Mapping Poisson's Ratio of Unconsolidated Materials from a Joint Analysis of Surface‐Wave and Refraction Events

2000 ◽  
Author(s):  
Julian Ivanov ◽  
Choon B. Park ◽  
Richard D. Miller ◽  
Jianghai Xia
Keyword(s):  
Surface Wave ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Joint Analysis

Surface-wave dispersion in Byrd Land, Antarctica

1972 ◽  
Vol 62 (4) ◽  
pp. 955-959 ◽  
Author(s):  
H. K. Acharya
Keyword(s):  
Surface Wave ◽  
Ultrasonic Velocity ◽  
Poisson’S Ratio ◽  
Wave Dispersion ◽  
Poisson's Ratio ◽  
Constant Density ◽  
Velocity Measurements ◽  
Land Area ◽  
Surface Wave Dispersion ◽  
Ice Cap

Abstract Assuming constant density and Poisson's ratio of 0.25, theoretical surface-wave dispersion has been computed for the Byrd Land area in Antarctica, where the velocity increases monotonically with depth. Comparison with observed dispersion indicates 8 to 10 per cent anisotropy in the ice cap. Such anisotropy was also detected from ultrasonic velocity measurements on snow cores.

The azimuthal and polar radiation patterns obtained from a horizontal stress applied at the surface of an elastic half space

1962 ◽  
Vol 52 (1) ◽  
pp. 27-36
Author(s):  
J. T. Cherry
Keyword(s):  
Surface Wave ◽  
Half Space ◽  
Rayleigh Waves ◽  
Poisson’S Ratio ◽  
Horizontal Stress ◽  
Elastic Half Space ◽  
The Body ◽  
Body Waves ◽  
Poisson's Ratio ◽  
A Value

Abstract The body waves and surface waves radiating from a horizontal stress applied at the free surface of an elastic half space are obtained. The SV wave suffers a phase shift of π at 45 degrees from the vertical. Also, a surface wave that is SH in character but travels with the Rayleigh velocity is shown to exist. This surface wave attenuates as r−3/2. For a value of Poisson's ratio of 0.25 or 0.33, the amplitude of the Rayleigh waves from a horizontal source should be smaller than the amplitude of the Rayleigh waves from a vertical source. The ratio of vertical to horizontal amplitude for the Rayleigh waves from the horizontal source is the same as the corresponding ratio for the vertical source for all values of Poisson's ratio.

REFLECTION OF AN ACOUSTICAL PRESSURE PULSE FROM A LIQUID‐SOLID PLANE BOUNDARY

Geophysics ◽  
1956 ◽  
Vol 21 (1) ◽  
pp. 71-87 ◽  
Author(s):  
T. W. Spencer
Keyword(s):  
Surface Wave ◽  
Poisson’S Ratio ◽  
Velocity Ratio ◽  
Elastic Solid ◽  
Vertical Axis ◽  
Vertical Displacement ◽  
Poisson's Ratio ◽  
Plane Boundary ◽  
The Laplace Transform ◽  
Compressional Velocity

The problem treated is concerned with predicting the transient response of a system composed of a liquid layer, bounded above by a vacuum and below by a perfectly elastic solid, when excited by an arbitrary pressure applied uniformly over the surface of a spherical cavity located in the fluid. The Laplace transform of the displacement response is expressed in terms of an integral which is expanded in such a way that each term describes the contribution from one of the image sources. Each term may be evaluated exactly at points located on a vertical axis passing through the source. The final expression for the vertical displacement at axial points is composed of the acoustic, after‐flow, and correction terms. In solids for which Poisson’s ratio is greater than one third the initial variation of the correction is toward positive values (corresponding to motion directed toward the interface). For Poisson’s ratio less than one third the initial variation may be either positive or negative depending on the magnitude of the compressional velocity ratio. A surface wave is shown to exist regardless of the choice of parameters. The surface wave velocity is always less than it would be in the absence of the liquid.

Multi-modal surface wave tomography to obtain S- and P-wave velocities applied to the recordings of UAV deployed sensors.

Geophysics ◽  
2021 ◽  
pp. 1-56
Author(s):  
Farbod Khosro Anjom ◽  
Thomas Jules Browaeys ◽  
Laura Valentina Socco
Keyword(s):  
Surface Wave ◽  
Wave Velocity ◽  
Poisson’S Ratio ◽  
P Wave ◽  
Poisson's Ratio ◽  
Surface Wave Tomography ◽  
Higher Modes ◽  
Wave Tomography ◽  
Irregular Geometry ◽  
The Impact

Exploration seismic surveys in hard-to-access areas such as foothills and forests are extremely challenging. The Multiphysics Exploration Technologies Integrated System (METIS) research project was initiated to design an exploration system, facilitating the acquisition in these areas by delivering the receivers from the sky using unmanned aerial vehicles. Air dropping of the sensors in vegetated areas results in an irregular geometry for the acquisition. This irregularity can limit the application of conventional surface wave methods. We have developed a surface wave workflow for estimating the S-wave velocity ( VS) and P-wave velocity ( VP) models and that supports the irregular geometry of the deployed sources and receivers. The method consists of a multimodal surface wave tomography (SWT) technique to compute the VS model and a data transform method (the wavelength/depth [W/D] method) to determine the Poisson’s ratio and VP model. We applied the method to the METIS’s first pilot records, which were acquired in the forest of Papua New Guinea. Application of SWT to the data resulted in the first 90 m of the VS model. The W/D method provided the Poisson’s ratio averaged over the area and the VP model between 10 and 70 m from the surface. The impact of the acquisition scale and layout on the resolution of the estimated model and the advantages of including the higher modes of surface waves in the tomographic inversion are assessed in detail. The presence of shots from diverse site locations significantly improves the resolution of the obtained model. Including the higher modes enhances the data coverage and increases the investigation depth.

