Effects of anelasticity on reflection and transmission coefficients

Autor: F. Hron, S. Nechtschein
Rok vydání: 1997
Předmět:
Zdroj: Geophysical Prospecting. 45:775-793
ISSN: 1365-2478
0016-8025
Popis: It is known that the reflection and transmission coefficients used in the zeroth order approximation of asymptotic ray theory (ART) are identical to those obtained for the plane wave impinging on a plane interface separating two perfectly elastic half-spaces. We have used ART to compute reflection and transmission coefficients for two viscoelastic media separated by a plane interface. Our method is different from the plane-wave approach because the ART approach requires only a local application of the boundary conditions both for the eikonal and the ray amplitudes. Several types of viscoelastic media were studied. For a given model, the elastic case was emulated by setting all the quality factors Q equal to each other. Several anelastic cases were computed by keeping the same velocities and densities while changing the Q s. The quality factor is a relatively difficult parameter to measure exactly. Hence elastic coefficients are used in most synthetic seismogram computations, and the quality factors are chosen from experimental measurements or simply estimated. From these computations, amplitude and phase differences between elastic coefficients and coefficients for dissipative media are observed in some cases. These differences show the importance of knowing the exact values of Q . Incorrect Q values can lead to unrealistic moduli and to noticeable phase differences of these viscoelastic coefficients.
Databáze: OpenAIRE
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