Abstract
We examine dynamic propagation of a screw-type crack in relation to crack-resistance force, i.e., energy dissipation per unit extension. We show that a crack may have any terminal velocity only when the resistance force is proportional to crack length. In this case, the value of (1-υ/β), where v and β are, respectively, crack and shear wave velocities, gives a measure of the irreversible effect associated with the fracturing process. Next, we consider such a resistance force in relation to the deformational properties of material, and show that the linear dependence ofthe resistance force on crack length can be related to elastic-plastic properties. Finally, we try to apply these results to earthquake mechanism studies.
