ISSN:
1365-246X
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Geologie und Paläontologie
Notizen:
We compute synthetic seismograms of SH waves that are multiply scattered by randomly distributed cracks. All the cracks are assumed to have the same length and strike direction; the crack surfaces are assumed to be stress-free, or to undergo viscous friction. We analyse the deterministic wave equation, and rigorously treat multiple crack interactions. We first calculate the wavefield in the wavenumber domain, and then we obtain the time-domain solution by its Fourier transform.A plane wave whose time dependence is described by the Ricker wavelet is assumed to be incident upon the region of crack distribution. The scattered waves are efficiently excited when the half-wavelength of the incident wave is close to or shorter than the crack length. High-wavenumber components are shown to be more abundant in the scattered waves when the crack distribution is denser. The time delay of the arrival of the primary wave, due to crack scattering, is shown to be prominent when the wavelength of the incident wave is much longer than the crack length. When the crack surfaces are subject to viscous friction, both the amplitudes of the scattered waves and the time delay of the primary-wave arrivals are smaller than those for the case of stress-free crack surfaces. When the crack distribution is statistically homogeneous, the calculated attenuation coefficient Q−1 and phase velocity v of the primary wave are generally consistent with those obtained by a stochastic analysis based on Foldy's approximation. A short analysis on the effect of inhomogeneous crack distribution shows that the wavenumber at which Q−1 is at its peak value is smaller than that expected from the stochastic analysis for homogeneous crack distribution.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1365-246X.1995.tb06846.x
