scholarly journals Frequency derivative of Rayleigh wave phase velocity for fundamental mode dispersion inversion: parametric study and experimental application

2020 ◽  
Vol 224 (1) ◽  
pp. 649-668
Author(s):  
A Wang ◽  
D Leparoux ◽  
O Abraham ◽  
M Le Feuvre
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Group Velocity ◽  
Fundamental Mode ◽  
Deep Layer ◽  
Wave Phase Velocity ◽  
Phase And Group Velocities ◽  
Velocity Derivative ◽  
Rayleigh Wave Phase Velocity ◽  
Group Velocities

SUMMARY Monitoring the small variations of a medium is increasingly important in subsurface geophysics due to climate change. Classical seismic surface wave dispersion methods are limited to quantitative estimations of these small variations when the variation ratio is smaller than 10 per cent, especially in the case of variations in deep media. Based on these findings, we propose to study the contributions of the Rayleigh wave phase velocity derivative with respect to frequency. More precisely, in the first step of assessing its feasibility, we analyse the effects of the phase velocity derivative on the inversion of the fundamental mode in the simple case of a two-layer model. The behaviour of the phase velocity derivative is first analysed qualitatively: the dispersion curves of phase velocity, group velocity and the phase velocity derivative are calculated theoretically for several series of media with small variations. It is shown that the phase velocity derivatives are more sensitive to variations of a medium. The sensitivity curves are then calculated for the phase velocity, the group velocity and the phase velocity derivative to perform quantitative analyses. Compared to the phase and group velocities, the phase velocity derivative is sensitive to variations of the shallow layer and the deep layer shear wave velocity in the same wavelength (frequency) range. Numerical data are used and processed to obtain dispersion curves to test the feasibility of the phase velocity derivative in the inversion. The inversion results of the phase velocity derivative are compared with those of phase and group velocities and show improved estimations for small variations (variation ratio less than 5 per cent) of deep layer shear wave velocities. The study is focused on laboratory experiments using two reduced-scale resin-epoxy models. The differences of these two-layer models are in the deep layer in which the variation ratio is estimated as 16.4 ± 1.1 per cent for the phase velocity inversion and 17.1 ± 0.3 per cent for the phase velocity derivative. The latter is closer to the reference value 17 per cent, with a smaller error.

Compressional‐wave velocities in attenuating media: A laboratory physical model study

Geophysics ◽  
2000 ◽  
Vol 65 (4) ◽  
pp. 1162-1167 ◽  
Author(s):  
Joseph B. Molyneux ◽  
Douglas R. Schmitt
Keyword(s):  
Phase Velocity ◽  
Group Velocity ◽  
Wave Velocity ◽  
Propagation Distance ◽  
Compressional Wave ◽  
Arrival Times ◽  
Wave Velocities ◽  
Amplitude Maximum ◽  
Phase And Group Velocities ◽  
Group Velocities

Elastic‐wave velocities are often determined by picking the time of a certain feature of a propagating pulse, such as the first amplitude maximum. However, attenuation and dispersion conspire to change the shape of a propagating wave, making determination of a physically meaningful velocity problematic. As a consequence, the velocities so determined are not necessarily representative of the material’s intrinsic wave phase and group velocities. These phase and group velocities are found experimentally in a highly attenuating medium consisting of glycerol‐saturated, unconsolidated, random packs of glass beads and quartz sand. Our results show that the quality factor Q varies between 2 and 6 over the useful frequency band in these experiments from ∼200 to 600 kHz. The fundamental velocities are compared to more common and simple velocity estimates. In general, the simpler methods estimate the group velocity at the predominant frequency with a 3% discrepancy but are in poor agreement with the corresponding phase velocity. Wave velocities determined from the time at which the pulse is first detected (signal velocity) differ from the predominant group velocity by up to 12%. At best, the onset wave velocity arguably provides a lower bound for the high‐frequency limit of the phase velocity in a material where wave velocity increases with frequency. Each method of time picking, however, is self‐consistent, as indicated by the high quality of linear regressions of observed arrival times versus propagation distance.

scholarly journals Direct estimation of the Rayleigh wave phase velocity in microtremors

2006 ◽  
Vol 33 (18) ◽  
pp. n/a-n/a ◽  
Author(s):  
Hidetaka Shiraishi ◽  
Tatsuro Matsuoka ◽  
Hiroshi Asanuma
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Direct Estimation ◽  
Wave Phase ◽  
Wave Phase Velocity ◽  
Rayleigh Wave Phase Velocity

scholarly journals Rayleigh wave phase velocity analysis of the Ross Sea, Transantarctic Mountains, and East Antarctica from a temporary seismograph array

2006 ◽  
Vol 111 (B6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jesse F. Lawrence ◽  
Douglas A. Wiens ◽  
Andrew A. Nyblade ◽  
Sridhar Anandakrishnan ◽  
Patrick J. Shore ◽  
...  
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Ross Sea ◽  
East Antarctica ◽  
Velocity Analysis ◽  
Wave Phase ◽  
Wave Phase Velocity ◽  
Transantarctic Mountains ◽  
Rayleigh Wave Phase Velocity

scholarly journals Deformation of the Crust and Upper Mantle beneath the North China Craton and Its Adjacent Areas Constrained by Rayleigh Wave Phase Velocity and Azimuthal Anisotropy

2021 ◽  
Vol 14 (1) ◽  
pp. 110
Author(s):  
Xiaoming Xu ◽  
Dazhou Zhang ◽  
Xiang Huang ◽  
Xiaoman Cao
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Azimuthal Anisotropy ◽  
The Tibetan Plateau ◽  
Low Velocity ◽  
Crust And Upper Mantle ◽  
Fast Axis ◽  
Wave Phase ◽  
Wave Phase Velocity ◽  
Rayleigh Wave Phase Velocity

The North China Craton (NCC) has experienced strong tectonic deformation and lithospheric thinning since the Cenozoic. To better constrain the geodynamic processes and mechanisms of the lithospheric deformation, we used a linear damped least squares method to invert simultaneously Rayleigh wave phase velocity and azimuthal anisotropy at periods of 10–80 s with teleseismic data recorded by 388 permanent stations in the NCC and its adjacent areas. The results reveal that the anomalies of Rayleigh wave phase velocity and azimuthal anisotropy are in good agreement with the tectonic domains in the study area. Low-phase velocities appear in the rift grabens and sedimentary basins at short periods. A rotation pattern of the fast axis direction of the Rayleigh wave together with a distinct low-velocity anomaly occurs around the Datong volcano. A NW–SE trending azimuthal anisotropy and a low-velocity anomaly at periods of 60–80 s are observed subparallel to the Zhangbo fault zone. The whole lithosphere domain of the Ordos block shows a high-phase velocity and counterclockwise rotated fast axis. The northeastern margin of the Tibetan plateau is dominated by a low-velocity and coherent NW–SE fast axis direction. We infer that the subduction of the Paleo-Pacific plate and eastward material escape of the Tibetan plateau mainly contribute to the deformation of the crust and upper mantle in the NCC.

Sign in / Sign up

Export Citation Format

Share Document