ATTENUATION OF SEISMIC-WAVES IN DRY AND SATURATED ROCKS .1. LABORATORY MEASUREMENTS

The attenuation of compressional (P) and shear (S) waves in dry, saturated, and frozen rocks is measured in the laboratory at ultrasonic frequencies. A pulse transmission technique and spectral ratios are used to determine attenuation coefficients and quality factor (Q) values relative to a reference sample with very low attenuation. In the frequency range of about 0. 1-1. 0 MHz, the attenuation coefficient is linearly proportional to frequency (constant Q) both for P- and S-waves. In dry rocks, Q//p of compressional waves is slightly smaller than Q//s of shear waves. In brine and water-saturated rocks, Q//p is larger than Q//s. Attenuation decreases substantially (Q values increase) with increasing differential pressure for both P- and S-waves.