Holographic Study of Wave Propagation in Granite

Three techniques of holographic Interferometry were developed to study the response of geological materials to propagating stress waves. Two of these techniques, stored-beam Interferometry and double-exposure Interferometry, were found effective when applied to studying smallamplitude wave propagation. The third technique, a form of time-average holographic Interferometry (which produces fringes relating to velocities), was employed when studying higher stress levels (up to 30 kb). Low amplitude stress waves were generated by pendulum Impacts; a gas gun was used to obtain higher stress levels. A complete description of each technique is given herein, together with a comparison of experimental results (using Westerly granite) and theoretical predictions.