Seismic anisotropy caused by rock fabric

Autor: Shelton S. Alexander, Jung Mo Lee
Rok vydání: 1995
Předmět:
Zdroj: Geophysical Journal International. 122:705-718
ISSN: 1365-246X
0956-540X
DOI: 10.1111/j.1365-246x.1995.tb06829.x
Popis: SUMMARY As part of an experiment to investigate the influence of cracks produced by tectonic stress on the observed in situ anisotropic properties of crustal rocks at Kent Cliffs, New York, the contribution of rock fabric anisotropy was studied using laboratory core-sample ultrasonic measurements. Measured velocities of intact unfractured specimens, corrected to lithostatic pressure, allow the effect of rock fabric anisotropy to be evaluated. Computed phase-velocity surfaces and wave surfaces show varying degrees of anisotropy at different depths. These surfaces predict various anisotropic phenomena, such as S-wave splitting and anomalous amplitudes and polarizations. Some predictions can be applied to the case of a general transversely isotropic medium, including negligible P-wave, in contrast to large S-wave, polarization anomalies, generation of cusps in the wave surface by strong anisotropy, and the importance of the elastic stiffness coefficient, C1133, to the strength of anisotropy. Computed ray velocities in the borehole axis direction are compared with acoustic logging results. The comparison shows reasonable consistency. S-wave splitting caused by rock fabric for zero-offset vertical seismic profiling (VSP) is also predicted. These results can be used to separate the anisotropy caused by cracks and fractures from the overall observed in situ seismic anisotropy.
Databáze: OpenAIRE
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