theoretical DCs over 2-D models and multisize spatial windows for estimating the dispersion data. The forward algorithm calculates the theoretical dispersion considering the lateral variation beneath the receiver array; hence, the estimated DC is not treated as representative of the average properties but as data containing the lateral variation information. By inverting the dispersion data extracted from different spatial windows, the subsurface information at different depth ranges and lateral extensions are integrated to produce a shear wave velocity model. The dispersion curves analysed from smaller spatial windows retrieve the shallow structure with a higher lateral resolution, whereas the phase velocity data from larger spatial windows provide average information with a greater depth. We test the effectiveness of the MWASW method using three synthetic examples and two field data sets. Both results show the improved lateral resolution of the S-wave velocity structure retrieved with the MWASW method compared to the traditional multistation method in which the local horizontally layered model is adopted.
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Dean, E. A., and G. R. Keller. "Interactive processing to obtain interstation surface-wave dispersion." Bulletin of the Seismological Society of America 81, no. 3 (June 1, 1991): 931–47. http://dx.doi.org/10.1785/bssa0810030931.
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Abstract A processing scheme for the analysis of surface-wave dispersion is presented. This scheme involves preprocessing seismograms, computing the interstation Green's function, and determining the self-consistent phase and group dispersion with standard errors for one or more events for a two-station path. Time-variable filtering is employed, based on group velocity that is computer-selected by the multiple filter technique and refined by phase matching iteration. The interstation Green's function is frequency filtered to remove spikes from the spectrum. The interstation group velocity, perturbed by standard errors and refined by phase matching, is used to determine phase velocity and its uncertainty. Self-consistency between phase and group velocity is obtained by a simultaneous least-squares method, which ensures the correct functional relation for the two dispersed velocities. The uncertainty in dispersion is computed from the covariance matrix of the simultaneous least-squares solution. The technique is evaluated by comparing the analyzed dispersion for a path along the Andean Cordillera with results employing other techniques.
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Wang, Song Ling, Zheng Ren Wu, Y. L. Cheng, M. Liu, and D. Lu. "The Characteristic Analysis of the Surface Wave of Film under Different Surface Tension." Key Engineering Materials 373-374 (March 2008): 778–81. http://dx.doi.org/10.4028/www.scientific.net/kem.373-374.778.
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With the change of the relation between the Bond numbers and 1/3, the different control equations with different dispersion item for the surface wave was obtained. The equation under tension and bottom was reduced from the potential flow theory with the little parameter perturbation technique, and then was solved by using the pseudo-spectral method. The waterfall of the surface wave was simulated with software. The results show, that different surface tension has significant effect on the film surface and there are some solitary-like wave.
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Shaiban, A., S. A. L. de Ridder, and A. Curtis. "Wavefield reconstruction and wave equation inversion for seismic surface waves." Geophysical Journal International 229, no. 3 (February 4, 2022): 1870–80. http://dx.doi.org/10.1093/gji/ggac031.
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SUMMARY Surface waves are a particular type of seismic wave that propagate around the surface of the Earth, but which oscillate over depth ranges beneath the surface that depend on their frequency of oscillation. This causes them to travel with a speed that depends on their frequency, a property called dispersion. Estimating surface wave dispersion is of interest for many geophysical applications using both active and passive seismic sources, not least because the speed–frequency relationship can be used to infer the subsurface velocity structure at depth beneath the surface. We present an inversion scheme that exploits spatial and temporal relationships in the scalar Helmholtz (wave) equation to estimate dispersion relations of the elastic surface wave data in both active and passive surveys, while also reconstructing the wavefield continuously in space (i.e. between the receivers at which the wavefield was recorded). We verify the retrieved dispersive phase velocity by comparing the results to dispersion analysis in the frequency-slowness domain, and to the local calculation of dispersion using modal analysis. Synthetic elastic examples demonstrate the method under a variety of recording scenarios. The results show that despite the scalar approximation made to represent these intrinsically elastic waves, the proposed method reconstructs both the wavefield and the phase dispersion structure even in the case of strong aliasing and irregular sampling.
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Huda, Hisbulloh, and Bagus Jaya Santosa. "Characterization of Soil Profile Using Dispersion Curve Analysis." International Journal of Social Service and Research 2, no. 2 (February 21, 2022): 103–8. http://dx.doi.org/10.46799/ijssr.v2i2.80.
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Research has been carried out on the seismic refraction exploration method by utilizing piles on the construction project of the Geomatics Campus II FTSP ITS Surabaya as a source of vibration. Rayleigh waves are one type of surface wave that is good for identifying layered structures near the earth's surface because 67% of the energy The total amount released by the seismic wave source is transmitted in the form of Rayleigh waves. In the layered medium, Rayleigh waves have dispersive properties, speed as a function of frequency. This property can be used to determine the structure of the earth's layers based on the shear wave velocity (Vs) with depth (h). The inversion process is carried out to match the measurement dispersion curve and the model. The result of the inversion process is the shear wave velocity (Vs) function of depth. This research is expected to identify and characterize the soil profile at the research site. On the track, there are three layers indicated as clay layers, in the first layer 0-6 meters with an average speed of 250 m/s, the second layer 6-19 meters with an average speed of 971 m/s, and the third layer 19-57 meters with an average speed of 1564 m/s
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Olafsdottir, Elin Asta, Sigurdur Erlingsson, and Bjarni Bessason. "Tool for analysis of multichannel analysis of surface waves (MASW) field data and evaluation of shear wave velocity profiles of soils." Canadian Geotechnical Journal 55, no. 2 (February 2018): 217–33. http://dx.doi.org/10.1139/cgj-2016-0302.
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Multichannel analysis of surface waves (MASW) is a fast, low-cost, and environmentally friendly technique to estimate shear wave velocity profiles of soil sites. This paper introduces a new open-source software, MASWaves, for processing and analysing multichannel surface wave records using the MASW method. The software consists of two main parts: a dispersion analysis tool (MASWaves Dispersion) and an inversion analysis tool (MASWaves Inversion). The performance of the dispersion analysis tool is validated by comparison with results obtained by the Geopsy software package. Verification of the inversion analysis tool is carried out by comparison with results obtained by the software WinSASW and theoretical dispersion curves presented in the literature. Results of MASW field tests conducted at three sites in south Iceland are presented to demonstrate the performance and robustness of the new software. The soils at the three test sites ranged from loose sand to cemented silty sand. In addition, at one site, the results of existing spectral analysis of surface waves (SASW) measurements were compared with the results obtained by MASWaves.
