Finite-Difference Modeling and Characteristics Analysis of Love Waves in Anisotropic-Viscoelastic Media

2021 ◽  
Author(s):  
Shichuan Yuan ◽  
Zhenguo Zhang ◽  
Hengxin Ren ◽  
Wei Zhang ◽  
Xianhai Song ◽  
...  
Keyword(s):  
Finite Difference ◽  
Phase Velocity ◽  
Velocity Dispersion ◽  
Love Waves ◽  
Velocity Anisotropy ◽  
Viscoelastic Media ◽  
Phase Velocities ◽  
Phase Velocity Dispersion ◽  
Anisotropic Elastic ◽  
Attenuation Anisotropy

ABSTRACT In this study, the characteristics of Love waves in viscoelastic vertical transversely isotropic layered media are investigated by finite-difference numerical modeling. The accuracy of the modeling scheme is tested against the theoretical seismograms of isotropic-elastic and isotropic-viscoelastic media. The correctness of the modeling results is verified by the theoretical phase-velocity dispersion curves of Love waves in isotropic or anisotropic elastic or viscoelastic media. In two-layer half-space models, the effects of velocity anisotropy, viscoelasticity, and attenuation anisotropy of media on Love waves are studied in detail by comparing the modeling results obtained for anisotropic-elastic, isotropic-viscoelastic, and anisotropic-viscoelastic media with those obtained for isotropic-elastic media. Then, Love waves in three typical four-layer half-space models are simulated to further analyze the characteristics of Love waves in anisotropic-viscoelastic layered media. The results show that Love waves propagating in anisotropic-viscoelastic media are affected by both the anisotropy and viscoelasticity of media. The velocity anisotropy of media causes substantial changes in the values and distribution range of phase velocities of Love waves. The viscoelasticity of media leads to the amplitude attenuation and phase velocity dispersion of Love waves, and these effects increase with decreasing quality factors. The attenuation anisotropy of media indicates that the viscoelasticity degree of media is direction dependent. Comparisons of phase velocity ratios suggest that the change degree of Love-wave phase velocities due to viscoelasticity is much less than that caused by velocity anisotropy.

New techniques for the determination of surface wave phase velocities

1968 ◽  
Vol 58 (3) ◽  
pp. 1021-1034 ◽  
Author(s):  
S. Bloch ◽  
A. L. Hales
Keyword(s):  
Phase Velocity ◽  
Rayleigh Waves ◽  
World Wide ◽  
Velocity Dispersion ◽  
Cross Product ◽  
New Techniques ◽  
Phase Velocities ◽  
Phase Velocity Dispersion ◽  
The World

abstract A number of new techniques have been developed for the determination of phase velocities from the digitized seismograms from pairs of stations. One of these techniques is to Fourier analyze the sum (or difference) of the two seismograms after time shifting in steps to correspond to steps in phase velocity. The amplitude of the summed seismogram is a maximum for any particular period when both seismograms are in phase at that period. Another method is to pass both seismograms through a narrow bandpass digital filter centered at various periods and form the cross product of the filtered seismograms, after time shifting. The average of the resultant time series is a maximum when the two signals are in phase. The computer output is a matrix consisting of amplitudes or averages as a function of phase velocity and period. The phase velocity dispersion is determined from the contoured matrix. Using these techniques, interstation phase velocities of Rayleigh waves have been determined for the “World Wide Network Standard Stations” at Pretoria, Bulawayo and Windhoek. The method using cross-products is the most efficient.

scholarly journals Theoretical and experimental revision of surface acoustic waves on the (100) plane of silicon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alexander Tarasenko ◽  
Radim Čtvrtlík ◽  
Radim Kudělka
Keyword(s):  
Experimental Data ◽  
Phase Velocity ◽  
Acoustic Waves ◽  
Basal Plane ◽  
Velocity Dispersion ◽  
Surface Acoustic Waves ◽  
Azimuthal Angle ◽  
Acoustic Method ◽  
Phase Velocities ◽  
Phase Velocity Dispersion

AbstractThe phase velocity dispersion of the surface acoustic waves on a basal plane of Si(100) has been calculated in the whole range of the azimuthal angle of propagation. We present a detailed description of the calculations. These calculations are compared with the experimental data obtained by a laser acoustic method. Our data convincingly demonstrate the existence of a gap in the spectrum of the phase velocities. The gap means that in a definite range of the phase velocities the SAWs are absent in the whole interval of the azimuthal angles. There is an excellent coincidence between the numerical and experimental data.

scholarly journals A Robust Workflow for Acquiring and Preprocessing Ambient Vibration Data from Small Aperture Ocean Bottom Seismometer Arrays to Extract Scholte and Love Waves Phase-Velocity Dispersion Curves

2021 ◽  
Author(s):  
Agostiny Marrios Lontsi ◽  
Anastasiia Shynkarenko ◽  
Katrina Kremer ◽  
Manuel Hobiger ◽  
Paolo Bergamo ◽  
...  
Keyword(s):  
Phase Velocity ◽  
Surface Waves ◽  
Dispersion Curve ◽  
Velocity Dispersion ◽  
Love Waves ◽  
Ambient Vibration ◽  
Ocean Bottom ◽  
Small Aperture ◽  
Phase Velocity Dispersion ◽  
Phase Velocity Dispersion Curve