Investigation of surface-wave dispersion in an inhomogeneous medium by the finite difference method

1978 ◽  
Vol 68 (5) ◽  
pp. 1381-1386
Author(s):  
H. K. Acharya ◽  
C. R. Bentley
Keyword(s):  
Surface Wave ◽  
Poisson’S Ratio ◽  
Previous Analysis ◽  
Equations Of Motion ◽  
Ice Sheet ◽  
Wave Dispersion ◽  
Poisson's Ratio ◽  
Constant Density ◽  
Surface Wave Dispersion ◽  
Simplifying Assumptions

abstract Surface-wave dispersion for the ice sheet of Marie Byrd Land, Antarctica, in which velocity and density increase continuously with depth and gradients near the surface are steep, has been computed by solving the equations of motion directly by finite differences. No simplifying assumptions or approximations about parameter variations with depth have been made. Computer results agree well with observed data without the introduction of any anisotropy, as was needed in a previous analysis (Acharya, 1972). Tests of the assumptions made in the previous analysis show that (a) the approximation Poisson's ratio = 14 introduces no significant error even though Poisson's ratio actually varies from 14 to 13 in the upper part of the ice sheet, and (b) the assumption of a constant density, required if one is to separate compressional and shear-wave displacement potentials, is unsatisfactory.

P- and S-wave velocity models of shallow dry sand formations from surface wave multimodal inversion

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. R197-R209 ◽  
Author(s):  
Paolo Bergamo ◽  
Laura Valentina Socco
Keyword(s):  
Surface Wave ◽  
Wave Velocity ◽  
Power Law ◽  
Poisson’S Ratio ◽  
Real Data ◽  
P Wave ◽  
Poisson's Ratio ◽  
S Wave ◽  
Data Set ◽  
Seismic Characterization

Surficial formations composed of loose, dry granular materials constitute a challenging target for seismic characterization. They exhibit a peculiar seismic behavior, characterized by a nonlinear seismic velocity gradient with depth that follows a power-law relationship, which is a function of the effective stress. The P- and S-wave velocity profiles are then characterized by a power-law trend, and they can be defined by two power-law exponents [Formula: see text] and two power-law coefficients [Formula: see text]. In case of depth-independent Poisson’s ratio, the P-wave velocity profile can be defined using the [Formula: see text] power-law parameters and Poisson’s ratio. Because body wave investigation techniques (e.g., P-wave tomography) may perform ineffectively on such materials because of high attenuation, we addressed the potential of surface-wave method for a reliable seismic characterization of shallow formations of dry, uncompacted granular materials. We took into account the dependence of seismic wave velocity on effective pressure and performed a multimodal inversion of surface-wave data, which allowed the [Formula: see text] and [Formula: see text] profiles to be retrieved. The method requires the selection of multimodal dispersion curve points referring to surface-wave frequency components traveling within the granular media formation and their inversion for the S-wave power-law parameters and Poisson’s ratio. We have tested our method on a synthetic dispersion curve and applied it to a real data set. In both cases, the surficial layer was made of loose dry sand. The test on the synthetic data set confirmed the reliability of the proposed procedure because the thickness and the [Formula: see text], [Formula: see text] profiles of the sand layer were correctly estimated. For the real data, the outcomes were validated by other geophysical measurements conducted at the same site and they were in agreement with similar studies regarding loose sand formations.

Significance and evaluation of Poisson's ratio in Rayleigh wave testing

2008 ◽  
Vol 45 (5) ◽  
pp. 624-635 ◽  
Author(s):  
Mourad Karray ◽  
Guy Lefebvre
Keyword(s):  
Surface Wave ◽  
Rayleigh Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Soil Characterization ◽  
Inversion Process ◽  
Multi Mode

Important progress has been made in the past 20 years in the use of surface-wave testing in soil characterization. However, the effect of Poisson's ratio on the construction of the theoretical dispersion relationships, associated with the inversion process, has not received enough attention and remains poorly documented. Five ideal profiles with different degrees of variation of shear-wave velocity with depth and three published case records are considered in this paper to study the effect of Poisson's ratio on Rayleigh wave phase velocities. The effect of the variation of Poisson's ratio on the evaluation of shear-wave velocity profiles (Vs) is also examined. Poisson's ratio is generally assumed in surface-wave testing, and therefore the paper also examines the possibility of evaluating its value using a multi-mode inversion process. The results of surface-wave testing obtained at two experimental sites are then used to illustrate the potential of surface-wave testing to evaluate the Poisson's ratio profile in addition to the Vs profile. The impact of Poisson's ratio in Rayleigh wave testing is shown to be significantly more important than previously demonstrated. The error resulting from Poisson's ratio does not depend solely on the magnitude of the inaccuracy. A multi-mode inversion process is shown to be a useful tool to determine the Poisson's ratio profile, leading to a more accurate soil characterization.

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