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Guo, Feiyu, Yinfeng Dong, Yiping Wang, Xingyu Zhang, and Qingshuang Su. "Estimation of wave velocity and analysis of dispersion characteristics based on wavelet decomposition." Vibroengineering Procedia 53 (November 27, 2023): 20–26. http://dx.doi.org/10.21595/vp.2023.23749.
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Due to the complexity of the crustal medium and stratigraphic boundaries, seismic waves typically exhibit attenuation and dispersion after propagation through the medium. By studying the regularity of seismic wave dispersion, soil layer information can be extracted. Current spectral decomposition techniques take less account of signal filtering processing of seismic waves, and the complexity of the stratigraphy tends to reduce the accuracy of dispersion analysis. Based on the above, a new method for calculating the dispersion characteristics of a site from surface and downhole ground vibration recordings is proposed, which is simpler than the spectra analysis of surface waves (SASW) method and eliminates the need for multiple pickups and additional equipment. This method is based on wavelet decomposition and seismic wave filtering, and a numerical simulation example is established to verify the effectiveness of the method. Then, the records of the Tohoku earthquake on March 11, 2011 are used as actual strong earthquake examples for filtering and dispersion analysis. Finally, it is concluded that the seismic wave dispersion analysis method based on wavelet decomposition can effectively filter and analyze seismic waves in specific frequency bands.
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PLESSKY, VICTOR, and JULIUS KOSKELA. "COUPLING-OF-MODES ANALYSIS OF SAW DEVICES." International Journal of High Speed Electronics and Systems 10, no. 04 (December 2000): 867–947. http://dx.doi.org/10.1142/s0129156400000684.
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The coupling-of-modes approach for modeling and analyzing surface-acoustic wave devices is reviewed. We discuss the established formalism and survey the modifications introduced to account for phenomena such as resistivity, dispersion and in particular, the effects related to surface transverse wave and leaky surface-acoustic wave devices. The extraction of the COM parameters from experiments and theoretical simulations are considered. The design of various SAW devices such as resonators and resonator filters as well as practical aspects are discussed. Finally, the unresolved modeling problems are addressed.
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Zhang, Youqi, Rongyu Xia, Jie Xu, Kefu Huang, and Zheng Li. "Theoretical analysis of surface waves in piezoelectric medium with periodic shunting circuits." Applied Mathematics and Mechanics 44, no. 8 (July 31, 2023): 1287–304. http://dx.doi.org/10.1007/s10483-023-3011-7.
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AbstractThe investigations of surface waves in the piezoelectric medium bring out great possibility in designing smart surface acoustic wave (SAW) devices. It is important to study the dispersion properties and manipulation mechanism of surface waves in the semi-infinite piezoelectric medium connected with periodic arrangement of shunting circuits. In this study, the extended Stroh formalism is developed to theoretically analyze the dispersion relations of surface waves under different external circuits. The band structures of both the Rayleigh wave and the Bleustein-Gulyaev (BG) wave can be determined and manipulated with proper electrical boundary conditions. Furthermore, the electromechanical coupling effects on the band structures of surface waves are discussed to figure out the manipulation mechanism of adjusting electric circuit. The results indicate that the proposed method can explain the propagation behaviors of surface waves under the periodic electrical boundary conditions, and can provide an important theoretical guidance for designing novel SAW devices and exploring extensive applications in practice.
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Su, Qin, Xingrong Xu, Zhinong Wang, Chengyu Sun, Yaozong Guo, and Dunshi Wu. "A high-resolution dispersion imaging method of seismic surface waves based on chirplet transform." Journal of Geophysics and Engineering 18, no. 6 (December 2021): 908–19. http://dx.doi.org/10.1093/jge/gxab061.
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Abstract The surface-wave analysis method is widely adopted to build a near-surface shear-wave velocity structure. Reliable dispersion imaging results form the basis for subsequent picking and inversion of dispersion curves. In this paper, we present a high-resolution dispersion imaging method (CSFK) of seismic surface waves based on chirplet transform (CT). CT introduces the concept of chirp rate, which could focus surface-wave dispersion energy well in time-frequency domain. First, each seismic trace in time-distance domain is transformed to time-frequency domain by CT. Thus, for each common frequency gather, we obtain a series of 2D complex-valued functions of time and distance, which are called pseudo-seismograms. Then, we scan a series of group velocities to obtain the slanting-phase function and perform a spatial Fourier transform on the slanting-phase function to get its amplitude. In addition, power operation is adopted to increase the amplitude difference between dispersion energy and noise. Finally, we generate the dispersion image by searching for the maximum amplitude of a slanting-phase function. Because the CSFK method considers the position of surface-wave energy in the time-frequency domain, this largely eliminates the noise interference from other time locations and improves the resolution and signal-to-noise ratio of the dispersion image. The results of synthetic test and field dataset processing demonstrate the effectiveness of the proposed method. In addition, we invert all 120 sets of dispersion curves extracted from reflected wave seismic data acquired for petroleum prospecting. The one-dimensional inversion shear-wave velocity models are interpolated into a two-dimensional profile of shear-wave velocity, which is in good agreement with the borehole data.
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Syamsuddin, Erfan, Sabrianto Aswad, Muhammad Alimuddin Hamzah Assegaf, Syamsurijal Rasimeng, Sakka Sakka, Syamsuddin Syamsuddin, Muhammad Nasri, and Mufly Fadla Syihab. "Seismic Site Classification Using the Multichannel Analysis of Surface Waves Method." POSITRON 12, no. 2 (November 30, 2022): 149. http://dx.doi.org/10.26418/positron.v12i2.53869.
