Crack breakout dynamics

Abstract The fusion of coplanar, antiplane strain, shear cracks in the presence of barriers can be considered to be a model for inhomogeneous earthquake faulting. We consider two cases of fracture. In the first case, two cracks grow separately at different times, and each is prevented from extending into the fracture zone of the other by a barrier zone of large strength. In the second case, the second of the cracks breaks through the barrier between the two and links up or fuses with the first. The long-period seismic energy radiated in the second case is found to be significantly greater than in the first, even though the stress on the already fractured segment has been dropped to a very low value. The model can be extended to describe cascading sequences of dynamic fusion.