An informal workshop on the effect of cracks and voids in rocks on various elastic and transport properties was held at the Center for Earth and Planetary Physics, Harvard University, Cambridge, Massachusetts, all day Thursday, January 30, 1975. The workshop developed from a conversation between Ted Madden and T. J. Shankland and was organized by Shankland together with R. J. O'Connell.
Motivation for the workshop lay in observations, both theoretical and experimental, that the shape and volume of cracks in rocks exert a strong influence on the effective elastic wave velocities, on electrical and thermal conductivities, and on the fluid transport of rocks. These observations are in turn of interest because of their application to earthquake prediction, to the location of crustal fluids, and to the circulation of fluids near and in geothermal reservoirs. At the meeting, however, attention was focused on the rocks themselves rather than on these applications, and thus talks were concerned with the modeling of physical properties of rocks in terms of the theory of composites, with the direct observation of cracks and voids, and with the estimation of the distributions of certain crack properties.