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The soil has a variety of qualities that affect its ability to support the weight of a structure. One of these features is soil stiffness, which can be determined using the surface wave method to prevent soil collapse. Multichannel Analysis of Surface Waves (MASW) is one of the non-invasive methodologies used in this study to investigate subsurface structures in North Sumatra, Indonesia. This method utilizes the dispersion properties of Rayleigh waves, producing a dispersion curve to get the shear wave velocity (Vs) through inversion. The shear wave velocity can be used to examine the soil stiffness qualities. The dispersion curve explains the relationship between shear wave velocity and depth, which can subsequently be used as a site class parameter. This survey uses three lines with one shot for each line which uses thirty geophones. The seismic source used is a gun with the type M16.38 Cal. Each line consists of 30 geophones with a distance of 5 m. The entire track is 160 m long and lasts for 2048 seconds with a sampling rate of 0.00025 seconds. The average shear wave velocity measured at three measurements was 372.5 m/s on line P1, 347.1 m/s on line P2A, and 311.0 m/s on line P2B, respectively. Overall, the soil classification on the P1 line is class C, and the P2A and P2B lines are class D, which is suitable for development planning areas.
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Li, Hongyi, Fabrizio Bernardi, and Alberto Michelini. "Surface wave dispersion measurements from ambient seismic noise analysis in Italy." Geophysical Journal International 180, no. 3 (March 2010): 1242–52. http://dx.doi.org/10.1111/j.1365-246x.2009.04476.x.
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KARSLI, Hakan, and Mustafa ŞENKAYA. "INFLUENCES OF DATA ACQUISITION AND LAYER PARAMETERS ON FUNDAMENTAL DISPERSION CURVE IN ACTIVE MULTICHANNEL ANALYSIS OF SURFACE WAVE (A-MASW) METHOD." Mühendislik Bilimleri ve Tasarım Dergisi 10, no. 3 (September 30, 2022): 943–62. http://dx.doi.org/10.21923/jesd.1067576.
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Obtaining a continuous and high resolution dispersion curve in a wide frequency range is one of the most important steps to determine a reliable shear (S) wave velocity-depth profile of the shallow subsurface in active MASW method. In this article, the effects of layer (or physical) (S- and P-wave velocities, density and thickness) and data acquisition (source offset-X0, receiver spacing-dx and number-N, spread length-L=(N-1)*dx) parameters on the fundamental mode dispersion curve of the surface wave field were investigated by analyzing the synthetic shot gathers. The synthetic data were generated by harmonic mode summation technique at each receiver with using of the dispersion curve calculated by the layer reflection/transmission coefficient technique. Accordingly, it was observed that low S-wave velocity interlayers may cause shifting the dispersion curve to low velocities in the low frequency band, while high velocity interlayers may cause both discontinuity on the dispersion curve at high frequencies (zig-zag effect) and high-mode effect error. It was seen that while the source offset is effective in the formation of full waveforms of surface waves, the distance between the first and last receiver affects the frequency band and resolution of the dispersion curve. In addition, it is observed that wide receiver sampling increases the reliability of the dispersion curve in the low frequency region, though it disrupts the continuity of the dispersion curve at high frequencies due to wavenumber aliasing. As a result, the analyses made on the synthetic data generated for various subsurface layer models with different wave velocities demonstrate that the combinations of N
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Ikeda, Tatsunori, Takeshi Tsuji, and Toshifumi Matsuoka. "Window-controlled CMP crosscorrelation analysis for surface waves in laterally heterogeneous media." GEOPHYSICS 78, no. 6 (November 1, 2013): EN95—EN105. http://dx.doi.org/10.1190/geo2013-0010.1.
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CMP crosscorrelation (CMPCC) analysis of surface waves enhances lateral resolution of surface wave analyses. We found the technique of window-controlled CMPCC analysis, which applies two kinds of spatial windows to further improve the lateral resolution of CMPCC analysis. First, a spatial weighting function given by the number of crosscorrelation pairs is applied to CMPCC gathers. Because the number of crosscorrelation pairs is concentrated near the CMP, the lateral resolution in extracting dispersion curves on CMPs can be improved. Second, crosscorrelation pairs with longer receiver spacing are excluded to further improve lateral resolution. Although removing crosscorrelation pairs generally decreases the accuracy of phase velocity estimations, the required accuracy to estimate phase velocities is maintained by considering the wavenumber resolution defined for given receiver configurations. When applied to a synthetic data set simulating a laterally heterogeneous structure, window-controlled CMPCC analysis improved the retrieval of the lateral variation in local dispersion curves beneath each CMP. We also applied the method to field seismic data across a major fault. The window-controlled CMPCC analysis improved lateral variations of the inverted S-wave velocity structure without degrading the accuracy of S-wave velocity estimations. We discovered that window-controlled CMPCC analysis is effective in improving lateral resolution of dispersion curve estimations with respect to the original CMPCC analysis.
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Valentina Socco, Laura, and Cesare Comina. "Time-average velocity estimation through surface-wave analysis: Part 2 — P-wave velocity." GEOPHYSICS 82, no. 3 (May 1, 2017): U61—U73. http://dx.doi.org/10.1190/geo2016-0368.1.
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Surface waves (SWs) in seismic records can be used to extract local dispersion curves (DCs) along a seismic line. These curves can be used to estimate near-surface S-wave velocity models. If the velocity models are used to compute S-wave static corrections, the required information consists of S-wave time-average velocities that define the one-way time for a given datum plan depth. However, given the wider use of P-wave reflection seismic with respect to S-wave surveys, the estimate of P-wave time-average velocity would be more useful. We therefore focus on the possibility of also extracting time-average P-wave velocity models from SW dispersion data. We start from a known 1D S-wave velocity model along the line, with its relevant DC, and we estimate a wavelength/depth relationship for SWs. We found that this relationship is sensitive to Poisson’s ratio, and we develop a simple method for estimating an “apparent” Poisson’s ratio profile, defined as the Poisson’s ratio value that relates the time-average S-wave velocity to the time-average P-wave velocity. Hence, we transform the time-average S-wave velocity models estimated from the DCs into the time-average P-wave velocity models along the seismic line. We tested the method on synthetic and field data and found that it is possible to retrieve time-average P-wave velocity models with uncertainties mostly less than 10% in laterally varying sites and one-way traveltime for P-waves with less than 5 ms uncertainty with respect to P-wave tomography data. To our knowledge, this is the first method for reliable estimation of P-wave velocity from SW data without any a priori information or additional data.
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Lu, Jian Qi, Shan You Li, and Wei Li. "Surface Wave Dispersion Imaging Using Improved τ-p Transform Approach." Applied Mechanics and Materials 353-356 (August 2013): 1196–202. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.1196.
