### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 2aPA2. High amplitude, bifrequency experiments in porous rocks.

**Thomas J. Plona
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Bikash Sinha
**

**
Ralph D'Angelo
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**
Chris Kimball
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**
**
*Schlumberger-Doll Res., Ridgefield, CT 06776
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*
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**B. J. Landsberger
**

**
Mark F. Hamilton
**

**
**
*Univ. of Texas, Austin, TX 78713
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*
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Fluid-filled, porous, sedimentary rocks have the general characteristic
that the sound speeds are strongly dependent on the state of stress and
therefore, the third-order elastic coefficients (i.e., A, B, C) are generally
much larger than for normal solids. However, the linear attenuation can also be
very large such that in nonlinear wave propagation, the Gol'dberg number is
small. Experiments studying harmonic generation in porous rocks have been made
using an ultrasonic immersion system (i.e., water/solid/water) where a high
amplitude (e.g., 500 kPa), bifrequency (0.95 and 1.05 MHz), tone burst is
emitted and then sum and difference frequencies are detected after propagation
through the water/solid/water system. A frequency domain numerical
implementation of the KZK (Khokhlov--Zabolotskaya--Kuznetsov) nonlinear
parabolic wave equation is used to describe the nonlinear propagation in the
three layer system. Experiments on solids with well-known acoustic properties
(linear and nonlinear) were used to validate the model. Measurements were then
made on several sandstones and limestones and the model used to derive the
nonlinear propagation parameter, (beta)=f(A,B,C). Finally, these results are
compared with independent measurements of A, B, C for these rocks.