Analysis of shear-wave attenuation in unconsolidated sands and glass beads

2014 ◽  
Vol 136 (5) ◽  
pp. 2478-2488 ◽  
Author(s):  
Michael J. Buckingham
Keyword(s):  
Shear Wave ◽  
Wave Attenuation ◽  
Glass Beads ◽  
Unconsolidated Sands

scholarly journals Minor Squirt in Unconsolidated Sands versus Strong Squirt in Compressed Glass Beads

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Guangquan Li ◽  
Yuchao Wang ◽  
Xiang Li
Keyword(s):  
High Frequency ◽  
Wave Attenuation ◽  
Pore Space ◽  
Glass Beads ◽  
P Wave ◽  
Local Pressure ◽  
Unconsolidated Sands ◽  
Solid Stress ◽  
Dynamic Permeability ◽  
Improved Model

Squirt driven by local pressure imbalance between contact of grains (or throat) and the main pore space is a mechanism of P-wave attenuation in consolidated rocks. In this paper, we investigate squirt in unconsolidated and consolidated porous media (represented by Toyoura sands and compressed glass beads, respectively). The former sample has very small bulk modulus and shear modulus, manifested by relatively free/mobile grains. As such, solid stress on the surface tends to be uniform and squirt should be minor. Biot’s theory improved with dynamic permeability successfully predicts the ultrasonic velocity and quality factor of P wave measured in the unconsolidated sands, confirming the aforementioned judgment. Dynamic permeability inverted at a high frequency is far lower than Darcy permeability. However, the improved model remains to be incapable of predicting velocity and attenuation measured in the latter sample; the reason is that the compressed beads allows a high pressure at compliant throat which drives strong squirt between throat and the main pore space.

scholarly journals Lorentz force induced shear waves for magnetic resonance elastography applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guillaume Flé ◽  
Guillaume Gilbert ◽  
Pol Grasland-Mongrain ◽  
Guy Cloutier
Keyword(s):  
Magnetic Resonance ◽  
Shear Wave ◽  
Lorentz Force ◽  
Wave Attenuation ◽  
Shear Waves ◽  
Estimation Method ◽  
Biological Tissues ◽  
Magnetic Resonance Elastography ◽  
Motion Generation ◽  
Wave Source

AbstractQuantitative mechanical properties of biological tissues can be mapped using the shear wave elastography technique. This technology has demonstrated a great potential in various organs but shows a limit due to wave attenuation in biological tissues. An option to overcome the inherent loss in shear wave magnitude along the propagation pathway may be to stimulate tissues closer to regions of interest using alternative motion generation techniques. The present study investigated the feasibility of generating shear waves by applying a Lorentz force directly to tissue mimicking samples for magnetic resonance elastography applications. This was done by combining an electrical current with the strong magnetic field of a clinical MRI scanner. The Local Frequency Estimation method was used to assess the real value of the shear modulus of tested phantoms from Lorentz force induced motion. Finite elements modeling of reported experiments showed a consistent behavior but featured wavelengths larger than measured ones. Results suggest the feasibility of a magnetic resonance elastography technique based on the Lorentz force to produce an shear wave source.

scholarly journals Imaging of shear wave attenuation along the central part of the North Anatolian Fault Zone, Turkey

2019 ◽  
Vol 23 (4) ◽  
pp. 913-927 ◽  
Author(s):  
Peter Gaebler ◽  
Tuna Eken ◽  
Hüseyin Önder Bektaş ◽  
Tom Eulenfeld ◽  
Ulrich Wegler ◽  
...  
Keyword(s):  
Shear Wave ◽  
Fault Zone ◽  
Wave Attenuation ◽  
North Anatolian Fault ◽  
North Anatolian Fault Zone ◽  
The North
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