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Surface wave dispersion imaging approach is crucial for multi-channel analysis of surface wave (MASW). Because the resolution of inversed S-wave velocity and thickness of a layer are directly subjected to the resolution of imaged dispersion curve. The τ-p transform approach is an efficient and commonly used approach for Rayleigh wave dispersion curve imaging. However, the conventional τ-p transform approach was severely affected by waves amplitude. So, the energy peaks of f-v spectrum were mainly gathered in a narrow frequency range. In order to remedy this shortage, an improved τ-p transform approach was proposed by this paper. Comparison has been made between phase shift and improved τ-p transform approaches using both synthetic and in situ tested data. Result shows that the dispersion image transformed from proposed approach is superior to that either from conventionally τ-p transform or from phase shift approaches.
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Papadopoulou, Myrto, Farbod Khosro Anjom, Mohammad Karim Karimpour, and Valentina Laura Socco. "Advances in surface-wave tomography for near-surface applications." Leading Edge 40, no. 8 (August 2021): 567–75. http://dx.doi.org/10.1190/tle40080567.1.
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Surface-wave (SW) tomography is a technique that has been widely used in the field of seismology. It can provide higher resolution relative to the classical multichannel SW processing and inversion schemes that are usually adopted for near-surface applications. Nevertheless, the method is rarely used in this context, mainly due to the long processing times needed to pick the dispersion curves as well as the inability of the two-station processing to discriminate between higher SW modes. To make it efficient and to retrieve pseudo-2D/3D S-wave velocity (VS) and P-wave velocity (VP) models in a fast and convenient way, we develop a fully data-driven two-station dispersion curve estimation, which achieves dense spatial coverage without the involvement of an operator. To handle higher SW modes, we apply a dedicated time-windowing algorithm to isolate and pick the different modes. A multimodal tomographic inversion is applied to estimate a VS model. The VS model is then converted to a VP model with the Poisson's ratio estimated through the wavelength-depth method. We apply the method to a 2D seismic exploration data set acquired at a mining site, where strong lateral heterogeneity is expected, and to a 3D pilot data set, recorded with state-of-the-art acquisition technology. We compare the results with the ones retrieved from classical multichannel analysis.
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Liu, Ya, Jianghai Xia, Feng Cheng, Chaoqiang Xi, Chao Shen, and Changjiang Zhou. "Pseudo-linear-array analysis of passive surface waves based on beamforming." Geophysical Journal International 221, no. 1 (January 11, 2020): 640–50. http://dx.doi.org/10.1093/gji/ggaa024.
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SUMMARY Linear arrays are usually deployed for passive surface-wave investigations because of their high efficiency and convenience. In populated urban areas, it is almost impossible to set up a 2-D array in terms of the restriction from the existing infrastructures. The limited azimuthal coverage, however, lacks the ability to attenuate velocity overestimation caused by directional noise sources. We came up with a novel idea to compensate the azimuthal coverage by adding two more offline receivers to a conventional linear array, which is called pseudo-linear-array analysis of passive surface waves (PLAS). We used a beamforming algorithm to capture noise sources distribution and extract accurate dispersion curves. We used array response function to explain the superiority of the pseudo-linear array over the linear array and present the basic workflow of PLAS. Synthetic tests and field examples demonstrated the feasibility of PLAS to measure unbiased dispersion image. Comparison with mostly used passive surface wave methods (refraction microtremor, multichannel analysis of passive surface waves, spatial autocorrelation method, frequency–wavenumber analysis) suggested that PLAS can serve as an alternative passive surface wave method, especially in urban areas with restricted land accessibility and short-time acquisition demands.
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Ryberg, Trond, Christian Haberland, Robert G. Green, and Christoph Sens-Schönfelder. "A Fast GUI-Based Tool for Group-Velocity Analysis of Surface Waves." Seismological Research Letters 92, no. 4 (May 5, 2021): 2640–46. http://dx.doi.org/10.1785/0220200425.
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Abstract We present an interactive graphical tool for extraction of group-velocity dispersion curves of seismic traces for rapid manual picking of large amounts of data: a task commonly encountered in ambient-noise tomography. The program can be used for group-velocity analysis of surface waves from earthquakes and controlled source data as well as of Green’s functions from cross-correlated ambient-noise data. The presented tool is especially suited to datasets in which automatic picking algorithms fail and so dispersion analysis is only possible by visual inspection. Such situations can occur in highly heterogeneous regions with complex surface-wave dispersion or where surface-wave arrivals are poorly emerged (as can often be the case with ambient-noise-derived Green’s functions from temporary seismic deployments). In these datasets, the poor signal-to-noise ratio, spectral holes, or limited bandwidth may therefore mean that manual analysis is the only choice. However, without an efficient workflow the feasibility of this can be seriously constrained by the analysis time for the potentially vast number of traces to be analyzed. We tackled this problem by implementing well-known techniques of dispersion curve analysis (traditional frequency–time analysis) in a fast and interactive graphical environment. It is specifically developed for high user processing speed, prioritizing fast computation, and high display responsiveness. This solution retains the benefits of manual dispersion picking for complex datasets, while maintaining good user processing efficiency. An experienced analyst can measure upward of 200 traces per hour. xdcpick stands for an X-window-based picking of dispersion curves.
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Pedersen, Helle A., Jérôme I. Mars, and Pierre‐Olivier Amblard. "Improving surface‐wave group velocity measurements by energy reassignment." GEOPHYSICS 68, no. 2 (March 2003): 677–84. http://dx.doi.org/10.1190/1.1567238.
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Surface waves are increasingly used for shallow seismic surveys—in particular, in acoustic logging, environmental, and engineering applications. These waves are dispersive, and their dispersion curves are used to obtain shear velocity profiles with depth. The main obstacle to their more widespread use is the complexity of the associated data processing and interpretation of the results. Our objective is to show that energy reassignment in the time–frequency domain helps improve the precision of group velocity measurements of surface waves. To show this, full‐waveform seismograms with added white noise for a shallow flat‐layered earth model are analyzed by classic and reassigned multiple filter analysis (MFA). Classic MFA gives the expected smeared image of the group velocity dispersion curve, while the reassigned curve gives a very well‐constrained, narrow dispersion curve. Systematic errors from spectral fall‐off are largely corrected by the reassignment procedure. The subsequent inversion of the dispersion curve to obtain the shear‐wave velocity with depth is carried out through a procedure combining linearized inversion with a nonlinear Monte Carlo inversion. The diminished uncertainty obtained after reassignment introduces significantly better constraints on the earth model than by inverting the output of classic MFA. The reassignment is finally carried out on data from a shallow seismic survey in northern Belgium, with the aim of determining the shear‐wave velocities for seismic risk assessment. The reassignment is very stable in this case as well. The use of reassignment can make dispersion measurements highly automated, thereby facilitating the use of surface waves for shallow surveys.
