Precise P and S wave velocity variations, crack density, and saturation changes


  • G. G. R. Buchbinder


Precise observations of travel time changes of P and S waves from 11 explosions at the same shot point in the Charlevoix region, Quebec, have been determined by separate cross correlations of the P and S waveforms. The changes in P and S wave travel times are equal to within ±4 ms and lead to the relation that = 3. From the theory of O'Connell and Budiansky (1977) the derivatives of the normalized P and S wave velocities with respect to the normalized S wave velocity define the changes in crack density parameter ε and the partial saturation parameter ζ. Increases in travel time observed in the Charlevoix region suggest that the crack density parameter ε increases, while the partial saturation parameter ζ decreases, in agreement with the dilatancy hypothesis (Nur, 1972).