On the rapidity spectrum of the energy flux model

1975 ◽  
Vol 14 (5) ◽  
pp. 153-157
Author(s):  
G. Calucci
Keyword(s):  
Energy Flux ◽  
Flux Model ◽  
Rapidity Spectrum

Further Validation and Implementation of an Algebraic Energy Flux Model for High Speed Gaseous Shear Flows

2022 ◽  
Author(s):  
Casey Broslawski ◽  
Bryan Morreale ◽  
Rodney D. Bowersox ◽  
Gary Nicholson ◽  
Lian Duan
Keyword(s):  
Energy Flux ◽  
High Speed ◽  
Shear Flows ◽  
Flux Model

Calibration of an energy flux model over bare soils during the HAPEX-MOBILHY experiment

1992 ◽  
Vol 58 (3-4) ◽  
pp. 257-283 ◽  
Author(s):  
M.Ben Mehrez ◽  
O. Taconet ◽  
D. Vidal-Madjar ◽  
Y. Sucksdorff
Keyword(s):  
Energy Flux ◽  
Flux Model ◽  
Bare Soils

Energy-flux model of seismic coda: Separation of scattering and intrinsic attenuation

1987 ◽  
Vol 77 (4) ◽  
pp. 1223-1251
Author(s):  
Arthur Frankel ◽  
Leif Wennerberg
Keyword(s):  
Decay Rate ◽  
Energy Flux ◽  
Single Scattering ◽  
Coda Q ◽  
Scattering Attenuation ◽  
Seismic Coda ◽  
Wide Range ◽  
Flux Model ◽  
Strong Scattering ◽  
Q Values

Abstract A new model of seismic coda is presented, based on the balance between the energy scattered from the direct wave and the energy in the seismic coda. This energy-flux model results in a simple formula for the amplitude and time decay of the seismic coda that explicitly differentiates between the scattering and intrinsic (anelastic) attenuation of the medium. This formula is valid for both weak and strong scattering and implicitly includes multiple scattering. The model is tested using synthetic seismograms produced in finite difference simulations of wave propagation through media with random spatial variations in seismic velocity. Some of the simulations also included intrinsic dissipation. The energy-flux model explains the coda decay and amplitude observed in the synthetics, for random media with a wide range of scattering Q. In contrast, the single-scattering model commonly used in the analysis of microearthquake coda does not account for the gradual coda decay observed in the simulations for media with moderate or strong scattering attenuation (scattering Q ≦ 150). The simulations demonstrate that large differences in scattering attenuation cause only small changes in the coda decay rate, as predicted by the energy-flux model. The coda decay rate is sensitive, however, to the intrinsic Q of the medium. The ratio of the coda amplitude to the energy in the direct arrival is a measure of the scattering attenuation. Thus, analysis of the decay rate and amplitude of the coda can, in principle, produce separate estimates for the scattering and intrinsic Q values of the crust. We analyze the coda from two earthquakes near Anza, California. Intrinsic Q values determined from these seismograms using the energy-flux model are comparable to coda Q values found from the single-scattering theory. These results indicate that coda Q values are, at best, measures of the intrinsic Q of the lithosphere and are unrelated to the scattering Q.

A NEW ENERGY-FLUX MODEL OF WAVEGUIDE REVERBERATION BASED ON PERTURBATION THEORY

2010 ◽  
Vol 18 (03) ◽  
pp. 209-225 ◽  
Author(s):  
J. R. WU ◽  
E. C. SHANG ◽  
T. F. GAO
Keyword(s):  
Perturbation Theory ◽  
Shallow Water ◽  
Energy Flux ◽  
Environmental Parameters ◽  
Water Area ◽  
Full Wave ◽  
Shallow Water Area ◽  
New Energy ◽  
Flux Model ◽  
Filtering Approach

The modal shallow water reverberation theory and the energy-flux shallow water reverberation theory were combined to get a new energy-flux model of waveguide reverberation based on Perturbation theory. There are only three environmental parameters (P, Q, μ) in the new reverberation model. It has clear physical picture and it is satisfied the waveguide constraint without any adjustable parameters. The new energy-flux reverberation model was compared with the modal reverberation model (full-wave reverberation model). The results show that the new model can explain the shallow water reverberation in most cases. It is shown that the contributions of parameter P and Q are mutual compensated (coupled) for a fixed reverberation data, therefore it is hard to extract both of them simultaneously. Finally, parameters P and μ at different frequencies were extracted from the reverberation data of "Qingdao-2005 experiment" in Yellow sea shallow-water area where the parameter Q has been extracted from mode filtering approach previously.

scholarly journals Small-scale lithospheric heterogeneity characterization using Bayesian inference 

2021 ◽  
Author(s):  
Itahisa González Álvarez ◽  
Sebastian Rost ◽  
Andy Nowacki ◽  
Neil Selby
Keyword(s):  
Bayesian Inference ◽  
Energy Flux ◽  
Single Layer ◽  
The Other ◽  
Small Scale ◽  
Quality Factors ◽  
Layer Model ◽  
Velocity Fluctuations ◽  
Trade Offs ◽  
Flux Model

<div> <p>Heterogeneities on the scale of the seismic wavelength in the Earth's crust and mantle cause complex wavefield fluctuations in time and amplitude which are known to affect velocity and source inversions, as well as other seismic characterisations. However, many seismic models ignore these heterogeneities for simplicity. As part of our longer-term goal to account for these, we attempt to rigorously and probabilistically characterise these lithospheric small-scale heterogeneities by combining a single-layer and a multi-layer energy flux models with a new Bayesian inference algorithm. The first technique characterizes energy losses to the ballistic arrival as intrinsic, diffusion and scattering quality factors, which allows us to compare the effects of these attenuation mechanisms on our data. With the second method, we can obtain synthetic coda envelopes for 1- and 2- layer models with different values of the correlation length and fractional velocity fluctuations in each layer. We then use the Metropolis-Hastings algorithm to sample the likelihood space and obtain the posterior probability distributions for each parameter and layer in the model. Our thorough testing of these methods reveals complicated trade-offs between the parameters and highly non-unique solutions, thus highlighting the importance of the Bayesian approach for scattering studies. Previous studies applying these methods used a more traditional grid search for their coda inversion, which may have affected their results. We applied this approach to a data set of over 300 events from three seismic arrays in Australia: Alice Springs array (ASAR), Warramunga Array (WRA) and Pilbara Seismic Array (PSA). The results from the single-layer energy flux model show that all quality factors take higher values for PSA than for the other two arrays, indicating that the structure beneath this array is less attenuating and heterogeneous than for the other arrays. Intrinsic and diffusion attenuation are strongest for ASAR, while scattering and total attenuation are similarly strong for ASAR and WRA. Our multi-layer model results show the crust is more heterogeneous than the lithospheric mantle for all arrays, with crustal values of the correlation length and velocity fluctuations being lower for PSA than for the other arrays, indicating the presence of weaker and smaller scale heterogeneity beneath this array. We attribute these differences and similarities in the attenuation and heterogeneity structure beneath the arrays to variations in the tectonic history of the areas they are located on. This new Bayesian approach to the multi-layer energy flux model, in combination with the single-layer model, not only allows us to determine and compare the different quality factors, but also gives us detailed information about the trade-offs and uncertainties in the determination of the scattering parameters, making it a useful tool for future scattering and small-scale structure studies. </p> </div>

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