TY - JOUR
T1 - Stochastic features of scattering
AU - Hong, Tae Kyung
AU - Wu, Ru Shan
AU - Kennett, B. L.N.
PY - 2005/2
Y1 - 2005/2
N2 - The characteristics of scattering of scalar waves in stochastic random media are investigated in through the behaviour of the meanfield, scattering attenuation, and transmission fluctuations of amplitude and phase. Coherent scattered waves develop with increase of perturbation level, with the strength of the coherency varying with the type of media. The frequency content of the coherent scattered waves is close to that of the incident waves, and the phase is dependent on the statistical effect of the heterogeneities along the propagation path. The normalized scattering attenuation (Qs-1/ ε2) is stable at low normalized wavenumbers (ka < 1) regardless of the perturbation strength, but varies with the perturbation strength at high normalized wavenumbers (ka > 1). The coherent scattered waves, which strengthen with the perturbation level, add energy to the primary waves and reduce the apparent scattering attenuation. Stable measurements of normalized scattering attenuation can be made for sufficiently large distances. An empirical distance criterion for such stable measurements of scattering attenuation is presented in terms of propagation distance, incident wavelength, and the correlation length of the heterogeneities in the medium. The transmission fluctuation of amplitude and phase shows a high variation at large spatial lags, and the trend of the variation is dependent on the nature of heterogeneities. The ensemble average of amplitude fluctuation closely follows the theoretical prediction, but rather poor agreement is displayed for phase fluctuation. The effect of self-averaging during propagation in random media can not replace the ensemble averaging for mean transmission fluctuations of the amplitude and phase in random media.
AB - The characteristics of scattering of scalar waves in stochastic random media are investigated in through the behaviour of the meanfield, scattering attenuation, and transmission fluctuations of amplitude and phase. Coherent scattered waves develop with increase of perturbation level, with the strength of the coherency varying with the type of media. The frequency content of the coherent scattered waves is close to that of the incident waves, and the phase is dependent on the statistical effect of the heterogeneities along the propagation path. The normalized scattering attenuation (Qs-1/ ε2) is stable at low normalized wavenumbers (ka < 1) regardless of the perturbation strength, but varies with the perturbation strength at high normalized wavenumbers (ka > 1). The coherent scattered waves, which strengthen with the perturbation level, add energy to the primary waves and reduce the apparent scattering attenuation. Stable measurements of normalized scattering attenuation can be made for sufficiently large distances. An empirical distance criterion for such stable measurements of scattering attenuation is presented in terms of propagation distance, incident wavelength, and the correlation length of the heterogeneities in the medium. The transmission fluctuation of amplitude and phase shows a high variation at large spatial lags, and the trend of the variation is dependent on the nature of heterogeneities. The ensemble average of amplitude fluctuation closely follows the theoretical prediction, but rather poor agreement is displayed for phase fluctuation. The effect of self-averaging during propagation in random media can not replace the ensemble averaging for mean transmission fluctuations of the amplitude and phase in random media.
KW - Meanfield
KW - Numerical modelling
KW - Scalar waves
KW - Scattering
KW - Scattering attenuation
KW - Stochastic effect
KW - Transmission fluctuation
KW - Wavelet-based method
KW - Wavelets
UR - http://www.scopus.com/inward/record.url?scp=13144297788&partnerID=8YFLogxK
U2 - 10.1016/j.pepi.2004.08.002
DO - 10.1016/j.pepi.2004.08.002
M3 - Article
SN - 0031-9201
VL - 148
SP - 131
EP - 148
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
IS - 2-4
ER -