Wave propagation in layered elastic media has been the focus of much work both in seismology and for nondestructive evaluation (NDE) applications. In much of this work, the layers are assumed to be perfectly bonded to each other. Structures are not always ideal however, and can contain flaws such as interface cracks or debonding between layers. One concern in NDE is the location and characterization of these regions of debonding. With this purpose in mind, in this paper we investigate the elastic wave scattering by a crack at the interface between a layer and a half space.