Influence of Initial Stress and Inhomogeneity on Propagation of Torsional Type Surface Wave in a Crustal Layer

2016 ◽  
Vol 16 (4) ◽  
pp. 06015012 ◽  
Author(s):  
Shishir Gupta ◽  
Mostaid Ahmed ◽  
Santanu Manna ◽  
Abhijit Pramanik
Keyword(s):  
Surface Wave ◽  
Initial Stress ◽  
Crustal Layer

Torsional Waves in a Fiber Composite Medium at a Loosely Bonded Interface Constrained Between Dry Sandy Layer and Gravitating Poroelastic Substrate

2019 ◽  
Vol 16 (06) ◽  
pp. 1840030 ◽  
Author(s):  
Shishir Gupta ◽  
Santimoy Kundu ◽  
Prasenjit Pati
Keyword(s):  
Surface Wave ◽  
Dispersion Relation ◽  
Initial Stress ◽  
Fiber Composite ◽  
Whittaker Function ◽  
Composite Medium ◽  
Bonded Interface ◽  
Surface Wave Propagation ◽  
Sandy Layer ◽  
Torsional Surface Wave

The objective of this paper is to study the effect of loosely bonded interface on torsional surface wave propagation in a fiber reinforced composite medium constrained between dry sandy layer and an anisotropic gravitating poroelastic substrate. All the media are assumed to be under initial stress. The dispersion relation on this proposed multilayer ground structure has been derived in closed form under certain boundary conditions, which contain Whittaker function and its derivative, which is further expanded asymptotically, retaining up to only the linear terms. The numerical solution for the limiting case of torsional surface waves is also discussed. As a special case of the problem, when the entire medium is isotropic and one of the upper layer vanishes and removing the initial stress and gravity, the dispersion relation obtained is in agreement with the classical Love type wave equation. The influence of various technical constants, such as sandy parameter, reinforcement parameter, porosity parameter, Biot’s gravity parameter, loosely bonded parameters, initial stress of both the layers and half spaces on the phase velocity of torsional surface wave has been pointed out by means of graphs.

Influence of initial stress and gravity on torsional surface wave in heterogeneous medium

2016 ◽  
Vol 23 (6) ◽  
pp. 970-979
Author(s):  
Anup Kr Mukhopadhyay ◽  
Asit Kr Gupta ◽  
Santimoy Kundu ◽  
Santanu Manna
Keyword(s):  
Surface Wave ◽  
Initial Stress ◽  
Heterogeneous Medium ◽  
Torsional Surface Wave

Ambient seismic noise tomography in west-central and Southern Brazil, characterizing the crustal structure of the Chaco-Paraná, Pantanal and Paraná basins

2019 ◽  
Vol 220 (3) ◽  
pp. 2074-2085
Author(s):  
Taghi Shirzad ◽  
Marcelo Assumpcao ◽  
Marcelo Bianchi
Keyword(s):  
Surface Wave ◽  
Crustal Structure ◽  
Seismic Noise ◽  
Velocity Model ◽  
Dispersion Curves ◽  
Ambient Seismic Noise ◽  
Inversion Method ◽  
Crustal Layer ◽  
West Central ◽  
Lower Crustal

SUMMARY Surface wave analysis provides important information on crustal structure, but it is challenging to obtain accurate/robust models in aseismic regions because of the lack of local earthquake records. In this paper, interstation empirical Green's functions retrieved by ambient seismic noise in 75 broad-band stations from 2016 January to 2018 September were used to study crustal structure in west-central Brazil. Fast marching method was applied to calculate the 2-D surface wave tomographic maps, and local dispersion curves were estimated in the period range of 4–80 s for each geographic cell. 1-D damped least squares inversion method was then conducted to obtained shear wave velocity model. Finally, the average ($\tilde{\rm V}$S) of the calculated VSV and VSH quasi 3-D models were used to characterize the crustal structure. Besides the checkerboard test resolution, a stochastic test with the effect of errors in the dispersion curves and choice of inversion parameters were carried out to better evaluate model uncertainties. Our results show a clear relation between the sedimentary thickness and geological units with the shorter period tomographic maps. Agreement has also been observed in longer periods such as the clear N–S anomaly along the Asuncion and Rio Grande Arches representing the boundary between the Chaco-Paraná and the Paraná basins. A 3-D composite velocity model shows a crustal structure consisting of three main layers. Some differences in lower crustal properties were found between the Paraná and Chaco-Paraná basins, consistent with a recently postulated, gravity-derived Western Paraná suture zone. However, no high velocities along the SW–NE axis of the Paraná basin were found to confirm proposed underplating. At the eastern edge of the Pantanal basin, the thin crust seems to be associated with a very thin (or lack of) lower crustal layer, consistent with a recently proposed crustal delamination hypothesis for the formation of the Pantanal basin.

Surface-wave propagation under initial tension or compression

1973 ◽  
Vol 63 (6-1) ◽  
pp. 1895-1899
Author(s):  
E. J. Brunelle
Keyword(s):  
Wave Propagation ◽  
Surface Wave ◽  
Initial Stress ◽  
Half Space ◽  
Rayleigh Waves ◽  
Love Waves ◽  
Initial Tension ◽  
Linearized Equations ◽  
Compressive Stresses ◽  
Surface Wave Propagation

Abstract The propagation of Rayleigh waves in a half-space and the propagation of Love waves in a welded layer and half-space are examined when initial tensile or compressive stresses are present. Using the perturbed and linearized equations of elasticity, which include the effects of initial stress, a modified Rayleigh equation and a modified Love equation are obtained. The solution of the equations shows a dramatic change in the phase speeds of the two wave types under initial tension or compression. Numerical results are presented.

Exit-surface wave reconstruction using a focal series

1992 ◽  
Vol 50 (2) ◽  
pp. 988-989
Author(s):  
W.J. de Ruijter ◽  
M.R. McCartney ◽  
David J. Smith ◽  
J.K. Weiss
Keyword(s):  
Surface Wave ◽  
Spherical Aberration ◽  
Data Extraction ◽  
High Sensitivity ◽  
Geometric Distortion ◽  
Variation Method ◽  
Objective Lens ◽  
Immediate Reconstruction ◽  
Exit Surface ◽  
Electron Microscopes

Further advances in resolution enhancement of transmission electron microscopes can be expected from digital processing of image data recorded with slow-scan CCD cameras. Image recording with these new cameras is essential because of their high sensitivity, extreme linearity and negligible geometric distortion. Furthermore, digital image acquisition allows for on-line processing which yields virtually immediate reconstruction results. At present, the most promising techniques for exit-surface wave reconstruction are electron holography and the recently proposed focal variation method. The latter method is based on image processing applied to a series of images recorded at equally spaced defocus.Exit-surface wave reconstruction using the focal variation method as proposed by Van Dyck and Op de Beeck proceeds in two stages. First, the complex image wave is retrieved by data extraction from a parabola situated in three-dimensional Fourier space. Then the objective lens spherical aberration, astigmatism and defocus are corrected by simply dividing the image wave by the wave aberration function calculated with the appropriate objective lens aberration coefficients which yields the exit-surface wave.

Surface Wave Utility in Composite Materia] Characterization

1989 ◽  
Vol 1 (1) ◽  
pp. 247-265
Author(s):  
Joseph Rose ◽  
Aleksander Pilarski ◽  
Yimei Huang
Keyword(s):  
Surface Wave

Analysis of focused surface wave transducers

1990 ◽  
Vol 137 (6) ◽  
pp. 467 ◽  
Author(s):  
M. Kirci ◽  
E. Akcakaya
Keyword(s):  
Surface Wave
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