AbstractThe phase-velocity dispersion curve (DC) is an important characteristic of the propagation of surface waves in sedimentary environments. Although the procedure for DC estimation in onshore environments using ambient vibration recordings is well established, the DC estimation in offshore environments using Ocean Bottom Seismometers (OBS) array recordings of ambient vibrations presents three additional challenges: (1) the localization of sensors, (2) the orientation of the OBS horizontal components, and (3) the clock error. Here, we address these challenges in an inherent preprocessing workflow to ultimately extract the Love and Scholte wave DC from small aperture OBS array measurements performed between 2018 and 2020 in Lake Lucerne (Switzerland). The arrays have a maximum aperture of 679 m and a maximum deployment water depth of 81 m. The challenges related to the OBS location on the lake floor are addressed by combining the multibeam bathymetry map and the backscatter image for the investigated site with the differential GPS coordinates of the OBS at recovery. The OBS measurements are complemented by airgun surveys. Airgun data are first used to estimate the misorientation of the horizontal components of the OBS and second to estimate the clock error. To assess the robustness of the preprocessing workflow, we use two array processing methods, namely the three-component high-resolution frequency-wavenumber and the interferometric multichannel analysis of surface waves, to estimate the dispersion characteristics of the propagating Scholte and Love waves for one of the OBS array sites. The results show the effectiveness of the preprocessing workflow. We observe the phase-velocity dispersion curve branches in the frequency range between 1.2 and 3.2 Hz for both array processing techniques.

scholarly journals The Lamb waves phase velocity dispersion evaluation using an hybrid measurement technique

2018 ◽  
Vol 184 ◽  
pp. 1156-1164 ◽  
Author(s):  
L. Draudviliene ◽  
H. Ait Aider ◽  
O. Tumsys ◽  
L. Mazeika
Keyword(s):  
Phase Velocity ◽  
Measurement Technique ◽  
Velocity Dispersion ◽  
Lamb Waves ◽  
Phase Velocity Dispersion

Multifrequency full-waveform sonic logging in the screened interval of a large-diameter production well

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. B243-B257 ◽  
Author(s):  
Majed Almalki ◽  
Brett Harris ◽  
J. Christian Dupuis
Keyword(s):  
Phase Velocity ◽  
Velocity Dispersion ◽  
Large Diameter ◽  
Low Frequency ◽  
Production Well ◽  
Frequency Wave ◽  
Full Waveform ◽  
Phase Velocity Dispersion ◽  
Production Wells ◽  
Sonic Logging

A set of field experiments using multiple transmitter center frequencies was completed to test the application potential of low-frequency full-waveform sonic logging in large-diameter production wells. Wireline logs were acquired in a simple open drillhole and a high-yield large diameter production well completed with wire-wound sand screens at an aquifer storage and recovery site in Perth, Western Australia. Phase-shift transform methods were applied to obtain phase-velocity dispersion images for frequencies of up to 4 kHz. A 3D representation of phase-velocity dispersion was developed to assist in the analysis of possible connections between low-frequency wave propagation modes and the distribution of hydraulic properties. For sandstone intervals in the test well, the highest hydraulic conductivity intervals were typically correlated with the lowest phase velocities. The main characteristics of dispersion images obtained from the sand-screened well were highly comparable with those obtained at the same depth level in a nearby simple drillhole open to the formation. The sand-screened well and the open-hole displayed an expected and substantial difference between dispersion in sand- and clay-dominated intervals. It appears that for clay-dominated formations, the rate of change of phase velocity can be associated to clay content. We demonstrated that with appropriate acquisition and processing, multifrequency full-waveform sonic logging applied in existing large-diameter sand-screened wells can produce valuable results. There are few wireline logging technologies that can be applied in this setting. The techniques that we used would be highly suitable for time-lapse applications in high-volume production wells or for reassessing formation properties behind existing historical production wells.

Dispersion analysis for wave equations with fractional Laplacian loss operators

2019 ◽  
Vol 22 (6) ◽  
pp. 1596-1606
Author(s):  
Sverre Holm
Keyword(s):  
Phase Velocity ◽  
Fractional Derivative ◽  
Fractional Derivatives ◽  
Wave Equations ◽  
Fractional Laplacian ◽  
Velocity Dispersion ◽  
Dispersion Analysis ◽  
Phase Velocity Dispersion ◽  
Loss Term ◽  
Kronig Relation

Abstract Several wave equations for power-law attenuation have a spatial fractional derivative in the loss term. Both one-sided and two-sided spatial fractional derivatives can give causal solutions and a phase velocity dispersion which satisfies the Kramers–Kronig relation. The Chen–Holm and the Treeby–Cox equations both have the two-sided fractional Laplacian derivative, but only the latter satisfies this relation. There also exists several seemingly different expressions for the phase velocity for these equations and it is shown here that they are approximately equivalent. Causality of the Chen–Holm equation has also been a topic of some discussion and it is found that despite the lack of agreement with the Kramers–Kronig relation, it is still causal.

Sign in / Sign up

Export Citation Format

Share Document