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Xu, Jing Lei, Bin Lin, and Ya Xu Wei. "Study on the Influence of Roughness on the Detection for Mechanical Characteristics of the Machined Surface by Surface Acoustic Wave Dispersion Theory." Key Engineering Materials 693 (May 2016): 1447–52. http://dx.doi.org/10.4028/www.scientific.net/kem.693.1447.
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The surface acoustic wave (SAW) technique is a precise and nondestructive method to detect the mechanical characteristics of the precision-machined surface. The paper is concerned with the effect of the roughness of the machined surface on the dispersion of surface acoustic waves propagating in the precision-machined surface which indicates mechanical characteristics of the machined surface. The finite element method (FEM) is employed by establishing a series of models with different roughness Ra value to analyze influences from different roughness Ra value on surface acoustic wave dispersion. The models are established by applying a combined method based on fractal theory and wavelet analysis. The simulation results showed that the roughness of machined surface will cause the dispersion of surface acoustic wave propagation, the effect varies with the different roughness Ra values. A critical Ra value influencing on the surface acoustic wave propagation exists. Accordingly, that the factor of roughness should be considered in advance or not, the situation can be determined through studying and determining the critical roughness Ra value above mentioned. Consequently, the study has the important meaning regarding the detection for mechanical characteristics of the machined surface.
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Sert, Ahmet, Eyup Aslan, Muammer Buyukınan, and Ozgur Pirgon. "Correlation of P-wave dispersion with insulin sensitivity in obese adolescents." Cardiology in the Young 27, no. 2 (April 8, 2016): 229–35. http://dx.doi.org/10.1017/s1047951116000366.
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AbstractBackgroundP-wave dispersion is a new and simple electrocardiographic marker that has been reported to be associated with inhomogeneous and discontinuous propagation of sinus impulses. In the present study, we evaluated P-wave dispersion in obese adolescents and investigated the relationship between P-wave dispersion, cardiovascular risk factors, and echocardiographic parameters.MethodsWe carried out a case–control study comparing 150 obese adolescents and 50 healthy controls. Maximum and minimum P-wave durations were measured using a 12-lead surface electrocardiogram, and P-wave dispersion was calculated as the difference between these two measures. Echocardiographic examination was also performed for each subject. Multivariate linear regression analysis with stepwise variable selection was used to evaluate parameters associated with increased P-wave dispersion in obese subjects.ResultsMaximum P-wave duration and P-wave dispersion were significantly higher in obese adolescents than control subjects (143±19 ms versus 117±20 ms and 49±15 ms versus 29±9 ms, p<0.0001 for both). P-wave dispersion was positively correlated with body mass index, waist and hip circumferences, systolic and diastolic blood pressures, total cholesterol, serum levels of low-density lipoprotein cholesterol, triglycerides, glucose, and insulin, homoeostasis model assessment for insulin resistance score, left ventricular mass, and left atrial dimension. P-wave dispersion was negatively correlated with high-density lipoprotein cholesterol levels. By multiple stepwise regression analysis, left atrial dimension (β: 0.252, p=0.008) and homoeostasis model assessment for insulin resistance (β: 0.205; p=0.009) were independently associated with increased P-wave dispersion in obese adolescents.ConclusionsInsulin resistance is a significant, independent predictor of P-wave dispersion in obese adolescents.
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Chen, Zhuoshi, Baofeng Jiang, Jingjing Song, and Wentao Wang. "Accurate Sparse Recovery of Rayleigh Wave Characteristics Using Fast Analysis of Wave Speed (FAWS) Algorithm for Soft Soil Layers." Applied Sciences 8, no. 7 (July 23, 2018): 1204. http://dx.doi.org/10.3390/app8071204.
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This paper presents a novel fast analysis of wave speed (FAWS) algorithm from the waveforms recorded by a random-spaced geophone array based on a compressive sensing (CS) platform. Rayleigh-type seismic surface wave testing is excited by a hammer source and conducted to develop the phase velocity characteristics of the subsoil layers in Shenyang Metro line 9. Data are filtered by a bandpass filter bank to pursue the dispersive profiles of phase velocity at various frequencies. The Rayleigh-type surface-wave dispersion curve for the soil layers at each frequency is conducted by the ℓ1-norm minimization algorithm of CS theory. The traditional frequency-wavenumber transform technique and in-site downhole observation are employed as the comparison of the proposed technique. The experimental results indicate the proposed FAWS algorithm has a good agreement with both the results of conventional even-spaced geophone array and the in-site measurements, which provides an effective and efficient way for accurate non-destructive evaluation of the surface wave dispersion curve of the soil.
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Sun, Lixia, Yun Wang, and Xinming Qiu. "Rayleigh-Wave Dispersion Analysis and Inversion Based on the Rotation." Sensors 22, no. 3 (January 27, 2022): 983. http://dx.doi.org/10.3390/s22030983.
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Rotational observation is essential for a comprehensive description of the ground motion, and can provide additional wave-field information. With respect to the three typical layered models in shallow engineering geology, under the assumption of linear small deformation, we simulate the 2-dimensional radial, vertical, and rotational components of the wave fields and analyze the different characteristics of Rayleigh wave dispersion recorded for the rotational and translational components. Then, we compare the results of single-component inversion with the results of multi-component joint inversion. It is found that the rotational component has wider spectral bands and more higher modes than the translational components, especially at high frequencies; the rotational component has better anti-interference performance in the noisy data test, and it can improve the inversion accuracy of the shallow shear-wave velocity. The field examples also show the significant advantages of the joint utility of the translational and rotational components, especially when a low-velocity layer exists. Rotational observation shall be beneficial for shallow surface-wave exploration.
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Giancarlo, Dal Moro. "Insights on surface wave dispersion and HVSR: Joint analysis via Pareto optimality." Journal of Applied Geophysics 72, no. 2 (October 2010): 129–40. http://dx.doi.org/10.1016/j.jappgeo.2010.08.004.
