scholarly journals Geometrical theory of diffraction for high‐frequency coherence functions in a weakly random medium with inhomogeneous background profile

1987 ◽  
Vol 81 (S1) ◽  
pp. S21-S21
Author(s):  
R. Mazar ◽  
L. B. Felsen
Keyword(s):  
High Frequency ◽  
Random Medium ◽  
Geometrical Theory ◽  
Geometrical Theory Of Diffraction ◽  
Frequency Coherence

SCATTERING NEAR A PLANE INTERFACE USING A GENERALIZED METHOD OF IMAGES APPROACH

2004 ◽  
Vol 12 (02) ◽  
pp. 233-256 ◽  
Author(s):  
ARNAUD COATANHAY ◽  
JEAN-MARC CONOIR
Keyword(s):  
Plane Wave ◽  
Acoustic Field ◽  
High Frequency ◽  
Plane Interface ◽  
Geometrical Theory ◽  
Method Of Images ◽  
Asymptotic Results ◽  
Plane Wave Incident ◽  
Geometrical Theory Of Diffraction ◽  
Long Cylinder

A new method for predicting the scattered acoustic field due to a plane wave incident upon an infinitely long cylinder lying near an penetrable plane interface is presented. The method generalizes the method of images which is restricted to rigid and soft plane interfaces. Validity domains, physical interpretations, simulations and numerical results are described for sedimentary medium-fluid plane interfaces. And, they are well compared with high frequency asymptotic results based on the Geometrical Theory of Diffraction(G.T.D.).

High-frequency seismic noise as a function of depth

1991 ◽  
Vol 81 (4) ◽  
pp. 1101-1114
Author(s):  
Jerry A. Carter ◽  
Noel Barstow ◽  
Paul W. Pomeroy ◽  
Eric P. Chael ◽  
Patrick J. Leahy
Keyword(s):  
New York ◽  
High Frequency ◽  
Seismic Noise ◽  
Low Frequency ◽  
Time Variability ◽  
Orthogonal Components ◽  
The Difference ◽  
Frequency Coherence ◽  
Cultural Noise ◽  
Natural Wind

Abstract Evidence is presented supporting the view that high-frequency seismic noise decreases with increased depth. Noise amplitudes are higher near the free surface where surface-wave noise, cultural noise, and natural (wind-induced) noise predominate. Data were gathered at a hard-rock site in the northwestern Adirondack lowlands of northern New York. Between 15- and 40-Hz noise levels at this site are more than 10 dB less at 945-m depth than they are at the surface, and from 40 to 100 Hz the difference is more than 20 dB. In addition, time variability of the spectra is shown to be greater at the surface than at either 335- or 945-m depths. Part of the difference between the surface and subsurface noise variability may be related to wind-induced noise. Coherency measurements between orthogonal components of motion show high-frequency seismic noise is more highly organized at the surface than it is at depth. Coherency measurements between the same component of motion at different vertical offsets show a strong low-frequency coherence at least up to 945-m vertical offsets. As the vertical offset decreases, the frequency band of high coherence increases.

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