Velocity measurements

The ¶ and § velocities measured for the stainless-steel core, = 5743 $\pm$ 75 m/s and = 3092 $\pm$ 22 m/s, are approximately twice the Massillon Sandstone values, which seems reasonable. The measured stainless-steel / ratio is 1.86 $\pm$ .04, which is slightly stiffer than the Poisson solid value of = 1.73, as expected.

The ¶ and § velocities measured for the dry Massillon Sandstone are = 2918 $\pm$ 32 m/s and = 1731 $\pm$ 99 m/s. This represents an / ratio of = 1.69 $\pm$ .12, which is a Poisson solid to within error bounds. The ¶ and § velocities measured for the saturated Massillon Sandstone are = 3380 $\pm$ 78 m/s and = 1744 $\pm$ 201 m/s. This represents an / ratio of = 1.94 $\pm$ .25, which is not very Poisson-like, and is similar to the stainless-steel sample, neglecting the pessimistic error bounds. When water fills the pores, its effect is to ``stiffen'' the resulting saturated sample. This has a tendency to increase K_s and hence , compared to K_d and . However, , and the increase in saturated density over implies that will be slightly smaller than . These intuitive predictions are fairly well validated by our lab measurements.