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Forghani-Arani, Farnoush, Mark Willis, Roel Snieder, Seth S. Haines, Jyoti Behura, Mike Batzle, and Michael Davidson. "Dispersion analysis of passive surface-wave noise generated during hydraulic-fracturing operations." Journal of Applied Geophysics 111 (December 2014): 129–34. http://dx.doi.org/10.1016/j.jappgeo.2014.09.008.
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Zhang, H., M. Singh, F. Zvietcovich, K. Larin, and S. Aglyamov. "Age-related changes in the viscoelasticity of rabbit lens characterised by surface wave dispersion analysis." Quantum Electronics 52, no. 1 (January 1, 2022): 42–47. http://dx.doi.org/10.1070/qel17964.
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Abstract The viscoelastic properties of the young and mature rabbit lenses in situ are evaluated using wave-based optical coherence elastography (OCE). Surface waves in the crystalline lens are generated using acoustic radiation force (ARF) focused inside the eyeball. Surface-wave dispersion is measured with a phase-stabilised optical coherence tomography (OCT) system. The Young’s modulus and shear viscosity coefficient are quantified based on a Scholte wave model. The results show that both elasticity and viscosity are significantly different between the young and mature lenses. The Young’s modulus of the lenses increased with age from 7.74 ± 1.56 kPa (young) to 15.15 ± 4.52 kPa (mature), and the shear viscosity coefficient increased from 0.55 ± 0.04 Pa s (young) and 0.86 ± 0.13 Pa s (mature). It is shown that the combination of ARF excitation, OCE imaging, and dispersion analysis enables nondestructive quantification of lenticular viscoelasticity in situ and shows promise for in vivo applications.
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Kakar, Rajneesh, and Shikha Kakar. "The torsional surface wave in a prestressed anisotropic intermediate poroelastic layer of varying heterogeneities." Journal of Vibration and Control 24, no. 9 (September 5, 2016): 1687–706. http://dx.doi.org/10.1177/1077546316668060.
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The aim of this paper is to study the behavior of the torsional surface wave in a heterogeneous initially stressed vertical fluid-saturated anisotropic layer sandwiched between inhomogeneous and homogeneous porous half-spaces. It has been considered that the mass density and rigidity of the upper half-space and intermediate layer are space dependent. The proposed model is solved to obtain different dispersion relations for the torsional surface wave in a heterogeneous poroelastic medium lying between two half-spaces. The influence of compressive stress and heterogeneity on torsional surface wave dispersion is shown numerically. It has been observed that heterogeneity, porosity, initial stress of the layer and inhomogeneity of the upper and porosity of lower half-spaces affect the torsional wave speed much. The wave analysis further indicates that the torsional surface waves travel faster in elastic half-spaces in comparison than in the fluid-saturated porous layer.
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Pan, Yudi, Jianghai Xia, Yixian Xu, and Lingli Gao. "Multichannel analysis of Love waves in a 3D seismic acquisition system." GEOPHYSICS 81, no. 5 (September 2016): EN67—EN74. http://dx.doi.org/10.1190/geo2015-0261.1.
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Multichannel analysis of Love waves (MALW) analyzes high-frequency Love waves to determine near-surface S-wave velocities, and it is getting increasing attention in the near-surface geophysics and geotechnique community. Based on 2D geometry spread, in which sources and receivers are placed along the same line, current MALW fails to work in a 3D seismic acquisition system. This is because Love-wave particle motion direction is perpendicular to its propagation direction, which makes it difficult to record a Love-wave signal in 3D geometries. We have developed a method to perform MALW with data acquired in 3D geometry. We recorded two orthogonal horizontal components (inline and crossline components) at each receiver point at the same time. By transforming the raw data from rectangular coordinates (inline and crossline components) to radial-transverse coordinates (radial and transverse components), we recovered Love-wave data along the transverse direction at each receiver point. To achieve a Love-wave dispersion curve, the recovered Love-wave data were first transformed into a conventional receiver offset domain, and then transformed into the frequency-velocity ([Formula: see text]-[Formula: see text]) domain. Love-wave dispersion curves were picked along the continuous dispersive energy peaks in the [Formula: see text]-[Formula: see text] domain. The validity of our proposed method was verified by two synthetic tests and a real-world example.
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Eslick, Robert, Georgios Tsoflias, and Don Steeples. "Field investigation of Love waves in near-surface seismology." GEOPHYSICS 73, no. 3 (May 2008): G1—G6. http://dx.doi.org/10.1190/1.2901215.
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We examine subsurface conditions and survey parameters suitable for successful exploitation of Love waves in near-surface investigations. Love-wave generation requires the existence of a low shear-velocity surface layer. We examined the minimum thickness of the near-surface layer necessary to generate and record usable Love-wave data sets in the frequency range of [Formula: see text]. We acquired field data on a hillside with flat-lying limestone and shale layers that allowed for the direct testing of varying overburden thicknesses as well as varying acquisition geometry. The resulting seismic records and dispersion images were analyzed, and the Love-wave dispersion relation for two layers was examined analytically. We concluded through theoretical and field data analysis that a minimum thickness of [Formula: see text] of low-velocity material is needed to record usable data in the frequency range of interest in near-surface Love-wave surveys. The results of this study indicate that existing guidelines for Rayleigh-wave data acquisition, such as receiver interval and line length, are also applicable to Love-wave data acquisition.
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Chen, X.-B. "Highly oscillatory properties of unsteady ship waves." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 6 (June 1, 2000): 813–23. http://dx.doi.org/10.1243/0954406001523803.
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The singular and highly oscillatory properties of unsteady ship waves are studied by considering potential flows generated by a point source pulsating and advancing at a uniform forward speed located close to or at the free surface. The wave component of the free-surface potential defined by Noblesse and Chen by a single integral along the dispersion curves defined by the dispersion relation is analysed by developing asymptotic expansions of the open dispersion curves at large wave numbers. The asymptotic analysis of the wave component contributed by the leading asymptotic term of a parabolic form shows that unsteady ship waves are highly oscillatory with infinitely increasing amplitude and infinitely decreasing wavelength, when a field point approaches the track of the source point at the free surface. The highly oscillatory property and complex singular behaviour of unsteady ship waves are further expressed in an original and analytically closed form.
