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The effect of frequency on P- and S-wave velocity dispersions on a few samples of sandstones
and limestones from Chabahar region in both dry and saturated states under low axial stress has been studied. Three pairs of piezoelectric transducers with the central frequencies of 63, 200 and
500 kHz are employed to measure P-wave velocity dispersions. Two pairs of similar transducers but with the central frequencies of 33 and 100 kHz have been used for S-wave velocity dispersion
measurements.
The results obtained in these experiments show that P-wave velocities in both dry and saturated states increase with increase of the frequency. However, the rate of velocity increase
form 63 kHz to 200 kHz is greater than that from 200 kHz to 500 kHz. It is also observed that
S-wave velocities increase with increase of the frequency, although in a few cases the velocity
dispersions was not normal. For both P and S waves the velocity dispersions in saturated samples
are greater than dry ones.
A dispersion equation has been used to extract quality factors (Q) from two sets of velocity
data
(
63 and 200 kHz for P waves and 33 and 100 kHz for S waves
.
samples are found to be greater than those for water saturated rocks