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Chashechkin, Yuli D., and Artem A. Ochirov. "Periodic Waves and Ligaments on the Surface of a Viscous Exponentially Stratified Fluid in a Uniform Gravity Field." Axioms 11, no. 8 (August 15, 2022): 402. http://dx.doi.org/10.3390/axioms11080402.
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The theory of singular perturbations in a unified formulation is used, for the first time, to study the propagation of two-dimensional periodic perturbations, including capillary and gravitational surface waves and accompanying ligaments in the 10−4<ω<103 s−1 frequency range, in a viscous continuously stratified fluid. Dispersion relations for flow constituents are given, as well as expressions for phase and group velocities for surface waves and ligaments in physically observable variables. When the wave-length reaches values of the order of the stratification scale, the liquid behaves as homogeneous. As the wave frequency approaches the buoyancy frequency, the energy transfer rate decreases: the group velocity of surface waves tends to zero, while the phase velocity tends to infinity. In limiting cases, the expressions obtained are transformed into known wave dispersion expressions for an ideal stratified or actually homogeneous fluid.
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Naskar, Tarun, and Jyant Kumar. "MATLAB codes for generating dispersion images for ground exploration using different multichannel analysis of surface wave transforms." GEOPHYSICS 87, no. 3 (March 10, 2022): F15—F24. http://dx.doi.org/10.1190/geo2020-0928.1.
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A set of codes has been developed in MATLAB for generating multimodal dispersion images by using three different transformation techniques. While performing the multichannel analysis of surface waves (MASW), the field data obtained by using multiple geophones, in the distance and time domain, become the required input data for these developed programs. The dispersion images have been evaluated by generating synthetic data and performing field tests using a 20 lb hammer at two different chosen sites with 48 geophones. The dispersion plots from the three different transformation techniques are found to match each other closely. In general, the circular frequency-phase velocity ([Formula: see text]- c) transform provides the best clarity. An increase in the spread length, however, without increasing the number of sensors, often leads to the appearance of aliased modes in the dispersion images.
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Olafsdottir, Elin Asta, Sigurdur Erlingsson, and Bjarni Bessason. "Open-Source MASW Inversion Tool Aimed at Shear Wave Velocity Profiling for Soil Site Explorations." Geosciences 10, no. 8 (August 17, 2020): 322. http://dx.doi.org/10.3390/geosciences10080322.
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The shear wave velocity profile is of primary interest for geological characterization of soil sites and elucidation of near-surface structures. Multichannel Analysis of Surface Waves (MASW) is a seismic exploration method for determination of near-surface shear wave velocity profiles by analyzing Rayleigh wave propagation over a wide range of wavelengths. The inverse problem faced during the application of MASW involves finding one or more layered soil models whose theoretical dispersion curves match the observed dispersion characteristics. A set of open-source MATLAB-based tools for acquiring and analyzing MASW field data, MASWaves, has been under development in recent years. In this paper, a new tool, using an efficient Monte Carlo search technique, is introduced to conduct the inversion analysis in order to provide the shear wave velocity profile. The performance and applicability of the inversion scheme is demonstrated with synthetic datasets and field data acquired at a well-characterized geotechnical research site.
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Vignoli, Giulio, Claudio Strobbia, Giorgio Cassiani, and Peter Vermeer. "Statistical multioffset phase analysis for surface-wave processing in laterally varying media." GEOPHYSICS 76, no. 2 (March 2011): U1—U11. http://dx.doi.org/10.1190/1.3542076.
Full textAbstract:
Standard procedures for dispersion analysis of surface waves use multichannel wavefield transforms. By using several receivers, such procedures integrate the information along the entire acquisition array. That approach improves data quality and robustness significantly, but its side effects are spatial averaging and loss of lateral resolution. Recently, a new approach was developed to address that issue and maximize lateral resolution. The new method uses multioffset phase analysis to detect and locate sharp lateral variations in velocity. By using the phase analysis approach, the number of usable channels can be maximized, thereby gaining data quality without compromising lateral resolution. In fact, such preliminary data analysis also allows selection of the appropriate traces on which to perform multichannel processing. Such multioffset phase analysis can be enhanced by f-k filtering, which assures the selection of only one wave-propagation mode, and by a statistical analysis that takes advantage of data redundancy of multishot data, usually collected, for example, in land refraction surveys. Moreover, this novel statistical method with f-k filtering can be used to retrieve a dispersion curve, in principle, for each receiver location. The quasi-continuous pseudoimage of shear-wave velocity as a function of offset and frequency allows a characterization of lateral variations in velocity, whether they are sharp or smooth.
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Shragge, Jeffrey, Jihyun Yang, Nader Issa, Michael Roelens, Michael Dentith, and Sascha Schediwy. "Low-frequency ambient distributed acoustic sensing (DAS): case study from Perth, Australia." Geophysical Journal International 226, no. 1 (March 26, 2021): 564–81. http://dx.doi.org/10.1093/gji/ggab111.
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SUMMARY Ambient wavefield data acquired on existing (so-called ‘dark fibre’) optical fibre networks using distributed acoustic sensing (DAS) interrogators allow users to conduct a wide range of subsurface imaging and inversion experiments. In particular, recorded low-frequency (<2 Hz) surface-wave information holds the promise of providing constraints on the shear-wave velocity (VS) to depths exceeding 0.5 km. However, surface-wave analysis can be made challenging by a number of acquisition factors that affect the amplitudes of measured DAS waveforms. To illustrate these sensitivity challenges, we present a low-frequency ambient wavefield investigation using a DAS data set acquired on a crooked-line optical fibre array deployed in suburban Perth, Western Australia. We record storm-induced microseism energy generated at the nearby Indian Ocean shelf break and/or coastline in a low-frequency band (0.04−1.80 Hz) and generate high-quality virtual shot gathers (VSGs) through cross-correlation and cross-coherence interferometric analyses. The resulting VSG volumes clearly exhibit surface wave energy, though with significant along-line amplitude variations that are due to the combined effects of ambient source directivity, crooked-line acquisition geometry and the applied gauge length, fibre coupling, among other factors. We transform the observed VSGs into dispersion images using two different methods: phase shift and high-resolution linear Radon transform. These dispersion images are then used to estimate 1-D near-surface VS models using multichannel analysis of surface waves (MASW), which involves picking and inverting the estimated Rayleigh-wave dispersion curves using the particle-swarm optimization global optimization algorithm. The MASW inversion results, combined with nearby deep borehole information and 2-D elastic finite-difference modeling, show that low-frequency ambient DAS data constrain the VS model, including a low-velocity channel, to at least 0.5 km depth. Thus, this case study illustrates the potential of using DAS technology as a tool for undertaking large-scale surface wave analysis in urban geophysical and geotechnical investigations to depths exceeding 0.5 km.
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Kim, Yoon Young. "Uncoupled Wave Systems and Dispersion in an Infinite Solid Cylinder." Journal of Applied Mechanics 56, no. 2 (June 1, 1989): 347–55. http://dx.doi.org/10.1115/1.3176089.
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In this study, it is shown that there exist uncoupled wave systems for general non-axisymmetric wave propagation in an infinite isotropic cylinder. Two cylindrical surface conditions corresponding to the uncoupled wave systems are discussed. The solutions of the uncoupled wave systems are shown to provide proper bounds of Pochhammer’s equation for a free cylindrical surface. The bounds, which are easy to construct for any Fourier number in the circumferential direction, can be used to trace the branches of Pochhammer’s equation. They also give insight into the modal composition of the branches of Pochhammer’s equation at and between the intersections of the bounds. More refined dispersion relations of Pochhammer’s equation are possible through an asymptotic analysis of the itersections of the branches of Pochhammer’s equation with one family of the bounds. The asymptotic nature of wave motion corresponding to large wave numbers, imaginary or complex, for Pochhammer’s equation is studied. The wave motion is asymptotically equivoluminal for large imaginary wave numbers, and is characterized by coupled dilatation and shear for large complex wave numbers.
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Li, Jing, and Sherif Hanafy. "Skeletonized inversion of surface wave: Active source versus controlled noise comparison." Interpretation 4, no. 3 (August 1, 2016): SH11—SH19. http://dx.doi.org/10.1190/int-2015-0174.1.
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We have developed a skeletonized inversion method that inverts the S-wave velocity distribution from surface-wave dispersion curves. Instead of attempting to fit every wiggle in the surface waves with predicted data, it only inverts the picked dispersion curve, thereby mitigating the problem of getting stuck in a local minimum. We have applied this method to a synthetic model and seismic field data from Qademah fault, located at the western side of Saudi Arabia. For comparison, we have performed dispersion analysis for an active and controlled noise source seismic data that had some receivers in common with the passive array. The active and passive data show good agreement in the dispersive characteristics. Our results demonstrated that skeletonized inversion can obtain reliable 1D and 2D S-wave velocity models for our geologic setting. A limitation is that we need to build layered initial model to calculate the Jacobian matrix, which is time consuming.
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Matsuura, Hiroshi, Hiromitsu Furukawa, Atsushi Kondo, Tamio Tanikawa, and Hideki Hashimoto. "Acoustic analysis of jet atomization for uniform dispersion of nano- and micro-droplets." Journal of Applied Physics 132, no. 22 (December 14, 2022): 224502. http://dx.doi.org/10.1063/5.0125547.
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In this study, the mechanisms of jet atomization were analyzed based on a frequency analysis of atomization sounds in the audible range (∼20 kHz). Jet atomization is a two-dimensional, high-speed atomization using a diaphragm, and interesting acoustic signals and atomization phenomena were detected on hydrophobic and hydrophilic diaphragms. The hydrophilic diaphragm strongly interacted and resonated with the surface wave, resulting in symmetrical jet atomization relative to the diaphragm. The resonance between the diaphragm and the surface wave was supported by a calculation of the eigenfrequency of the diaphragm and the coincidence of the droplet diameters as calculated from Lang's equation. Notably, the diaphragm excited by the ultrasonic transducer acted as a new transducer vibrating perpendicular to the transducer. As a result, when the diaphragm and the surface wave were in resonance at 2.4 MHz, a symmetrical two-dimensional high-speed jet atomization was generated in the direction perpendicular to the transducer’s vibration direction. This study also revealed that the atomization state can be determined based on the acoustic analysis. This acoustic analysis of atomization sounds can be applied in more advanced atomization control, such as for providing uniform dispersions of droplets containing DNA, drugs, or microplastics.
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Kakar, Rajneesh, and Shikha Kakar. "Dispersion of torsional surface wave in an intermediate vertical prestressed inhomogeneous layer lying between heterogeneous half spaces." Journal of Vibration and Control 23, no. 19 (February 11, 2016): 3292–305. http://dx.doi.org/10.1177/1077546316628706.
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The purpose of this study is to illustrate the propagation of the torsional surface waves in an intermediate inhomogeneous initially stressed vertical elastic layer sandwiched between two heterogeneous half-spaces. It is considered that the mass density and the rigidity of upper and lower half-spaces are space dependent. The proposed model is solved to obtain the different dispersion relations for the torsional surface wave in the elastic medium of different properties. The effects of compressive and tensile stresses along with the heterogeneity on the dispersion of torsional surface wave in the intermediate layer are shown numerically. The wave analysis further indicates that the inhomogeneity, the initial stress of the layer and the heterogeneity of both the half spaces affect the wave velocity remarkably. The results may be useful to understand the nature of seismic wave propagation in geophysical applications and in the field of earthquake engineering.
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Witherspoon, W., and R. N. Parthasarathy. "Breakup of Viscous Liquid Sheets Subjected to Symmetric and Asymmetric Gas Flow." Journal of Energy Resources Technology 119, no. 3 (September 1, 1997): 184–92. http://dx.doi.org/10.1115/1.2794988.
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A study of the breakup of planar viscous liquid sheets subjected to gas flow on both sides was conducted. A linear spatial stability analysis was used to determine the instability wave characteristics. The analysis included the effects of liquid properties such as viscosity, density, and surface tension; the gas was treated as inviscid. Dispersion relations were obtained relating the wave growth rates to the frequency and other flow variables. The wave characteristics were determined by numerical solution of the governing dispersion relations for a wide range of operating conditions. In all cases, the gas velocity was found to be destabilizing; increases in the liquid density, viscosity, and surface tension were all found to have stabilizing effects. When the liquid sheet was exposed to unequal gas velocities, the wave propagation characteristics were found to be altered from the case of equal gas velocities.